Discovery of Long-Lived Sleptons

@The LHC

Bryan SmithWest Coast Theory NetworkUniversity of California, Irvine

4th May 2007

Work with Jonathan Feng, Arvind Rajaraman, and Mario Bondioli

Meta-Stable Charged Particles are Generic

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Meta-stable Charged Particles Not Heavily Studied

Discounted because of cosmology, SuperWIMPs evade constraintMeta-Stable Particles have long lifetimes

Decay to super weakly interacting particle (ie. Gravitino, Axino,…)

Offers spectacular signals at collidersCharged 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 muonsNo Hadronic InteractionCharged TracksExit Detector

Long Lived Sleptons look different than muonsDifferent IonizationDifferent Velocity for given momentum

Background is from muon mismeasurementsTime Delay resolutionIonization

Cross Section w/ Time Delay Cuts

For S > 10 S/sqrt(B) > 5Model A Model B

Discovery

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

Drell-Yan Angular DistributionScalar or Fermion?

Model A Model B Number of Events Needed 22 27 Luminosity Estimate 1.5 fb-1 7.6fb-1

We can go back to the center of mass

For R = 104

Discovery: A Comparison

Baer et alhep-ph/9503271

10 fb-1 Missing EnergyDiscovery Contour

Conclusions?

Sleptons can be discovered in first physics runSearches require computer time for reconstructionPriority over missing energy searches?

Estimates suggest spin can be determined after first runestimates are naïve (hopeful for model A)more detailed analysis needs to be doneusing angular distributions from cascades viable optionbeing more clever?

Many Experimental Concerns for serious PhenomenologyCan 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 datarequires computer timesomeone 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 distancesome ATLAS notes talk about measuring momentum b ~ 0.6ATLAS collaborators suggest slow moving = random momentum measurementtrigger different than momentum measurementHow different is this from muon momentum resolution?

Can the experiment measure what you want?

IonizationMuons and Sleptons have different ionization

ATLAS measures high/low threshold hitMuon can have transition radiationCan we distinguish between the two if both give the similar high/low distribution?

-: p=100GeV/c~- p=100GeV/c

m=200GeV/c2

Plots thanks to Mario

Conclusions IIResults 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 getHow 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 builtIs 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 CutsRequire two charged tracks leaving the muon system

reduction of single SM muon backgroundcan use invariant mass to reduce Z di-muon background

Require that both tracks have a rapidity less than 2.4necessary 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 backgroundseparates from R-hadrons

Both Particles must have momentum greater than 100GeVmuons 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 GeVCascade Only: 4 energetic objects with transverse energy greater than 70 GeV