Discovery of Long-Lived The LHC Bryan Smith West Coast Theory Network University of California, Irvine 4 th May 2007 Work with Jonathan Feng, Arvind Rajaraman, and Mario Bondioli

Meta-Stable Charged Particles are Generic Feng & Moroi Cembranos, Feng, and Strigari Feng,Rajaraman, BTS  lsp

Meta-stable Charged Particles Not Heavily Studied Discounted because of cosmology, SuperWIMPs evade constraint Meta-Stable Particles have long lifetimes Decay to super weakly interacting particle (ie. Gravitino, Axino,…) Offers spectacular signals at colliders Charged tracks leaving detector (life times are long) Easy to see (Will show you just how easy)

mSugra Example Models 18 pb Cross Section 43 fb Cross Section Model B Model A

How to Discover Long lived Sleptons look like heavy muons No Hadronic Interaction Charged Tracks Exit Detector Long Lived Sleptons look different than muons Different Ionization Different Velocity for given momentum Background is from muon mismeasurements Time Delay resolution Ionization

Cross Section w/ Time Delay Cuts For S > 10 S/sqrt(B) > 5 Model A Model B

Discovery LHC first physics run is expected to have 1-4 fb -1 luminosity

Drell-Yan Angular Distribution Scalar or Fermion? Model AModel B Number of Events Needed Luminosity Estimate 1.5 fb fb -1 We can go back to the center of mass For R = 10 4

Discovery: A Comparison Baer et al hep-ph/ fb -1 Missing Energy Discovery Contour

Conclusions? Sleptons can be discovered in first physics run Searches require computer time for reconstruction Priority over missing energy searches? Estimates suggest spin can be determined after first run estimates are naïve (hopeful for model A) more detailed analysis needs to be done using angular distributions from cascades viable option being more clever? Many Experimental Concerns for serious Phenomenology Can the experiment measure what you want?

Can the experiment measure what you want? Time Delay Time Delay is not measured in event (At ATLAS…CMS?) reconstructed from event data requires computer time someone has to find the data to reconstruct (can you reconstruct all?) Is Time Delay resolution 1ns? Better? Worse? Atlas notes estimate resolution is better, but not clear on the process Conversation with ATLAS collaborators suggest resolution better Still not clear where time delay comes from

Can the experiment measure what you want? Momentum Measurement Momentum measurement at ATLAS designed for  ~ 1 track reconstruction error? Slow moving = longer drift time = longer distance some ATLAS notes talk about measuring momentum b ~ 0.6 ATLAS collaborators suggest slow moving = random momentum measurement trigger different than momentum measurement How different is this from muon momentum resolution?

Can the experiment measure what you want? Ionization Muons and Sleptons have different ionization ATLAS measures high/low threshold hit Muon can have transition radiation Can we distinguish between the two if both give the similar high/low distribution?  - : p=100GeV/c ~  - p=100GeV/c m=200GeV/c 2 Plots thanks to Mario

Conclusions II Results depend on momentum and time delay measurements Can these observable be measured accurately? Our Discover results can change drastically based on real measurements What we want vs. what we get How are non-standard models seen in detector? Detector was not designed for slow moving muons (not interesting?) Was the detectors designed to see your observables? How adaptable are the detectors? Detector is built Is there information measured but not recorded? Can we change/add information written to tape? Which schemes work best for your model?

Example Model And SM Background

Drell-Yan and Cascade Cuts Require two charged tracks leaving the muon system reduction of single SM muon background can use invariant mass to reduce Z di-muon background Require that both tracks have a rapidity less than 2.4 necessary for triggering the detector with sleptons Require both tracks are isolated (less than 10 GeV in a cone with R < 0.2) reduces top and QCD background separates from R-hadrons Both Particles must have momentum greater than 100GeV muons will exhibit transition radiation in TRT (not used) sleptons will have this minimum momentum from trigger requirements Drell-Yan: Invariant Mass must be larger than 120 GeV Cascade Only: 4 energetic objects with transverse energy greater than 70 GeV