论文标题
解开Lepton风味通用和Lepton风味普遍性违反$ b \ to s \ ell^+\ ell^ - $ transitions
Disentangling Lepton Flavour Universal and Lepton Flavour Universality Violating Effects in $b\to s\ell^+\ell^-$ Transitions
论文作者
论文摘要
在这封信中，我们提出了一种策略，以辨别威尔逊系数中的新物理学$ {\ cal c} _ {9μ} $是主要的Lepton风味普遍性，或者是否包含Lepton Flavor Universal Component（$ {\ Cal C} _9^_9^{\ rm U} $）。区分这两种情况，相关场景的模型独立拟合也表现出相似的拉力W.R.T.标准模型对于促进我们对$ b $异常的理解至关重要。我们首先确定了这两种情况的退化的起源，并指出可以打破它的关键可观察物。特别是，虽然迄今为止测量的可观察结果表现出与所有相关的威尔逊系数相似的依赖性，但即将进行的测量$ q_5 = p_ = p_ {5}^{\primeμ} -p_p_ {5}^{5}^{\ prime e} $尤其敏感C} _ {9e} $。实际上，如果发现$ q_5 $很小（即接近其标准型号值），这将意味着一个小$ {\ cal c} _ {9μ} - {\ cal c} _ {9e} $，但要撰写的较大的preferation groutiation of a grountion groutiation $ {\ cal c} _ {9}} $ a { $ {\ cal c} _ {9μ} $。我们讨论$ {\ cal c} _9^{\ rm u} $的可能起源，特别是它如何源自新物理学。在这里，一个有希望的场景，甚至可以将$ b \链接到s \ ell^+\ ell^ - $ to $ r_ {d^{（*）}} $，是$ {\ cal c} _9^{\ cal c} _9^{\ rm u} $是从tau loop通过非shell phothell phothell phothell Photon Pengengram生成的。此设置预测$ b_s \toτ^+τ^ - $和$ b \ to K^{（*）}τ^+τ^ - $的分支比率在LHCB，CMS和Belle II的范围内。另外，如果不观察这些陶器过程，我们表明，生成$ {\ cal c} _9^{\ rm u} $的最自然可能性是$ z^\ prime $，具有部分Lepton Flavity Universal Autplings。
In this letter we propose a strategy for discerning if new physics in the Wilson coefficient ${\cal C}_{9μ}$ is dominantly lepton flavour universality violating or if it contains a sizable lepton flavour universal component (${\cal C}_9^{\rm U}$). Distinguishing among these two cases, for which the model independent fit of the related scenarios exhibits similar pulls w.r.t. the Standard Model, is crucial to advance our understanding of the $B$ anomalies. We first identify the origin of the degeneracy of these two cases and point out the key observables that can break it. In particular, while the observables measured so far that test lepton flavour universality exhibit similar dependencies to all the relevant Wilson coefficients, the forthcoming measurement of $Q_5=P_{5}^{\primeμ}-P_{5}^{\prime e}$ is particularly sensitive to ${\cal C}_{9μ}-{\cal C}_{9e}$. In fact, if $Q_5$ were found to be small (i.e. close to its Standard Model value), this would imply a small ${\cal C}_{9μ}-{\cal C}_{9e}$ but a sizable ${\cal C}_{9}^{\rm U}$, given the preference of global fits for a large negative new physics contribution in ${\cal C}_{9μ}$. We discuss the possible origins of ${\cal C}_9^{\rm U}$, in particular how it could originate from new physics. Here, a promising scenario, that could even link $b\to s \ell^+\ell^-$ to $R_{D^{(*)}}$, is the one in which ${\cal C}_9^{\rm U}$ is generated from a tau loop via an off-shell photon penguin diagram. This setup predicts the branching ratios of $B_s\toτ^+τ^-$ and $B\to K^{(*)}τ^+τ^-$ to lie within the reach of LHCb, CMS and Belle II. Alternatively, in case of a non-observation of these tauonic processes, we show that the most natural possibility to generate ${\cal C}_9^{\rm U}$ is a $Z^\prime$ with partially lepton flavour universal couplings.
