Isospin asymmetries in B→(K∗,ρ)γ/l+l− and B→Kl+l− in and beyond the standard model
Isospin asymmetries in B→(K∗,ρ)γ/l+l− and B→Kl+l− in and beyond the standard model
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DOI：
10.1103/physrevd.88.094004
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发表时间：
2013-05
影响因子：
5
通讯作者：
J. Lyon;R. Zwicky
中科院分区：
文献类型：
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作者：
J. Lyon;R. Zwicky
在一般的六维算符基下，计算了标准模型（SM）内和标准模型（BSM）外低轻子对不变质量q ^2 $下$B \to（K^*，\rho）\gamma$和$B\to（K，K^*，\rho）l^+l^-$中的同位旋不对称性.在SM中，CP平均的同位旋不对称性对于B \to（K，K^*，\rho）ll$，在1 {\rm GeV}^2 \leq q^2 \leq 4m_c^2$之间，预测是小的（低于1.5%），尽管有显著的抵消。在SM中，$B至\rho ll$的非CP平均不对称性与CP平均不对称性的偏差约为5%。我们提供了物理参数，共振的基础上，为什么同位旋不对称性必须减少大$q^2$（向端点）。计算了两种类型的同位旋破坏效应：由于耦合到上夸克和下夸克的算子之间的差异而导致的紫外（UV）同位旋破坏，以及从旁观者夸克发射光子并因此与上夸克和下夸克电荷之间的差异成比例的红外（IR）同位旋破坏。这些同位旋破坏过程可以细分为弱湮灭（WA）、夸克圈旁观者散射（QLSS）和色磁贡献。此外，我们讨论了通用的选择规则的基础上的宇称和角动量的$B \到KLL$过渡，以及具体的选择规则有效的WA在领导秩序中的强耦合常数。我们澄清了K和K^* 的纵向部分之间的关系只适用于超前扭转和左手流。一般来说，$B \to \rho ll$和$B \to K^*ll$Isosin不对称性在结构上是不同的，但$\alpha_{\rm CKM}$与九十度的接近程度允许我们从各自的Isosin对称性中构建SM的（准）零测试。我们提供了对WA敏感的${\cal B}（B^0 \to K^{*0}\gamma）/{\cal B}（B_s \to \phi \gamma）$的更新。
We compute the isospin asymmetries in $B \to (K^*,\rho) \gamma$ and $B\to (K,K^*,\rho) l^+l^-$ for low lepton pair invariant mass $q^2$, within the Standard Model (SM) and beyond the SM (BSM) in a generic dimension six operator basis. Within the SM the CP-averaged isospin asymmetries for $B \to (K,K^*,\rho) ll$, between $1{\rm GeV}^2 \leq q^2 \leq 4m_c^2$, are predicted to be small (below 1.5%) though with significant cancellation. In the SM the non-CP averaged asymmetries for $B \to \rho ll$ deviate by $\approx \pm 5%$ from the CP-averaged ones. We provide physical arguments, based on resonances, of why isospin asymmetries have to decrease for large $q^2$ (towards the endpoint). Two types of isospin violating effects are computed: ultraviolet (UV) isospin violation due to differences between operators coupling to up and down quarks, and infrared (IR) isospin violation where a photon is emitted from the spectator quark and is hence proportional to the difference between the up- and down-quark charges. These isospin violating processes may be subdivided into weak annihilation (WA), quark loop spectator scattering (QLSS) and a chromomagnetic contribution. Furthermore we discuss generic selection rules based on parity and angular momentum for the $B \to Kll$ transition as well as specific selection rules valid for WA at leading order in the strong coupling constant. We clarify that the relation between the $K$ and the longitudinal part of the $K^*$ only holds for leading twist and for left-handed currents. In general the $B \to \rho ll$ and $B \to K^*ll$ isospin asymmetries are structurally different yet the closeness of $\alpha_{\rm CKM}$ to ninety degrees allows us to construct a (quasi) null test for the SM out of the respective isospin symmetries. We provide an update on ${\cal B}(B^0 \to K^{*0}\gamma)/{\cal B}(B_s \to \phi \gamma)$ which is sensitive to WA.