Dark Matter @ LHC 2020 (DM@LHC)

2 Jun 2020, 14:00 → 5 Jun 2020, 18:00 Europe/Zurich

The 7th Dark Matter @ LHC 2020 workshop will take place from June 2nd to June 5th 2020.

Due to the current covid-19 related travel restrictions, there will be no in-person meeting in Hamburg, as originally planned.

However, the conference will go ahead as an online event with a modified timetable (afternoons only, same dates). In addition to the main conference room, we plan to provide a number of smaller "breakout" rooms for informal discussions with the sessions speakers. We will also set up a virtual coffee break to facilitate discussions on specific topics.

Further connection details will follow in the next weeks.

The goal of the conference is to bring together the experimental and theory communities to discuss the latest results from dark matter searches at the LHC and plans for the future. In particular, there will be a dedicated session on strategies for dark matter searches during the upcoming LHC Run 3. Further topics include the fast-growing area of dark sectors and LLPs, flavour and dark matter, and machine learning tools for dark matter searches. We will also have speakers from non-LHC dark matter experiments to discuss common topics, such as the comparability of results from different experiments in common theoretical frameworks and ideas for cross-experimental collaborations.

The conference will feature invited and contributed talks as well as a poster session. Furthermore, we foresee a number of shorter lightning talks on specific topics. These are meant to highlight individual and/or unusual ideas and can also help increase the visibility of younger scientists.

Previous editions:

• Seattle (2019)
• Heidelberg/KIP (2018)
• Irvine (2017)
• GRAPPA/Nikhef (2016)
• Merton (2014)
• Chicago (2013)

Tuesday 2 June

Tuesday: Session 1: Introduction + simplified models

Conveners: Katherine Pachal (Duke University (US)), Stefan Vogl (Max Planck Institute for Nuclear Physics)

1 Welcome and Introduction

Speaker: Janna Katharina Behr (Deutsches Elektronen-Synchrotron (DE))

Intro_DMatLHC.pdf

Video

2 Dark Matter Working Group report (15'+5')

Speaker: Oleg Brandt (University of Cambridge (GB))

LHC DM WG activities & goals.pdf

Video

3 Simplified models: s-channel (15'+5')

Speaker: Chad Wells Freer (Northeastern University (US))

S-channel_DM.pdf

Video

4 A universal framework for t-channel dark matter models (15'+5')

Speaker: Chiara Arina (CP3 UCLouvain)

CArina_talk_tchannel.pdf

Video

5 Interference effects in dilepton resonance searches for Z' bosons and dark matter mediators (8'+2')

New $Z^{\prime}$ gauge bosons arise in many extensions of the Standard Model and predict resonances in the dilepton invariant mass spectrum. We present ZPEED ($Z^{\prime}$ Exclusions from Experimental Data), an open-source code providing fast likelihoods and exclusion bounds for general $Z^{\prime}$ models based on the most recently published 139 fb$^{-1}$ ATLAS dilepton data. PDF and detector effects as well as higher-order corrections are effectively implemented by tabulated functions enabling a fast computation of various test statistics. Moreover, interference effects with the Standard Model Drell-Yan background can be added to the signal cross section in the analysis, which can strengthen constraints on model parameters substantially. For generic $Z^{\prime}$ models, upper bounds on the couplings can improve by up to a factor of 1.5. In simplified dark matter models, in which the dark matter contributes to the decay width of the $Z^{\prime}$, the sensitivity of dilepton resonance searches on the mediator mass can be increased by 40%.

Speaker: Stefan Schulte (Max Planck Institute for Physics (Munich))

Schulte_DMatLHC2020.pdf

Video

15:30 Virtual coffee break + Q&A with speakers

Tuesday: Session 2: Dark matter and Higgs

Conveners: Lailin Xu (Brookhaven National Laboratory (US)), Ulrich Andreas Haisch (University of Oxford (GB))

6 Invisible Higgs decays (15'+5')

Speaker: Vukasin Milosevic (Imperial College (GB))

Video

VM_DM_at_LHC2020_final.pdf

7 The Inert Doublet Model at current and future colliders (15' + 5')

I will discuss the Inert Doublet Model, a Two Higgs Doublet Model with an exact Z_2 symmetry that provides a dark matter candidate. I will elaborate on current constraints on the parameter space as well as discovery prospects at current and future colliders.

Speaker: Tania Natalie Robens (Rudjer Boskovic Institute (HR))

idm.pdf

Video

8 A less simplified model: 2HDM+pseudoscalar (15'+5')

Speaker: Kristian Bjoerke (University of Oslo (NO))

kbjorke-DMLHC2020-200602.pdf

Video

9 Theory overview (25'+5')

Speaker: Hitoshi Murayama (University of California Berkeley (US))

DM@LHC.key

DM@LHC.pdf

Video

17:30 Virtual coffee break + Q&A with speakers

Wednesday 3 June

Wednesday: Session 3: Dark sectors and flavour

Conveners: Dr Florian Goertz (Max-Planck-Gesellschaft (DE)), Torben Ferber (DESY)

10 LHCb dark sector searches (15'+5')

Speaker: Martino Borsato (Ruprecht Karls Universitaet Heidelberg (DE))

DarkSectorsLHCb_Borsato.pdf

Video

11 DM-flavour connection (15'+5')

Speaker: Giorgio Arcadi

DMatLHCarcadi.pdf

Video

12 Lepton Flavour Universality: LHCb results and prospects (15'+5')

Speaker: Guy Henri Maurice Wormser (Université Paris-Saclay (FR))

DarkMatter_workshop_v2.pdf

DarkMatter_workshop_v2.pptx

Video

13 Strongly interacting dark sectors (15'+5')

Speaker: Dr Giovanni Grilli di Cortona (University of Sao Paulo)

DM@LHC2020_Grilli.pdf

Video

14 Baryogenesis and Dark Matter from B Mesons (8'+2')

In this talk, based on arXiv:1810.00880 and ongoing work, I will present a new mechanism of Baryogenesis and Dark Matter production in which both the dark matter relic abundance and the baryon asymmetry arise from neutral B meson oscillations and subsequent decays in the early Universe.

This mechanism would have distinctive experimental signals that I will discuss in detail:

i) the new decay mode of B mesons into a baryon and missing energy, with a BR > 10^{-3}.
ii) a positive semileptonic asymmetry in neutral B meson decays, > 10^{-5}.
iii) the new decay mode of b-flavored baryons into mesons and missing energy, with BR > 10^{-3}.

These unique collider signatures are testable at current collider experiments, such as the LHC and Belle-II, allowing for a distinct probe of this mechanism.

Speaker: Miguel Escudero (King's College London)

Escudero_BaryoDM_DMatLHC.pdf

Video

15:30 Virtual coffee break + Q&A with speakers

Wednesday: Session 4: New light particles

Conveners: Jose Miguel No Redondo (Conseil Europeen Recherche Nucl. (CERN)-Unknown-Unknown), Matthias Schott (CERN / University of Mainz)

15 Axion-like particles (15'+5')

Speaker: Martin Bauer (Heidelberg University)

DM@LHC2020_MartinBauer.pdf

Video

16 Dark photons and axion-like particles at the LHC (15'+5')

Speaker: Rafael Coelho Lopes De Sa (University of Massachusetts (US))

slides.pdf

Video

17 Long-lived Particle Experiments at the LHC: FASER, MATHUSLA, and others (15'+5')

Speaker: Samuel Ross Meehan (CERN)

meehan_DM@LHC2020_LLPExtraExperiments.pdf

Video

18 Search for millicharged particles in proton-proton collisions at √s=13 TeV with the milliQan Demonstrator (8' + 2')

In this talk, we will present the results of a recent search for fractionally charged particles using a data sample of proton-proton collisions provided by the CERN Large Hadron Collider in 2018. This search was carried out with a prototype scintillator-based detector, which allows the first sensitivity to particles with charges ≤0.1e at a hadron collider. The existence of new particles with masses between 20 and 4700 MeV is excluded at 95% confidence level for charges between 0.006e and 0.3e, depending on their mass. New sensitivity is achieved for masses larger than 700 MeV. We will discuss the concept of the experiment, the results of the search, and the plan for the full milliQan detector given the successful operation of the prototype.

Speaker: Ryan Schmitz (UCSB)

Search for millicharged particles in proton-proton collisions using the milliQan demonstrator_lightningTalk (1).pdf

Video

19 Intensity frontier (15'+5')

Speaker: Felix Kling (SLAC)

DM@LHC.pdf

Video

17:30 Virtual coffee break + Q&A with speakers

Thursday 4 June

Thursday: Session 5: Cross-experimental topics

Conveners: Filippo Sala, Giorgio Busoni (MPI-HD)

20 Dark Matter Capture in Neutron Stars (15'+5')

Speaker: Nicole Bell (University of Melbourne)

Bell.mp4

DM@LHC_NBell_2020.pdf

21 Gravitational waves and dark matter (15'+5')

Speaker: Toby Opferkuch (CERN)

Opferkuch_DMatLHC.pdf

Opferkuch.mp4

22 Robust cosmological constraints on axion-like particles (8'+2')

Axion-like particles with masses in the keV-GeV range have a profound impact on the cosmological evolution of our Universe, in particular on the abundance of light elements produced during Big Bang Nucleosynthesis. The resulting limits are complementary to searches in the laboratory and provide valuable additional information regarding the validity of a given point in parameter space. A potential drawback is that altering the cosmological history may potentially weaken or even fully invalidate these bounds. The main objective of this article is therefore to evaluate the robustness of cosmological constraints on axion-like particles in the keV-GeV region, allowing for various additional effects which may weaken the bounds of the standard scenario. Employing the latest determinations of the primordial abundances as well as information from the cosmic microwave background we find that while bounds can indeed be weakened, very relevant robust constraints remain.

Speaker: Paul Frederik Depta (Deutsches Elektronen-Synchrotron (DESY))

Depta.mp4

DMatLHC_PFDepta.pdf

23 SUSY dark matter searches (15'+5')

Speaker: Sicheng Wang (Univ. of California Santa Barbara (US))

SUSY_DMatLHC2020_SichengWang_200604.pdf

Wang.mp4

24 Global fits of supersymmetry - can we still have light neutralino DM? (15'+5')

Speaker: Are Raklev (University of Oslo (NO))

DMatLHC2020.pdf

Raklev.mp4

25 Conference picture!

15:32 Virtual coffee break + Q&A with speakers

Thursday: Session 6: Analysis tools

Conveners: Sarah Malik (Imperial College (GB)), Steven Schramm (Universite de Geneve (CH))

26 Performance improvements at ATLAS (15'+5')

Speaker: Jeanette Miriam Lorenz (Ludwig Maximilians Universitat (DE))

Lorenz.mp4

performance_DMLHC_ATLAS.pdf

27 Object performance improvements at CMS (15'+5')

Speakers: Laurent Thomas (Universite Libre de Bruxelles (BE)), Laurent Thomas (Universite Libre de Bruxelles (BE))

CMSPerformanceImprovement.pdf

Thomas.mp4

28 ML approaches in phenomenology (15'+5')

Speaker: Sascha Caron (Nikhef National institute for subatomic physics (NL))

Caron.mp4

DMLHCHamburg2020.pdf

29 ML for Jet Tagging and Event Classification on ATLAS and CMS (15'+5')

Speaker: Michael Aaron Kagan (SLAC National Accelerator Laboratory (US))

Kagan_ML_DMLHC_2020.pdf

Kagan.mp4

30 A novel density estimator and its use for LHC signal detection (8'+2')

We introduce a new density estimator based on Markov Chains. This estimator presents several benefits with respect to the usual ones and can be used straightforwardly in all density-based approaches to data science. After showing its consistency, we will present some promising results when applied to general scope datasets. Finally, we perform a preliminary analysis of a subset of the latest high energy physics dataset from darkmachines, establishing encouraging prospects for future use.

Speaker: Alessandro Morandini (SISSA)

MCDE_Morandini.pdf

Morandini.mp4

17:30 Virtual coffee break + Q&A with speakers

Friday 5 June

Friday: Session 7: Long-lived particles + lightning talks

Conveners: Albert De Roeck (CERN), Dr Jan Heisig (Université catholique de Louvain (UCL))

31 Dark matter and long-lived particles at the LHC (15'+5')

Speaker: Andreas Goudelis (LPTHE - Paris)

Andreas_Goudelis.pdf

Video

32 Long-lived particle searches in ATLAS and CMS (15'+5')

Speaker: Masahiro Morinaga (Waseda University (JP))

DMLHC2020_morinaga.pdf

Video

33 Exploring jet substructure in semi-visible jets (8'+2')

Semi-visible jets arise in strongly interacting dark sectors, where parton evolution includes dark sector emissions, resulting in jets overlapping with missing transverse momentum. The implementation of semi-visible jets is done using the Pythia Hidden valley module to duplicate the dark sector showering. In this work, several jet substructure observables have been examined to compare semi-visible jets and light quark/gluon jets. These comparisons were performed using different dark hadron fraction in the semi-visible jets (signal). The extreme scenarios where signal consists either of entirely dark hadrons or visible hadrons offers a chance to understand the effect of the specific dark shower model employed in these comparisons.

Speaker: Sukanya Sinha (University of Witwatersrand)

S_Sinha svj-jss DM@LHC.pdf

Video

34 Casting a GraphNet to catch dark showers (8'+2')

Strongly interacting dark sectors predict dark showers, which give rise to novel LHC signatures such as semi-visible jets. However, these are difficult to search for with conventional analysis techniques. In my talk I will first consider the sensitivity of existing and prospective LHC searches to semi-visible jets and then discuss how deep learning can help to distinguish dark showers from background. I will compare different network architectures and show that dynamic graph convolutional networks are particularly well suited to this task. I will then demonstrate that a deep-learned dark shower tagger can strongly improve the sensitivity of existing and prospective searches.

Speaker: Elias Bernreuther (RWTH Aachen University)

graphnet_darkshowers.pdf

Video

35 Dark photons from hadronic showers (8'+2')

Neutral mesons decay is often considered the dominant production mechanism for light dark photons in proton-proton and proton-nucleus collision. However, the produced hadronic showers also transfer a relevant amount of their energies into electromagnetic subshowers. We show that in certain cases, the positrons created in these sub-showers can lead to dark photon production rates significantly larger than the meson decay ones. We present the main characteristics of this production mode and update correspondingly standard limits on vector-mediator scenarios for light dark matter.

Speaker: Luc Jean Marie Darmé (INFN - National Institute for Nuclear Physics)

Darme_DMLHC2020.pdf

Video

36 Probing the real triplet scalar dark matter at colliders (8'+2')

We study discovery prospects of the real triplet model at the LHC and a future 100TeV $pp$ collider. The model provides a dark matter candidate and its smoking-gun signature is the so-called "disappearing charged tracks". We recast current 13TeV LHC searches for disappearing tracks and find that the LHC presently excludes a real triplet scalar lighter than 287GeV with $\mathcal{L}=\rm36\,$fb$^{-1}$. The reach will extend to 608GeV and 761GeV with $\mathcal{L}=300\,$fb$^{-1}$ and $3000\,$fb$^{-1}$ respectively. We extrapolate the 13TeV analysis to a prospective 100TeV $pp$ collider and find that a $\sim3$TeV triplet scalar could be discoverable with $\mathcal{L}=30$ ab$^{-1}$ depending on the degree to which pileup effects are under control. We also investigate present and prospective constraints on this model from dark matter direct detection. We find that currently, XENON1T can exclude a real triplet dark matter lighter than $\sim3$TeV for a Higgs portal coupling of order one or larger, and the future XENON20T will cover almost the entire dark matter viable parameter space except for vanishingly small portal coupling.

Speaker: Yong Du (University of Massachusetts-Amherst)

DM-LHC-Yong Du.pdf

Video

15:30 Virtual coffee break + Q&A with speakers

Friday: Session 8: Future strategies

Conveners: Caterina Doglioni (Lund University (SE)), Suchita Kulkarni (Austrian Academy of Sciences (AT))

37 Closing remarks

Speaker: Felix Kahlhoefer (RWTH Aachen)

Conclusion.pdf

Video

38 DM and feebly-interacting particles: ideas for cross-experimental collaborations (15'+5')

Speaker: Gaia Lanfranchi (INFN e Laboratori Nazionali di Frascati (IT))

DM@LHC_Lanfranchi.pdf

Video

39 Reinterpretation tools for dark matter searches (20'+5')

Speaker: Prof. Jonathan Butterworth (UCL)

reint.pdf

reint.pptx

Video

40 Panel discussion

Speakers: Caterina Doglioni (Lund University (SE)), Suchita Kulkarni (Austrian Academy of Sciences (AT))

DM@LHC - Slides to guide final discussion.pdf