Searches for scalar top and scalar bottom quarks at LEP2

Searches for scalar top and bottom quarks have been performed with data collected by the ALEPH detector at LEP. The data sample consists of 21.7 pb(-1) taken at root s = 161, 170, and 172 GeV and 5.7 pb(-1) taken at root s = 130 and 136 GeV. No evidence for scalar top quarks or scalar bottom quarks was found in the channels (t) over tilde --> c chi, (t) over tilde --> bl<(nu)over tilde>, and (b) over tilde --> b chi. For the channel (t) over tilde --> c chi a limit of 67 GeV/c(2) has been set on the scalar top quark mass, independent of the mixing angle between the supersymmetric partners of the left and right-handed states of the top quark. This limit assumes a mass difference between the (t) over tilde and the chi of at least 10 GeV/c(2). For the channel (t) over tilde --> bl<(nu)over tilde> the mixing-angle independent scalar top limit is 70 GeV/c(2), assuming a mass difference between the (t) over tilde and the <(nu)over tilde> of at least 10 GeV/c(2). For the channel (b) over tilde --> b chi, a limit of 73 GeV/c(2) has been set on the mass of the supersymmetric partner of the left-handed state of the bottom quark. This limit is valid if the mass difference between the (b) over tilde and the chi is at least 10 GeV/c(2). (C) 1997 Elsevier Science B.V. RI ANTONELLI, ANTONELLA/C-6238-2011; Jones, Roger/H-5578-2011; Passalacqua, Luca/F-5127-2011; Murtas, Fabrizio/B-5729-2012; O'Shea, Val/G-1279-2010; St.Denis, Richard/C-8997-2012; Sanchez, Federico/F-5809-2012; Ferrante, Isidoro/F-1017-2012