Bs0−B¯s0mixing parameters from unquenched lattice QCD

We determine hadronic matrix elements relevant for the mass and width differences, $\Delta M_s$ and $\Delta {\Gamma }_s$, in the $B_s^0-{\overline{B}}_s^0$ meson system using fully unquenched lattice QCD. We employ the MILC Collaboration gauge configurations that include $u$, $d$, and $s$ sea quarks using the improved staggered quark (AsqTad) action and a highly improved gluon action. We implement the valence $s$ quark also with the AsqTad action and use nonrelativistic QCD for the valence $b$ quark. For the nonperturbative QCD input into the standard model expression for $\Delta M_s$ we find $f_{B_s}\sqrt{{\widehat{B}}_{B_s}}=0.281(21)\mathrm{GeV}$. Results for four-fermion operator matrix elements entering standard model formulas for $\Delta {\Gamma }_s$ are also presented.