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We calculate the bag parameters for neutral $B$-meson mixing in and beyond the Standard Model, in full four-flavour lattice QCD for the first time. We work on gluon field configurations that include the effect of $u$, $d$, $s$ and $c$ sea quarks with the Highly Improved Staggered Quark (HISQ) action at three values of the lattice spacing and with three $u/d$ quark masses going down to the physical value. The valence $b$ quarks use the improved NRQCD action and the valence light quarks, the HISQ action. Our analysis was blinded. Our results for the bag parameters for all five operators are the most accurate to date. For the Standard Model operator between $B_s$ and $B_d$ mesons we find: $hat{B}_{B_s}=1.232(53)$, $hat{B}_{B_d}=1.222(61)$. Combining our results with lattice QCD calculations of the decay constants using HISQ quarks from the Fermilab/MILC collaboration and with experimental values for $B_s$ and $B_d$ oscillation frequencies allows determination of the CKM elements $V_{ts}$ and $V_{td}$. We find $V_{ts} = 0.04189(93)$, $V_{td} = 0.00867(23)$ and $V_{ts}/V_{td} = 0.2071(27)$. Our results agree well (within $2sigma$) with values determined from CKM unitarity constraints based on tree-level processes (only). Using a ratio to $Delta M$ in which CKM elements cancel in the Standard Model, we determine the branching fractions ${text{Br}}(B_srightarrow mu^+mu^-) = 3.81(18) times 10^{-9}$ and ${text{Br}}(B_drightarrow mu^+mu^-) = 1.031(54) times 10^{-10}$. We also give results for matrix elements of the operators $R_0$, $R_1$ and $tilde{R}_1$ that contribute to neutral $B$-meson width differences.
We study $B_d$ and $B_s$ mixing in unquenched lattice QCD employing the MILC collaboration gauge configurations that include u, d, and s sea quarks based on the improved staggered quark (AsqTad) action and a highly improved gluon action. We implement
We present the first lattice QCD calculation of the $B_s$ and $B_d$ mixing parameters with physical light quark masses. We use MILC gluon field configurations that include $u$, $d$, $s$ and $c$ sea quarks at 3 values of the lattice spacing and with 3
We report on the status of our calculation of the hadronic matrix elements for neutral $B$-meson mixing with asqtad sea and valence light quarks and using the Wilson clover action with the Fermilab interpretation for the $b$ quark. We calculate the m
We extend the picture of $B$-meson decay constants obtained in lattice QCD beyond those of the $B$, $B_s$ and $B_c$ to give the first full lattice QCD results for the $B^*$, $B^*_s$ and $B^*_c$. We use improved NonRelativistic QCD for the valence $b$
We present an update of the Fermilab-MILC Collaborations calculation of hadronic matrix elements for B^0-bar{B^0} mixing. This work is a more extended analysis than our recent publication of the SU(3)-breaking ratio xi [arXiv:1205.7013]. We use the a