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Recent Topics of Particle Theory

Thursdays 16:15 in Seminar Room P1-01-306.

Date Title Speaker
                                                                                                              Upcoming Sessions Winter Term 2018


to be announced Prof. Jim Cline, McGill University, Montreal, Canada


to be announced Dr. Michael Baker


Recent four- and five-loop results in QCD Prof. Andreas Vogt, Univ. of Liverpool, GB

We report on recent calculations in perturbative Quantum Chromodynamics (QCD) and its generalization to Yang-Mills theories with fermions.  We summarize the present status of four-loop calculations of the splitting functions for the scale dependence (evolution) of the quark and gluon distributions of hadrons.  Five-loop results are presented for the beta function, i.e. the running of the coupling constant, and for hadronic decays of the Higgs boson.


The recent anomaly in b -> s mu mu and possible correlations to other observables. Dr. Ryoutaro Watanabe, Univ. of Montreal, Canada

In this talk, I will show two my recent works (arXiv:1609.09078 and arXiv:1702.00395) regarding new physics to accommodate the anomaly in b -> s mu mu which has been standing on these days. First, I will discuss whether or not new physics scenarios can explain the b -> s mu mu anomaly and simultaneously the R_D(*) measurement, which also has a large deviation from the SM prediction. Second, I will show some new physics scenario that includes a dark matter can explain the b -> s mu mu and the cosmic ray anomalies [AMS anti-proton excess], interpreted as dark matter annihilation. The possible explanation is consistent with LHC direct searches and dark matter direct detection.

Sessions Summer Term 2017

02.08.2017, 11:15 h

Radiative neutrino mass and the flavour anomalies John Gargalionis (Univ. of Melbourne, AUS)

Recently there have been a number of measurements hinting towards lepton flavour universality violation in b--> and b-->s transitions.  In this talk I will discuss a possible connection between these experimental anomalies and radiative models of Majorana neutrino mass.  I will first present a general formalism for writing down minimal, radiative models starting from lepton-number violating effective operators, then proceed to illustrate the connection between these and the B anomalies by discussing a particular scalar leptoquark model in detail.  The model can accommodate the anomalous magnetic moment of the muon as well as the observables R_D, R_D*, R_K and R_K*.  I will show that, for this particular model, agreement with neutrino oscillation data compromises the explanation of R_K and R_K*.  I will finish by discussing ways in which other models in this class can overcome this limitation.

Montag, 24.07.2017,

16:15 h, CP-03-123

epsilon'/epsilon in the Standard Model Dr. Martin Gorbahn (Univ. of Liverpool)
The parameter epsilon'/epsilon describes direct CP violation in the Kaon system.  In this talk I will discuss the status of the theory prediction of this parameter and its sensitivity to physics beyond the Standard Model.  A particular focus will be on the perturbative side of the calculation that complements recent progress of Lattice QCD.

13.07.2017, 11:15 Uhr,

AV Raum

Search for new physics in B-->D(*) tau nu Dr. Andrey Tayduganov (CCPM, Univ. Aix-Marseille)
Recent experimental results for the ratios of the branching fractions of the decays B-->D(*) tau nu and B-->D(*) mu nu came as a surprise and lead to a discussion of possibility of testing new physics beyond the Standard Model through these modes.  We show that these decay channels can provide us with good constraints on new physics and several new physics models are favored by the present experimental data. In order to discriminate various Physics scenarios, we examine the full angular distributions and discuss the spectra on each angle separately.
13.07.2017, 16:15 Uhr Leptogenesis and Non-Equilibrium Field Theory Dr. Björn Garbrecht (TU München)
I will summarize derivations of the fluid equations governing leptogenesis starting from first principles (in the form of Schwinger-Dyson equations), that have been carried out in the recent years.  In that context, I will also present improved phenomenological predictions for flavoured and resonant leptogenesis as well as for the scenario involving light (GeV scale) right-handed neutrinos.
29.06.2017 The SMEFT - Integrating UV models via Functional Methods Fagner Cintra Correia (Sao Paulo State Univ.)
The Standard Model Effective Field Theory may be defined as a method for parametrizing New Physics through the insertion of higher-dimension operators, invariant under the SM gauge group and suppressed by powers of a heavy scale.  In this seminar the principles behind the SMEFT methodology must be covered, from the matching procedure to the extraction of covariant operators.  The technique will then be applied for specific sectors of the so-called 3-3-1 models.
22.06.2017 3-dimensional QED at low energies from the epsilon expansion Dr. Emanuel Stamou (Univ. of Chicago)
In 3 dimensions, QED is a free theory at high energies.  However, like QCD in 4 dimensions, QED3 becomes strongly coupled when evolved to low energies.  If the number of fermions/flavours Nf is large, the strongly coupled theory is conformal, but this can change for small values of Nf.  In this talk, I discuss a mechanism that may dynamically force the theory out of conformality; a strong RG flow can render four-fermion operators relevant and destabilize the conformal fixed point. In discuss how to quantify this via the method of epsilon expansion at one- and two-loop.  I will also discuss the scheme and evancescent (in)dependence of this approach.
01.06.2017 The Fuzzy Dark Matter cosmological simulation for Lyman-alpha forest Dr. Yue-Lin Sming Tsai (Nat. Center for Theor. Science, Taiwan)

The recent Lyman-alpha forest data from BOSS and XQ100 reveal that the lower mass limit of the Fuzzy dark matter (FDM) has been pushed up to 1e-21 eV.  However, such limits are mainly based on a Lambda CDM simulation with FDM initial condition but neglect the quantum pressure effects in the N-body simulation.

For a 1e-22 eV DFM mass, the solitonic core is around kpc size and the quantum pressure can still have a non-negligible impact at the structure formation.  By including the quantum pressure into a cosmological simulation, we revise the current BOSS and XQ100 constraints on 1e-22 eV FDM.  We found the statistics strength can even be slightly improved by using all range of data.  If focusing on the region k>0.02 km-1s where quantum pressure is dominating, a 1e-22 eV FDM is more disfavored than CDM but it is still not statistically significant.

11.05.2017 Lepton flavor violation at high and low energies Dr. Alexey Petrov (Wayne State Univ., Detroit, MI, USA)
Lepton-flavor violating (LFV) effective Lagrangian at low energies contains over a dozen distinct operator structures.  We discuss how to constrain Wilson coefficients of those operators from the data obtained in various LFV leptonic and radiative leptonic transitions of B/D/K mesons, LFV decays of various quarkonia, as well as from high energy LHC data.
04.05.2017 The Axiflavon:  A Minimal Axion Model from Flavor Dr. Robert Ziegler
I will discuss a simple QCD axion model that arises from identifying Peccei-Quinn with Froggatt-Nielsen symmetries.  In this scenario the flavor problem of the Standard Model is addressed by U(1) flavor symmetry, which naturally leeds to an axion that solves the strong CP problem and constitutes a viable Dark Matter candidate.  The ratio of the axion mass and its coupling to photons is related to SM fermion masses and predicted within a small range, as a direct result of the observed hierarchies in quark and charged lepton masses.  The same hierarchies determine the axion couplings to fermions, making the framework very predictive and experimentally testable by future axion and precision flavor experiments.
27.04.2017 Chiral Effective Theory of Dark Matter Direct Detection Dr. Jure Zupan (Univ. of Cincinnati and CERN)

I will present the effective field theory for dark matter interactions with the visible sector that is valid at scales of O(1 GeV). Starting with an effective theory describing the interaction of fermionic and scalar dark matter with quarks, gluons and photons via higher dimension operators that would arise from dimension-five and dimension-six above electroweak scale, we perform a non-perturbative matching onto a heavy baryon chiral perturbation that describes dark matter interactions with light mesons and nucleons.  This is then used to obtain the coefficients of the nuclear response functions using a chiral effective theory of nuclear forces. Our results keep the leading contributions in chiral counting for each of the initial Wilson coefficients.

20.04.2017 Neutrino oscillations in the three-flavor framework and beyond Dr. Mariam Tórtola (Univ. Valencia)
In this seminar, I will summarize the current status of global neutrino oscillation analyses in the three-neutrino framework.  I will also discuss how the standard picture of neutrino oscillations and in particular the measurement of the CP violation phase in the near future can be affected by the presence of neutrino physics beyond the Standard Model.
Sessions Winter Term 2016/17
15.12.2016 Investigating electroweak symmetry breaking with colliders and gravitational waves Prof. Stephan Huber (University of Sussex)
In many extensions of the standard model, electroweak symmetry breaking in the early universe occurred via a first-order phase transition.  In a first part I will concentrate on models with a second Higgs doublet, and discuss how the parameter space with a strong phase transition can be probed at LHC.  In the second part I will report on large scale numerical simulations to compute the gravitational wave signal generated by first-order phase transitions.  I will discuss the prospects of detecting gravitational waves with LISA, the future space based interferometer.
08.12.2016 Angular Observables for Spin Discrimination in Boosted Diboson Final States Dr. Malte Buschmann (Universität Mainz)
We investigate the prospects for spin determination of a heavy diboson resonance using angular observables.  Focusing in particular on boosted fully hadronic final states, we detail both the differences in signal efficiencies and distortions of differential distributions resulting from various jet substructure techniques.
                                                                          Previous Sessions:  Summer Term 2016
21.07.2016, 10:15 h Time, timelessness, and the conscious self Prof. Marc Wittmann (Department für Empirische und Analytische Psychophysik, Institut für Grenzgebiete der Psychologie und Psychohygiene, Freiburg)
and Prof. Heinrich Päs, TU Dortmund

"What is consciousness?" has been dubbed "The Hard Problem" by philosopher of science David Chalmers.  From a physics perspective though, "The Hard Problem" is only one specific aspect of three "Big Questions": 1. What is "self"?  2. What is time?  How does "classical reality" emerge from a quantum Universe?  It is argued that these problems, i.e. the emergence of "self", time and reality are strongly interrelated, both in physics and in psychology.  Various facets of this relation in physics and in psychology are illustrated, compared and contrasted.

14.07.2016 Sum Rules for Flavor Parameters

Dr. Martin Spinrath (Karlsruhe Institute for Technology)

The flavor sector of the Standard Model with its large number of parameters is still rather badly understood.  A plethora of models has been developed in the past to shed some light on the origin and structure of flavour.  Nevertheless, the situation is still not very satisfactory and no vastly preferred approach has been firmly established.  Instead of reviewing various model attempts we want to discuss a class of predictions which many of the models have: sum rules.  We put an emphasis on the lepton sector, but we will also briefly mention sum rules in the quark sector.

07.07.2016, 10:15 h The Charged Lepton Flavour Violation Window on Sterile Neutrinos Prof. Jean Orloff (Univ. Clermont-Ferrand)
Neutrino oscillations require an extension of the Standard Model.  Adding sterile neutrinos is a serious, and in some ways minimal, possibility to cover this gap in our understanding of particle physics.  After reviewing the arguments for sterile neutrino extensions of the SM, and the potential merits of sterile states for other questions like dark matter or the matter-antimatter asymmetry, we will address the difficult but essential question of experimentally probing this hypothesis through the example of charged lepton flavour violation.
30.06.2016 Gluino Annihilation

Dr. Feng Luo (Institute for the Physics and Mathematics of the Universe, Japan)

Some variants of the minimal supersymmetric extension of the Standard Model (MSSM) feature a strip in parameter space where the lightest neutralino is identified as the lightest supersymmetric particle (LSP), the gluino is the next-to-lightest supersymmetric particle (NLSP) and is nearly degenerate with the LSP, and the relic cold dark matter density is brought into the range allowed by astrophysics and cosmology by coannihilation with the gluino NLSP.  We calculate the relic density along this gluino coannihilation strip in the MSSM, including the effects of gluino-gluino bound states, and taking into account the decoupling of the gluino and LSP densities that occurs for a squark to gluino mass ratio larger than order of 100.  We find that the LSP may weigh up to ~ 8 TeV with the correct dark matter density.

23.06.2016 - cancelled --- Prof. Maxim Polyakov (Ruhr-Universität Bochum)
09.06.2016 Cosmological relaxation of the weak scale Dr. Christophe Grojean (DESY, Hamburg)
A naturally small electroweak scale can result from the cosmological evolution of the Universe.  The crucial ingredients for this to happen are a coupling of the Higgs to an axion-like field and a long epoch of inflation where the axion unchains a dynamical screening of the Higgs mass.  I'll discuss the original proposal and a new realization of this idea with the characteristic feature that it leaves no signs of new physics up to a rather large scale, 10^9 GeV, except for two very light and weakly coupled axion-like states.  One of the scalars can be a viable Dark Matter candidate.  Such a cosmological Higgs-axion interplay could be tested with a number of experimental strategies.
02.06.2016 Looking for the effects of lepton flavor (universality) violation at low energies Prof. Damir Becirevic (LPT, CNRS & Univ. Paris Saclay)
I will review the current situation concerning the studies of lepton flavor violation and of the departures from the lepton flavor universality limit, especially those recently hinted in the B-physics experiments.  I will make a critical assessment of theoretical uncertainties and then describe the main features of the scenarios of physics beyond the Standard Model that can accommodate the current B-physics anomalies including the original one that we propose.
19.05.2016 Quantized Space and Time Dr. Peter Schupp (Universität Bremen)

Quantum Field Theory and General Relativity provide a very precise description of physics at almost all scales.  But these theories are also known to be fundamentally incompatible and hence incomplete.  In particular it is generally expected that we will need to replace the notion of smooth spacetime geometry with more general concepts.  While the ultimate unified description of nature is not yet known, we can nevertheless explore potential quantum gravitational effects with the help of mathematical models of quantized space and time.  I will present some of these models and give an outlook on recent work on gravity in a generalized geometry setting.

28.04.2016 Symmetries for low and high energy CP phases Dr. Claudia Hagedorn (Univ. of Southern Denmark, Odense)
Leptonic low energy CP phases, of Dirac as well as Majorana type, can be predicted with the help of flavor and CP symmetries.  However, the high energy CP phases in the lepton sector, relevant for leptogenesis, are in general unrelated to those at low energies and thus represent new sources of CP violation.  We discuss a scenario in which all CP phases are constrained by flavor and CP symmetries.  In this way, the CP violation at low and high energies becomes intimately related and, in particular, the sign of the baryon asymmetry of the Universe, generated via the mechanism of unflavored leptogenesis, is fixed.
                                                                   Previous Sessions: Winter Term 2015/16
Sondertermin! 31.03.2016 Impact of leptonic tau decays on the distribution of B --> mu nubar decays Dr. Danny van Dyk (Univ. Zürich)
I will present the fully-differential rate of the decays B --> P tau (--> mu nu nubar) nubar, where P = D, pi, which is a background to the semimuonic decays B --> P mu nubar.  The decays with a 3 nu final state can have a sizeable impact on the experimental analyses of the ratios R_D and R_pi, depending on the event selection in the analysis.  I outline a strategy which permits the extraction of R_P B(tau --> mu nu nubar) from the neutrino-inclusive rate.  The analytic results can also be used to test both existing and upcoming experimental analyses. 
04.02.2016 Another look at collective neutrino oscillations Dr. Evgeny Akhmedov (MPI Heidelberg)

In dense neutrino backgrounds present in supernovae and in the early Universe neutrino oscillations may exhibit complex collective phenomena, such as snychronized oscillations, bipolar oscillations and spectral splits and swaps.  I will discuss in detail possible decoherence effects on the simplest of these phenomena - synchronized neutrino oscillations.

An analytic approach is developed that allows one to study decoherence effects on the late-time behaviour of the system.  This turns out to be possible due to the existence of the (previously unknown) exact conservation law satisfied by the quantities describing a uniform gas of self-interacting neutrinos and antineutrinos.  Interpretation of the decoherence effects in terms of neutrino wave packet separation is also given.

21.01.2016 Interpretation of results on high-energetic cosmic neutrinos Dr. Walter Winter (DESY Zeuthen)
The discovery of cosmic neutrinos beyond TeV energies has started a new era in multi-messenger astrophysics.  We illustrate the particle physics of their sources, and we discuss the possible origin of these neutrinos and the interpretation of recent results.  We furthermore sketch the potential and challenges for multi-messenger models connecting neutrinos with the origin of the cosmic rays.
14.01.2016 Neutralino dark matter:  Lessons from the LHC for direct and indirect detection searches Dr. Enrico M. Sessolo (National Centre for Nuclear Research, Warsaw)

I will review the observational status of neutralino dark matter and investigate the prospects for detection in current and future experiments.  The talk will be divided in two parts.  The first part will be dedicated to some minimal SUSY models defined at the scale of Grand Unification.  I will show that the discovery of the Higgs boson at 125 GeV provides in these cases specific hints on the nature and detection prospects of the dark matter particle, whose mass is in the TeV range, and whose scattering cross section will be exhaustively probed by tonne-scale underground detectors.  In the second part I will cover the general case of the phenomenological MSSM, showing that the Cherenkov Telescope Array, whose construction start is planned for 2016, will provide a highly sensitive way of searching for dark matter that will be partially overlapping and partially complementary with tonne-scale detectors and collider searches.

07.01.2016 Renormalisation group flow of perturbative gauge-Yukawa theories Andrew Bond (Univ. of Sussex)
In this talk I will discuss the ideas of the renormalisation group and running couplings, and how fixed points of the renormalisation group flow can be used to define quantum field theories valid to arbitrarily high energies.  I will describe the structure of the beta functions of perturbative four-dimensional quantum field theories, and how this impacts the possible ultraviolet behaviour of couplings, and outline a few concrete scenarios for the ultraviolet behaviour of such theories.
17.12.2015 SUSY and Higgs in the Light of LHC Run II Prof. Sven Heinemeyer (Univ. Santander)
We discuss the status and prospect of SUSY and Higgs searches in the light of recent LHC data, combined with low-energy, flavor and astrophysical data.

The Leptonic CP Phase from Residual Symmetry and Muon Decay at Rest Experiments

Dr. Shao-Feng Ge (MPIK Heidelberg)
With the 1-3 mixing angle measured at reator neutrino experiments, Daya Bay and RENO, there are still three unknown oscillation variables, the neutrino mass hierarchy, the octant of the atmospheric mixing angle, and the leptonic CP phase. Of these three, the CP phase is the most difficult to measure precisely and important for distinguishing flavor symmetries. In this talk I will first talk about residual symmetries that can predict the CP phase from the measured mixing angles and then introduce a new type of neutrino experiment to measure the CP phase. Currently, T2K and NOvA are designed for this measurement. Nevertheless, they suffer from degeneracy and efficiency problems. The situation can be improved by adding a muon decay at rest (muDAR) source. With T2(H)K running in neutrino mode and muDAR in anti-neutrino mode, both using the same detector, the CP measurement becomes more precise and can break the degeneracy between \delta and 180^o - \delta. The same configuration can also be applied to next-generation medium baseline reactor neutrino experiments like JUNO and RENO-50, enhancing their physics potential. With only one source and no extra detectors, this dessign is much better than DAEdLAS which requires 3 sources, but only 20% duty factor and 4 times higher luminosity for each.
19.11.2015 Symmetry violation weak decays Keri Vos (Univ. Groningen)
Symmetry and symmetry violation are an important tool in the search for beyond the Standard Model physics. Symmetry violation in beta decay played a major role in uncovering the structure of the weak interaction, but also remains important today in searches for non-SM couplings. These searches for non-SM physics are, however, not independent from searches in other fields, such as searches at the LHC or searches for electric dipole moments. In this talk I will discuss the significance of beta decay compared to various other observables.  Besides I will also discuss the possible breakdown of Lorentz symmetry in the weak interaction and how weak decays can put limits on Lorentz symmetry breaking.
08.10.2015 Naturally light uncolored and heavy colored superparticles Prof. Gautam Bhattacharyya (Saha Institute of Nuclear Physics, Kolkata, India)
I will discuss the phenomenology of Gauge Mediated Supersymmetry Breaking scenarios where the messengers of gauge mediation transform in the adjoint representation of the gauge group.
                                                           Sessions Summer Term 2015
16.07.2015 Searching for Supersymmetry using signatures of “Z+ETmiss+Jets” at ATLAS Dr. Andreas Redelbach (Univ. Würzburg)
In the last years there has been an enormous scientific program at LHC detectors, utilizing unprecedented proton beam energies and intensities.  These measurements have tested the Standard Model of particle physics at high precision and have also probed many models beyond the Standard Model such as supersymmetry.  In this talk, I briefly review basic strategies for data analysis that have been established at the ATLAS detector in search for supersymmetry.  The focus of this talk will be on recent results from a search for supersymmetry using signatures of “Z+missing transverse energy+jets” at 8 TeV. Summarizing this analysis, the excess found in signal events over background will be discussed and also some implications for models of supersymmetry are outlined.
09.07.2015 Gravity-improved hydrodynamics of heavy ion collisions Henning Gerber (Universität Bielefeld)
The late time behaviour of quark-gluon plasma produced in heavy ion collisions at LHC and RHIC is well described by viscous relativistic hydrodynamics.  However, it fails to describe the early, preequilibrium phase.  Starting off by introducing basic ideas and features of string theory I will motivate a correspondence between string theory in Anti-de Sitter space and conformal field theory known as the AdS/CFT correspondence.  I will then explain how the correspondence can be used to improve the hydrodynamic description of strongly interacting conformal plasmas.
Sondertermin: Mittwoch, d. 01.07.2015, 10:15 Uhr, Ort: P1-O1-306 Charm CP Asymmetry Sum Rules Dr. Stefan Schacht (KIT Karlsruhe)
In order to probe for new physics in nonleptonic charm decays, we extract unknown topological amplitudes including linear SU(3)F breaking and a 1/Nc expansion from a global fit to branching ratios.  Charm CP asymmetries contain even further hadronic parameters not constrained by the fit.  We eliminate these in new sum rules, giving nontrivial predictions which can be used to test the Standard Model.
25.06.2015 Dark matter origins of neutrino masses Dr. Wei-Chih Huang (UCL, London)
We propose a simple scenario that directly connects the dark matter (DM) and neutrino mass scales.  Based on an interaction between the DM particle chi and the neutrino nu of the form chi chi nu nu/Lambda^2, the DM annihilation cross section into the neutrino is determined and a neutrino mass is radiatively induced.  Using the observed neutrino mass scale and the DM relic density, the DM mass and the effective scale Lambda are found to be of the order MeV and GeV, respectively.  We construct an ultraviolet-complete toy model based on the inverse seesaw mechanism which realizes this potential connection between DM and neutrino physics.
Sondertermin:Dienstag, d. 16.06.2015, 14:15 Uhr, AV-Raum (P2-O4-414) Higgs to tau mu: Experiment and Theory Avital Dery (Weizmann Institut, Rehovot, Israel)
The search for a Higgs decay into a tau and a muon is receiving a lot of attention over the past few months, after CMS have reported a slight excess (2.4 sigma) from zero.  I will discuss our implementation of such a search within the ATLAS collaboration, using a data-driven method we have developed to search for LFV decays. On the theoretical side, I will review recent work by us and others, analyzing the possible implications of such a signal.
21.05.2015 Flavor of Supersymmetry Dr. Kamila Kowalska (National Centre for Nuclear Research, Warsaw)
I discuss the most general flavor structure of the Minimal Supersymmetric Standard Model.  I review the experimental constraints on the magnitude of flavor-violating entries in the soft SUSY-breaking matrices and specify those that are currently only weakly constraint.  Accidentally, the presence of such terms have interesting phenomenological implications.  I discuss several examples of how a non-trivial flavor structure of the MSSM can affect the determination of the Higgs boson mass, the Yukawa coupling unification and the direct SUSY searches at the LHC.
07.05.2015 Lepton flavour violation in the inverse seesaw and its supersymmetric realization Dr. Cedric Weiland (IPPP, Durham)
The discovery of neutrino oscillations more than a decade ago called for an extension of the Standard Model that would generate neutrino masses and mixing.  We considered a specific mechanism, the inverse seesaw, that introduces new fermionic gauge singlets around the TeV scale with large couplings to SM leptons.  This leads to a rich phenomenology and makes it easily testable at current and future experiments.  After describing the inverse seesaw and its embedding in a supersymmetric framework, we will discuss their predictions for lepton flavour violating (LFV) observables in light of the recent CMS excess in the Higgs to tau mu channel and future experimental sensitivities to LFV lepton decays.


                                                                                                                           Sessions Winter Term 2014/15
11.12.2014 Neutrino masses and mixing from discrete symmetries Dr. Christoph Luhn (Univ. Siegen)
It is a well-established fact that quarks and leptons come in three families.  Yet the principles governing their origin and structure remain shrouded in mystery.  In my talk, I will review the symmetry approach to this flavor puzzle.  Originally, family symmetries were largely motivated by the idea of tri-bimaximal lepton mixing.  In 2012, this simple pattern was ruled out by the measurement of the so-called reactor mixing angle of about 9 degrees.  I will present an overview of new strategies in constructing models of neutrino masses and mixing, highlighting possible ways of testing such scenarios.  A benchmark model based on the family symmetry S4 enlarged by a (generalized) CP symmetry is sketched for illustrative purposes.

Energising Higgs Phenomenology at the LHC

Dr. Michael Spannowsky (Univ. Durham)

The High-Energy community is only now in the process of fully appreciating the opportunities the LHC provides by producing electroweak-scale resonances beyond threshold.  This is on the one hand reflected by moving form the so-called 'kappa framework’ to effective operators but on the other hand also by looking into Higgs and gauge boson production in processes with large momentum transfer.  This allows to discover or at least constrain New Physics contributing to these processes at the microscopic level.  I will discuss implications of and tools necessary for these measurements, with a focus on Higgs and Dark Matter phenomenology.

27.11.2014 Falsifying High-Scale Models of Baryogenesis Dr. Frank Deppisch (University College, London)
Finding the mechanism of baryogenesis in the Universe is one of the main outstanding issues of modern (astro)particle physics and there is wide range of physics models that attempt to explain the generation of a net baryon number. Many of these models operate at very high scales, not directly accessible in particle physics experiments, with the Seesaw and the associated leptogenesis mechanism as the most prominent example. I will discuss how such models can be falsified by observing lepton and baryon number violating processes at the LHC and at low energies (such as neutrinoless double beta decay). For example, observing any lepton number violating (LNV) process at the LHC would put a strong lower limit on the washout of the lepton number density in the early universe around the electroweak scale. In particular, leptogenesis models with right-handed neutrinos heavier than the LNV mass scale observed at the LHC would be falsified or at least strongly constrained as the associated washout would erase the generated net lepton number.
20.11.2014 Dr. Ulrich Mosel unfortunately had to cancel his talk in Dortmund.  

14.11.2014 (Friday), 12:00 h sharp

Lattice Flavor Physics

Prof. Andreas Kronfeld (Fermilab, Batavia, IL, USA)

In this talk, I will cover a few calculations from lattice QCD pertaining to lattice flavor physics.  The discussion will be shaped in a way that exposes some of the issues in these calculations, particularly how systematic uncertainties are adressed.  (In the end, it comes down to effective field theories.) I will give some outlook, including a preview of work relevant to neutrino scattering experiments.
13.11.2014 Supersymmetric Axion Cosmology Dr. Frank Steffen (Max-Planck-Inst. f. Physik, München)
The standard model is highly successful in describing phenomena at accelerators but contains no particle that can describe dark matter. There are also fine-tuning problems such as the hierarchy problem or the strong CP problem that call independently for new physics. Those problems can be alleviated by postulating two new fundamental symmetries: supersymmetry and the Peccei–Quinn symmetry. Extending the standard model with those symmetries, new extremely weakly interacting particles (EWIPs) are predicted to exist: the axion, the saxion, the axino, and the gravitino. These fields are compelling candidates for dark matter and/or dark radiation, which has been probed by the Planck satellite. In this talk I will discuss various cosmological aspects of supersymmetric axion models in light of recent experimental/observational insights.
06.11.2014 Testing New Physics Effects in B→K*ℓℓ Dr. Diganta Das (TU Dortmund)
It is generally believed that the decay mode B>K*ℓℓ is one of the best modes to search for physics beyond the standard model. The plethora of independent observables obtained from the angular distribution enable unique tests of the standard model contributions.  We start by writing the most general parametric forms of the standard model amplitudes for B>K*ll, taking into account comprehensively all contributions within the standard model.  These include all short-distance and long-distance effects, factorizable and non-factorizable contributions, complete electromagnetic corrections to hadronic operators up to all orders, resonance contributions and the finite lepton and quark masses.  The parametric forms of the amplitudes in the standard model result a new relation involving all the CP conserving observables.  The violation of this relation will provide a smoking gun signal of new physics.
30.10.2014 Reactor mixing angle from hybrid neutrino masses Dr. Ivo de Medeiros-Varzielas (Univ. Basel)
It is useful to write the neutrino mass matrix in terms of the eigenvectors of the lepton mixing matrix. In terms of this decomposition, the neutrino mass matrix can be seen as originating from a tribimaximal dominant structure with small departures required by the reactor mixing angle. Such a structure arises very naturally in cases with more than one mechanism responsible for neutrino masses - "hybrid seesaw".



Sessions Summer Term 2014

10.07.2014 Nonrelativistic Quantum Chromodynamics at NNLO Dr. Dirk Seidel (Univ. Siegen)
Bound states of a heavy quark and antiquark provide an ideal laboratory to study nonrelativistic quantum chromodynamics (NRQCD). Recently, important perturbative contributions at NNNLO have been completed which are used to compute the rate of the Upsilon(1S) meson into a lepton pair at that order within perturbation theory.
12.06.2014 Extended scalar sectors in the LHC era Antonio Celis (IFIC, València)
The recent discovery of a SM-like Higgs boson seems to be telling us that the simple or minimal scenario of electroweak symmetry breaking of the SM is on the right path, to say the least.   After reviewing the crucial role of the scalar sector of the SM in the theory, I will move to discuss the main implications of having a Higgs-like bosonwithin the framework of extended scalar sectors.   Minimal extensions of the SM scalar sector can have profound implications and connections with some of the "big" pending questions in high energy physics like: Dark Matter, the baryon asymmetry of the universe, the strong CP problem, neutrino masses, among others.
05.06.2014 New Physics in The Higgs Sector - An Effective Theory Approach Prof. Gerhard Buchalla (LMU München)
The discovery of a Higgs-like particle at the LHC in 2012 has been a major breakthrough towards a deeper understanding of electroweak symmetry breaking.  Measurements of Higgs properties are so far compatible with the Standard Model (SM) within uncertainties.  Since the Higgs sector of the SM is unnatural, it is generally expected to be only an approximation to some underlying, more fundamental dynamics, which would lead to deviations from the SM.  A systematic description of new physics, independent of specific models, can be achieved using effective field theory.  The motivation for this approach is reinforced by the absence of further new resonances in the LHC data analysed until now.  A general formulation should allow for the possibility of new strong dynamics in the electroweak sector.  The systematics of the resulting effective theory will be discussed.  Applications of this framework to electroweak processes, such as e+e- -> W+W- or h -> Z l+l-, will be considered for illustration.
08.05.2014 CP Violation in the Lepton Sector through rare K decays. Miguel Campos (Univ. Técnica Federico Santa Maria, Valparaíso, Chile)
As a consequence of the massiveness of neutrinos, the mixing matrix known as the PMNS matrix arises in the lepton sector.  It is now established that all its entries are non-zero opening the possibility of having CP asymmetries in the lepton sector. If one considers Majorana neutrinos with masses in the range around 10² MeV, rare meson decays like K+→π-|+|+ (l = e, μ) can exhibit CP Violation. I present a scenario where this asymmetry could be sizeable, which is the case if there are two or more nearly degenerate Majorana neutrinos. I will also consider the advantages and disadvantages of this kind of decays in comparison with other processes that also violate Lepton Number.

(Room P2-EO-414 !)

Fermion masses and mixings in an SU(5) Grand Unified Model with an Extra Flavor Symmetry Dr. Antonio Cárcamo Hernández (Univ. Técnica Federico Santa Maria, Valparaíso, Chile)
Abstract: We propose a model based on the SU(5) Grand Unification with an extra A4xZ2xZ2'xZ2''xU(1)f flavor symmetry, which accounts for the pattern of the SM fermion masses and mixings. The observed hierarchy of charged fermion masses and quark mixing matrix elements arises from a generalized Froggatt-Nielsen mechanism triggered by a scalar 24 representation of SU(5) charged under the global U(1)f and acquiring a VEV at the GUT scale. The light neutrino masses are generated via a radiative seesaw mechanism with a single heavy Majorana neutrino and neutral scalars running in the loops. The model predictions for both quark and lepton sectors are in good agreement with the experimental data. The model predicts an effective Majorana neutrino mass, relevant for neutrinoless double beta decay, with values m??= 4 meV and 50 meV for the normal and the inverted neutrino spectrum, respectively. The model also features a suppression of CP violation in neutrino oscillations, a low scale for the heavy Majorana neutrino (few TeV) and, due to the unbroken Z2 symmetry, a natural dark matter candidate.

Previous Sessions Winter Term 2013/14

06.02.2013 U(2)^5 Flavour Symmetry in SUSY for the Quark and Lepton Sector Joel Jones Perez (Univ. Valencia)
From the naturalness point of view, the first LHC results seem to disfavour any constrained MSSM realization with universal conditions at the SUSY-breaking scale.  A more motivated scenario is given by split-family SUSY, in which the first two generations of squarks are heavy.  This scenario is compatible with a U(2)^3 flavour symmetry, instead of the U(3)^3 normally invoked by Minimal Flavour Violation. In this talk, we build such a framework and extend it to the lepton sector, such that neutrino data can also be used to gain information on the sfermion sector. We then analyse the consequences for quark and lepton phenomenology.
30.01.2014 Searching for spectral features in the gamma-ray sky Alejandro Ibarra (TU München)
The search for the gamma-rays which are presumably produced in dark matter annihilations is hindered by the existence of large, and still poorly understood, astrophysical backgrounds. In this talk we will emphasize the importance of sharp spectral features for the identification of a dark matter signal. We will review the status of the search of the various spectral features that arise in Particle Physics scenarios and we will discuss the interplay with other search strategies.
23.01.2014 Noncommutative Geometry in the LHC-Era Christoph Stefan (Univ. Potsdam)
Noncommutative geometry (NCG) allows to unify the basic building blocks of particle physics, Yang-Mills-Higgs theory and General relativity, into a single geometrical framework.  The resulting effective theory constrains the couplings of the Standard Model (SM) and reduces the number of degrees of freedom.  After briefly introducing the basic ideas of NCG, I will present its predictions for the SM and the few known models beyond the SM based on aclassification scheme for finite spectral triples . Most of these models,  including the Standard Model, are now ruled out  by LHC data.  But interesting extensions of the SM which agree with the presumed Higgs mass predict new particles (Fermions, Scalars and Bosons) and await further experimental data.
16.01.2014 LHC constraints on long-lived stop Federico Dradi (Univ. Göttingen)
We consider scenarios of gravitino LSP and DM with stop NLSP both within R-parity conserving and R-parity violating supersymmetry.  We discuss cosmological bounds from BBN and gravitino abundance and then concentrate on the signals of long-lived stops at the LHC.  Finally we discuss as well how to distinguish R-parity conserving and R-parity breaking stop decays if such decays happen in the detector.
05.12. Unbroken Baryon and Lepton Numbers Julian Heeck (MPIK Heidelberg)
We scrutinize the existence of unbroken gauge symmetries beyond electromagnetism and color. Such a symmetry can only be a linear combination of baryon and lepton number, the global symmetries of the Standard Model. The new gauge boson can have a Stückelberg mass without an unnaturally tiny coupling constant, but anomaly cancelation requires new chiral fermions with electroweak masses, highly constrained by collider experiments, precision data, cosmology, and direct searches for dark matter.
28.11. Trilepton Signatures of Light Charged and CP-odd Higgs Bosons in Top Quark Decays Enrico Lunghi (Univ. of Indiana)
In singlet extensions of the two Higgs doublet model, a light CP-odd Higgs boson (A) can significantly modify decay modes of the charged Higgs.  We study a scenario in which the charged Higgs is produced in top quark decays, t -> H+ b, with dominant H+ -> W+ A.  We discuss search strategies based on A -> tau tau and on the subleading decay mode A -> mu mu.  We show that the searches we propose can constrain, with 20 fb^−1 of 8TeV LHC data, most of the currently allowed parameter space and that existing trilepton searches are not sensitive to this signal due to the adopted isolation criteria.
21.11. Neutrino mass models with large mixing originating from the
right-handed sector
Erik Schumacher (TU Dortmund)
We discuss neutrino masses and mixing in the context of seesaw type I models with three right-handed Majorana neutrinos. The flavor structure in the right-handed Majorana masses is responsible for large mixing, whereas the small mixing angle originates from an approximately diagonal Dirac sector in analogy to CKM mixing. This ansatz leads to interesting consequences for CP violation and leptogenesis.
14.11. Bayesian Constraints on Wilson Coefficients from Radiative
and (Semi)leptonic b → s Decays
Danny van Dyk (Univ. Siegen)
We perform a global Bayesian analysis of available data on rare radiative and (semi)leptonic B decays. Allowing for new physics contributions, we derive constraints on the Wilson Coefficients C_7, C_9 and C_10 and their chirality-flipped counterparts. In all considered scenarios we find agreement with the Standard Model, and see hints of subleading power corrections beyond known contributions from QCD factorization calculations.  We also derive constraints on the parameters for hadronic form factors in exclusive B->K* and B->K transitions.
24.10.   Chaotic strings - test tubes for the universe? Stefan Groote (Univ. Mainz u. Tartu, Estland)
Chaotic strings, not to be mixed up with ordinary string theory, are cyclic mathematical objects with quasi-chaotic (ergodic) behavior.  In this talks I explain how these objects which can be tested on a personal computer like in a "test tube" provide surprizing answers to several yet unsolved problems and questions of modern physics like the masses of elementary particles, a possible scenario for Grand Unification and Big Bang, the emergence of spacetime out of mathematics, and possible explanations for dark matter and energy.  As the framework of emergence is on the way to be traced by us in Tartu and London, in the talk I will mostly follow my intuition to speculate about the different scenarios provided by this fresh and rarely investigated subject.

Previous Sessions Summer Term 2013

11.7. Warm inflation after Planck Dr. Joao Rosa (Univ. Aveiro, Portugal)
Warm inflation models give an alternative to the standard inflationary paradigm, which takes into account dissipative effects from interactions between the scalar inflation and other fields. This not only yields an additional friction that helps sustaining slow-roll inflation but also produces a nearly-thermal radiation bath concurrent with accelerated expansion. Although sub-dominant during inflation, radiation may take over towards the end of the slow-roll regime and yield a smooth exit into the standard cosmological evolution. Inflation fluctuations are also modified by the dissipative dynamics and may, in particular, be in a nearly thermalized rather than vacuum state. This changes the form of the primordial spectrum of density perturbations and, consequently, the landscape of inflationary models that are in agreement with observations. In this talk, I will review the dynamics and construction of warm inflation models in the light of the recently announced results of the Planck mission.
4.7. Flavor Mix and Fluxes of High Energy Astrophysical Neutrinos Prof. Dr. Sandip Pakvasa (Univ. of Honolulu, Hawaii)
I will discuss the flavor mix expected from astrophysical sources of high energy neutrinos, and how the flavor mix changes with propagation and the effects of new physics. There are some implications for the absolute fluxes as well.
20.6. Economics, the Physics of the Social Sciences? The Use and Abuse of Methods from Physics and Mathematics in Economics Dr. Torsten Heinrich (Univ. Bremen)
This presentation will discuss several examples of concepts from physics being used in economics. Historically this starts in the 19th century with the equilibrium model for markets which follows classical mechanics. While this enabled economists to describe the economy as a whole in a formal model for the first time, employing this model comes with certain problems, most importantly that there is no useful equivalent for conservation principles in economics. Further, the specific way in which the methods are used in economics requires a number of problematic assumptions which have been critizised from different perspectives ever since. The employment of the model has undergone several major modifications but the basic framework as well as most of the assumptions in question remain. Other examples of concepts from physics (and mathematics and mathematical biology) employed in economics which will also be discussed in the presentation include self-organization, scale-free distributions (commonly investigated by recently emerging econophysics research groups), entropy, game theory, as well as evolution.
13.6. LSP sneutrino novel decay modes in bilinear R-parity violating models Dr. Diego Aristizabal (Universite de Liege)
In bilinear R-parity (BRpV), in which the superpotential includes a bilinear term between the lepton doublet and the up-type Higgs superfields, a sneutrino LSP can decay into pairs of heavy standard model states (Ws, Zs, tops or Higgs bosons), neutrinos or different-flavor charged lepton modes. These final states can dominate over the traditionally considered bottom pair final state and would lead to unique and novel supersymmetric signals: multileptons events or pairs of heavy standard model fields. In this talk, I will discuss these scenarios and show under which conditions the aforementioned modes govern the sneutrino phenomenology.
6.6. Sterile neutrinos and violations of lepton flavor universality Dr. Avelino Vicente (Universite Paris-Sud)
We study the violation of lepton flavour universality in light meson decays due to the presence of non-zero mixings between the active neutrinos with new sterile states. The modified $W \ell \nu$ vertices, arising from a non-unitarity leptonic mixing matrix intervening in charged currents, might lead to a tree-level enhancement of $R_P = \Gamma (P \to e \nu) / \Gamma (P \to \mu \nu)$, with $P=K, \pi$. These enhancements are illustrated in the case of the inverse seesaw, showing that one can saturate the current experimental bounds on $\Delta r_{K}$ (and $\Delta r_{\pi}$), while in agreement with the different experimental and observational constraints.
23.5. Helicity Conservation and Beltrami Fields Prof. Thomas W. Kephart (Vanderbilt Univ.)
We propose a covariant generalization of the magnetic helicity, Beltrami equation and Woljter-Taylor states. Covariant variational principle, gauge invariance, conserved currents and boundary conditions elucidate the subject.
16.5. Renormalisation Group of Gravity - State of the Art Dr. Christoph Rahmede (KIT, Karlsruhe)
I will give an overview over recent developments in applying renormalisation group techniques to gravity. The results point at the suitable structure of the renormalisation group flow to achieve the property of asymptotic safety on which a viable theory of quantum gravity can be based.
29.4.2013, 17:00

TIII/TIV conference room

Exceptional date and room

Impact of the Higgs discovery on two models of new physics Prof. Dr. Ulrich Nierste (KIT, Karlsruhe)
A combined fit of electroweak precision data and data on Higgs decays lead to an exclusion of the Standard Model with a sequential fourth generation at the level of 5 standard deviations. In my talk I discuss the methodology of the corresponding statistical analysis, which involved so-called non-tested hypotheses. Then I discuss a supersymmetric GUT model, in which the atmospheric neutrino mixing angle affects b->s transitions. The model, originally proposed by Chang, Masiero and Murayama, is challenged by the mass of 126 GeV of the lightest neutral Higgs boson and the recent observation of the large neutrino mixing angle theta_13.
Previous Sessions Winter Term 2012/2013
10.1.2013 Composite t' triplets from QCD-like dynamics and t t-bar asymmetries Dr. Joachim Brod (U. of Cincinnati)
The CDF and D0 experiments at Tevatron measure a top-quark forward-backward asymmetry significantly larger than the standard-model prediction. New models with a flavour symmetry can account for the difference while at the same time satisfying constraints from flavor physics and other collider observables. In this talk I present a specific realization of such a model involving new strong interactions at the electroweak scale.
13.12.2012 Sensitivity to charged scalars in leptonic and semileptonic b->c tau nu transition Dr. Martin Jung (TU Dortmund)
The recent experimental evidence for an excess of tau-lepton production in several exclusive semileptonic B-meson decays is analyzed in the context of two-Higgs-doublet models. Several new observables are discussed that are sensitive to a hypothetical charged-scalar contribution, demonstrating that they are well suited to distinguish between different scenarios of new physics in the scalar sector, and also between this group and models with different Dirac structures.
29.11.2012 Antimatter fluxes in the Milky Way Prof. Michael Kachelriess (NTNU, Trondheim)

Measurements of the nuclear composition and of the antimatter fraction of cosmic rays (CR) are a main tool to understand the origin of CRs. If the antimatter fluxes from astrophysical sources can be estimated sufficiently reliable, a search for possible excesses can be used to detect dark matter (DM).

After a general introduction, I discuss the suggestion that the re-acceleration of CR secondaries in supernova remnants leads to positron and antiproton ratios increasing with energy. I present also results for the B/C ratio which can be soon tested by the AMS-2 experiment.

In the second part of the talk, I review the production of antideuterons, both in DM annihilations and in pp collisions. In the former case, I stress the importance of event-by-event simulations of antideuteron coalescence and discuss the model uncertainties. Finally, I argue that the antideuteron yield especially at low energies is underestimated in commonly used models.

22.11.2012 Anomalously large O_8 & large-distance chirality A_CP(D^0->(rho^0,omega) gamma) Dr. Roman Zwicky (The University of Edinburgh)
15.11.2012 Charginos and neutralinos at the LHC/ICL at higher orders Dr. Federico von der Pahlen (Univ. Santander)

Searches for the production of Dark Matter (DM) and analyses of the Higgs boson are currently performed at the LHC. Similar measurements will also be possible at a future linear e^+e^- collider (ILC, CLIC). In order to determine the underlying model it is crucial to measure the masses and couplings of Higgs and DM particles with highest precision.

If Supersymmetry is realized in nature, the lightest SUSY particle (LSP) is a perfect candidate for DM. An interesting production mechanism for the Higgs and the LSP is the decay of heavier SUSY particles. Measuring these decays to high accuracy will provide important information on the Higgs and DM.

We provide high-precision predictions for these decays, which are crucial for the correct interpretation of the experimental data. Our predictions are obtained in the Minimal Supersymmetric Standard Model (MSSM) including complex phases and constitute the most advanced calculations of these decays.

18.10.2012 No seminar  
Previous Sessions Summer Term 2012
10.07.2012, 12:15

Exceptional Date

Constraining SUSY extensions of the SM with B->K* mu+ mu- Siavash Neshatpour (Clermont Universite)
The rare decays B_s -> mu+mu-  B->K* mu+ mu- are sensitive probes of New Physics. These decays provide important constraints on the dynamics of extensions of the SM. In this talk we will conduct an overview of the Delta B=1 effective framework for these processes. Wen then address in detail the implications of recent LHCb results for B -> K* mu+ mu- observables, and consider the constraining power of these observables on well motiviated extensions of the SM, as is the case of the Constrained Minimal Supersymmetric Standard Model (CMSSM).
14.06.2012 Composite Two Higgs Doublet Models Dr. Tirtha Sankar Ray (Saha Institute for Nuclear Physics, Kolkata, India)
The generic framework for building custodial non-minimal composite Higgs models will be discussed through illustration with the cosets SU(5)/SU(4)*U(1) and SU(5)/SU(4). Some phenomenological consequences of these class of models will be discussed with emphasis on the model independent/dependent source of their origin.
31.05.2012 Pseudoscalar Meson Form Factors and The BaBar Puzzle Dr. Nils Offen (Universität Regensburg)
Nearly three years ago the BaBar-collaboration published their data on the pi to gamma gamma* form factor which showed a steep slope in the region of Q^2=10-20 GeV^2 and a rise beyond the asymptotic prediction of QCD. These results together with their later published data on eta to gamma gamma* which do not show this behavior triggered an intense theoretical interest in these decays. In this talk I will introduce the BaBar-puzzle i.e. the challenge originally posed by these results to our understanding of these processes and give an overview on proposed solutions. With the recent advent of the Belle-result the BaBar-puzzle has lost some of its significance but a final resolution of the situation will probably require more data.
03.05.2012 Electroweak Symmetry Breaking Beyond the Standard Model Prof. Gautam Bhattacharyya (Saha Institute for Nuclear Physics, Kolkata, India)
Previous Sessions Winter Term 2011/2012
26.01.2012 Phenomenology of Field Theory Completions to Gravity Dr. Eric Gerwick (Univ. Göttingen)
Searches for extra dimensions at the LHC severely bound many popular solutions to the Hierarchy problem. I will review some of the assumptions which enter these bounds, and emphasize the deficiencies when defining the cut-off in the KK integration. As an example for a more reliable prediction, I will present our most recent implementation of Asymptotic safety for the virtual graviton signal. At this point, I will outline techniques for the consistent calculation of further low-energy observables in quantum gravity, and speculate on some future directions.
19.01.2012 B\to K_2 l^+l^-: another FCNC process to test the standard model Dr. Wei Wang (DESY Hamburg)
We analyze the B\to K_2^*(\to K\pi)l^+l^-$ (with l=e,\mu,\tau) decay in the standard model and two new physics scenarios: vector-like quark model and family non-universal Z' model. We derive its differential angular distributions, using the recently calculated form factors in the perturbative QCD approach. Branching ratios, polarizations, forward-backward asymmetries and transversity amplitudes are predicted, from which we find a promising prospective to observe this channel in the future experiment. We update the constraints on effective Wilson coefficients and/or free parameters in these two new physics scenarios by making use of the B\to K^*l^+l^- and b\to sl^+l^- experimental data. Their impact on B\to K_2^*l^+l^-$ is subsequently explored and in particular the zero-crossing point for the forward-backward asymmetry in these new physics scenarios can sizably deviate from the standard model.
12.01.2012 - Termin belegt -  
17.11.2011 Theoretical and Phenomenological Constraints on Form Factors for Radiative and Semi-Leptonic B-meson Decays Dr. Aoife Bharucha (Univ. Hamburg)
We study transition form factors for radiative and rare semi-leptonic B-meson decays into light pseudoscalar or vector mesons, combining theoretical constraints and phenomenological information from Lattice QCD, light-cone sum rules, and dispersive bounds. We pay particular attention to form factor parameterisations which are based on the so-called series expansion, and study the related systematic uncertainties on a quantitative level. In this context, we also provide the NLO corrections to the correlation function between two flavour-changing tensor currents, which enters the unitarity constraints for the coefficients in the series expansion.
03.11.2011 Vector boson production at the LHC Dr. Tobias Kasprzik (Univ. Karlsruhe)
A profound understanding of vector-boson production processes is of crucial importance at the LHC. The corresponding cross sections are large, and the final states are easy to reconstruct due to the clean signatures in the leptonic decay modes. Therefore, such processes play an important role as backgrounds in a large variety of new-physics signals, and they may furthermore help to better understand the well-established Standard-Model physics in a hadron-collider environment. We review the recent progress in the theoretical description of higher-order QCD and electroweak effects in vector-boson production at the LHC and present new results on electroweak corrections to W-pair production.
27.10.2011 New Physics in Γ12s: b → s tau+ tau- transitions Dr. Christoph Bobeth (TU München & Excellence Cluster Universe)
Currently, the D0 measurement of the like-sign dimuon charge asymmetry is the most pronounced deviation from the standard model expectations in B-meson physics pointing towards new CP phases in Delta B = 2 transitions. Related is the mixing induced CP asymmetry in B_s--> J/psi phi and B_s--> J/psi f_0 decays, which are also explored at LHCb. An intriguing explanation could be new physics contributing to Gamma_{12}^s which is governed by b--> s F involving light states F. We investigate model-independently the possibility of F being a pair of tau^+ tau^- leptons. The according rather loose Delta B = 1 tree- and loop-level mediated constraints are summarised and their implications on Gamma_{12}^s. Loop-level mediated constraints from exclusive B->K^(*) mu^+ mu⁻ decays are presented in some detail.
Previous Sessions Summer Term 2011
07.07.2011 Double parton scattering at the LHC Dr. Steve Kom (Oxford Univ.)
At the LHC, the high centre of mass energies implies a high probability of multiple parton scatterings, i.e. (hard) scatterings of more than one pair of partons in the same hadron-hadron collision. We will concentrate on double parton scattering, and discuss what a class of purely leptonic final states, which were not accessible in previous hadron colliders, might offer, and strategies that are likely required in search for those signals.
  Supersymmetry without prejudice at the LHC Dr. John Conley (Universität Bonn)
The discovery and exploration of Supersymmetry in a model-independent fashion will be a daunting task due to the large number of soft-breaking parameters in the MSSM. In this talk, I describe an exploration of the capability of the ATLAS detector at the LHC to find SUSY within the 19-dimensional pMSSM subspace of the MSSM using their standard transverse missing energy and long-lived particle searches that were essentially designed for mSUGRA. To this end, we made use of a set of 71k previously generated model points in the 19-dimensional parameter space that satisfy all of the existing experimental and theoretical constraints. Employing ATLAS-generated SM backgrounds and following their approach in each of 11 missing energy analyses as closely as possible, we explored all of these 71k model points for a possible SUSY signal. I will describe the results of this analysis at both the 7 TeV and 14 TeV LHC. I will touch on many different aspects of our results, including the reasons why some models are missed in all the analyses, the effect of systematic error on the parameter space coverage, the impact of changing the analysis cuts, fine-tuning in the model set, and implications for the linear collider.
16.06.2011 Light Neutrinos from a Little Warped Space Dr. Kristian McDonald (MPI Heidelberg)
Most proposed mechanisms for generating neutrino mass rely on the existence of heavy fields, making them (extremely) difficult to experimentally probe. However, if the right-handed neutrinos are composite objects of a hidden sector gauge group, light neutrino masses can be generated naturally without invoking high energy physics. In this talk I will use the ideas of AdS/CFT to construct a calculable model whose dual is a 4D theory with light, composite right-handed neutrinos. Beyond realizing naturally light neutrinos, such scenarios can offer more optimistic prospects for new signals in forthcoming experiments.  
09.06.2011 Asymptotically safe gravity and implications for cosmology Dr. Christoph Rahmede (Sussex Univ., UK)
During the last decades, several candidates for a theory of quantum gravity have emerged. A viable approach has been proposed by Steven Weinberg:standard quantum field theory methods could be applied to gravity up to arbitrarily high energies if its renormalization group flow is controlled by a fixed point and therefore asymptotically safe. I will present the details of this idea and in how far we have been able to test this proposal within various approximations. I will also disuss implications for early universe cosmology.
12.05.2011 Stückelberg covariant perturbation theory Dr. Chris Oakley
Methods developed originally by Stückelberg in 1934 and rediscovered by the speaker 50 years later enable one to do quantum field theory in 3+1 dimensions without the interaction picture, time-ordered products or infinite subtractions.
 Previous Sessions Winter Term 2010/2011
03.03.2011 b-baryon light-cone distribution amplitudes and hidden-bottom-tetraquarks Dr. Christian Hambrock (DESY)
Experiments at the Tevatron and the LHC provide great opportunities to study the physics of the b-baryons and the B mesons. In particular, LHCb is expected to precisely measure the properties of the $B_s$ meson and the entire multiplet of b-baryons, complementing our understanding of the lighter $B$ mesons. In the first part of my talk, I will report on the progress made in the construction of the light-cone distribution amplitudes for $b$-baryons needed to develop a quantitative theory of their weak decays. In the second part of my talk, I will present a dynamical model developed at DESY for the production of tetraquark (diquark-antidiquark) states containing a $b\bar{b}$ quark pair in $e^+e^-$ annihilation and their decays. At the center of this discussion is our analysis of the Belle data on $Y_b(10890)$, a $J^{PC}= 1^{--}$ state, which provides the first observation of a tetraquark state having a $\bar{b}$ pair.
02.03.2011 Constraining New Physics from Flavour Observables Dr. Martin Jung (Univ. Valencia)
Particle Physics today is at a crossroad: while so far all direct measurements are basically compatible with the Standard Model, there are compelling arguments for the necessity of New Physics, preferably at the TeV-scale. To probe this scale, there exist two complementary ways, both of which are being pursued now at the LHC: besides the direct search, e.g. by the production of new heavy particles, there is the possibility to observe indirect effects from this part of the spectrum, especially in precision mesurements of low-energy flavour observables. The latter are the focus of my talk. After a general introduction I will discuss a selection of obsevables within the framework of the Aligned Two-Higgs-Doublet Model as an application.
10.02.2011 Rare B decay form factors from lattice QCD Dr. Matthew Wingate (Univ. Cambridge, UK)
In the past decade, unquenched lattice QCD calculations have increasingly helped to test CKM unitarity. While work continues to further improve the precision of these tests, another avenue of exploration is opening up: rare B decays. As LHC experiments more precisely measure FCNC decays, such as B to K* plus either a photon or a lepton--anti-lepton pair, new theory calculations are needed to test the Standard Model. This talk will present ongoing unquenched lattice calculations of B to K and B to K* form factors.
20.01.2011 Hyperbolic Monopoles Prof. Dr. Lorenz Schwachhöfer
A Monopole consist of a connection and a Higgs field associated to a principal SU(2)-bundle over some 3-dimensional base space which satisfy Bogomolny's equation. Monopoles can be associated to a solution of the Yang-Mills equation in dimension 4 with certain symmetries. If the base space is Euclidean or Hyperbolic space, we call these solutions Euclidean or Hyperbolic monopoles. It was shown by Atiyah and Hitchin that the space of Euclidean monopoles carries a canonical hyper-Kähler metric. In contrast, the space of Hyperbolic monopoles does not carry such a structure, but its complexification has a hyper-Kähler space. This induces a canonical connection on this moduli space and more geometric structure.
25.11.2010 Black holes and asymptotic safety Dr. Kevin G. Falls (Univ. of Sussex, GB)
Quantum gravitational corrections to black holes in four and higher dimensions are presented using a renormalisation group improvement of the metric. It is shown that a weakening of gravity implies a decrease of the event horizon, and the existence of a smallest black hole mass Planck scale mass. We apply our findings to the phenomenology of mini-black hole production at colliders
11.11.2010 Charm-loop effect in B -> K l^+ l^- and B > K^* l^+ l^- decays Prof. Dr. Alexander Khodjamirian (Universität Siegen)
Rare decays of B-meson into the kaon (or K^*-meson) and lepton-antilepton pair are very promising channels to study the electroweak transitions generated by the loops of heavy particles: W,Z,top-quark and maybe even something beyond the Standard Model. However, accessing the fundamental flavour-changing interaction in these exclusive processes demands an accurate knowledge of the B -> K or B -> K^* form factors and other hadronic effects which have to be calculated in Quantum Chromodynamics (QCD). I will overview the current status of this problem and will further concentrate on the important background effect in these decays, generated by the "normal" weak interaction with intermediate charmed quarks ("charm-loops"). Recently we investigated this effect and estimated its magnitude employing the operator-product expansion of quark-gluon operators and the method of QCD sum rules. The results of our work will be presented in more details.
04.11.2010 Family Symmetries and Neutrino Mixing Dr. I. de Medeiros Varzielas (TU Dortmund)
I will give an introductory overview about family symmetries. I will focus on neutrino mixing through sequential dominance, a framework that is particularly well suited to embed the family symmetry into GUTs with seesaw mechanisms (standard or extended). I will cover other topics related to family symmetry if time permits.
28.10.2010 Adiabatic & Non-adiabatic perturbation theory for coherence vector descriptions of neutrino oscillations (tentative) Sebastian Hollenberg (TU Dortmund)
We propose a unified approach to both adiabatic and non-adiabatic two flavor neutrino oscillations with generic potentials. To this end we study the evolution of a neutrino ensemble governed by the associated Quantum Kinetic Equations (QKE), which also pertain to systems with finite temperature. The QKE are solved formally by means of the Magnus expansion and it is shown that both a convenient choice of the quantum mechanical picture as well as the convergence properties of the expansion itself reveal suitable parameters to characterize the physics of the underlying system. Some limiting cases and possible extensions of the formalism will be briefly sketched.
Previous Sessions Summer Term 2010
08.07.2010 Knots and Glueballs Dr. Tom Kephart (Vanderbilt University, Nashville, TN, USA)
We argue that a systems of tightly knotted, linked, or braided flux tubes have a universal mass-energy spectrum, since the length of fixed radius flux tubes depend only on the topology of the configuration. We motivate the discussion with plasma physics examples, then concentrate on the model of glueballs as knotted chromoelectric QCD flux tubes. A few other applications will also be discussed.
20.05.2010   Prof. Palash B. Pal (Saha Institute, Kolkata)
When elementary particles propagate or interact in a background medium, many of the symmetries of the vacuum theory are violated. For example, CPT-violating conclusions are obtained because a normal medium is CPT-asymmetric. The most surprising is processes which violate angular momentum conservation, even though the medium may be isotropic and there is no obvious asymmetry of isotropy. We will discuss such possibilities using a form-factor approach.
Previous Sessions Winter Term 2009
17.12.2009 Evaporating black holes in the presence of a minimal length Dr. Piero Nicolini (Universität Frankfurt)
After implementing an effective minimal length, we will present a new class of spacetimes, describing both neutral and charged black holes. As a result, we will improve the conventional Schwarzschild and Reisner-Nordstroem spacetimes, smearing out their singularities at the origin. On the thermodynamic side, we will show how the new black holes admit a maximum temperature, followed by the ``SCRAM phase'', a thermodynamic stable shut down, characterized by a positive black hole heat capacity. As a consequence, also for the neutral solution, in place of the runaway behavior of the temperature, one finds that the evaporation ends up with a zero temperature extremal black hole, i.e. a final configuration entirely governed by the minimal length. For the charged case, both the Hawking and Schwinger pair creation will be discussed in this new scenario. We will also analyze the above solutions in the presence of extradimensions and the connections with the production of mini black holes, which is foreseen in the extreme energy hadron collisions at the LHC in the next few months. Finally we will discuss further developments and possible connections with other approaches in this field.
17.12.2009 Flavour Physics, while waiting for LHC Prof. Dr. Alexander Lenz (Universität Regensburg)
Flavour Changing Neutral Current Processes are particularly well suited to search for effects of physics beyond the standard model (SM). In my talk I will discuss two examples for those processes: the mixing of neutral B_s mesons and the mixing of neutral D mesons. Besides explaining the status of the theory predictions for these systems within the SM, a general strategy to search for new physics effects will also be presented. As an example for new physics we introduce the "most boring extension of the SM".
10.12.2009 Rare meson decays into very light neutralinos Dr. Sebastian Grab (University of California at Santa Cruz, CA, USA)
Within the Minimal Supersymmetric Standard Model (MSSM), the mass of the lightest neutralino is experimentally unconstrained by LEP if the GUT relation between the gaugino mass parameters M1 and M2 is dropped. We investigate bounds on very light neutralinos from rare meson decays with and without minimal flavor violation. We find that the supersymmetric branching ratios are strongly suppressed within the MSSM with minimal flavor violation, and that no bounds on the neutralino mass can be inferred from experimental data, i.e. a massless neutralino is allowed. The branching ratios for kaon and B meson decays into light neutralinos may, however, be enhanced when one allows for non-minimal flavor violation. We find new constraints on the MSSM parameter space for such scenarios and discuss prospects for future kaon and B meson experiments.
19.11.2009 Local Grand Unification and String Theory Dr. Patrick Vaudrevange (Universität München)
String theory might serve as a framework for a unified description of all fundamental particles (quarks and leptons) and their interactions (electroweak, strong and gravitational). However, it is still unkown whether compactifications of ten-dimensional string theory to 4D can reproduce the Minimal Supersymmetric Standard Model (MSSM), the prime candidate theory for physics beyond the Standard Model (SM). In this talk, I will present some recent progress in model building for the so-called heterotic string. The focus will be on two aspects: first, "local grand unification", i.e. the possibility that GUT models (like SU(5)) are not realized in 4D but only locally in higher dimensional space-time, and second, discrete symmetries which naturally emerge in the process of compacification.
29.10.2009 Collider Signatures of Minimal Flavor Mixing from Stop Decay Length Measurements Henning Sedello (TU Dortmund)
Irrespective of the severe constraints from FCNC observables, the flavor structure of the MSSM can be richer than the SM's. To test whether flavor is SM-like is difficult at hadron colliders such as the LHC. An observation of macroscopic decay lengths or impact parameters of light scalar tops may be possible and would help to classify the flavor structure of the MSSM.
22.10.2009 Inverted sparticle hierarchies from natural particle hierarchies Dr. Yonit Hochberg (Weizmann Institute of Science, Rehovot, Israel)
We'll start by reviewing the Nelson-Strassler mechanism (hep-ph/0006251) for solving the flavor puzzle, in which the hierarchical structure of the Yukawas is dynamically generated by exploiting the dynamics of a (super)conformal sector. We'll then discuss some work in progress, in which this mechanism is economically implemented along with SUSY breaking.
15.10.2009 Rapidity Gap Events in Squark Pair Production at the LHC Dr. Jong Soo Kim (TU Dortmund)
The exchange of electroweak gauginos in squark pair production at hadron colliders allows for rapidity events. This can give rise to events where little or no energy is deposited between the squark decay products. We discuss the detection of such rapidity gap events at the LHC.

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