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利用B_s -> phi gamma中的宽度差

Exploiting the width difference in B_s -> phi gamma

Franz Muheim, Yuehong Xie, Roman Zwicky

备注：
13 pages, 2 figures
发表信息：
Phys.Lett.B664:174-179,2008
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摘要：

B → V γ中的光子极化是右手电流的灵敏探针。在B_s -> phi_gamma随时间变化的衰减率中，sin（Delta m_s t）和sinh（Delta Gamma_s /2 t）项前的系数S和H对这些右手电流敏感。与B_d系统相比，B_s介子的宽度有很大的差别，这导致了额外的可测H。我们用蒙特卡罗模拟表明，在LHCb实验中，当Delta Gamma_s/Gamma_s = 0.15，数据样本为2 fb^{-1}时，S和H的预期分辨率约为0.15。我们还指出，可以从B_s介子的未标记衰变率测量可观测的H，这具有相当大的实验优势，因为不需要味标记。H上的分辨率与B_s宽度差Δ Gamma_s成反比。这些实验前景必须与本文提出的标准模型预测值S_{phi gamma} = 0 \pm 0.002和H_{phi γ} = 0.047 \pm 0.025+0.015进行比较。我们还给出了B_s -> phi γ中直接CP不对称性的标准模型预言和实验灵敏度。

英文摘要：

The photon polarization in B -> V gamma is a sensitive probe of right-handed currents. In the time dependent decay rate of B_s -> phi gamma the coefficients S and H in front of the sin(Delta m_s t) and the sinh(Delta Gamma_s /2 t) terms are sensitive to those right-handed currents. As compared to the B_d system there is a sizable width difference in B_s mesons which leads to the additional measurable observable H. We show with a Monte Carlo simulation that the expected resolution on S and H will be about 0.15 at the LHCb experiment for Delta Gamma_s/Gamma_s = 0.15 and a data sample of 2 fb^{-1}. We also show that the observable H can be measured from the untagged decay rate of B_s mesons which has considerable experimental advantages as no flavour tag will be required. The resolution on H is inversely proportional to the B_s width difference Delta Gamma_s. These experimental prospects have to be compared with the Standard Model predictions S_{phi gamma} = 0 \pm 0.002 and H_{phi γ} = 0.047 \pm 0.025+0.015 presented in this paper. We also give the Standard Model prediction and the experimental sensitivity for the direct CP asymmetry in B_s -> phi gamma.

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