Search for scalar quarks in $e^{+} e^{-}$ collisions at $\sqrt{s}$ up to 209-GeV

Search for Scalar Quarks in e+e- Collisions at sqrt(s) up to 209 GeV Searches for scalar top, scalar bottom and mass-degenerate scalar quarks are performed in the data collected by the ALEPH detector at LEP, at centre-of-mass energies up to 209 GeV, corresponding to an integrated luminosity of 675 pb-1. No evidence for the production of such particles is found in the decay channels stop->c/u chi, stop->b l snu, sbottom-> b chi, squark-> q chi or in the stop four-body decay channel stop-> b chi f f' studied for the first time at LEP. The results of these searches yield improved mass lower limits. In particular, an absolute lower limit of 63GeV/c2 is obtained for the stop mass, at 95% confidence level, irrespective of stop lifetime and decay branching ratios.