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Search for MSSM Particles at LEP and Interpretations by Giacomo Sguazzoni at CERN

Explore primary signal searches for MSSM particles at LEP, with focus on acoplanar leptons and jets, multi-body events, and interpretations like CMSSM and mSUGRA. Discover mass limits, topological variables, and extending horizons in particle physics.

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Search for MSSM Particles at LEP and Interpretations by Giacomo Sguazzoni at CERN

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  1. Search for MSSM Particles at LEP and Interpretations Giacomo Sguazzoni CERN –EP Division on behalf of LEP collaborations

  2. Wish list • Primary signal searches • Acoplanar leptons (sleptons) • Acoplanar jets (squarks) • Multi-body + missing energy • ... • Interpretations • CMSSM • mSUGRA • LEP vs. the future • Tevatron • LHC G.Sguazzoni

  3. Disclaimer • MSSM • R parity conservation • Pair production • LSP stable • (cosmology  neutral and weakly interacting) • …will show LEP SUSY Working Group (preliminary!!! ) combination when available! • …all limits @ 95% Conf. level Time-saving phenomenology intro™ ALEPH DELPHI L3 OPAL G.Sguazzoni

  4. LEP2 Data sample 1999 1998 2000 • Good for searches: • High energy • up to ~209GeV • High luminosity • s200GeV • 10pb-1 @ s208GeV ECM (GeV) 161+172 183 189 192-202 204-209 tot Int.Lumi (pb-1) 25 63 200 254 233 775 1996 1997 /experiment G.Sguazzoni

  5. Acoplanar e, m, t • Missing energy/momentum • Lepton/Tau ID c c c c t • Searching for: • sleptons t c c G.Sguazzoni

  6. …limits stauR s<40-60fb Tau ID M>85.9 GeV/c2 smuonR s<10-30fb M>94.2 GeV/c2 selectronR s<10-30fb Higher expected s M>99.6 GeV/c2 ELEP=183-208GeV Mass Limits DM>10GeV/c2 G.Sguazzoni

  7. Topological variables • E, P / / Acoplanar jets • Searching for: • squarks • b-tagging • +leptons jet c Pmiss jet New! stop 4body decay c • Multi-jets G.Sguazzoni

  8. q=56o q=68o q=56o q=56o Squark limits • similar sensitivity for any decay channel!!! Mc Mc Mc(GeV/c2) MSNEU MSBOT<Mc+mb MSTOP<MSNEU+mb MSTOP<Mc+mb MSTOP<Mc+mc q=0o q=0o q=0o D0 q=0o CDF CDF LEP1 NEW! ADLO ADLO ADLO ALEPH MSTOP MSTOP MSBOT MSTOP(GeV/c2) MSBOT>92GeV/c2 >95GeV/c2 >77GeV/c2 MSTOP>94GeV/c2 DM>10GeV/c2, any q G.Sguazzoni

  9. Stable hadrons • absolute stop mass lower limit • 63 GeV/c2 • (any q, BR, lifetime) MSTOP-MLSP<5GeVlifetime!!!! l~LDET kink/IP l~LDET dE/dx PLB 488 (2000) 234 G.Sguazzoni

  10. / / • gg with E, P Topologies with g(g) c1 s<10-30fb c1 g g • Single g g • Search for • ci>1c1radiative decays • very powerful for not-MSSM scenarios c1 c1 s<40-100fb G.Sguazzoni

  11. Topological variables • E, P • multi-body / / 2/4 fermions+(EMISS,PMISS) • searches for: • charginos • neutralinos G.Sguazzoni

  12. …example of s limits • high m0 (heavy sleptons) s100-300fb s100-200fb OPAL Preliminary OPAL Preliminary G.Sguazzoni

  13. ...extending the horizon • …other sparticles mass limits • Phenomenology: • new topologies • loop-holes? cMSSM mSUGRA • LSP (not directly observable!) mass limits  SUSY grinder reasonable model warranty …all results are grinder-dependent!!! G.Sguazzoni

  14. C-MSSM • M1=5/3tan2qWM2~0.5M2 • m0 for sfermions • no mixing • tanb, m Playing with CMSSM m0= 500GeV/c2 tanb=2 • small m0: •smaller s(c+c-) •light sleptons!!! 109 kin. limit M(c)[GeV/c2] 103 97 91 cicj 102 103 m0=75GeV/c2 tanb=2 M2 c+c- sleptons LEP1 M2 [GeV/c2] M2 [GeV/c2] m [GeV/c2] m [GeV/c2] small m0 large m0 G.Sguazzoni

  15. (m,M2)Mass limits M(c)=100GeV/c2 • MGAUGINOS(m,M2) •  mass limits M(c)=40GeV/c2 m m0>500GeV/c2 M(c)[GeV/c2] any m0 39.4GeV/c2 93.9GeV/c2 tanb tanb lightest neutralino (LSP) lightest chargino G.Sguazzoni

  16. The MSSM Higgs role m0=75GeV/c2 tanb=2 • MSSM Higgs limit small M2 exclusionsmall tanb exclusion ADLO Higgs m0<1TeV/c2 MTOP=175GeV/c2 Higgs charginos (large m0) M2 [GeV/c2] Higgs m [GeV/c2] in the corridor sleptons • Radiative corrections on the higgs mass!! MLSP>45.6GeV/c2 1 2 5 10 tanb G.Sguazzoni

  17. 3rd family mixing M(c)[GeV/c2] • Stau mixing • chargino “holes” • Robusteness checks: • mixing in sbottom, stop and stau sector (At=At=Ab=0) • only stau mixing any m0 INVISIBLE! mixing tanb tanb=35 m=-1000GeV/c2 M(c)[GeV/c2] charginos selectrons hole driven selections G.Sguazzoni

  18. ...absolute selectron mass limit • selectrons/charginos • search for to cover small vs.c DM Higgs c1c3 + hole-driven selections chargino 2B-3B corridor invisible! G.Sguazzoni

  19. ADLO preliminary mSUGRA m1/2 [GeV/c2] A0=0, MTOP=175GeV/c2 • mSUGRA • m1/2 • m0 • A0 • tanb • sign(m) • more constrained model • complementary benchmark!!! • M(c)53-60GeV/c2 (A0=0) • A0 scan!!! • ~10GeV/c2 weaker limits higgs m1/2 [GeV/c2] m1/2 [GeV/c2] tanb=10 m<0 tanb=40 m<0 Theory excluded Heavy Stable Staus neutralino-stau cascade m1/2 [GeV/c2] A0=0 A0=0 sleptons any A0 charginos m0[GeV/c2] LEP1 m0[GeV/c2] m0[GeV/c2] G.Sguazzoni

  20. SUSY paper? • Nice SUSY paper, will be ready for the WC* • read it! …in your relaxed moments. *Winter Conferences G.Sguazzoni

  21. Heavy Stable Staus Neutralino-stau cascade higgs Fermilab Theory excluded LEP1 The LEP legacy mSUGRA benchmark • M(SPARTICLES)  abouts/2 • high energy/luminosity • DM0 • clean environment!!! m1/2 [GeV/c2] charginos m0[GeV/c2] G.Sguazzoni

  22. Semileptonic c candidate • (26<DM<31 GeV/c2) • ECM=195.6, run #50140, evt #18802 • E(tot)=45.5GeV, M(tot)=35.8GeV/c2 • E12=0 (no small angle activity) • M(miss)=147.6GeV/c2 • P(miss)=28.1GeV/c, PT(miss)=20.7GeV/c Conclusion • SUSY search @ LEP • hunting for events not compatible with SM!!! • not trivial experimental task • MC simulation/detector effects/unusual topologies P(m)=8.52GeV/c M(hadr)=16.0GeV/c2 G.Sguazzoni

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