A search for sleptons using the DELPHI detector at LEP2

Data collected by the DELPHI detector at centre-of-mass energies between 192 and 209 GeV were used to search for the supersymmetric partners of the leptons. Under the R-parity conserving Minimal Supersymmetric Standard Model, sleptons (l-tilde) can be pair produced at e+e- colliders such as LEP. The slepton will predominantly decay to a lepton of the same flavour and the lightest neutralino (x-tilde10). The x-tilde10 is only weakly interacting and will escape undetected. The search topology for slepton production were therefore two acoplanar leptons of the same flavour and missing energy. A conservative assumption was made that only right handed sleptons can be pair produced at LEP. Candidate selection routines were used to reduce the data sample to events consistent with the slepton signal topology. The number of data candidates was found to be in agreement with Standard Model expectations for each of the three slepton channels. In the absence of a signal, limits were placed on the mass of the sleptons. At low mx-tilde10, me-tilder > 98 GeV/c2, mμ-tilder > 83 GeV/c2 and mτ-tilder > 74 GeV/c2. Slepton masses below these limits were excluded to a 95% Confidence Level. These mass limits were calculated using tan β = 1.5, μ = -200 GeV/c2 and A0 = 0 as input values. The stability of the slepton mass limits under different values for the MSSM input parameters was investigated. The mass limits were found to be representative of a large range of MSSM input parameter values. The work for this thesis has been presented by the author and others on behalf of the DELPHI collaboration and has provided the basis for DELPHI publications on these supersymmetric channels. The search results presented in this thesis are also consistent with the scalar lepton searches from the other LEP experiments. (author)