Searching for long-lived particles at the LHC: Third workshop of the LHC LLP Community

16 May 2018, 09:00 → 18 May 2018, 17:10 Europe/Zurich

500/1-001 - Main Auditorium (CERN)

Albert De Roeck (CERN), Brian Shuve (SLAC National Accelerator Laboratory), Giovanna Cottin (National Taiwan University), James Beacham (Ohio State University (US)), José Francisco Zurita (KIT), Juliette Alimena (Ohio State University (US)), Martino Borsato (Universidade de Santiago de Compostela (ES)), Michelangelo Mangano (CERN), Nishita Desai (LUPM, Montpellier), Will Buttinger (CERN), Xabier Cid Vidal (Universidade de Santiago de Compostela)

Following the successes of the LHC Long-Lived Particle (LLP) Workshops in April and October of 2017 -- and continuing the robust and rich tradition defined by prior workshops such as “LHC Searches for Long-Lived BSM Particles: Theory Meets Experiment", at U. Mass, Amherst, in November of 2015; “Experimental Challenges for the LHC Run II", at the Kavli Institute for Theoretical Physics in May of 2016; and the “LHC Long-Lived Particles Mini-Workshop" at CERN in May of 2016 -- the LHC LLP Community, composed of members of the CMS, LHCb, and ATLAS collaborations as well as theorists, phenomenologists and those interested in LLP searches with dedicated LHC detectors such as milliQan, MoEDAL, MATHUSLA, FASER, Codex-b, etc., convenes again to discuss the outcomes presented in the community white paper, assess the state of searches for long-lived particles beyond the Standard Model at the LHC, brainstorm about new ideas for LLP searches, and focus on the future of LLP searches in HEP, both at the LHC and for future detectors and projects.

The format will likely be similar to that of our previous workshops, i.e., a working-workshop, where we focus on discussion and collaboration, with any talks functioning to set the stage for that collaboration.

This workshop is unique, however, because after months of work by our community, the white paper is currently nearing completion.  Thus, while we will definitely feature a component devoted to a review of the content of the white paper, the focus of this workshop will be on the future:

• What's next for LLP searches at the LHC?
• What didn't we get to cover in the first white paper?
• What recommendations for triggers and upgrade studies have arisen since we started this work?
• How well do we really, quantitatively understand where our searches for prompt objects have sensitivity for LLPs, and how can we encourage the experimental collaborations to address this question comprehensively?
• What about future detectors?
• And what about new ideas for thinking critically about the ultimate sensitivity for LLP signatures / benchmark simplified models at the LHC and about what will be learned at future machines?

And yes, of course there will be at least one lightning round!  Please contact the organizers with your proposal or idea.

The first day of the workshop features collaborative sessions with the Re-interpretations workshop concluding that same day, also at CERN.

The agenda is taking shape now, but please register now!

Note that while we hope to see you in person at CERN, remote participation will indeed be available via Vidyo.  Please register whether you will participate in person or remotely and indicate so in your registration.

Wednesday 16 May

1 Introduction to the LLP Community and Whitepaper

Speakers: Brian Shuve (Harvey Mudd College), James Beacham (Ohio State University (US))

Beacham_LHC_LLP_CERN_Intro_and_Goals_2018May16.pdf

2 Long-lived particles at the LHC: A theorist's perspective

Speaker: Brian Shuve (Harvey Mudd College)

LHC-LLP_Shuve.pdf

10:00 Coffee

LLP search snapshots

3 ATLAS snapshot

Speaker: Jennifer Kathryn Roloff (Harvard University (US))

llpAtlasSummary.pdf

4 CMS snapshot

Speaker: Steven Lowette (Vrije Universiteit Brussel (BE))

Lowette_180516_LHCLLPWorkshop_CMSSnapshot.pdf

5 LHCb snapshot

Speaker: Elena Dall'Occo (Nikhef National institute for subatomic physics (NL))

LLP_snapshot_elena.pdf

Material for re-interpretation - I

6 Re-interpretation of long-lived particle searches: Whitepaper recommendations

Speaker: Nishita Desai (LUPM, Montpellier)

LLP-reinterpretation.pdf

7 Fast detector simulation for LLPs: Delphes and MA5

Speakers: Eric Conte (Universite de Haute Alsace (FR)), Eric Conte (Laboratoire de Physique Corpusculaire (LPC))

MA5-LLP.pdf

8 Update on public tools for LLP recasts: Checkmate / Gambit discussion

Speakers: Anders Kvellestad (Nordita), Jong Soo Kim (IFT Madrid)

LLP-CheckMATE.pdf

LLPs_with_GAMBIT_Kvellestad.pdf

12:45 Lunch

Material for re-interpretation - II

9 CMS material for re-interpretation

Speaker: Juliette Alimena (Ohio State University (US))

reinterpretationMaterialFromCMS_CernLLPWorkshop_16May2018.pdf

10 ATLAS material for re-interpretation

Speaker: Hideyuki Oide (INFN-Genova)

ATLAS_LLP_reinterpretation.pdf

11 Discussion

15:30 Coffee

Contributed Talks

12 Dark photon interpretation of LHCb search

Speaker: Wei Xue (CERN)

Slides

13 Reinterpretation of long-lived particles searches within SModelS

Speaker: Jan Heisig (RWTH Aachen University)

14 Freeze-in and LLPs

Speaker: Mr Bryan Zaldivar (LAPTh, Annecy)

llp_freezein_zaldivar.pdf

15 Recasting the scotogenic FIMP

Speaker: Stefan Vogl (Max Planck Institute for Nuclear Physics)

LLP.pdf

16 Novel signatures for long-lived particles at the LHC

Speaker: Ms Swagata Mukherjee (Rheinisch Westfaelische Tech. Hoch. (DE))

Swagata_LLP.pdf

17 Long-lived neutrinos in the left-right symmetric model

Speaker: Goran Popara

Popara_LLP2018.pdf

18:00 DIY welcome drink in CERN Restaurant 1

Thursday 17 May

18 Top-down theory overview and simplified models yielding LLPs

Speaker: Prof. David Curtin (University of Toronto)

davidcurtin_MATHUSLA_physics_case_CERN_LHCLLPworkshop_40m_17may2018_v3_after_talk.key.pdf

19 White paper chapter 3 -- Experimental coverage of LLP signatures

Speaker: José Francisco Zurita (KIT)

LLP_EXP_coverage_CERN.pdf

Elevator pitch session: Your idea goes here

Convener: Will Buttinger (CERN)

10:30 Coffee

Lightning round: Session 1

20 Neutrino reinterpretation and particle masses with displaced vertices

Speaker: Giovanna Cottin (National Taiwan University)

LLP_Workshop_May2018.pdf

21 Singlet-Doublet Dark Matter Freeze-in: LHC displaced signatures

Speaker: Alberto Mariotti (VUB Brussels)

SDFI_Mariotti_4.pdf

22 Discerning the left sneutrino LSP with displaced-vertex searches

Speaker: Iñaki Lara Pérez (UAM-CSIC)

LLP_ILara.pdf

23 Long lived right-handed neutrinos, oscillations and leptogenesis

Speaker: Oliver Fischer (Unibas)

LHC-LLP18_HeavyNeutrinoOscillations_Fischer.pdf

24 White paper chapter 5 -- Triggers and detector upgrades

Speaker: Yangyang Cheng (Cornell University (US))

llp_upgrade_ycheng_051718.pdf

12:10 Lunch

Dedicated LLP experiments: Session 1

25 MATHUSLA

Speaker: Mason Proffitt (University of Washington (US))

MATHUSLA LLP Workshop.pdf

26 SHiP

Speaker: Federico Leo Redi (EPFL - Ecole Polytechnique Federale Lausanne (CH))

redi_LLP_2018.pdf

27 SeaQuest

Speakers: Stefania Gori (University of Cincinnati (US)), Stefania Gori (Perimeter Institute/Cincinnati University)

TalkLLP.pdf

28 MilliQan

Speaker: Chris Hill (Ohio State University (US))

milliQan_LLP_CERN_051818.pdf

15:00 Coffee

Breakout working group sessions: Parallel and hands-on

breakoutLLPSim.pdf

JZ_Blue_Sky_Session_report.pdf

LHC-LLP18-HNL_BreakoutSession_Summary.pdf

29 Breakout #1

Geant4, Pythia, and the challenges of LLP simulation(-over-beers)

Speaker: Will Buttinger (CERN)

Simulating travelling rhadrons

- 2 grids in the Whitepaper where the LLP carries SM (except weak) charge. We need to know how to simulate these.
- Important to let G4 interact the rhadron because it can hadronize as it goes through all the material (travels through more than a bhadron because of lifetime) so cannot decide how to decay it before g4 does its thing (unlike bhadrons, as is done in evtgen, where assumption that bhadron wont change state is reasonable given lifetime/material).
- G4 can decay slepton, but not things like rhadrons ...  need to use pythia.
- Have been technical issues in being able to reinitialize pythia after G4 runs and make it decay an rhadron that’s given to it (Reported by Jennifer, Somewhat resolved by Steve?).
- How do we pass configuration information from pythia->G4->pythia in this chain ... ATLAS moving away from HepMC, making it harder to do this in a unified way, each collaboration just deals with it themself?
- The current mass spectrum ("generic" or "intermediate") used by ATLAS for rhadrons is a hacked-together incoherent(?) mess. Its a choice. Last update was 5 years ago, before that was 15 years ago. Store deltas (are masses relative to the input gluino state). Rather than adding up the constituent quark masses to get Rhadron mass in pythia, we should just specify the masses for each Rhadron. 
- Regge model determines hadronic interactions - is what is in use in ATLAS atm. Not the same as “regge model” mass spectrum that is used in pythia6. CMS uses the "cloud model" for the hadronic interactions, which we hope is the same thing.
- At the moment spin correlations are completely neglected - nobody can think of an important case where it matters.

Simulating stopping rhadrons

- At the moment ATLAS uses a simple stopping threshold criteria (Beta < A^(-2/3)). This doesnt simulate the deceleration of stopping rhadrons, which would occur as they drag ions along. 

- Concern that efficiencies measured in stopping particle searches are overestimated (by factors of maybe 2, not 10-100). Would like to be able to simulate these correctly.

Simulating quirks

- Chris Hill made his argument for why quirks are basically non-existent (all but shortest string lengths were killed by fractional charge search).
- Could reinterpret Heavy Stable Charged Particle searches in terms of (short length) quirks if we had a reliable simulation. But it's going to be driven by best effort, and effort seems lacking.

Fast simulation

- There was reasonable interest in understanding how far validity of fast simulation can go when it comes to LLPs (non-pointing tracks/photons etc).

 

Action items

- It is very important that each simplified model in the white paper that features long-lived interacting (SM-charged) particles should come with a corresponding description of the interaction model. Experts should be assembled to define/document for each case (rhadrons, HIP, monopole, ..) where relevent:

   - Particle mass spectrum
   - Particle fragmentation function
   - G4 interaction model
   - Other relevant parameters of the model (e.g. initial qluino/gluon fraction)

- At very least there needs to be effort to compare/contrast what is currently done by ATLAS and CMS and LHCb to check for differences

- Would like to call for studies on both sides that compare fast and full sim in LLP scenarios to try to quantify geometric/phase space where fast sim is reasonable

 

Participants in discussion

Zach Marshall (ATLAS)
Larry Lee (ATLAS)
Chris Hill (CMS)
Steve Mrenna (CMS/Pythia)
Jennifer Roloff (ATLAS)
...

30 Breakout #2

Heavy Neutral Leptons

Speakers: Carlos Vazquez Sierra (Nikhef National institute for subatomic physics (NL)), Daniele Trocino (Ghent University (BE)), Oliver Fischer (Unibas), Philippe Mermod (Universite de Geneve (CH))

HNL breakout session.pdf

IMG_2211.JPG

IMG_2212.JPG

IMG_2213_good.jpg

31 Breakout #3

Blue-Sky Thinking / Go-Nuts / Brainstorming-Over-Beers / No-Idea-Too-Crazy

Speaker: José Francisco Zurita (KIT)

Blue_Sky_Session.pdf

19:30 Workshop dinner

Friday 18 May

32 The challenging diversity of hidden gauge theories

Speaker: Matt Strassler (Harvard University)

LLP2018d.pdf

Dedicated LLP experiments: Session 2

33 Codex-b

Speaker: Biplab Dey (CCNU)

codexb_llp_wksp.pdf

34 NA62

Speaker: Babette Dobrich (CERN)

llp_2018_BD.pdf

10:25 Coffee

Dedicated LLP experiments: Session 2 continued

35 MoEDAL

Speaker: James Pinfold (University of Alberta (CA))

LHC-LLP-talk.pdf

36 FASER

Speaker: Jamie Boyd (CERN)

FASER_18.5.18.pdf

Breakout working group sessions: Reports

Convener: Martino Borsato (Universidade de Santiago de Compostela (ES))

breakoutLLPSim.pdf

JZ_Blue_Sky_Session_report.pdf

LHC-LLP18-HNL_BreakoutSession_Summary.pdf

12:15 Lunch

Synergies and the future: Allied working groups and projects

37 Higgs XS WG -- Thoughts about LLPs

Speaker: Roger Caminal Armadans (University of Massachusetts (US))

20180518_BSMHiggs_LLPworkshop_RogerCaminal.pdf

38 Dark matter WG -- Perspective on LLP signatures

Speaker: Philip Coleman Harris (Massachusetts Inst. of Technology (US))

PCH_DMWG_LL_15_05.pdf

39 Monopoles / Highly-ionizing particles / High electric charge objects at ATLAS

Speaker: Wendy Taylor (York University (CA))

MagneticMonopoles-LLPWorkshop.pdf

15:00 Coffee

Lightning round: Session 2

40 Long-lived particles from a flavoured dark sector

Speaker: Sophie Renner (CERN)

SRennerSlides.pdf

41 Timing BSM

Speaker: Zhen Liu (Fermilab)

2_TimingLLP_LLPCERN18_ZhenLiu.pdf

42 RPV meets RPC in ATLAS

Speaker: Karri Folan Di Petrillo (Harvard University (US))

2018.05.18.kdp.RPCmeetsRPV.pdf

43 LLPs at electron-proton colliders

Speaker: Oliver Fischer (Unibas)

LHC-LLP18-LLP@ep_Fischer.pdf

44 Reinterpretation of long-lived particles searches within SModelS

Speaker: Jan Heisig (RWTH Aachen University)

Heisig_LLP_SModelS_CERN_May2018.pdf

45 Closeout and taking stock

Speaker: Xabier Cid Vidal (Universidade de Santiago de Compostela)

LLP18_closeout_CidVidal.pdf