Search for Neutralinos and Sfermions

A search for the production of neutralinos has been conducted with the data collected by the DELPHI experiment during the high energy run in 1995 at centre-of-mass energies of 130 and 136 $\GeV$, and in 1996 at 161 and 172 $\GeV$ . The integrated luminosity for each energy is given in Tab. 2.

Table 2: The table shows the collected integrated luminosity so far, for each energy during the LEP 1.5 and LEP 2 periods.

Year	1995		1996
Energy ($\GeV$)	130	136	161	172
$\int{Ldt}$ (pb-1)	2.92	3.01	9.70	10.0

The results from these searches have been reported in Publication II ( $\sqrt{s}=130-136~\GeV$) and in Publication III ( $\sqrt{s}=161-172~\GeV$).

In Publication II, the search for neutralinos is presented together with a search for sleptons and the supersymmetric partners of the top and bottom quarks. In the search for scalar fermions the same analysis as for the corresponding neutralino channel was used, with the inclusion of a dedicated analysis for the $\tilde{b}$ case.

In Publication III a search for neutralinos and charginos is presented, this also include the light gravitino scenario, that received a great interest after the report from the CDF collaboration of an event consisting of a pair of electrons, two energetic photons and missing transverse energy [22]. Following this there was an increased interest in certain models with the possibility for the lightest neutralino to decay into a light gravitino and a photon [23], and models with an enhancement of the radiative decay mode of $\XN {2}$ [24].