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##### Searches for Physics Beyond the Standard Model at LEP

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**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**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**Not so far….**SM results and predictions DIS2003 A.Tilquin**Higgs is needed by SM**Higgs mass constraint DIS2003 A.Tilquin**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**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**ALEPH**DELPHI L3 OPAL LEP data set Per experiments: LEP1: L175 pb-1 LEP2: L700 pb-1 Energies: 90209 GeV DIS2003 A.Tilquin**~** ~ ~ 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**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**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**e+**,Z* e+ e- e- Slepton searches 2 acoplanar leptons + missing energy Main background from WWll DIS2003 A.Tilquin**Squark missing angle**Squark an gluino qL and qR are mixingq1,q2 e+ ,Z* e- To compare with Tevatron,LEP results are translated into an exclusion limit in gluino an squark masses DIS2003 A.Tilquin**e+**,Z* e- W(*) Z(*) Chargino and neutralino Production at LEP: Decay: DIS2003 A.Tilquin**Neutralino**Chargino, neutralino slepton and Higgs results are combined. LSP mass limit obtained at high tan() DIS2003 A.Tilquin**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**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 hbb or could be suppressed w.r.t hcc or gg • Searches for hadronic decay without b tagging. DIS2003 A.Tilquin**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**For =SM and B(hInv.)=100%**Mh>114.4 GeV/c2 Invisible Higgs • Predicted in different models: • In MSSM: • h00 • Majoron • hJJ • Cross section can be different from standard model. • Search for acoplanar jets and leptons from Z decay DIS2003 A.Tilquin****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**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**l,q**W ,q e+ t b e- Anomalous top quark coupling SM10-9fb Single top production at LEP (FCNC) R-parity violation kZ ,kg Delphi DIS2003 A.Tilquin**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**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**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**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**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 choosingMDEWNo 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**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**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