LEPSUSYWG/02-06.2

Interpretation of the results in Minimal SUGRA

The LEP-SUSY Working Group

The following results have been obtained from:

People involved:

References:


Method

The ISAJET package, version 7.51 has been used to get the minimal SUGRA solution at the scale MZ as a function of the parameters

The relevant masses, couplings, cross sections and branching ratios are calculated using MSMLIB. Radiative corrections to chargino and neutralino masses are included. The Higgs bosons masses and couplings are calculated using the improved Carena et al. treatment implemented in HZHA.

For a given (tan(beta),sign(mu)) choice, the following procedure has been followed:

For the points surviving these checks, expected confidence levels in the bayesian approach have been calculated for the processes The process with the lowest expected CL is then applied to test the point versus observation. The results of different experiments have been combined using the Likelyhood Ratio method.

RESULTS

Disclaimer
All the results given below are preliminary !
All the limits given below are at 95 % CL

Excluded regions in the (M0,M1/2) planes for fixed tan(beta), sign(Mu), A0


  Comments: increasing TanBeta the regions with no Minimal SUGRA solution enlarge and eventually close the
                           regions kinematically accessible to LEP; there is a sort of maximum TanBeta above which none
                           of the regions in the plane is within the kinematic reach of LEP, typically larger for positive Mu.
                          A better  quantitative estimate of the TanBeta range will be given for the final analysis.

Scanning over A0
The extension of LEP exclusions in the (m0,m1/2) planes is quite sensitive to the chosen value for A0; as an example the (m0,m1/2) plane for TanBeta=10, Mu<0 and A0 = -1 TeV/c2 is shown here:eps .
The impact of this strong dependence on the results of the interpretation has been studied by scanning, for fixed TanBeta, sign of Mu, m0 and m1/2, all the theoretically allowed range for A0. The extension of this range increase with m0 and m1/2; for the m1/2  values of interest for LEP, the typical A0 range is [-2 TeV/c2,2 TeV/c2]. These ranges have been scanned with a typical granularity of 20 GeV/c2.

Examples of domains excluded by any A0 are given here (Mtop = 175 GeV/c2):
 

  • TanBeta = 10 :
  • TanBeta = 30 :
    • The LEP coverage of the (m0,m1/2) planes is reduced mainly because large negative A0 values are allowed; this is shown in here: eps .
    This plot is made in the following way. For a given TanBeta, sign(Mu) and m0,  there is a maximum m1/2 value - m1/2(max) - excluded for all A0 considered; m1/2(max)+100 MeV/c2 is then excluded by all but one A0. This A0  is the value which enter in the plot.
    Lower limit on MLSP
    The lower limit on M1/2 translates into a lower limit on MLSP. The limit is always found at large m0 and has been calculated for m0=1 TeV/c2.

    As usual, the Higgs constraints cut out the small tan(beta) region, the effect being larger for mu<0. At large tan(beta) the limit is determined by the chargino sensitivity.

    MLSP vs tan(beta):

    This results are valid for m0<1 TeV/c2. The result obtained setting Mtop=180 GeV/c2 is also shown on the plot.

    Mass Lower Limits:
    Mu  A0  Mtop Mass Lower Limit 
    Positive 

     

    		 0 

    any 

    		 175 GeV/c2
    180 GeV/c2
    175 GeV/c2    		 59.0 GeV/c2
    53.9 GeV/c2
    50.8 GeV/c2
    Negative 

     

    		 0 

    any 

    		 175 GeV/c2
    180 GeV/c2
    175 GeV/c2    		 58.6 GeV/c2
    52.0 GeV/c2
    50.3 GeV/c2
     Edited by Gerardo Ganis November 25, 2002 -Gerardo.Ganis@cern.ch