Study of ${\mathrm B^0_s}$-$\overline{\mathrm B^0_s}$ oscillations and ${\mathrm B^0_s}$ lifetimes using hadronic decays of ${\mathrm B^0_s}$ mesons

The DELPHI Collaboration:     P. Abreu - et al.

doi:doi:10.1007/s100520000531

2022 Impact factor 4.4

Particles and Fields

Eur. Phys. J. C 18, 229-252
DOI 10.1007/s100520000531

Study of B⁰_s- $\overline{\mathrm B^0_s}$ oscillations and B⁰_s lifetimes
using hadronic decays of B⁰_s mesons

The DELPHI Collaboration

P.Abreu²² - et al.

²² LIP, IST, FCUL - Av. Elias Garcia, 14-1^o, 1000 Lisboa Codex, Portugal

Received: 5 July 2000 / Revised version: 25 September 2000 /
Published online: 8 December 2000 - © Springer-Verlag 2000

Abstract
Oscillations of $\mbox{B}^0_{\mathrm{s}}$ mesons have been studied in samples selected from about 3.5 million hadronic Z decays detected by DELPHI between 1992 and 1995. One analysis uses events in the exclusive decay channels: $\mathrm{B^0_s} \rightarrow \rm {D}_{s}^{-} \pi^{+}$ or $\rm {D}_{s}^{-}\mathrm{a_1^+}$ and $\mathrm{B^0_s} \rightarrow \overline{\mathrm{D}}^0\mathrm{K}^- \pi^+$ or $\overline{\mathrm{D}}^0\mathrm{K}^-\mathrm{a_1^+}$ , where the D decays are completely reconstructed. In addition, $\mbox{B}^0_{\mathrm{s}}-\overline{\mbox{B}^0_{\mathrm{s}}}$ oscillations have been studied in events with an exclusively reconstructed D_s accompanied in the same hemisphere by a high momentum hadron of opposite charge. Combining the two analyses, a limit on the mass difference between the physical $\mbox{B}^0_{\mathrm{s}}$ states has been obtained:

$\begin{eqnarray*}\begin{array}{c} \Delta m_{\mathrm{B^0_s}} > 4.0~\mbox{ps}^{-1... ...$ }~\Delta m_{\mathrm{B^0_s}} = 3.2~\mbox{ps}^{-1}. \end{array} \end{eqnarray*}$

Using the latter sample of events, the B⁰_s lifetime has been measured and an upper limit on the decay width difference between the two physical B⁰_s states has been obtained:

$\begin{displaymath}\tau_{\mathrm{B^0_s}} = 1.53^{+0.16}_{-0.15}(\rm {stat}.)\pm{0.07}(\rm {syst}.)~\mathrm{ps} \end{displaymath}$

$\begin{displaymath}\Delta \Gamma_{\mathrm{B^0_s}}/\Gamma_{\mathrm{B^0_s}} < 0.69~\mbox{at the 95\% C.L.} \end{displaymath}$

The combination of these results with those obtained using ${\rm {D}_{s}^{\pm}} \ell^{\mp}$ sample gives:

$\begin{eqnarray*}\begin{array}{c} \Delta m_{\mathrm{B^0_s}} > 4.9~\mbox{ps}^{-1... ...$ }~\Delta m_{\mathrm{B^0_s}} = 8.7~\mbox{ps}^{-1}. \end{array} \end{eqnarray*}$

$\begin{displaymath}\tau_{\mathrm{B^0_s}} = 1.46\pm{0.11}~\mathrm{ps}\quad \mbox... ...^0_s}}/\Gamma_{\mathrm{B^0_s}} < 0.45~\mbox{at the 95\% C.L.} \end{displaymath}$