Search for scalar quarks in e+e- collisions at sqrt(s) up to 209GeV

TL;DR

This paper reports a search for scalar quarks in electron-positron collisions at energies up to 209 GeV, finding no evidence but setting new lower mass limits, notably 63 GeV/c2 for the stop.

Contribution

First LEP search for scalar top, bottom, and degenerate scalar quarks across multiple decay channels, establishing improved mass lower bounds.

Findings

No evidence for scalar quark production.

Set lower mass limit of 63 GeV/c2 for the stop.

Improved constraints on scalar quark masses.

Abstract

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.