F.Cerutti, M.Fanti, P.Giacomelli, P.Kluit, R.McNeil, C.Rembser, U.Schwickerath

Introduction :

Limits on the masses of Heavy Stable Charged Particles have been obtained by combining the results from the Aleph, Delphi, L3 and Opal experiments at LEP from 130 to 208 GeV.

In this combination it is assumed that the particles are stable or sufficiently long lived to cross the detectors without decay. The results obtained here occur as limiting case within the GMSB (for smuons and staus) and the low delta M scenario (for charginos).

Data used for combination :

Combined results for s-leptons :

The results of the experiments from 130 to 208 GeV have been combined, using a likelihood ratio method, to obtain a combined limit at 208 GeV.

ADLO Combined results, 133-208GeV	Zoom of intersection region

Combined results for stable charginos :

The results of the experiments from 130 to 208 GeV have been combined, using a likelihood ratio method, to obtain a combined limit at 208 GeV.

ADLO Combined results, 133-208GeV	Zoom of intersection region

The figure shows a scan over the MSSM parameter space. The cross section for chargino pair production is marked at each scan point by a dot. Blue dots indicate parameter combinations for which the sneutrino mass is above 500GeV, for green points it is below 500GeV but above 41GeV. The cross sections are calculated at a centre-of-mass energy of 208 GeV, using SUSYGEN. The yellow region indicates the experimentally excluded cross section region at 95% confidence level, combining all available data of the four LEP experiments, between 133 and 208 GeV.

The excluded mass ranges for different sneutrino masses are:

	Msneu > 500GeV	41GeV > Msneu > 500GeV
Combined	45-102.5 GeV/c2	45-101.2 GeV/c2

The histogram which gives the excluded cross section for stable sleptons has a dip in the exclusion around a mass of 60 GeV. The same dip can be seen in the combination for long lived sleptons within the GMSB, see there. The 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 particles. Possible candidates would appear in the region indicated by the orange boxes on the left plot. In the region in between the boxes, new heavy particles can not be separated from SM particles. 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 once enter the "separation regions".