Introduction :

The LEP experiments have searched for staus/smuons/selectrons in the data taken during year 2000 at centre-of-mass energies ranging from 204 GeV to 209 GeV. In the GMSB model, the gravitino is the LSP and the sleptons can be the NLSP. Their decay length is arbitrary and depends on the gravitino mass (proportional to the SUSY breaking scale). Hence the LEP experiments used various analyses to be sensitive to all ranges of slepton lifetime:

• search for leptons plus missing energy;
• search for tracks with large impact parameter;
• search for kinked tracks;
• search for heavy stable charged particles.

References to individual experiments:

•  ALEPH Collaboration:
• Search for gauge mediated SUSY breaking topologies in e^+ e^- collisions at centre-of-mass energies up to 209 GeV, hep-ex/0203024 ; CERN-EP-2002-021. Subm. to: Eur. Phys. J., C
• Single- and multi-photon production in e^+ e^- collisions at sqrt{s} up to 209 GeV, CERN-EP-2002-033 Subm. to: Eur. Phys. J., C
• DELPHI Collaboration:
• Update of the search for supersymmetric particles in light gravitino scenarious, DEPLPHI 2002-024-CONF-558, Summer conferences 2002
• L3 Collaboration, Search for Supersymmetry in e+ e- collisions at sqrt(s) = 202-208 GeV;
• OPAL Collaboration:
• Searches for Gauge-Mediated SUSY Breaking Topologies in e+e- Collisions at sqrt(s) = 189-209 GeV.

The OPAL Collaboration, 15th July 2002
Preliminary results obtained using the analyses documented in [1  , 2] using the full OPAL years 1999 and 2000 data with sqrt(s) =192-209 GeV; preliminary results using these data were previously reported in [3] , and are updated here using the final processing of the OPAL data.
• [1] Searches for Prompt Light Gravitino Signatures in e+e- Collisions at sqrt(s) = 189 GeV

The OPAL Collaboration, G. Abbiendi et al., 19th May 2000, CERN-EP-2000-078, Phys. Lett. B501 (2001) 12-27
• [2] Searches for Intermediate Lifetime Signatures in GMSB Models with a Slepton NLSP in e+e- Collisions at sqrt(s)=189-209 GeV.

The OPAL Collaboration, 6th July 2001
• [3] New Particle Searches in e+e- Collisions at sqrt(s) = 200-209 GeV''

The OPAL Collaboration, 23rd February 2001

• G.F.Giudice, R.Rattazzi: Theories with gauge mediated supersymmetry breaking Phys.Rept.322:419-499,1999, hep-ph/9801271;
• S.Dimopoulos, S.Thomas, J.D.Wells: Sparticle spectroscopy and electroweak symmetry breaking with gauge mediated supersymmetry breaking. Nucl.Phys.B488:39-91,1997, hep-ph/9609434;
• S.Ambrosanio, G.L.Kane, G.D.Kribs, S.P.Martin , S.Mrenna Search for supersymmetry with a light gravitino at the Fermilab Tevatron and CERN LEP colliders. Phys.Rev.D54:5395-5411,1996, hep-ph/9605398;

Analysis:

Cross sections and branching ratios have been calculated in the framework of the GMSB model (S.Dimopoulos, S.Thomas, J.D.Wells), performing a scan over the parameters

• Lambda (5,6,...150 TeV)
• tan beta(2,2.2,...,50)
• M (1.01*Lambda,250 TeV, 10E6 TeV)
• N (1,2,3,4,5)
• sign(mu) (+1,-1),

(You can click on the image to get the postscript file.)

Preliminary results:

stau1 (stau NLSP) ADLO, 189-209 GeV	smuonR (slepton NSLP) ADO, 189-209 GeV	selectronR (slepton NLSP) ADO, 189-209 GeV
number of obs./exp./signal events, sqrt(s)=189-209 GeV (1.-CLB), sqrt(s)=189-209 GeV (on logarithmic scale) excluded cross section times branching ratio squared, sqrt(s)=189-209 GeV excluded mass as a function of stau lifetime, sqrt(s)=189-209 GeV, expected limit and 1,2-sigma bands are shown excluded mass as a function of stau lifetime, sqrt(s)=189-209 GeV, expected limit and lines of equal beta*gamma*c*tau at sqrt(s)=208 GeV are shown to indicate the different lifetime regimes maximum excluded cross section x B.R.^2 + mass limit for all lifetimes, sqrt(s)=189-209 GeV	number of obs./exp./signal events, sqrt(s)=189-209 GeV (1.-CLB), sqrt(s)=189-209 GeV (on logarithmic scale) excluded cross section times branching ratio squared, sqrt(s)=189-209 GeV excluded mass as a function of smuon lifetime, sqrt(s)=189-209 GeV, expected limit and 1,2-sigma bands are shown excluded mass as a function of smuon lifetime, sqrt(s)=189-209 GeV, expected limit and lines of equal beta*gamma*c*tau at sqrt(s)=208 GeV are shown to indicate the different lifetime regimes maximum excluded cross section x B.R.^2 + mass limit for all lifetimes, sqrt(s)=189-209 GeV	number of obs./exp./signal events, sqrt(s)=189-209 GeV (1.-CLB), sqrt(s)=189-209 GeV (on logarithmic scale) excluded cross section times branching ratio squared, sqrt(s)=189-209 GeV excluded mass as a function of selectron lifetime, sqrt(s)=189-209 GeV (N=1,2,3,4,5), expected limit and 1,2-sigma bands are shown excluded mass as a function of selectron lifetime, sqrt(s)=189-209 GeV (N=1,2,3,4,5), expected limit and lines of equal beta*gamma*c*tau at sqrt(s)=208 GeV are shown to indicate the different lifetime regimes maximum excluded cross section x B.R.^2 + mass limit for all lifetimes (N=1,2,3,4,5), sqrt(s)=189-209 GeV
limit staus (all lifetimes) for all N m(stau) > 86.9 GeV at 95%C.L.	limit smuons (all lifetimes) for all N m(smu) > 96.3 GeV at 95%C.L.	limit selectrons (all lifetimes) (N=1,2,3,4,5), m(sel) > 65.8 GeV at 95%C.L.

 

The left plot shows an example of the excluded /\-tan(beta) region for a fixed set of parameters (N=2, M=250TeV and mu>0) combining the slepton results (yellow) with the results of the LEP acoplanar photon search (blue). For this particular scenario, assuming a short lifetime of the NLSP, values of /\ less than 35.5 TeV can be excluded for tan(beta) = 15. On the plot, the black region indicates the LEP1 search region, grey regions are not excluded (here the light grey indicates the region which can not be reached with LEP2 energies). The parameters were chosen to compare the LEP results to prospects of the TEVATRON run 2 (right plot).

(You can click on the image to get the postscript file.)

Search for long lived / stable charged particles:

In case for the search for long lived particles with a lifetime greater/equal 10E-6 s, slepton masses less than 97.5 GeV can be excluded at 95% C.L.. This limit corresponds to the long lifetime results of the stau and smuon GMSB searches, see above.
If the slepton is stable, then the large impact parameter and kinked track search do not contribute to the analysis. Results of the search for stabkle particles are given on a separate page.
 

Search for long lived charged particles, tau greater/equal 10E-6 s ADLO, sqrt(s)=189-209 GeV	Search for STABLE heavy charged particles ADLO, sqrt(s)=189-209 GeV
excluded cross section and mass for a slepton, lifetime > 10E-6s, sqrt(s)=189-209 GeV	results of the search for STABLE heavy charged particles are given on a seperate page.
M > 97.5 GeV at 95% C.L.

The histogram which gives the excluded cross section for long lived sleptons has a dip in the exclusion around the mass of 60 GeV. Reason for this dip is a reduced efficiency of the experiments which use as their main search tool an analysis of the specific ionisation energy loss in the tracking chambers to separate heavy charged particles from Standard Model (SM) particles. Possible candidates would appear in the region indicated by the green boxes on the left plot, the example of a particle with a mass of 45 GeV is given by the dark green line. In the region in between the boxes, new heavy particles can not be separated from SM particles. Examples of SM particles are given by the blue lines. But as LEP2 was running at various beam energies (which means that the momentum of a pair produced new particle with a certain mass varied, too), new heavy charged particles at all masses at least once should appear in the "separation regions". The two additional dips in the excluded cross section for particles with a lifetime of tau=10E-6s are caused by two ALEPH candidates in the large impact parameter search at 189 GeV and 198 GeV. These candidates contribute to the long lifetime region as for particles with a mass close to the beam energy, their beta*gamma (=p/e * e/m = p/m = sqrt(E**2 - m**2)/m, with E = half of the beam energy) gets very small, hence the decay can still occure inside the detector.