arXiv 2212.028972022-12-06hep-phhep-exhep-lat

研究$B_c$半轻子衰变

Investigating $B_c$ semileptonic decays

Francesco Loparco

备注：: 6 pages, 3 figures. Talk given at ICHEP 2022, Bologna 6-13/07/22

摘要：

我提出了半轻子$B_c$衰变的分析。本文首先讨论了在标准模型和由含左手中微子的$D = 6$半轻子$c \to s, d$算符的低能哈密顿量组成的扩展模型中，由$c \to \{s, d \}$跃迁引起的衰变，特别是由$a = \{s, d \}$和$\ell = \{ e, μ\}$引起的$B_c \to B_a \, \bar{\ell} \, ν_\ell$和$B_c \to B_a^*(\to B_a \, γ) \, \bar{\ell} \, ν_\ell$衰变。此外，我认为$b \to c$模式，特别侧重于确定的形状因子参数化的$B_c \to J/ψ,η_c$矩阵元素的运营商在一个广义的低能量$b \to c$半轻子哈密顿。在这种情况下，我考虑在非相对论性\qcd中的展开，以及在逆重夸克质量中的展开，这允许形状因子在选定的运动学范围内用普适函数表示。重夸克自旋对称性用于这两种分析。在第一种情况下，它允许相关的强子矩阵元素相关和$B_c$形状因子的晶格\qcd \结果被利用。选择优化的观测量，并研究它们之间的相关性，以确定各种运营商在扩展的低能哈密顿量的影响。在第二种方法中，使用标准模型运算符的$B_c \to J/ψ$矩阵元素的晶格\qcd \结果作为输入，可以获得有关其他形状因子的信息。外推到整个运动范围也提出。

英文摘要：

I present analyses of semileptonic $B_c$ decays. I first discuss the decays induced by $c \to \{s, d \}$ transitions, in particular $B_c \to B_a \, \bar{\ell} \, ν_\ell$ and $B_c \to B_a^*(\to B_a \, γ) \, \bar{\ell} \, ν_\ell$ decays, with $a = \{s, d \}$ and $\ell = \{ e, μ\}$, in the Standard Model and in the extension based on the low-energy Hamiltonian comprising the full set of $D = 6$ semileptonic $c \to s, d$ operators with left-handed neutrinos.\\ Moreover, I consider $b \to c$ modes, with particular focus on the determination of the form factors parametrizing the $B_c \to J/ψ,η_c$ matrix elements of the operators in a generalized low-energy $b \to c$ semileptonic Hamiltonian. In this case I consider an expansion in nonrelativistic \qcd\ together with an expansion in the inverse heavy-quark mass which allows the form factors to be expressed in terms of universal functions in a selected kinematical range.\\ The Heavy Quark Spin Symmetry is used for both analyses. In the first case, it allows the relevant hadronic matrix elements to be related and the lattice \qcd\ results on $B_c$ form factors to be exploited. Optimized observables are selected, and correlations among them is studied to identify the effects of the various operators in the extended low-energy Hamiltonian. In the second one, using as an input the lattice \qcd\ results for the $B_c \to J/ψ$ matrix element of the Standard Model operator, it is possible to obtain information on other form factors. The extrapolation to the full kinematical range is also presented.

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摘要：

英文摘要：

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