Scalar quark searches in e+e− collisions at s=181−184 GeV

Abstract Searches for scalar top, scalar bottom and degenerate scalar quarks have been performed with data collected with the ALEPH detector at LEP. The data sample consists of 57 pb −1 taken at s = 181–184 GeV. No evidence for scalar top, scalar bottom or degenerate scalar quarks was found in the channels t → c χ , t → b l ν , b → b χ , and q → q χ . From the channel t → c χ a limit of 74 GeV /c 2 has been set on the scalar top quark mass, independent of the mixing angle. This limit assumes a mass difference between the t and the χ in the range 10–40 GeV /c 2 . From the channel t → b l ν the mixing-angle-independent scalar top limit is 82 GeV /c 2 , assuming m t −m ν > 10 GeV /c 2 . From the channel b → b χ , a limit of 79 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 for m b −m χ > 10 GeV /c 2 . From the channel q → q χ , a limit of 87 GeV /c 2 has been set on the mass of supersymmetric partners of light quarks assuming five degenerate flavours and the production of both “left-handed” and “right-handed” squarks. This limit is valid for m q −m χ > 5 GeV /c 2 .