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Gaugino searches and SUSY constraints

Gaugino searches and SUSY constraints. Paolo Azzurri CERN. On behalf of :. Aachen, July 18, 2003 EPS HEP 2003 - International Europhysics Conference on high energy physics. R-parity conserved MSSM. Minimal Supersymmetric extension of the Standard Model

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Gaugino searches and SUSY constraints

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  1. Gaugino searches andSUSY constraints Paolo Azzurri CERN On behalf of : Aachen, July 18, 2003 EPS HEP 2003- International Europhysics Conference on high energy physics

  2. R-parity conserved MSSM • Minimal Supersymmetric extension of the Standard Model • R-parity conserves lepton and baryon numbers. ⇨Stable and weakly interacting LSP (WIMP) ★ The lightest neutralino is assumed to be the LSP ☼Candidate for non-baryonic Cold Dark Matter (CDM) P.Azzurri - Gaugino searches and SUSY contraints

  3. Gaugino and sfermion mass relations: Mixing in the first two sfermion families constrained by smallness of FCNC and CP violation . The third family is less constrained: MSSM parameters • GUT universality of gauginos and sfermions reduces the number of fundamental MSSM parameters (C-MSSM) P.Azzurri - Gaugino searches and SUSY contraints

  4. The plane scenario Higgsino region lower mass limits for particles with large and stable Z couplings Mixed region No limit on masses asthey can have very small Z couplings Gaugino region Impact of LEP1 data Precision measurements of Z width P.Azzurri - Gaugino searches and SUSY contraints

  5. _ + + MSSM exclusions (quoted at 95% CL) But… No signal found Susy signal searches at LEP2 P.Azzurri - Gaugino searches and SUSY contraints

  6. heavy sfermions (W* decay) light sfermions Chargino pair searches 4jets, 2jets+1lepton, 2leptons + Missing Energy P.Azzurri - Gaugino searches and SUSY contraints

  7. No forward activity transverse missing energy in the detector ET(miss)=21 GeV Chargino pair candidate ΔM=26-30 GeV/c2 ECM=196 GeV M(miss)=148 GeV/c2 M(hadr)=16 GeV/c2 P(μ)=8.5 GeV/c SM: WW*→τνqq P.Azzurri - Gaugino searches and SUSY contraints

  8. excluded production cross-section (down to a fraction of pb) excluded chargino masses in C-MSSM near the kinematic production threshold small ΔM large ΔM Chargino pair results with heavy sfermions (W* decays) combined ADLO results: P.Azzurri - Gaugino searches and SUSY contraints

  9. GUT unification: small ΔM in the higgsino region (|µ| << M2) M1 and M2 degenerate: small ΔM in the gaugino region (|µ| << M2) Low ΔM chargino searches The standard searches cover the region ΔM>3GeV/c2 Searches for soft events with an ISR photon cover0.2<ΔM<3GeV /c2 Searches for events with tracks displaying kinks, impact parameter offsets, heavy stable charged particles coverΔM< 200MeV /c2 P.Azzurri - Gaugino searches and SUSY contraints

  10. excluded production cross-sections to a fraction of pb Multi-jets and missing energy Multi-jets + photon and missing energy Neutralino pair searches Acoplanar jets Acoplanar leptons P.Azzurri - Gaugino searches and SUSY contraints

  11. The LSP limit grows as (s)/4 Lower LSP mass limit (with heavy sfermions) 95% CL exclusions from gaugino pair productions close to the kinematic limit The lowest not-excluded neutralino-LSP masses are found in the mixed region at tan=1 and μ<0 P.Azzurri - Gaugino searches and SUSY contraints

  12. Both the cross sections and sensitivity increase. For example in the case of dominant leptonic decays as + Need to identify the new decay topologies taking into account different BR Need to include the sensitivity of direct searches of sfermion pair productions ! Inclusion of slepton signal exclusions under the assumption of scalar mass unification What changes with light sfermions Chargino pair cross sections decrease and new decay channels are opened (cascade or invisible decays as for the “corridor” where is dominant). _ P.Azzurri - Gaugino searches and SUSY contraints

  13. The limit derived in the case of heavy sfermions remains similar for light sfermions under mass unification assumptions Lower LSP mass limit (with light sfermions) Combined exclusions from LEP1 data (1) charginos(2) neutralinos(3) sleptons(4) the (μ,M2,tanβ) space is covered in a similar way for low m0 values as in the case of heavy sfermions P.Azzurri - Gaugino searches and SUSY contraints

  14. LSP limit in higgsino region The LSP mass limit with Higgs constraints moves at higher tan regions LSP limit in gaugino region LSP limit in mixed region Impact of Higgs searches mh<mZ |cos2β| + radiative corrections from top and stop: P.Azzurri - Gaugino searches and SUSY contraints

  15. Impact of mixing on MSSM exclusions (DELPHI) Previous limits with no-mixing scenario : Stau mixing leads to chargino blind spots when Search for SUSY signals from : P.Azzurri - Gaugino searches and SUSY contraints

  16. gaugino region mixed region without higgs constrants Impact of stau mixing on MSSM exclusions (ALEPH) More general approach: Stau mixing decoupled from other families. Study the effects vs mixing angle P.Azzurri - Gaugino searches and SUSY contraints

  17. Invisible charginos corridor in the gaugino region. Small χ+ M sensitivity is covered with special searches (ISR tags, stable) Other lower mass limits From the same scan of the C-MSSM parameter space lower mass limits on other SUSY particles can be obtained P.Azzurri - Gaugino searches and SUSY contraints

  18. Even with the standard assumptions the precision is not better than 1 GeV • Higher order corrections to the GUT relation • M1=f(M2) are of the order of~3%. • Radiative correction to to gaugino masses • decrease the limit of 1-2 GeV. J.Ellis, T.Falk, G.Ganis, K.Olive, M.Schmitt Robustness of the neutralino-LSP limits • The unification relation M1/ M2≃1/2 is driving the final result. • If M1/ M2<1/2 the LSP limits deteriorate. • If M1/ M2≫1 (AMSB) we can find very low not-excluded LSP masses • (E.g. small chargino M in gaugino and mixed regions) • Sfermion mass unification is important in the case of light sfermions. P.Azzurri - Gaugino searches and SUSY contraints

  19. (LEP-208 GeV) Scan of the plane: Regions excluded by: 1. Theory 2. Z width () 3. Charginos 4. Selectrons/Staus 5. Higgs 6. Stable heavy charged Exclusions in minimal SuperGravity (mSUGRA) • Dynamic EWSB : • GUT unification of scalar and Higgs sector: • GUT unification of trilinear couplings: P.Azzurri - Gaugino searches and SUSY contraints

  20. Lower LSP mass limit in mSUGRA (LEP-208 GeV) 7. Neutralino stau cascades P.Azzurri - Gaugino searches and SUSY contraints

  21. ~ ~ • In the same framework m(χ+)>90 GeV/c2 , m(eR)>90 GeV/c2,m(ν)>90 GeV/c2 Conclusions • If sfermions are heavy, direct gaugino searches yield a mass limit for the neutralino LSP: m(χ0)>38-39 GeV/c2 at tan=1 (mixed region) • Same limit with universal light sfermions using selectron searches. • The absence of MSSM signals at LEP2 translate into strong constraints on the domains of the model parameters and on the gaugino masses • higgs searches exclude low tan m(χ0)>45 GeV/c2 (gaugino). • The exclusions are robust for stau mixing effects • With full mSUGRA constraints m(χ0)>50-60 GeV/c2 (gaugino -mixed). P.Azzurri - Gaugino searches and SUSY contraints

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