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Searches for Physics Beyond the Standard Model at LEP
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  1. Searches for Physics Beyond the Standard Model at LEP Andre Tilquin CPPM Marseille • What is the Standard Model • Why to go beyond and how • Supersymmetry • Higgs sector • Exotica • Summary DIS2003 A.Tilquin

  2. Is it working ? One principle Gauge symmetry or local invariance ,Z0,W,g Exact symetry Yukawa m=0 Broken with a Higgs SU(2) doublet One observable H0 What is Standard Model Three families Three groups DIS2003 A.Tilquin

  3. Not so far…. SM results and predictions DIS2003 A.Tilquin

  4. Higgs is needed by SM Higgs mass constraint DIS2003 A.Tilquin

  5. Why to go beyond ? The NuTeV measurement: -ratio of neutral current to charged current reactions in neutrino-nucleon scattering. -When interpreted as a measurement of the mass of the W boson, a 2.9 standard deviations, from the other direct constraints is found. Why not ? DIS2003 A.Tilquin

  6. How to go beyond SM • New symmetries: • -Super Symmetry • -New Gauge bosons • News Higgs fields: Doublets/triplets • New fermions • Anomalous coupling, contact interaction • Compositeness • More exotica: • Technicolor • Extra dimensions DIS2003 A.Tilquin

  7. ALEPH DELPHI L3 OPAL LEP data set Per experiments: LEP1: L175 pb-1 LEP2: L700 pb-1 Energies: 90209 GeV DIS2003 A.Tilquin

  8. ~  ~ ~ h,H ~ Z In exact SUSY no new parameters } ~ H± ~ 01-4 ~ W± } ~ g ~ ~ lL,R ±1,2 = ~ L ~ q L,R ~ G SUSY should be broken The word of SUSY • Additional symmetry between bosons and fermions • Associates a SUSY partner to each SM particle New multiplicative quantum number:  h,H,A Z0 Rp=1 for SM particle Rp=-1 for SUSY particle H± W± g Conserve lL,R L LSP stable Pair production G q L,R DIS2003 A.Tilquin

  9. Breaking down SUSY • Its mechanism is unknown: Many models • SUGRA (Super Gravity) • LSP=neutralino • GMSB (Gauge mediated Super symmetry breaking) • LSP=gravitino • AMSB (Anomaly Mediated Super Symmetry breaking) • LSP=wino-like Standard MSSM DIS2003 A.Tilquin

  10. All final states characterised by missing energy Standard MSSM • Supergravity inspired minimal models with R parity • Heavy gravitino and gluino • Stable, neutral and weakly interacting LSP 10 • Low energy parameters: •  Higgs mixing mass term tan() v.e.v mA CP odd higgs mass m1/2 Common gaugino masse at GUT scale m0 Common sfermion mass at GUT scale A0 Common trilinear mass at GUT scale (mixing) Production at LEP: DIS2003 A.Tilquin

  11. e+ ,Z* e+ e- e- Slepton searches 2 acoplanar leptons + missing energy Main background from WWll DIS2003 A.Tilquin

  12. Squark missing angle Squark an gluino qL and qR are mixingq1,q2 e+ ,Z* e- To compare with Tevatron,LEP results are translated into an exclusion limit in gluino an squark masses DIS2003 A.Tilquin

  13. e+ ,Z* e- W(*) Z(*) Chargino and neutralino Production at LEP: Decay: DIS2003 A.Tilquin

  14. Neutralino Chargino, neutralino slepton and Higgs results are combined. LSP mass limit obtained at high tan() DIS2003 A.Tilquin

  15. e+ Observed limit in the mhmax scenario: mh>91.0 GeV (94.6) mA>91.9 GeV (95.0) ,Z* e- e+ ,Z* e- MSSM Higgs • Two Higgs doublets: • 5 physical states: • h,H,A and H • Two free parameters at tree level: mA,tan=v2/v1 • Searches by combining two complementary processes Dominant at low tan() Dominant at high tan() DIS2003 A.Tilquin

  16. Observed limit for: =SM Br(h hadrons) = 100% mh>112.9 GeV/c2 Flavor independent Higgs search • Some extension of standard model: • Two Higgs doublet (type II models), the mixing angle in the CP-even Higgs sector is a free parameters • standard decay hbb or  could be suppressed w.r.t hcc or gg • Searches for hadronic decay without b tagging. DIS2003 A.Tilquin

  17. e+ ,Z* e- mH>78.6 GeV/c2 Charged Higgs Predicted by 2 HDM models. Decays:H/cs B(H) free parameter Main background WW DIS2003 A.Tilquin

  18. For =SM and B(hInv.)=100% Mh>114.4 GeV/c2 Invisible Higgs • Predicted in different models: • In MSSM: • h00 • Majoron • hJJ • Cross section can be different from standard model. • Search for acoplanar jets and leptons from Z decay DIS2003 A.Tilquin

  19. Fermiophobic: mh>109.7 GeV/c2 h W(*)  Fermiophobic Higgs:h • In some models: • Type I 2HDM • No couplings to fermions. Coupling to photons through W loop: • Anomalous couplings DIS2003 A.Tilquin

  20. OPAL: mH>98.5 GeV/c2 Double charged Higgs Predicted by LR super symmetric model (Higgs triplet): Decay in two charged leptons, mainly in tau’s. Yukawa coupling to lepton is free parameter. h>10-7 : look for 4 ’s close to interaction point h<10-7 : search for kick of charged tracks h<10-8 : search for anomalous ionisation DIS2003 A.Tilquin

  21. l,q W ,q e+ t b e- Anomalous top quark coupling SM10-9fb Single top production at LEP (FCNC) R-parity violation kZ ,kg Delphi DIS2003 A.Tilquin

  22. f/ ,Z,W,g  e+ e* e-  Excited fermions In composite models, fermion & boson are composite with and associated energy scale . gauge group weights factor Lot of decay channel at LEP: From differencial x-section DIS2003 A.Tilquin

  23. e+ ,Z LQ LQ e- I3 OPAL Preliminary OPAL e+ LQ e- Lepto-quark • Very similar to excited leptons: • New color triplets bosonic fields mediating interaction between quark and leptons (LQ) DIS2003 A.Tilquin

  24. L+(N) e+ ,Z e- L-(N) l,L(stable)/l+ L±/N f W* Heavy Leptons • One way to explain the  mass in the see-saw mechanism • New heavy leptons with DIS2003 A.Tilquin

  25. e+ e+ e- e- Technicolor Alternative mechanism of Electro-weak Symmetry Breaking: • Breaking of global chiral symmetry of technifermions generates Golstone boson used for longitudinal polarisation of massive W and Z bosons. • Techniquark condensate replace non zero VEV of Higgs field • Need a large number of technidoublets (ND=9) • Vector states r0T, w0T p+T p-T or g p0T • Technipions couple to quarks and leptons µmass DIS2003 A.Tilquin

  26. Number of ED Planck mass Planck mass in ED Radius of extra dimensions Extra dimensions • Trying to solve the hierarchy problem: • Weakness of Gravity at electroweak scale • Our word confined to four dimensions • Gravity propagates in extra dimensions (ADD) By choosingMDEWNo hierarchy problem Small but large number of states (GKK) 1/MPl f,V d=1 R=1013 m Excluded d=2 R=1 mm d=3 R=1 nm …. d=7 R=1 fm Max in M-theory G f,V DIS2003 A.Tilquin

  27. For n=2 MD>1.36 TeV Extra dimensions (cont) Direct search: missing energy LEP average: MS>1.2 TeV (=+1) MS>1.09TeV (=-1) Indirect: look for deviation from (d/d)SM DIS2003 A.Tilquin

  28. Conclusions Lot of searches performed by the 4 LEP experiments SUSY: No evidence at LEP and CMSSM fully covered Chargino: m>94 GeV Neutralino: m>45 GeV Sparticles:m>100 GeV Higgs sector: No evidence of non standard Higgs mHiggs 100 GeV/c2 Exotica: New particles: m>100 GeV/c2 New scales > 1 TeV New coupling < 10% SM couplings No deviation from standard model, and no evidence of new physics. Hope that something will happened at LHC DIS2003 A.Tilquin