Test of lepton flavor universality and search for lepton flavor violation in decays

崩壊におけるレプトンユニバーサリティの試験とレプトンフレーバーの破れの探索

Choudhury, S.*; 谷田聖 ; Belle Collaboration*; 他221名*

Choudhury, S.*; Tanida, Kiyoshi; Belle Collaboration*; 221 of others*

We present measurements of the branching fractions for the decays $Bto K mu^{+}mu^{-}$ and $Bto K e^{+}e^{-}$ , and their ratio ( $R_{K}$ ), using a data sample of 711 ${rm fb^{-1}}$ that contains $772 times 10^{6}$ events. The data were collected at the resonance with the Belle detector at the KEKB asymmetric-energy $e^{+}e^{-}$ collider. The ratio $R_{K}$ is measured in five bins of dilepton invariant-mass-squared ( $q^{2}$ ): $q^{2} in (0.1, 4.0), (4.0, 8.12), (1.0, 6.0)$ , and ( $> 14.18) ;{rm GeV^{2}}/c^{4}$ , along with the whole region. The $R_{K}$ value for $q^{2} in (1.0, 6.0) ;{rm GeV^{2}}/c^{4}$ is $1.03^{+0.28}_{-0.24} pm 0.01$ . The first and second uncertainties listed are statistical and systematic, respectively. All results for $R_{K}$ are consistent with Standard Model predictions. We also measure -averaged isospin asymmetries in the same $q^{2}$ bins. The results are consistent with a null asymmetry, with the largest difference of 2.6 standard deviations occurring for the $q^{2}in(1.0,6.0) ;{rm GeV^{2}}/c^{4}$ bin in the mode with muon final states. The measured differential branching fractions, ${dcal B}/{dq^{2}}$ , are consistent with theoretical predictions for charged decays, while the corresponding values are below the expectations for neutral decays. We have also searched for lepton-flavor-violating $B rightarrow Kmu^{pm}e^{mp}$ decays and set confidence-level upper limits on the branching fraction in the range of $10^{-8}$ for $B^{+} rightarrow K^{+}mu^{pm}e^{mp}$ , and $B^{0} rightarrow K^{0}mu^{pm}e^{mp}$ modes.

使用言語	:	English
掲載資料名	:	Journal of High Energy Physics (Internet)
巻	:	2021
号	:	3
ページ数	:	p.105_1 - 105_19
発行年月	:	2021/03
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キーワード	:	no keyword

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論文URL	:	https://doi.org/10.1007/JHEP03(2021)105
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受委託・共同研究相手機関	:	高エネルギー加速器研究機構

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Web of Science® Times Cited Count	:	被引用回数：評価・統計等のため最新の被引用回数を確認したい場合は、直接Web of Science®をご確認ください。 http://www.webofknowledge.com/wos
InCites™	:	パーセンタイル：92.09 分野：Physics, Particles & Fields
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登録番号 : AA20220014
抄録集掲載番号 : 50000692
論文投稿番号 : 25422

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