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Test of lepton flavor universality and search for lepton flavor violation in B -> Kll decays

We present measurements of the branching fractions for the decays B -> K mu(+)mu(-) and B -> Ke(+)e(-), and their ratio (R-K), using a data sample of 711 fb(-1) that contains 772 x 10(6) B (B) over bar events. The data were collected at the Gamma(4S) resonance with the Belle detector at the KEKB asymmetric-energy e(+)e(-) collider. The ratio RK is measured in five bins of dilepton invariant-mass-squared (q(2)): q(2) is an element of (0.1, 4.0), (4.00, 8.12), (1.0, 6.0), (10.2, 12.8) and (> 14.18) GeV2/c(4), along with the whole q(2) region. The R-K value for q(2) is an element of (1.0, 6.0) GeV2/c(4) is 1.03(-0.24)(+0.28) +/- 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 CP-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) is an element of (1.0, 6.0) GeV2/c(4) bin in the mode with muon final states. The measured differential branching fractions, dB/dq(2), are consistent with theoretical predictions for charged B decays, while the corresponding values are below the expectations for neutral B decays. We have also searched for lepton-flavor-violating B -> K mu(+/-)e(-/+) decays and set 90% confidence-level upper limits on the branching fraction in the range of 10(-8) for B+ -> K+ mu(+/-)e(-/+), and B-0 -> K-0 mu(+/-) e(-/+) modes.

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Sun Hee Kim, Donghyun Kim, Lei Li, Yiming Li, Olivier Schneider, Mingkui Wang, Xiao Wang
SPRINGER, 2021
Article

Résumé

Official source

https://infoscience.epfl.ch/record/284964?ln=fr

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Concepts associés (11)

Concepts associés

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Publications associées (115)

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Rapport de branchement

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Écart type

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Study of B-0 -> rho(0)rho(0) decays, implications for the CKM angle phi(2) and search for other B-0 decay modes with a four-pion final state

Tagir Aushev, Donghyun Kim, Ji Hyun Kim, Jing Li, Olivier Schneider, Mingkui Wang, Xiao Wang

We present a study of the branching fraction of the decay B-0 -> rho(0)rho(0) and the fraction of longitudinally polarized rho(0) mesons in this decay. The results are obtained from the final data sample containing 772 x 10(6) B (B) over bar pairs collected at the gamma(4S) resonance with the Belle detector at the KEKB asymmetric-energy e(+)e(-) collider. We find 166 +/- 59 B-0 -> rho(0)rho(0) events (including systematic uncertainties), corresponding to a branching fraction of B(B-0 -> rho(0)rho(0)) = (1.02 +/- 0.30(stat) +/- 0.15(syst)) x 10(-6) with a significance of 3.4 standard deviations and a longitudinal polarization fraction f(L) = 0.21(-0.22)(+0.18()stat) +/- 0.15(syst). We use the longitudinal polarization fraction to determine the Cabibbo-Kobayashi-Maskawa matrix angle phi(2) = (84.9 +/- 13.5)degrees through an isospin analysis in the B ->rho rho system. We furthermore find 125 +/- 41 B-0 -> f(0)rho(0) events, corresponding to B(B-0 -> f(0)rho(0)) x B(f(0) -> pi(+)pi(-)) = (0.78 +/- 0.22(stat) +/- 0.11(syst)) x 10(-6), with a significance of 3.1 standard deviations. We find no other significant contribution with the same final state, and set upper limits at 90% confidence level on the (product) branching fractions, B(B-0 -> pi(+)pi(-)pi(+)pi(-)) < 11.2 x 10(-6), B(B-0 -> rho(0)pi(+)pi(-)) < 12.0 x 10(-6), B(B-0 -> f(0)pi(+)pi(-)) x B(f(0) -> pi(+)pi(-)) < 3.0 x 10(-6) and B(B-0 -> f(0)f(0)) x B(f(0) -> pi(+)pi(-))(2) < 0.2 x 10(-6).

Amer Physical Soc2014

Chargement

Search for the B -> Y(4260)K, Y(4260) -> J/psi pi(+)pi(-) decays

Tagir Aushev, Sun Hee Kim, Donghyun Kim, Ji Hyun Kim, Lei Li, Yiming Li, Olivier Schneider, Mingkui Wang, Xiao Wang

We report the results of a search for the B -> Y(4260)K, Y(4260) -> J/psi pi(+)pi thorn p-decays. This study is based on a data sample corresponding to an integrated luminosity of 711 fb(-1), collected at the Upsilon(4S) resonance with the Belle detector at the KEKB asymmetric-energy e(+)e(-) collider. We investigate the J/psi pi(+)pi(-) thorn p-invariant mass distribution in the range 4.0 to 4.6 GeV/c(2) using both B+ -> J/psi pi(+)pi K--(+) and B-0 -> J/psi pi(+)pi K--(S)0 decays. We find excesses of events above the background levels, with significances of 2.1 and 0.9 standard deviations for charged and neutral B -> Y(4260)K decays, respectively, taking into account the systematic uncertainties. These correspond to upper limits on the product of branching fractions, B(B+ -> Y(4260)K+) x B(Y(4260) -> J/psi pi(+)pi(-)) < 1.4 x 10(-5) and B(B-0 -> Y(4260)K-0) x B(Y(4260) -> J/psi pi(+)pi(-)) < 1.7 x 10(-5) at the 90% confidence level.

2019

Chargement

Measurement of properties of B$^0_\mathrm{s}\to\mu^+\mu^-$ decays and search for B$^0\to\mu^+\mu^-$ with the CMS experiment

Muhammad Ahmad, Benjamin William Allen, Georgios Anagnostou, Konstantin Androsov, Tagir Aushev, Thomas Berger, Michele Bianco, Alessandro Caratelli, Xin Chen, Yixing Chen, Tian Cheng, Giuseppe Codispoti, Pratyush Das, Abhisek Datta, Milos Dordevic, Dipanwita Dutta, Matthias Finger, Francesco Fiori, Sebastiana Gianì, Daniel Gonzalez, Ruchi Gupta, Seungkyu Ha, Csaba Hajdu, Peter Hansen, Ali Harb, Miao Hu, Alexis Kalogeropoulos, Viktor Khristenko, Ji Hyun Kim, Donghyun Kim, Vineet Kumar, Ajay Kumar, Sanjeev Kumar, Ekaterina Kuznetsova, Federica Legger, Wei Li, Lei Li, Yiming Li, Jing Li, Zhen Liu, Werner Lustermann, Bibhuprasad Mahakud, Maren Tabea Meinhard, Amr Mohamed, Thomas Muller, Ioannis Papadopoulos, Vladimir Petrov, Jessica Prisciandaro, Quentin Python, Andrea Rizzi, Paolo Ronchese, Valérie Scheurer, Sourav Sen, Varun Sharma, Ashish Sharma, Lesya Shchutska, Wei Shi, Kun Shi, Muhammad Shoaib, Jan Steggemann, Marco Trovato, Andromachi Tsirou, David Vannerom, Joao Varela, Jian Wang, Qian Wang, Siyuan Wang, Xiao Wang, Hui Wang, Mingkui Wang, Zheng Wang, Yi Wang, Muhammad Waqas, Matthias Weber, Matthias Wolf, Fan Xia, Meng Xiao, Yong Yang, Yi Zhang

Results are reported for the B

^0_\mathrm{s}\to\mu^+\mu^-

branching fraction and effective lifetime and from a search for the decay B

^0\to\mu^+\mu^-

. The analysis uses a data sample of proton-proton collisions accumulated by the CMS experiment in 2011, 2012, and 2016, with center-of-mass energies (integrated luminosities) of 7 TeV (5 fb

^{-1}

), 8 TeV (20 fb

^{-1}

), and 13 TeV (36 fb

^{-1}

). The branching fractions are determined by measuring event yields relative to B

^+\to

\psi

^+

decays (with J/

\psi\to\mu^+\mu^-

), which results in the reduction of many of the systematic uncertainties. The decay B

^0_\mathrm{s}\to\mu^+\mu^-

is observed with a significance of 5.6 standard deviations. The branching fraction is measured to be

\mathcal{B}

^0_\mathrm{s}\to\mu^+\mu^-

) = [2.9

^{+0.7}_{-0.6}

(exp)

\pm

0.2(frag)]

\times 10^{-9}

, where the first uncertainty combines the experimental statistical and systematic contributions, and the second is due to the uncertainty in the ratio of the B

^0_\mathrm{s}

and the B

^+

fragmentation functions. No significant excess is observed for the decay B

^0\to\mu^+\mu^-

, and an upper limit of

\mathcal{B}

^0\to\mu^+\mu^-

) < 3.6

\times

^{-10}

is obtained at 95% confidence level. The B

^0_\mathrm{s}\to\mu^+\mu^-

effective lifetime is measured to be

\tau_{\mu^+\mu^-}

= 1.70

^{+0.61}_{-0.44}

ps. These results are consistent with standard model predictions.

2019

Chargement