1. What prospects for Supersymmetry at the Large Hadron Collider ? A brief introduction to the techniques with which ATLAS and CMS intend to constrain Supersymmetry Christopher.Lester @ cern.ch

2. July 2001 HEP2001 : SUSY at the LHC : Christopher.Lester@cern.ch 2 LHC & Supersymmetry zWhat can the LHC provide if SUSY exists? yDISCOVERY ? ………………………………. YES! Excellent prospects Might even be “easy” ! Largely model-independent yPRECISE MEASUREMENTS ? …….... Plenty! but more likely to be model-dependent

3. July 2001 HEP2001 : SUSY at the LHC : Christopher.Lester@cern.ch 3 What do we want to know? zM.S.S.M. ySquark masses(12) yThe gluino mass(1) ySlepton masses(9) yNeutralino masses(4) yChargino masses(2) yMixing matrices(?) yPhases(?) y…..(plenty) Other models: z RP-Violating M.S.S.M. yRPV couplings(45) z mSUGRA model ym 0, m 1/2, A 0, tan β, sgn μ(5) z A.M.S.B. model ym 0, m 3/2, tan β, sgn μ(4) z G.M.S.B. model yλ, M mes, N 5, tan β, sgn μ, C grav (6) There is no shortage of parameters which need to be determined!

4. July 2001 HEP2001 : SUSY at the LHC : Christopher.Lester@cern.ch 4 Which can we measure? zThe kinds of measurements which can be made, very much depend on the SUSY model which nature has chosen! zIt is important to understand the physical effects of R-Parity conservation (or non- conservation) in SUSY models, before discussing measurements. “Lots, but it depends…”

5. July 2001 HEP2001 : SUSY at the LHC : Christopher.Lester@cern.ch 5 zTwo main SUSY scenarios: (RPV/RPC) yRP-Conserving yRP-Violating R-Parity: Conservation/Violation (L.S.P. = “lightest SUSY particle”) zR=+1 for Standard Model particles zR= -1 for SUSY particles

6. July 2001 HEP2001 : SUSY at the LHC : Christopher.Lester@cern.ch 6 R-Parity C onservation RPC yL.S.P. stable and weakly interacting, and so “goes missing” Missing energy signature Usually incomplete event reconstruction Need to rely on long decay chains and kinematic variables (endpoints and distributions) ySparticles are only produced in pairs double the trouble! L.S.P. = lightest SUSY particle

7. July 2001 HEP2001 : SUSY at the LHC : Christopher.Lester@cern.ch 7 events Signal Squark/gluon mass scale RPC Peak of M eff distribution correlates well with squark/gluon mass scale for mSUGRA and GMSB models. S.M. Background

8. SUGRA Reach (CMS) RPC

9. July 2001 HEP2001 : SUSY at the LHC : Christopher.Lester@cern.ch 9 Kinematic edges: l + l - edge RPC  The l + l - invariant mass from the decay chain (right) has a kinematic endpoint. zFor 100 fb -1, edge measured at 109.10±0.13 (stat) GeV zDominant systematic error on lepton energy scale also ~0.1% zIn progress: incorporation of widths, decay matrix elements, polarisations, photon radiation, etc

10. July 2001 HEP2001 : SUSY at the LHC : Christopher.Lester@cern.ch 10 Coverage of l + l - edge RPC However... … different processes can produce the same final state. zCan the process be identified? Detailed study of the shape of the m ll distribution can provide clues zLikely coverage? Lepton edge observable over significant region of m 0, m 1/2 parameter space (CMS plot left) zLikely outcome? yPrecise sparticle mass differences yWhen chains are long enough, resolution on absolute mass scale improves and can measure mass of L.S.P.

11. July 2001 HEP2001 : SUSY at the LHC : Christopher.Lester@cern.ch 11 R-Parity Violation RPV zRP-Violating: yL.S.P. decays into leptons or jets: If L.S.P. lifetime is short: åMulti-jet or multi-lepton signature åNo missing energy, so reconstruct full event If L.S.P. lifetime is long: looks like RPC scenario ySparticles may be produced singly L.S.P. = lightest SUSY particle

12. July 2001 HEP2001 : SUSY at the LHC : Christopher.Lester@cern.ch 12 Lepton number violating RPV zλ’ ijk couples a slepton to two quarks zCan have resonant sneutrino production zCross section can place lower bound on λ’ ijk zExpect to observe (within 3 years) either y900 GeV neutrino if λ’ 211 >0.05 y350 GeV neutrino if λ’ 211 >0.01 y(present limit: ) λ’ ijk =0.09 Reconstructed neutralino mass peak in m jjμ invariant mass distribution

13. July 2001 HEP2001 : SUSY at the LHC : Christopher.Lester@cern.ch 13 Baryon number violating RPV zEach L.S.P. decays to three quarks (u,d,s) forming three jets (jjj) zRequire 2 leptons and at least 8 jets: (j+jjj)+(j+ll+jjj) zLook for L.S.P. / chargino peak in m jjj / m jjjll plane m squark L = 638 ± 5±12 GeV m neutralino 2 = 212 ± 0.3± 4 GeV m slepton R = 155 ± 3± 3 GeV m neutralino 1 = 117 ± 3± 3 GeV

14. July 2001 HEP2001 : SUSY at the LHC : Christopher.Lester@cern.ch 14 Conclusions zWe can expect ATLAS and CMS to yObserve squarks and gluons below 2.5 TeV and observe sleptons below 300 GeV in inclus ive measurements. yAccurately measure squark, slepton and neutralino masses using cascade decays (provided chains are sufficiently long and rates are favourable) zSuccess is expected in both RPV and RPC scenarios zPrecise measurements: many can be made in principle, but which of them can measured in practice will depend strongly on the model which nature has chosen Other areas of completed and ongoing research which there was not time to discuss: yN.L.S.P. lifetime in G.M.S.B. models y(Non-pointing photons / slow heavy leptons) yA.M.S.B. models yLepton flavour violation (via slepton mixing) yMeasuring the gaugino mixing matrix yDirect slepton production yNon-minimal models ySUSY Higgs sector yEverything else which I have forgotten to mention... CMS

15. July 2001 HEP2001 : SUSY at the LHC : Christopher.Lester@cern.ch 15 z R=+1 for Standard Model particles z R= -1 for SUSY particles R-Parity: conservation/violation zTwo main SUSY scenarios: RPV/RPC yRP-Conserving: yRP-Violating:

16. July 2001 HEP2001 : SUSY at the LHC : Christopher.Lester@cern.ch 16 R-Parity: conservation/violation L.S.P. = lightest SUSY particle