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北美退伍军人节(Veterans Day),12 日无更新
arXiv 2007.06957hep-lathep-ph
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格点量子色动力学的全$q^2$范围的$B_c \rightarrow J/ψ$形状因子

$B_c \rightarrow J/ψ$ Form Factors for the full $q^2$ range from Lattice QCD

Judd Harrison, Christine T. H. Davies, Andrew Lytle

摘要:

我们首次用格点量子色动力学确定了$B_c \rightarrow J/ψ$矢量和轴矢量形状因子。这将使$B_c$半轻子衰变到$J/ψ$的速率的实验信息能够转换为$V_{cb}$的值。我们的计算涵盖了整个物理$q^2$范围内的衰变,并使用非微扰重整化晶格电流。我们对第二代MILC胶子场系综中的所有价夸克都采用了高度改进的交错夸克(HISQ)作用量,包括$u$、$d$、$s$和$c$ HISQ海夸克。我们的HISQ重夸克的质量在$c$以上,我们能够在最精细的晶格上达到$b$的质量。这使我们能够绘制出重夸克质量的依赖关系,并确定在$b$连续极限的结果。我们使用我们的形状因子来构造$B_c^- \rightarrow J/ψμ^- \barν_μ$的微分速率,并获得具有$7\%$不确定性的总速率:$Γ(B_c^-\rightarrow J/ψμ^-\barν_μ)/|η_{\mathrm{EW}}V_{cb}|^2 = 1.73(12)\times 10^{13} ~\mathrm{s}^{-1}$。包括$V_{cb}$、$η_{\mathrm{EW}}$和$τ_{B_c}$的值,得到该衰变模式的分支分数为0.0150(11)(10)(3)~,分别具有来自格点量子色动力学、$η_\mathrm{EW}V_{cb}$和$τ_{B_c}$的不确定性。

英文摘要:

We present the first lattice QCD determination of the $B_c \rightarrow J/ψ$ vector and axial-vector form factors. These will enable experimental information on the rate for $B_c$ semileptonic decays to $J/ψ$ to be converted into a value for $V_{cb}$. Our calculation covers the full physical $q^2$ range of the decay and uses non-perturbatively renormalised lattice currents. We use the Highly Improved Staggered Quark (HISQ) action for all valence quarks on the second generation MILC ensembles of gluon field configurations including $u$, $d$, $s$ and $c$ HISQ sea quarks. Our HISQ heavy quarks have masses ranging upwards from that of $c$; we are able to reach that of the $b$ on our finest lattices. This enables us to map out the dependence on heavy quark mass and determine results in the continuum limit at the $b$. We use our form factors to construct the differential rates for $B_c^- \rightarrow J/ψμ^- \barν_μ$ and obtain a total rate with $7\%$ uncertainty: $Γ(B_c^-\rightarrow J/ψμ^-\barν_μ)/|η_{\mathrm{EW}}V_{cb}|^2 = 1.73(12)\times 10^{13} ~\mathrm{s}^{-1}$. Including values for $V_{cb}$, $η_{\mathrm{EW}}$ and $τ_{B_c}$ yields a branching fraction for this decay mode of 0.0150(11)(10)(3) ~with uncertainties from lattice QCD, $η_\mathrm{EW}V_{cb}$ and $τ_{B_c}$ respectively.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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