1. Search for heavy stable charged particles Loïc Quertenmont Université Catholique de Louvain & FNRS Center for Particle Physics and Phenomenology BSM - CP3 - 24 September 2008

2. 24/09/2008 - BSM CP3Loïc Quertenmont - loic.quertenmont@cern.ch2 Outline  Introduction to Heavy Stable Charged Particles (HSCP)  Detection techniques  Simulation Results  Conclusions

3. 24/09/2008 - BSM CP3Loïc Quertenmont - loic.quertenmont@cern.ch3 HSCP Phenomenology  Properties  Very Heavy : O(100 GeV/c²) or more→ In general non-relativistic  cτ ~ O(m) or larger→ Usually, do not decay in a detector  Have electric and/or strong charge  Allowed by many models beyond SM (mGMSB, Split SUSY, MSSM, and UED)  In general, long lifetime is a consequence of a quantum number conservation → e.g. : SUSY with R-parity or UED with KK-parity → Heavier states could also be quasi stable if decay phase space is small  If coloured, HSCP will hadronize and form an “R-Hadron” → Fraction of gluino-balls is a relevant unknown parameter from the experimental point of view.  Main scenarios considered in CMS Lepton Like MSSM Stop’s Split SUSY Gluino’s Baryons gqqq, t 1 qq Mesons gqqbar, t 1 qbar Gluino-balls gg ~ ~ ~ ~ ~ (pure neutral state) XSection Up to ~1000pb CMS AN-2007/049

4. 24/09/2008 - BSM CP3Loïc Quertenmont - loic.quertenmont@cern.ch4 Interactions in the Detector  Lepton-like HSCPs, behave like heavy muons  Cross easily the whole detector  Non-relativistic → large ionization energy loss → long time of flight  R-Hadrons, do nuclear interactions in addition  heavy parton acts as spectator (interaction will be similar to a low energy hadron-hadron scattering)  R-Hadron does not shower in the calorimeters  Conversion to a different R-Hadron is possible → charge flipping

5. 24/09/2008 - BSM CP3Loïc Quertenmont - loic.quertenmont@cern.ch5 Signature HSCP → Non-relativistic track with High Momentum  Charge flipping is also a unique signature that can be used in offline analysis to confirm signal.

6. 24/09/2008 - BSM CP3Loïc Quertenmont - loic.quertenmont@cern.ch6 Detection techniques  Methods : 1. p measured from track bending in inner tracker/muon system 2. β from  Energy loss in inner tracking systems (ionization and transition radiation)  Time of Flight (T.O.F) in Muon systems 3.m from p / (βγc) 4.If m is heavier than any stable SM particle → HSCP  Issues :  Charge flipping  Deviation from expected muon trajectory, unmatched inner tracker/muon tracks and incompatible/missing track stubs in the muon system Neutral R-Hadronswill give no signals in the detectors  Charge flipping  Deviation from expected muon trajectory, unmatched inner tracker/muon tracks and incompatible/missing track stubs in the muon system Neutral R-Hadrons will give no signals in the detectors  Main backgrounds are Cosmic and SM Muons

7. 24/09/2008 - BSM CP3Loïc Quertenmont - loic.quertenmont@cern.ch7 T.O.F in muon systems  Principle: Use muon wire detectors to measure time of flight (of charged HSCP) Resistive Plate Chambers are only useful to confirm track and reject background.  Challenges : Charge flipping introduce some complications (iron yoke) Lower efficiency than for muons Momentum measured by Stand alone Muon system is biased upward (good for triggering) β of R-Hadron in muon system is generally lower than β at production due to energy loss. β>0.65 to have inner Tracker readout in the correct bunch crossing.  Background : Cosmic muons Badly measured muons

8. 24/09/2008 - BSM CP3Loïc Quertenmont - loic.quertenmont@cern.ch8 dE/dX in tracking detectors (1/2)  Principles : HSCP id based on dE/dx estimate of a track various estimators considered including an unbinned Landau fit use Z  μμ as control sample Mass reco: β -2 ≈ k dE/dX in 0.1<βγ<0.9 region obtain k from proton sample  Challenges : Few measurements per track (~ 10 Electronics response : saturation/cut-offs effects readout timing  Background : Overlapping tracks SM particles in the tail of the dE/dX distribution Heavy ions from nuclear interactions Non Relativistic Particle

9. 24/09/2008 - BSM CP3Loïc Quertenmont - loic.quertenmont@cern.ch9 dE/dX in tracking detectors (2/2) Stop of 500GeV CSA07 SM = Background X Scales are different   estimators make the assumption that all dE/dx measurements of a tracks come from the same Landau distribution.  In general, this assumption is not true because of different detector response  A calibration procedure has been designed to equalize the response of all tracker modules.

10. 24/09/2008 - BSM CP3Loïc Quertenmont - loic.quertenmont@cern.ch10 Global Trigger Strategies  Muon trigger : Useful for most models Efficiency depends on the HSCP mass and model Very robust with respect to the P T threshold (can be increased up to ~50 GeV)  Jet / Missing E T : Useful for certain models (in particular for mGMSB) Less sensitive to timing/β issues mGMSB τ 1 ~ 99% UED KK τ 1 ~ 80% MSSM t 1 ~ 40% to 70% Split SUSY g ~ 60% to 95% CMS Trigger Efficiency with full simulation ~ ~ ~ ~ CMS AN-2007/049

11. 24/09/2008 - BSM CP3Loïc Quertenmont - loic.quertenmont@cern.ch11 CMS : Offline Analysis  Samples : Signal : g, t 1, mGMSB τ 1, KK τ 1 : mass from 130 to 1500 GeV/c ², generated with (MadGraph), Pythia+R-hadron hadronization routines Backgrounds : all SM processes (QCD, W/Z, ttbar, bbbar + jets)  Simulation : Full Geant4 + specific routines for R-Hadron hadronic interactions  Selection : Muon Systems : p T >30 GeV Tracker : β tk 8, χ²/ndof < 5 Combined: β DT 100GeV  Mass Reconstruction : β = average (β tk,β DT ) p = p tk SM Muons t 1 500GeV t1t1t1t1 KK τ 1 mGMSB τ g ~ ~ ~ ~ 1fb -1 R Mackeprang & A Rizzi : Eur.Phys.J.C50:353-362,2007 1fb -1 4.6fb -1 ~~ ~~ CMS AN-2007/049

12. 24/09/2008 - BSM CP3Loïc Quertenmont - loic.quertenmont@cern.ch12 CMS : Offline Analysis Luminosity needed for Discovery with STA Tracker Luminosity needed for Exclusion With STA Tracker CMS AN-2007/049

13. 24/09/2008 - BSM CP3Loïc Quertenmont - loic.quertenmont@cern.ch13 Conclusions  HSCPs could be one of the first discovery of the LHC.  Distinctive signatures  High cross sections  Relatively simple experimental challenges  mGMSB stau and low mass R-Hadron can be discovered with a few hundred pb -1.  1fb -1 could be enough for gluino masses above 1TeV and for KK tau.  CMS are refining experimental techniques and analysis strategies.  Muon triggers, dEdX related techniques, Time Of Flight techniques  Not everything covered in this talk  e.g : Use of calorimeter to detect Stopped HSCP.

14. Backup Slides

15. 24/09/2008 - BSM CP3Loïc Quertenmont - loic.quertenmont@cern.ch15 Production : pp->t 1 t 1