Les Houches

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====== Recasting and Simplified models for long-lived particles ======

People interested: Nishita Desai, Stefania Gori, Andreas Goudelis, Sabine Kraml, Andre Lessa, Matthew McCullough, Dipan Sengupta, Benjamin Fuks, Eric Conte, Amit Chakraborty, Abhishek Iyer, Daniele Barducci, José Zurita, Jose Miguel No, Biplob Bhattacherjee, Shankha Banerjee, Haiying Cai, Sezen Sekmen, Gabriel Facini, Andy Buckley, Giovanna Cottin

We now have a mailing list: leshouches-llp-recast AT cern.ch

Topics:
===== Difficulties of recasting LLP searches =====

  * See references below.
  * How do detector simulations deal with LLPs?  
  * How much error from ignoring the magnetic field for recasting?
  * Track efficiency for reconstructing displaced vertices?
  * Simplified recasting? Efficiencies as a function of (few) relevant kinematical variables
  * How to estimate trigger efficiency for signal different from benchmark (a.k.a. are we throwing away the signal before starting?)


===== Task List =====

First task is to implement and validate a few analyses

^  ** Search ** | ** People ** |
^ Heavy Charged particles | Shankha Banerjee, Biplob Bhattacherjee, Abhishek Iyer, Dipan Sengupta |
^ Disappearing tracks | José Zurita |
^ Displaced vertices | Andre Lessa, Jan Heisig |
^ Displaced leptons / jets | Amit Chakraborty, Nishita Desai, Andre Lessa |
^ R-hadrons | Jan Heisig (?) |

=== What do we want from this exercise? ===

  * One document showing validation (or lack of it) for each category
  * A list of models people are interested in re-interpreting these searches for. Is there anything that changes that cannot be smoothly interpolated? e.g. number of tracks? Anything else?
===== Simplified models definitions =====
 
Three main signatures: long-lived charged track (long-lived charged particle), disappearing track or kink track (short-lived charged particle) and displaced vertices (short-lived neutral particle).  The long-lived neutral gives standard missing energy signature.

  * **MadGraph implementations:** 
  * **Parameterisation of results:** mass-vs-mass plane, mass-vs-lifetime, multi-dimensional grids, ...
  * **Complementarity:** Overlap of search strategies as lifetime changes
  * **Inclusive simplified models:** only the LLP branch topology and decay is relevant?

===== Efficiencies =====

  * Computing efficiencies as a function of the LLP kinematics and lifetime 
  * Efficiencies for R-hadrons
  * Efficiencies for displaced vertices/kinks
  * Demonstrate usefulness to motivate experimentalists to provide efficiencies

__Efficiencies wishlist__

  - **Displaced vertices:** e, mu eff(d0, pT); jets eff(pT, ctau)
  - **Heavy charged particles:** eff(pT, beta, eta) 
  - **LL charged particles:** eff(pT, beta, eta, ctau)

Q: What is the dependence on isolation? Do we need efficiencies for different isolation criteria?
   
===== Triggering =====

  * See Tuesday morning talks at [[https://indico.cern.ch/event/607314/timetable/ | April LLP workshop]] at CERN

===== Cross talks =====

  * Higgs group is interested in exotic decays into LLPs
  * Interplay with LHCb searches

===== References =====

  * **Simplified Models for Exotic BSM Searches**. Jan Heisig, Andre Lessa, Loic Quertenmont, [[https://arxiv.org/abs/1509.00473]]
  * **Long-Lived Staus and Displaced Leptons at the LHC.** Jared A. Evans, Jessie Shelton, [[https://arxiv.org/abs/1601.01326]] 
  * **Prompt Signals and Displaced Vertices in Sparticle Searches for Next-to-Minimal Gauge Mediated Supersymmetric Models.** B. C. Allanach, Marcin Badziak, Giovanna Cottin, Nishita Desai, Cyril Hugonie, Robert Ziegler, [[https://arxiv.org/abs/1606.03099]]



===== Current Experimental Analyses =====

Note: Many ATLAS 13 TeV analyses notes inaccessible without CERN credentials

CMS summary of the searches https://indico.cern.ch/event/550030/contributions/2417789/attachments/1432466/2201005/Antonelli_Aspen2017_CMSLLP.pdf


CMS efficiency parametrisation [[https://twiki.cern.ch/twiki/bin/view/CMSPublic/DisplacedSusyParametrisationStudyForUser]]

ATLAS summary of the searches (in progress)
[[https://docs.google.com/document/d/1DqDntN0_2dRLnWwmrMFV30BRkdnKTKYSN33BmQaMbzM/edit?usp=sharing]]

{{:2017:groups:np:atlas_susy_llpchargino.png?300|}} {{:2017:groups:np:atlas_susy_llp_rhadron.png?300|}}

^ ** Experiment ** | ** Energy ** | ** Type **| ** Analysis ** |
^ ATLAS | 13 TeV | DV| Search for long-lived, massive particles in events with displaced vertices and missing transverse momentum in 13 TeV pp collisions with the ATLAS detector [[http://inspirehep.net/record/1589909]]|
^ ATLAS | 13 TeV | DV| Search for long-lived neutral particles decaying in the hadronic calorimeter of ATLAS at TeV in 3.2/fb of data[[https://cds.cern.ch/record/2219571/files/ATLAS-CONF-2016-103.pdf]]|
^ ATLAS | 13 TeV | DV| Search for long-lived neutral particles decaying into displaced lepton-jets in proton–proton collisions at 13 TeV with the ATLAS detector [[http://inspirehep.net/record/1480022/files/ATLAS-CONF-2016-042.pdf]]|
^ ATLAS | 13 TeV | DT | Search for long-lived charginos based on a disappearing-track signature in p p collisions at 13 TeV with the ATLAS detector [[ https://cds.cern.ch/record/2258131/files/ATLAS-CONF-2017-017.pdf]] |
^ ATLAS | 13 TeV | Rhad. | Search for metastable heavy charged particles with large ionization energy loss in pp collisions at 13 TeV using the ATLAS experiment [[ https://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/SUSY-2016-03/]] |
^ ATLAS | 8 TeV | DT | Search for charginos nearly mass-degenerate with the lightest neutralino based on a disappearing-track signature in pp collisions at √s = 8 TeV with the ATLAS detector [[ http://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/SUSY-2013-01/]] |
^ ATLAS | 8 TeV | DV | Search for massive, long-lived particles using multitrack displaced vertices or displaced lepton pairs in pp collisions at sqrt(s)=8 TeV with the ATLAS detector [[https://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/SUSY-2014-02/ ]]|
^ ATLAS | 8 TeV | Tracks | Search for heavy long-lived multi-charged particles in pp collisions at sqrt(s) = 8 TeV using the ATLAS detector [[https://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/EXOT-2013-20/ ]] |
^ ATLAS | 8 TeV | DV | Search for long-lived, weakly-interacting particles that decay to displaced hadronic jets in proton-proton collisions at √s=8 TeV with the ATLAS detector [[ https://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/EXOT-2013-12/]] |
^ ATLAS | 8 TeV | Disp. jet | Search for pair-produced long-lived neutral particles decaying in the ATLAS hadronic calorimeter in pp collisions at √s = 8 TeV [[https://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/EXOT-2012-28/]] |
^ ATLAS | 8 TeV | Disp. leptons| Search for long-lived neutral particles decaying into lepton jets in proton-proton collisions at √s = 8 TeV with the ATLAS detector [[https://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/EXOT-2013-22/ ]] |
^ ATLAS | 8 TeV | Tracks | Searches for heavy long-lived particles with the ATLAS detector in proton-proton collisions at sqrt(s) = 8 TeV [[https://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/SUSY-2013-22/]] |
^ ATLAS | 8 TeV | R-had | Search for long-lived stopped R-hadrons decaying out-of-time with pp collisions using the ATLAS detector [[ https://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/SUSY-2013-03/]] |
^ CMS | 13 TeV | Disp. jets | Inclusive search for new particles decaying to displaced jets at √s = 13 TeV [[http://cms-results.web.cern.ch/cms-results/public-results/preliminary-results/EXO-16-003/index.html ]] |
^ CMS | 13 TeV | Stopped | Search for stopped long-lived particles produced in pp collisions at √s= 13 TeV [[http://cms-results.web.cern.ch/cms-results/public-results/preliminary-results/EXO-16-004/index.html]] |
^ CMS | 13 TeV | Tracks | Searches for Long-lived Charged Particles in Proton-Proton Collisions at √s= 13 TeV[[http://cms-results.web.cern.ch/cms-results/public-results/preliminary-results/EXO-15-010/index.html]] |
^ CMS | 13 TeV | Disp. leptons | Search for displaced leptons in the e-μ channel [[http://cms-results.web.cern.ch/cms-results/public-results/preliminary-results/EXO-16-022/index.html]] |
^ CMS | 8 TeV | Disp. leptons | Search for Displaced SUSY in Dilepton Final States [[http://cms-results.web.cern.ch/cms-results/public-results/preliminary-results/B2G-12-024/index.html]] |
^ CMS | 8 TeV | Disp. photons | Search for displaced photons using conversions at 8 TeV [[http://cms-results.web.cern.ch/cms-results/public-results/preliminary-results/EXO-14-017/index.html]] |
^ CMS | 8 TeV | Disp. photon + MET | Search for long-lived neutral particles in the final state of delayed photons and missing energy in proton-proton collisions at √s = 8 TeV [[http://cms-results.web.cern.ch/cms-results/public-results/preliminary-results/EXO-12-035/index.html]]  |
^ CMS | 8 TeV | Disp. muons | Search for long-lived particles that decay into final states containing two muons, reconstructed using only the CMS muon chambers [[http://cms-results.web.cern.ch/cms-results/public-results/preliminary-results/EXO-14-012/index.html ]] |
^ CMS | 8 TeV | DV | Search for long-lived particles decaying to final states that include dileptons [[http://cms-results.web.cern.ch/cms-results/public-results/preliminary-results/EXO-12-037/index.html]] |
^ CMS | 8 TeV | Stopped | Search for decays of stopped long-lived particles produced in proton-proton collisions at √s = 8 TeV [[http://cms-results.web.cern.ch/cms-results/public-results/publications/EXO-12-036/index.html ]] |
^ CMS | 7 & 8 TeV | Tracks | Searches for Long-lived Charged Particles [[http://cms-results.web.cern.ch/cms-results/public-results/preliminary-results/EXO-12-026/index.html]] |
^ CMS | 8 TeV | Disp. jets | Search for long-lived neutral particles decaying to dijets [[http://cms-results.web.cern.ch/cms-results/public-results/preliminary-results/EXO-12-038/index.html]] |
^ LHCb| 8 TeV | Disp. jets | Updated search for long-lived particles decaying to jet pairs [[https://lhcbproject.web.cern.ch/lhcbproject/Publications/LHCbProjectPublic/LHCb-PAPER-2016-065.html ]]; see also thesis: [[http://www.nikhef.nl/pub/services/biblio/theses_pdf/thesis_P_N_David.pdf]] |
^ LHCb | 7 & 8 TeV | |Search for massive long-lived particles decaying semileptonically in the LHCb detector [[ https://lhcbproject.web.cern.ch/lhcbproject/Publications/LHCbProjectPublic/LHCb-PAPER-2016-047.html ]] |
===== Simplified models definitions =====
Ideas for simplified models and analysis:
  * Displaced tops:  SUSY models with stop NLSP, simplified models (emerged from discussion as most interesting candidate model). See [[disptop|here]],
  * Disappearing R-hadrons:  SUSY models with coloured NLSP and small mass splittings (probably not the most interesting scenario to explore for now).
Les Houches

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