ALPS2017 -- an Alpine LHC Physics Summit

UZ Obergurgl

UZ Obergurgl

University Center Obergurgl Gaisbergweg 5 6456 Obergurgl Austria
Brigitte DeMonte, Felicitas Breibeck, Jochen Schieck (Austrian Academy of Sciences (AT)), Martin Flechl, Suchita Kulkarni, Wolfgang Adam (HEPHY-Vienna), Wolfgang Waltenberger (Austrian Academy of Sciences (AT))

April 23: Thanks to all participants. It was a great workshop!

ALPS2018: April 15 - 20, 2018. Save the date!


With a successful start and incredible performance, LHC is collecting data at 13 TeV centre-of-mass energy since 2015. The implications of LHC searches for new physics at TeV scale is a topic of intense interest. Together with the results from other experiments, the LHC results will define the theory landscape of possible new physics scenarios at TeV scale in the coming decade. The aim of this workshop is to take a fresh look at this theoretical landscape in the light of new LHC results at 13 TeV. The workshop will bring together particle theorists and experimentalists to brainstorm on questions ranging from the origin of the 16-decade hierarchy between Planck and Electroweak scale to particle nature of dark matter, from possible solutions to the hierarchy problem to the exciting prospects of finding new physics in flavour precision measurements. We will further discuss new strategies shaping the future of particle physics program and envisage the potential of high luminosity LHC program.

The days are divided into morning sessions with keynote talks, and  late afternoon sessions that will comprise shorter presentations on more specialized topics. In addition we aim for a Young Scientist Forum, where our younger colleagues are invited to claim the stage.

The meeting will take place at the Obergurgl University Centre, in the ski-resort town of Obergurgl, located in the upper Oetztal Valley in Tirol, Austria.


Opening speaker:

  • Matthias Neubert (Johannes Gutenberg-Universität Mainz)

Confirmed speakers:

  • Freya Blekman (Vrije Universiteit Brussel)
  • Alain Blondel (University of Geneva)
  • Roberto Franceschini (CERN) 
  • Patrick J. Fox (FNAL)
  • Belen Gavela (Universidad Autonoma de Madrid)
  • Graciela Gelmini (UCLA)
  • Rohini Godbole (IISc)
  • Bostjan Golob (Josef Stefan Institute)
  • Mark Goodsell (LATHE, Paris)
  • Diego Guadagnoli (LAPTh)
  • Ferdinand Hahn (CERN)
  • Julian Heeck (ULB)
  • Sabine Kraml (LPSC)
  • Greg Landsberg (Brown University) 
  • Ian Low (Argonne National Laboratory, Northwestern University)
  • Steven Lowette (Vrije Universiteit Brussel)
  • Axel Maas (Karl-Franzens-University Graz)
  • Franz Muheim (University of Edinburgh)
  • Florian Reindl (INFN - Sezione di Roma)
  • Frank Simon (MPI, Munich) 
  • Javier Tiffenberg (FNAL)
Scientific Advisory Board Local Organizers
  • Frank Deppisch (UCL London)
  • Tim Gershon (Warwick University)
  • Valentin Khoze (IPPP Durham)
  • Jenny List (DESY)
  • Filip Moortgart (CERN)
  • Federica Petricca (MPI München)
  • Tilman Plehn (Universität Heidelberg)
  • Markus Schumacher (Universität Freiburg)
  • Wolfgang Waltenberger
  • Wolfgang Adam
  • Felicitas Breibeck
  • Brigitte DeMonte
  • Martin Flechl
  • Suchita Kulkarni
  • Jochen Schieck
    • Dinner
      Convener: Wolfgang Waltenberger (Austrian Academy of Sciences (AT))
    • Opening Talk
      • 1
        LHC probes of axion-like particles

        We argue that the study of rare Higgs decays in the high-luminosity run at the LHC can probe axions and axion-like particles (ALPs) in a wide range of parameter space, which is otherwise inaccessible to experimental searches. Concerning the coupling of the ALP to photons, our strategy covers the current “gap” in the mass range between 1 MeV and 60 GeV down to photon-axion coupling as small as 10^(-6)/TeV. An ALP in this parameter range can explain the anomalous magnetic moment of the muon and is consistent with electroweak precisions tests and flavor constraints. In our analysis we consider the most general effective Lagrangian for a spin-0 particle protected by a shift symmetry, motivated by many extensions of the Standard Model with a spontaneously broken global symmetry.

        Speaker: Matthias Neubert (Johannes Gutenberg-Universität Mainz)
    • Reception
    • Tuesday Morning: Higgs and the Standard Model

      Tuesday Mornig: Higgs and the Standard Model

      Convener: Martin Flechl (Austrian Academy of Sciences (AT))
      • 2
        Experimental status of the scalar sector at the LHC
        Speaker: Reisaburo Tanaka (Universite de Paris-Sud 11 (FR))
      • 3
        Higgs phenomenology at the LHC
        Speaker: Rohini Godbole (Centre for Theoretical Studies (CTS))
      • 9:40 AM
      • 4
        CMS and ATLAS results on Standard Model and Top-quark Physics
        Speaker: Prof. Freya Blekman (IIHE, Vrije Universiteit Brussel (BE))
      • 5
        Just the one or many? Higgs and the BSM
        Speakers: Ian Low (Argonne National Laboratory (US)), Ian Low, Ian Low (Argonne National Lab/Northwestern Univ)
      • 6
        News on ALPs: effective theory and signals


        Speaker: Belen Gavela (Universidad Autonoma de Madrid (ES))
    • Tuesday Afternoon
      Convener: Martin Flechl (Austrian Academy of Sciences (AT))
      • 7
        Higgs Sector at Future e+e- Colliders

        [On behalf of ILD and CEPC Collaborations] Future e+e- colliders offer excellent possibilities for precision studies in the Higgs sector due to the clean experimental conditions and low backgrounds compared to hadron colliders. At lower energies i.e. below 500 GeV, the Higgstrahlung is the dominant Higgs production mechanism. With the recoil mass analysis technique being the unique feature of e+e- colliders, the Higgstrahlung allows model-independent studies of the Higgs couplings as well as the access to the invisible Higgs decays. If considered simultaneously with WW-fusion dominating Higgs production at higher energies, determination of the Higgs total width is possible at a percent level. Scalar sector searches are reviewed for ILC and CEPC using recent research updates obtained with the fully simulated ILD and ILD-like detector for CEPC.

        Speaker: Dr Junping Tian (The University of Tokyo)
      • 8
        Differential Top and Diboson Cross-Section Measurements with the ATLAS detector

        Measurements of the differential production cross-sections of the production of pairs of electroweak gauge bosons as well as top-quark pairs at the LHC provide stringent tests of advanced perturbative QCD calculations. In addition, these processes constitute a dominant background for many searches for signs of beyond Standard Model physics processes and are directly sensitive to anomalous couplings. The ATLAS collaboration has performed detailed measurements of those differential cross sections in various final states at centre-of-mass energies of 8 and 13 TeV. In this talk, the most recent results are presented and compared to predictions at NLO (and NNLO) in pQCD, highlighting observed differences and providing an overview of required improvements on the underlying physics modelling.

        Speaker: Kazuya Mochizuki (Universite de Montreal (CA))
      • 5:25 PM
      • 9
        New ALP collider signals

        We study the leading effective interactions between the Standard Model fields and a generic singlet CP-odd (pseudo)Goldstone boson. Two possible frameworks for electroweak symmetry breaking are considered: linear and non-linear. For the latter case, the basis of leading effective operators is determined and compared with that for the linear expansion. Associated phenomenological signals at colliders are explored for both scenarios, deriving new bounds and analyzing future prospects, including LHC and High Luminosity LHC sensitivities. Mono- Z, mono-W, W-photon plus missing energy and on-shell top final states are most promising signals expected in both frameworks. In addition, non-standard Higgs decays and mono-Higgs signatures are especially prominent and expected to be dominant in non-linear realizations.

        Speaker: Rocío del Rey (Universidad Autónoma de Madrid - IFT)
      • 10
        Vacuum stability from generalized Higgs interactions

        We investigate the non-perturbative renormalization group flow of the Higgs potential beyond conventional perturbative approximations and reanalyze arguments that relate a lower mass bound for the Higgs boson with vacuum stability. In addition, we study the impact of higher order operators on this lower bound from an effective field theory point of view.
        For the class of standard bare Higgs potentials of quartic type at a given ultraviolet cutoff scale, we show that a finite infrared Higgs mass range emerges naturally from the RG flow itself. Higgs masses outside the resulting bounds cannot be connected to any conceivable set of bare parameters in this standard model quartic class. A lower bound for the Higgs mass arises from the requirement of a well-defined partition function, i.e., stability of the bare potential. This consistency bound can, however, be relaxed considerably by more general forms of the bare potential without necessarily introducing new metastable minima. We identify a simple renormalization group mechanism for this diminishing of the lower bound. Thus, Higgs masses smaller than the conventional infrared window do not necessarily require new physics at low scales or give rise to instability problems.

        Speaker: Dr René Sondenheimer (FSU Jena)
      • 11
        Searches for double Higgs production at the LHC using the CMS detector

        The production of pairs of Higgs bosons provides a direct handle on the structure of the Higgs field potential. While the HH production within the SM is very small and essentially out of the experimental reach within the Run I or II, several beyond SM theories foresee an enhancement that can be already probed with the available data. The talk will present the searches for resonant and non-resonant productions of pairs of HH bosons made by the CMS collaboration in several final states. The interpretation of these results in the framework or BSM theories will be discussed, along with the future prospects for double Higgs boson production measurement.

        Speaker: Claudio Caputo (Universita e INFN, Bari (IT))
      • 12
        Measurement of cross sections and properties of the Higgs Boson using the ATLAS detector

        The final Run 1 and first Run 2 results on the measurement of the cross sections, couplings and properties of the Higgs boson with the ATLAS detector are presented.

        Speaker: Philip Clark (University of Edinburgh (GB))
    • YSF
      Convener: Martin Flechl (Austrian Academy of Sciences (AT))
      • 13
        Measurement of WW/WZ production in semileptonic decay channels and search for anomalous gauge couplings with the ATLAS detector

        The measurements of the production of two massive vector gauge bosons represent an important test of the Standard Model of particle physics since they probe the structure of the triple gauge boson couplings as well as test of higher-order calculations in quantum chromodynamics. In this talk, a new measurement of the production of WW or WZ boson pairs with one W decaying leptonically and one W or Z decaying hadronically is presented. The cross-section is measured in proton-proton collision data taken with the ATLAS detector at a center-of-mass energy of 8 TeV. The hadronic boson decay is reconstructed in two ways: as two resolved small-radius jets, and as a single large-radius jet. The transverse-momentum distribution of the hadronically-decaying boson is used to search for new physics, proving limits on anomalous triple gauge couplings.

        Speaker: Margherita Spalla (Universita di Pisa & INFN (IT))
      • 14
        Higgs boson and standard model physics in the tautau final state

        The focus of this talk is on Z and H boson decays to a pair of tau leptons. The presented analyses use pp collision data collected at center-of-mass energy of 13 TeV.

        Speaker: Johannes Brandstetter (Austrian Academy of Sciences (AT))
      • 15
        Implications of recent measurements in rare B decays
        Speaker: Peter Stangl (Excellence Cluster Universe, Technische Universität München)
      • 16
        Top quark differential cross-section measurement with the ATLAS detector

        The top quark is the heaviest known fundamental particle. The measurement of the differential top-quark pair production cross-section provides a stringent test of advanced perturbative QCD calculations. The ATLAS collaboration has performed detailed measurements of those differential cross sections at a centre-of-mass energy of 13 TeV. This talk focuses on differential cross-section measurements in the lepton+jets final state, including using boosted top quarks to probe our understanding of top quark production in the TeV regime.

        Speaker: Michael James Fenton (University of Glasgow (GB))
    • Wednesday Morning: Physics Beyond the Standard Model
      Convener: Freya Blekman (IIHE, Vrije Universiteit Brussel (BE))
      • 17
        Searches for SUSY at ATLAS and CMS
        Speaker: Jordi Duarte Campderros (Tel Aviv University (IL))
      • 18
        LHC exotica

        Placeholder for experimental talk, ATLAS+CMS, on exotica and/or unusual signatures

        Speaker: Greg Landsberg (Brown University (US))
      • 9:40 AM
      • 19
        Reinterpreting BSM Searches
        Speaker: Sabine Kraml (Centre National de la Recherche Scientifique (FR))
      • 20
        BSM Models Off The Beaten Tracks
        Speaker: Mark Dayvon Goodsell (LPTHE)
      • 21
        Beyond Vanilla SUSY
        Speaker: Roberto Franceschini (E)
    • Wednesday Afternoon: Physics Beyond the Standard Model
      Convener: Freya Blekman (IIHE, Vrije Universiteit Brussel (BE))
      • 22
        The BSM-AI project: SUSY-AI - Generalizing LHC limits on Supersymmetry with Machine Learning

        A key research question at the Large Hadron Collider (LHC) is the test of models of new physics. Testing if a particular parameter set of such a model is excluded by LHC data is a challenge: it requires time consuming generation of scattering events, simulation of the detector response, event reconstruction, cross section calculations and analysis code to test against several hundred signal regions defined by the ATLAS and CMS experiments. In the BSM-AI project we attack this challenge with a new approach. Machine learning tools are thought to predict within a fraction of a millisecond if a model is excluded or not directly from the model parameters. A first example is SUSY-AI, trained on the phenomenological supersymmetric standard model (pMSSM). About 300,000 pMSSM model sets – each tested against 200 signal regions by ATLAS – have been used to train and validate SUSY-AI. The code is currently able to reproduce the ATLAS exclusion regions in 19 dimensions with an accuracy of at least 93%. It has been validated further within the constrained MSSM and the minimal natural supersymmetric model, again showing high accuracy. SUSY-AI and its future BSM derivatives will help to solve the problem of recasting LHC results for any model of new physics.

        Speaker: Mr Bob Stienen (RU Nijmegen)
      • 23
        Searches for SUSY in resonance production, R-parity violating signatures and events with long-lived particles with ATLAS

        SUSY talk experimental contribution

        Speaker: Sigve Haug (Universitaet Bern (CH))
      • 5:25 PM
      • 24
        Search for vector-like quarks at ATLAS

        Exotica talk experimental contribution

        Speaker: Frank Ellinghaus (Bergische Universitaet Wuppertal (DE))
      • 25
        Natural SUSY at the ILC: from MZ to the GUT scale

        The most basic requirement for naturalness in supersymmetric models is the
        existence of rather light partners of the Higgs boson, the Higgsinos, at
        masses not too far above M_Z. Despite the pressure from LHC data on the simplest
        high-scale models (like the cMSSM), such light Higgsinos can still be
        realised in different types of GUT-scale models from NUHM2 to mirage
        unification models. The ILC will offer the unique discovery potential
        foThe most basic requirement for naturalness in supersymmetric models is the
        existence of rather light partners of the Higgs boson, the Higgsinos, at
        masses not too far above M_Z. Despite the pressure from LHC data on the simplest
        high-scale models (like the cMSSM), such light Higgsinos can still be
        realised in different types of GUT-scale models from NUHM2 to mirage
        unification models. The ILC will offer the unique discovery potential
        for the elusive higgsino particles and allow for precision measurements
        of their properties. In this contribution, prospects for the achievable
        precisions for masses, the very small mass splittings and polarised production
        cross sections will be presented. Based on these, we studied the possibilities to
        determine the SUSY parameters at the weak scale, and to extrapolate their
        running to the GUT scale. We will discuss the prospects to thereby
        differentiate between various GUT-scale models and SUSY breaking schemes and
        to predict the masses of the remaining SUSY particles. In particular the
        latter could provide important guidance for the energy scale of the
        next hadron collider after the LHC.
        r the elusive higgsino particles and allow for precision measurements
        of their properties. In this contribution, prospects for the achievable
        precisions for masses, the very small mass splittings and polarised production
        cross sections will be presented. Based on these, we studied the possibilities to
        determine the SUSY parameters at the weak scale, and to extrapolate their
        running to the GUT scale. We will discuss the prospects to thereby
        differentiate between various GUT-scale models and SUSY breaking schemes and
        to predict the masses of the remaining SUSY particles. In particular the
        latter could provide important guidance for the energy scale of the
        next hadron collider after the LHC.

        Speaker: Mikael Berggren (Deutsches Elektronen-Synchrotron (DE))
      • 26
        Searches for new phenomena in events with two opposite-sign same-flavour leptons, jets and missing transversre momentum recorded by the CMS detector in pp collisions at sqrt(s) = 13 TeV

        A search is presented for physics beyond the standard model in final states with two opposite-sign, same-flavor leptons, jets, and missing transverse mo- mentum. The data sample corresponds to dataset of proton-proton collisions at sqrt(s) = 13 TeV collected with the CMS detector at the LHC in 2016. The analysis uses the invariant mass of the lepton pair, searching for a kinematic edge or a resonant-like excess compatible with the Z boson mass. The search for a kinematic edge targets strong production while the resonance search targets both strongly and electroweakly produced new physics. Both search modes use several event categories in order to increase the sensitivity to new physics. These categories are based on several observables related to the lepton pair and the hadronic system in order to optimize signal efficiency and background rejection. A fit is employed to search for a possible kinematic edge position in the strong, non-resonant search. The observations in all signal regions are consistent with the expectations from the standard model, and the results are interpreted in the context of simplified models of supersymmetry.

        Speaker: Sergio Sanchez Cruz (Universidad de Oviedo (ES))
    • YSF: Physics Beyond the Standard Model
      Convener: Freya Blekman (IIHE, Vrije Universiteit Brussel (BE))
      • 27
        "(YSF) Search for supersymmetry in pp collisions at 13 TeV in the single lepton final state with the CMS experiment"

        In this talk, an inclusive search for Supersymmetry is presented. The search is performed in events containing a single lepton, multiple jets, and missing transverse energy in the final state. The proton-proton collision data were recorded by the CMS experiment during Run 2 of the LHC at a center-of-mass energy of 13 TeV. Selections on b-jet enriched and depleted regions target different signal models. The search uses delta phi, the azimuthal angle between the lepton and four-vector sum of the missing energy and lepton, as a powerful discriminating variable to distinguish between background and signal. Additionally, multiple exclusive search regions are defined in different kinematic observables to enhance sensitivity to a range of different mass scenarios. The latest results in this clean event topology will be discussed and interpreted in the context of simplified models.

        Speaker: Ece Asilar (HEPHY)
      • 28
        Search for New Phenomena in Dijet Events with the ATLAS Detector at √s = 13 TeV

        During the last two years the LHC produced pp collisions at the record center-of-mass energy of 13 TeV. The sensitivity of searches for new phenomena with a high mass scale greatly benefited from the energy increase with respect to the LHC run-1 data. Events with two hadronic jets in the final state are of particular interest: new phenomena produced in parton collisions are likely to produce final states with (at least) two partons. In this talk several searches performed by the ATLAS collaboration are presented. The very high mass and the low mass regions have both been investigated, by exploiting dedicated signatures and, in case of the latter, new techniques to overcome trigger limitations. Final states with b-jets have also been explored.

        Speaker: Karishma Sekhon (University of Michigan (US))
      • 29
        Search for gluino-mediated stop and sbottom pair production in events with b-jets and large missing transverse momentum

        A search for the pair production of gluinos decaying to sbottom and stop at the LHC is reported. It utilises the pp collisions of the LHC Run2 dataset collected with the ATLAS detector. The search targets final states containing several energetic jets, of which at least three must be b-tagged, large missing transverse energy and either zero or at least one charged lepton.

        Speaker: Chiara Rizzi (UAB and IFAE (Spain))
      • 30
        Constraining new physics with standard model measurements

        Constraints on New Theories Using Rivet (Contur), is a new program designed to utilise precision detector corrected measurements of SM processes at the LHC as a test for physics beyond the standard model. In this talk the methodology and design of Contur is introduced, alongside a brief review of the advantages and limitations of the process. Future directions of the project will also be motivated.

        Speaker: David Yallup (University College London)
    • Thursday Morning: Dark Matter
      Convener: Ian Low (Argonne National Laboratory (US))
      • 31
        Comparison of Direct Detections Data
        Speaker: Graciela Beatriz Gelmini (University of California Los Angeles (US))
      • 32
        Dark Matter direct detection, experimental overview
        Speaker: Florian Reindl
      • 9:40 AM
      • 33
        DM searches at the ATLAS and CMS
        Speaker: Steven Lowette (Vrije Universiteit Brussel (BE))
      • 34
        Fantastic WIMPs and where to find them [at the LHC]
        Speaker: Patrick Fox
      • 35
        Future Dark Matter Detectors
        Speaker: Javier Tiffenberg (Fermilab)
    • Thursday Afternoon: Dark Matter
      Convener: Julian Heeck
      • 36
        Single Top and Dark Matter

        To date, only two modes of production at hadron colliders of dark matter through new scalar or pseudoscalar mediators with Yukawa-like couplings to Standard Model particles have been considered in the existing literature: pairs of dark matter particles produced through top quark loops with an associated hadronic jet in the event (monojet), and production of dark matter with pairs of heavy flavoured top or bottom quarks. We present a third, previously overlooked channel, which consists of dark matter production in association with a single top quark. In spite of a generally lower production cross section at LHC when compared to the associated top-pair channel, non-flavour violating single top quark processes are kinematically favored and can greatly increase the sensitivity to these models. We will show that including dark matter production in association with a single top quark through scalar or pseudoscalar mediators significantly improves the current searches. In particular, the exclusion limit with the available data set by the LHC searches for dark matter and heavy flavours can be substantially improved from 30% to up to a factor 2 depending on the mass assumed for the mediator particle. We expect that, with a dedicated event selection, the single top and dark matter production mode would demonstrate its full potential, and become the leading channel in Run II and future LHC searches.

        Speaker: Alberto Zucchetta (Universitaet Zuerich (CH))
      • 37
        Search for Dark Matter in Events with a Single Boson and Missing Transverse Momentum using the ATLAS Detector
        Speaker: Hideki Okawa (University of Tsukuba (JP))
      • 5:25 PM
      • 38
        Invisible Decays in Higgs Pair Production

        In this talk we will discuss the present status of theoretical studies and experimental searches performed in order to measure the di-Higgs process in various standard model (SM) final states. Furthermore, we will review the prospects of observing such channels at the 14 TeV high luminosity (HL) run of the large hadron collider (LHC). We will then discuss the prospects of observing certain non-standard final states in the di-Higgs category. Our focus will especially be on the scenario where one of the Higgs decays to a pair of $b$-jets and the other decays invisibly. We discuss the reach of the HL-LHC when (i) the production cross-section is exactly SM-like and (ii) when one includes a heavy scalar coupled to the top quarks and the SM Higgs. We will also review some other potential exotic final states.

        Speaker: Shankha Banerjee (Unite Reseaux du CNRS (FR))
      • 39
        Beyond simplified models for dark matter searches @LHC: The pseudoscalar portal

        The Higgs sector is a well-motivated portal to dark matter (DM). I discuss scalar/pseudoscalar portal models for DM, as a powerful tool to exploit the complementarity between LHC searches and direct/indirect DM detection experiments, and their connection to Higgs physics. I then analyze the shortcomings of so-called "simplified DM models" in this context, highlighting the key physics these models fail to capture and its impact on LHC searches.

        Speaker: Mr Jose Miguel No (King's College London)
      • 40
        Dark sector searches at Belle (II)

        The dark photon, $A′$, the dark Higgs boson, $h′$, and the dark baryon, $B'$, are hypothetical constituents featured in a number of recently proposed Dark Sector Models. Search for these particles are performed in the so-called dark Higgs-strahlung and radiative processes, and in neutral $D-$meson decays channels. We will present results for the search of dark sector particles with prompt and displaced vertex decay topologies, when applicable, obtained using 1.0 \invab of data collected by the Belle detector. Finally we will discuss the discovery potential of the Belle II experiment when 50 \invab of data will be collected within the next decade.

        Speaker: Dr Gianluca Inguglia (DESY)
      • 41
        Searches for Dark Matter in Events with Hadronic Activity at ATLAS
        Speaker: William Kalderon (Lund University (SE))
      • 42
        The XENON1T dark matter search

        A direct approach to the dark matter detection is to measure the nuclear recoils produced in the scattering of DM particles off the nuclei of target materials in detectors placed deep underground.
        The XENON1T experiment is the third phase of the XENON program and is aiming at direct DM detection. It consists of a double phase time projection chamber filled with about 2 t of liquid xenon and deployed at the Laboratori Nazionali del Gran Sasso.
        At present is the largest operating double phase TPC with liquid xenon.
        Here we report on the status of the experiment which is currently taking the first science data.

        Speaker: Dr Gianmarco Bruno (INFN - LNGS)
      • 43
        AMS-02 and Dark Matter


        Speaker: Wei-Chih Huang (Technische Universität Dortmund)
    • YSF: YSF Session
      Convener: Julian Heeck
      • 44
        Natural dark matter in the pMSSM

        We evaluate the fine-tuning of the phenomenological minimal supersymmetric standard model (pMSSM). We show that, contrary to common believe, that the fine-tuning of the pMSSM is not large yet, nor under pressure by LHC searches. Low sbottom, stop and gluino masses turn out to be less relevant for low fine-tuning than commonly assumed. Fine-tuning arguments point to models with a dark matter candidate yielding the correct dark matter relic density: a bino-higgsino particle with a mass of 35−155 GeV. Some of these candidates are compatible with recent hints seen in astrophysics experiments such as Fermi-LAT and AMS-02. We argue that upcoming direct search experiments, such as XENON1T, will test all of the most natural solutions in the next few years.

        Speaker: Melissa van Beekveld (Radboud University Nijmegen)
    • Friday Morning: Flavor Physics of Quarks and Leptons
      Convener: Gianluca Inguglia (DESY)
    • Friday Afternoon: Flavor Physics of Quarks and Leptons
      Convener: Mark Dayvon Goodsell (Ecole Polytechnique (FR))
      • 50
        Neutrino mass determination

        The absolute neutrino mass scale is one of the big open questions in particle physics, astrophysics and cosmology. Different experimental approaches are currently pursued to answer this question. Cosmological observations and neutrinoless double beta decay experiments provide an indirect access to the absolute neutrino mass scale, but are model-dependent. Model independent, direct ways to measure the neutrino mass are the investigation of the kinematics of single beta decay via a precise measurement of the beta decay electron energy spectrum close to the endpoint, or the detailed study of the electron capture spectrum.

        This talk will present the status of different experiments aiming to measure the neutrino mass using the above mentioned methods. The emphasis will be on the KArlsruhe TRItium Neutrino experiment (KATRIN) which aims to determine the effective electron anti-neutrino mass with an unprecedented sensitivity of 200 meV/c² at 90% CL via precision beta-decay spectroscopy of molecular tritium near its kinematic endpoint at 18.6 keV.

        Speaker: Florian Fränkle (Institut für Kernphysik, Forschungszentrum Karlsruhe)
      • 5:20 PM
        Coffee Break
      • 51
        Competing mechanisms of the 0νββ-decay mediated by light and heavy neutrinos within left-right symmetric models

        The importance of the subject of the neutrinoless double-beta decay (0νββ-decay) is shortly maintained. The neutrino exchange mechanisms of the 0νββ-decay in left-right symmetric seesaw models with right-handed gauge bosons at TeV scale are presented. The corresponding 0νββ-decay nuclear matrix elements, which enter the decay rate, are calculated within the QRPA with isospin restoration and discussed. An impact of the quenching of the axial-vector coupling constant on double-beta decay processes is addressed. By assuming normal hierarchy of neutrino masses a qualitative comparison of the 0νββ-decay lepton number violating parameters is performed. The angular correlations and the single electron energy distributions for various combinations of the total lepton number violating parameters that can help to disentangle the possible mechanism are described and discussed. Finally, a novel mechanism of the 0νββ-decay associated with nuclear environment is presented.

        Speaker: Prof. Fedor Simkovic (Comenius University)
      • 52
        CP Violation sensitivity study of $B^0 \to \pi^0\pi^0$ at the Belle II Experiment.

        The measurement of the time-dependent CP violation parameters for $B$-meson decays is crucial for tightening the constraints on the unitarity triangle and for the search of new physics beyond the Standard Model. A clean environment for the study of $B$ decay channels is provided by $B$-factories. With a design luminosity of 8 $\cdot$ 10$^{35}$cm$^{-2}$s$^{-1}$, leading ultimately to an integrated luminosity beyond 50 ab$^{-1}$, the new $B$-factory SuperKEKB will exceed the record instantaneous luminosity of its predecessor KEKB by a factor 40.

        The new Belle II detector will exploit the expected high statistics data sample thanks to a major upgrade of the tracking system, including a novel pixel vertex detector in its innermost part. Additionally, the detector capabilities will be complemented by substantial improvements in the reconstruction software.

        We develop a strategy for CP violation analysis in order to maximally exploit the new data set and to characterize the sensitivity of Belle II for various benchmark $B$ decay channels. Here we focus on the decay channel $B^0 \to \pi^0\pi^0$, which plays an important role in the precise determination of the unitarity angle $\alpha$.

        Speaker: Mr Fernando Abudinén (Max-Planck-Institut für Physik)
      • 53
        Model-independent measurement of the CKM phase $\varphi_1$ in $b\to c\overline{u}d$ transitions

        A time-dependent analysis of the $B$ meson decays governed by $b\to c\overline{u}d$
        quark transition allows to measure the CKM angle $\varphi_1$ with a negligible effects
        of strong interactions. The binned Dalitz plot technique is a promising approach for a
        model-independent measurement of the angle $\varphi_1$ in the $B^0\to \overline{D}{}^0\pi^0$
        and $B^0\to \overline{D}{}^0\pi^+\pi^-$ decays followed by $\overline{D}{}^0$ decays into
        $K_S^0\pi^+\pi^-$ and CP-eigenstates. We apply this technique to a full data sample of
        the Belle experiment and perform a time-dependent analysis of $B^0 \to \overline{D}{}^{(*)0}h^0$,
        $\overline{D}{}^0\to K_S^0\pi^+\pi^-$ decays, where $h^0\in\{\pi^0, \eta^{(\prime)}, \omega\}$.
        The obtained value $\cos{2\varphi_1} = 1.06\pm0.33{}^{+0.21}_{-0.15}$ is the most precise
        single measurement of the $\cos{2\varphi_1}$ to date and resolves the twofold ambiguity at
        the confidence level exceeding five standard deviations. The binned Dalitz plot technique can
        be employed to measure the angle $\varphi_1$ in the $b\to c\overline{u}d$ transitions at
        the precision level of one degree with expected statistics of the LHCb and Belle II experiments.
        Such precise results together with measurements of the $b\to c\overline{c}s$ transition
        would provide a valuable check of the KM mechanism.

        Speaker: Vitaly Vorobyev (Novosibirsk State University)
      • 54
        The LHCb upgrades

        High-precision measurements performed by the LHCb collaboration have opened a new era in flavour physics and more generally in high precision measurements. LHCb has already performed crucial measurements in b physics, spectroscopy, rare decays and CP violation, but a challenging Phase-I upgrade program of the LHCb detector planned for the LHC Run3 is already on the way. These measurements will highly benefit from a dramatic increase of statistics in LHCb's measurements. The upgrade program of the LHCb detector, its detector upgrade, and its reach in flavour physics are discussed in detail followed by a brief introduction of a successive Phase-II upgrade to happen in parallel to the HL-LHC upgrades.

        Speaker: Federico Alessio (CERN)
    • YSF: YSF Session
      Convener: Mark Dayvon Goodsell (Ecole Polytechnique (FR))
      • 55
        Sensitivity study of the measurement of the branching fraction of $B^+ \rightarrow \tau^+ \nu$ decays at the Belle II experiment

        The Belle II experiment is located at the KEK High Energy Accelerator Research Organization in Tsukuba, Japan.
        It is designed to perform measurements in all fields of heavy flavour physics, including measurements of rare B decays.
        This talk presents the recent progress in the hadronic and semileptonic tagging algorithm, current sensitivity studies
        for the future measurement of $B^+ \rightarrow \tau^+ \nu$ at Belle II, and the validation of the newly developed reconstruction tools
        on the full dataset recorded by the preceding Belle experiment.

        Speaker: Mr Thomas Keck (Karlsruhe Institute of Technology)
      • 56
        Rebalance and Smear for predicting QCD backgrounds in searches for new physics

        Searches for new physics in events with multiple jets and large missing transverse momentum are sensitive to a broad set of R-parity conserving SUSY models at the LHC. These searches rely on having an accurate prediction for the QCD background, especially when probing regions of the models with compressed spectra and/or regions featuring the production of light-flavor jets. A method for predicting the QCD background, called rebalance and smear, has been developed to model the multi-jet background for such searches for supersymmetry. A CMS search that makes use the rebalance and smear method in analyzing proton-proton collisions at sqrt(s)=13 TeV is presented, and constraints on various regions of the MSSM are discussed.

        Speaker: Marek Adam Niedziela (Hamburg University (DE))
      • 57
        Search for top squark pair-production in the single-lepton channel in models with highly compressed mass spectra with the CMS experiment

        Supersymmetry (SUSY) is one of the most promising candidates to solve multiple problems with the Standard Model. In particular models with a compressed mass spectrum are highly motivated by naturalness arguments and cosmological constraints on the dark matter relic density. In this talk, a search for SUSY with a compressed mass spectrum using events with a high-momentum jet from initial state radiation, large missing transverse energy, and a low-momentum lepton is presented. In particular, a scenario of top squark pair-production is investigated, where the mass difference to the lightest SUSY particle (LSP) is smaller than the mass of the W boson. The search is performed in a sample of proton-proton collisions recorded with the CMS detector at a centre-of-mass energy of 13 TeV and the results are interpreted assuming a 100% branching fraction for the four-body decay of the top squark to a bottom quark, a fermion-antifermion pair and the LSP.

        Speaker: Navid K. Rad (Austrian Academy of Sciences (AT))
      • 58
        Dissipative Losses in Self-Interacting Dark Matter Collisions

        Dark matter self-interactions are frequently used in the explanation of small structure problems in the universe. Depending on the model and strength of the interactions they can have important implications on the formation of structures, from dwarf galaxies to large galaxy clusters. Using four generic dark matter toy models, we present the effects of inelastic processes (i.e. dark bremsstrahlung) in dark matter collisions on structure formation in the universe. For that purpose, we compare the cooling time due to dark bremsstrahlung of a gas of dark matter particles in a non-relativistic and non-degenerate limit to the elastic scattering time scale, the Hubble time and the gravitational timescale. Our models show that the energy loss in dark matter collisions with dark dipole radiation can have an influence on structure formation for much smaller dark matter densities than quadrupole radiation and is - assuming very light (eV range) mediators - important for dark matter densities > 1 GeV/cm3. However, in regions of the universe where the dark matter density is a few orders of magnitude higher, even dark bremsstrahlung in systems with vanishing dipole moment can influence structure formation while satisfying observational constraints. We also find that the energy loss rate due to dark bremsstrahlung gets enhanced in dark matter models with an attractive self-interaction, increasing the parameter space where effects on structure formation are important.

        Speaker: Lukas Semmelrock (Austrian Academy of Sciences (AT))
    • Dinner: Conference Dinner
      Convener: Wolfgang Waltenberger (Austrian Academy of Sciences (AT))
    • Saturday: Future Facilities
      Convener: Jenny List (Deutsches Elektronen-Synchrotron (DE))
      • 59
        Future collider projects: technology overview, status / timelines
        Speaker: Andreas Salzburger (CERN)
      • 60
        Linear e+e- colliders
        Speaker: Frank Simon (Max-Planck-Institut fuer Physik)
      • 9:25 AM
      • 61
        Rethinking Brout-Englert-Higgs Physics

        The discovery of the Higgs physics together with the excellent performance of the LHC allow to make precision tests of Brout-Englert-Higgs Physics.

        At this level, it becomes important to fully understand the theory behind this physics. As was pointed over the last decades, there are many subtleties which can have far-reaching consequences.

        In this talk, I will point out a few examples of these subtleties, and how they affect our understanding of the standard model and new physics. In particular, I will discuss options how to test them in experiment:

        1) Even without the Higgs QCD would provide masses to the W and Z bosons, just too small ones. The current experimental precision becomes good enough to detect this effect, and will invite similar problems as the muonic g-2.

        2) Non-trivial effects potentially alter the high-energy behavior of the Higgs sector and may resolve many issues of the standard model without new physics. Precision measurements of running couplings will be the key to distinguish scenarios.

        3) While a convenient picture, the idea of breaking the electroweak symmetry is on a fundamental level inadequate. For experiments so far this had little consequences, and we understand why this is the case. However, with the current precision we become sensitive to deviations. It will be shown how this could manifest in heavy-quark production at the LHC and next-generation lepton colliders. Moreover, in theories beyond the standard model this can have far-reaching consequences for the observable particle spectra.

        Speaker: Axel Torsten Maas (University of Graz)
      • 62
        Physics at FCCs
        Speaker: Alain Blondel (Universite de Geneve (CH))