Limit on B0 s oscillation using a jet charge method

A lower limit is set on the B-s(0) meson oscillation parameter Delta m(s) using data collected from 1991 to 1994 by the ALEPH detector. Events with a high transverse momentum lepton and a reconstructed secondary vertex are used. The high transverse momentum leptons are produced mainly by b hadron decays, and the sign of the lepton indicates the particle/antiparticle final state in decays of neutral B mesons. The initial state is determined by a jet charge technique using both sides of the event. A maximum likelihood method is used to set a lower limit of Delta m(s). The 95% confidence level lower limit on Delta m(s) ranges between 5.2 and 6.5(h/c(2)) ps(-1) when the fraction of b quarks from Z(0) decays that form. B-s(0) mesons is varied from 8% to 16%. Assuming that the B-s(0) fraction is 12%, the lower limit would be Delta m(s) > 6.1 (h/c(2)) ps(-1) at 95% confidence level. For x(s) = Delta m(s) tau B-s, this limit also gives x(s) > 8.8 using the B-s(0) lifetime of tau(Bs) = 1.55 +/- 0.11 ps and shifting the central value of tau(Bs) down by 1 sigma.