What prospects for Supersymmetry at the Large Hadron Collider ?

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

3. M.S.S.M. Squark masses (12) The gluino mass (1) Slepton masses (9) Neutralino masses (4) Chargino masses (2) Mixing matrices (?) Phases (?) ….. (plenty) Other models: RP-Violating M.S.S.M. RPV couplings (45) mSUGRA model m0, m1/2, A0, tan β, sgn μ (5) A.M.S.B. model m0, m3/2, tan β, sgn μ (4) G.M.S.B. model λ, Mmes, N5, tan β, sgn μ, Cgrav (6) What do we want to know? There is no shortage of parameters which need to be determined! HEP2001 : SUSY at the LHC : Christopher.Lester@cern.ch

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

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

6. R-Parity Conservation RPC L.S.P. = lightest SUSY particle • L.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) • Sparticles are only produced in pairs • double the trouble! HEP2001 : SUSY at the LHC : Christopher.Lester@cern.ch

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

8. SUGRA Reach (CMS) RPC

9. Kinematic edges: l+l-edge RPC • The l+l- invariant mass from the decay chain (right) has akinematic endpoint. • For 100 fb-1, edge measured at 109.10±0.13(stat) GeV • Dominant systematic error on lepton energy scale also ~0.1% • In progress: • incorporation of widths, • decay matrix elements, • polarisations, • photon radiation, etc 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. • Can the process be identified? • Detailed study of the shape of the mll distributioncan provide clues • Likely coverage? • Lepton edge observable over significant region of m0, m1/2 parameter space (CMS plot left) • Likely outcome? • Precise sparticle mass differences • When chains are long enough, resolution on absolute mass scale improves and can measure mass of L.S.P. HEP2001 : SUSY at the LHC : Christopher.Lester@cern.ch

11. R-Parity Violation RPV L.S.P. = lightest SUSY particle • RP-Violating: • L.S.P. decays into leptons or jets: • If L.S.P. lifetime is short: • Multi-jet or multi-lepton signature • No missing energy, so reconstruct full event • If L.S.P. lifetime is long: looks like RPC scenario • Sparticles may be produced singly HEP2001 : SUSY at the LHC : Christopher.Lester@cern.ch

12. Lepton number violating RPV • λ’ijk couples a slepton to two quarks • Can have resonant sneutrino production • Cross section can place lower bound on λ’ijk • Expect to observe (within 3 years) either • 900 GeV neutrino if λ’211>0.05 • 350 GeV neutrino if λ’211>0.01 • (present limit: ) Reconstructed neutralino mass peak in mjjμ invariant mass distribution λ’ijk =0.09 HEP2001 : SUSY at the LHC : Christopher.Lester@cern.ch

13. Baryon number violating RPV • Each L.S.P. decays to three quarks (u,d,s) forming three jets (jjj) • Require 2 leptons and at least 8 jets: (j+jjj)+(j+ll+jjj) • Look for L.S.P. / chargino peak in mjjj / m jjjll plane msquark L = 638 ± 5 ±12 GeV mneutralino 2 = 212 ± 0.3 ± 4 GeV mslepton R = 155 ± 3 ± 3 GeV mneutralino 1 = 117 ± 3 ± 3 GeV HEP2001 : SUSY at the LHC : Christopher.Lester@cern.ch

14. We can expect ATLAS and CMS to Observe squarks and gluons below 2.5 TeV andobserve sleptons below 300 GeV in inclusive measurements. Accurately measure squark, slepton and neutralino masses using cascade decays (provided chains are sufficiently long and rates are favourable) Success is expected in both RPV and RPC scenarios Precise 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: N.L.S.P. lifetime in G.M.S.B. models (Non-pointing photons / slow heavy leptons) A.M.S.B. models Lepton flavour violation (via slepton mixing) Measuring the gaugino mixing matrix Direct slepton production Non-minimal models SUSY Higgs sector Everything else which I have forgotten to mention ... CMS Conclusions HEP2001 : SUSY at the LHC : Christopher.Lester@cern.ch

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

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