Search for $B^0_s-\overline{B^0_s}$ oscillations and a measurement of $B^0_d-\overline{B^0_d}$ oscillations using events with an inclusively reconstructed vertex

Abstract.

Neutral B meson oscillations in the $B^0_s-\overline{B^0_s}$ and $B^0_d-\overline{B^0_d}$ systems were studied using a sample of about 4.0 million hadronic Z decays recorded by the DELPHI detector between 1992 and 2000. Events with a high transverse momentum lepton were removed and a sample of 770 k events with an inclusively reconstructed vertex was selected. The mass difference between the two physical states in the$B^0_d-\overline{B^0_d}$ system was measured to be:

\Delta m_d = (0.531 \pm 0.025 (stat.) \pm 0.007 (syst.)) \rm ps^{-1}.

The following limit on the width difference of these states was also obtained:

\vert\Delta\Gamma_{B_d}\vert / \Gamma_{B_d} < 0.18\ \ at \ \ 95\%\ \ CL.

As no evidence for $B^0_s-\overline{B^0_s}$ oscillations was found, a limit on the mass difference of the two physical states was given:

\Delta m_s > 5.0 \: \rm ps^{-1} \ \ at \ \ 95\%\ \ CL.

The corresponding sensitivity of this analysis is equal to 6.6 ps^-1.