Abstract
Searches for stable, hadronizing scalar quarks and gluinos are performed using the data collected with the ALEPH detector at LEP. Gluon splitting into a gluino or a squark pair is searched for at centre-of-mass energies around the Z resonance, in the e(+)e(-) --> q (q) over bar(gg) over tilde and q (q) over bar(q) over tilde )over bar> processes. Stable squark pair production, and stop pair production with subsequent decays into a stable gluino, (t) over tilde --> c (g) over tilde, are also directly searched for at centre-of-mass energies from 183 to 209 GeV. Altogether, stable hadronizing stop (sbottom) quarks are excluded up to masses of 95 (92) GeV/c(2), and stable hadronizing gluinos are excluded up to 26.9 GeV/c(2), at 95% confidence level. In the framework of R-parity-conserving supersymmetric models in which the gluino and the stop quark are the two lightest supersymmetric particles, a 95% C.L. lower limit of 80 GeV/c(2) is set on the stop quark mass.
Highlights
IntroductionA search for squark production in e+e− collisions is relevant at LEP energies because the stop quark and, to a lesser extent, the sbottom quark, could well be the lightest supersymmetric partner of all standard model fermions [1]
A search for squark production in e+e− collisions is relevant at LEP energies because the stop quark and, to a lesser extent, the sbottom quark, could well be the lightest supersymmetric partner of all standard model fermions [1].Searches for squarks have already been performed by ALEPH [2, 3] in the framework of the MSSM, the minimal supersymmetric extension of the standard model [4], with Rparity conservation and the assumption that the lightest supersymmetric particle (LSP) is the lightest neutralino or the sneutrino
These numbers are in agreement with the numbers of events expected from standard model background sources
Summary
A search for squark production in e+e− collisions is relevant at LEP energies because the stop quark and, to a lesser extent, the sbottom quark, could well be the lightest supersymmetric partner of all standard model fermions [1]. Searches for squarks have already been performed by ALEPH [2, 3] in the framework of the MSSM, the minimal supersymmetric extension of the standard model [4], with Rparity conservation and the assumption that the lightest supersymmetric particle (LSP) is the lightest neutralino or the sneutrino These searches yielded an absolute lower limit on the stop mass of 63 GeV/c2 at the 95% confidence level. The relative resolution on the total visible energy is 0.60/ E (E in GeV) for high-multiplicity final states This algorithm provides a list of reconstructed objects, classified as charged particles, photons and neutral hadrons, called energy-flow particles in the following, and used to determine the event characteristics for the selections presented in this paper
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