arXiv 2401.070902024-01hep-ex

在 √s = 13 TeV 质子-质子碰撞中对 B± → K±μ+μ− 和 B± → K±e+e− 衰变进行轻子味普适性检验

Test of lepton flavor universality in B$^{\pm}$ $\to$ K$^{\pm}μ^+μ^-$ and B$^{\pm}$ $\to$ K$^{\pm}$e$^+$e$^-$ decays in proton-proton collisions at $\sqrt{s}$ = 13 TeV

CMS Collaboration

备注：: Replaced with the published version. Added the journal reference and the DOI. All the figures and tables can be found at http://cms-results.web.cern.ch/cms-results/public-results/publications/BPH-22-005 (CMS Public Pages)
发表信息：: Rep. Prog. Phys. 87 (2024) 077802
DOI：: 10.1088/1361-6633/ad4e65

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AI总结：

本研究利用 CMS 在 13 TeV 质子-质子碰撞中的高统计 b 强子衰变数据，通过双比率法测量 R(K) 及 B±→K±μ+μ− 分支比，以检验轻子味普适性。

摘要：

本文介绍了对 B± → K±μ+μ− 和 B± → K±e+e− 衰变中轻子味普适性的检验，以及对非共振 B± → K±μ+μ− 衰变差分和积分分支比的测量。该分析得益于 LHC 上 CMS 实验于 2018 年记录的 √s = 13 TeV 质子-质子碰撞专用数据集；该数据集采用特殊的高事例率数据流，旨在收集约 100 亿个无偏 b 强子衰变。分支比 B(B± → K±μ+μ−) 与 B(B± → K±e+e−) 之比，通过测量这些衰变相对于 B± → J/ψK±（其中 J/ψ → μ+μ− 和 e+e−）各自分支比的双比率 R(K) 来确定，从而使系统不确定性得到显著抵消。R(K) 在 1.1 < q² < 6.0 GeV² 范围内测量，其中 q 为轻子对的不变质量，测得 R(K) = 0.78 +0.47−0.23，与标准模型预期 R(K) ≈ 1 相符。该测量受限于电子道的统计精度。在同一 q² 范围内，积分分支比 B(B± → K±μ+μ−) = (12.42 ± 0.68) × 10−8，与当前世界平均值一致，并具有相当的精度。

英文摘要：

A test of lepton flavor universality in B$^{\pm}$ $\to$ K$^{\pm}μ^+μ^-$ and B$^{\pm}$ $\to$ K$^{\pm}$e$^+$e$^-$ decays, as well as a measurement of differential and integrated branching fractions of a nonresonant B$^{\pm}$ $\to$ K$^{\pm}μ^+μ^-$ decay are presented. The analysis is made possible by a dedicated data set of proton-proton collisions at $\sqrt{s}$ = 13 TeV recorded in 2018, by the CMS experiment at the LHC, using a special high-rate data stream designed for collecting about 10 billion unbiased b hadron decays. The ratio of the branching fractions $\mathcal{B}$(B$^{\pm}$ $\to$ K$^{\pm}μ^+μ^-$) to $\mathcal{B}$(B$^{\pm}$ $\to$ K$^{\pm}$e$^+$e$^-$) is determined from the measured double ratio $R$(K) of these decays to the respective branching fractions of the B$^\pm$ $\to$ J/$ψ$K$^\pm$ with J/$ψ$ $\to$ $μ^+μ^-$ and e$^+$e$^-$ decays, which allow for significant cancellation of systematic uncertainties. The ratio $R$(K) is measured in the range 1.1 $\lt$ $q^2$ $\lt$ 6.0 GeV$^2$, where $q$ is the invariant mass of the lepton pair, and is found to be $R$(K) = 0.78 $^{+0.47}_{-0.23}$, in agreement with the standard model expectation $R$(K) $\approx$ 1. This measurement is limited by the statistical precision of the electron channel. The integrated branching fraction in the same $q^2$ range, $\mathcal{B}$(B$^{\pm}$ $\to$ K$^{\pm}μ^+μ^-$) = (12.42 $\pm$ 0.68) $\times$ 10$^{-8}$, is consistent with the present world-average value and has a comparable precision.

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