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arXiv · 2305.19116

Measurement of the $\tau$-lepton mass with the Belle~II experiment

Belle II Collaboration·I. Adachi·K. Adamczyk·L. Aggarwal·H. Ahmed·H. Aihara·N. Akopov·A. Aloisio·N. Anh Ky·D. M. Asner·H. Atmacan·T. Aushev·V. Aushev·M. Aversano·V. Babu·H. Bae·S. Bahinipati·P. Bambade·Sw. Banerjee·M. Barrett·J. Baudot·M. Bauer·A. Baur·A. Beaubien·F. Becherer·J. Becker·P. K. Behera·J. V. Bennett·F. U. Bernlochner·V. Bertacchi·M. Bertemes·E. Bertholet·M. Bessner·S. Bettarini·B. Bhuyan·F. Bianchi·T. Bilka·D. Biswas·A. Bobrov·D. Bodrov·A. Bolz·A. Bondar·J. Borah·A. Bozek·M. Bračko·P. Branchini·T. E. Browder·A. Budano·S. Bussino·M. Campajola·L. Cao·G. Casarosa·C. Cecchi·J. Cerasoli·M. -C. Chang·P. Chang·R. Cheaib·P. Cheema·V. Chekelian·B. G. Cheon·K. Chilikin·K. Chirapatpimol·H. -E. Cho·K. Cho·S. -J. Cho·S. -K. Choi·S. Choudhury·J. Cochran·L. Corona·L. M. Cremaldi·S. Das·F. Dattola·E. De La Cruz-Burelo·S. A. De La Motte·G. de Marino·G. De Nardo·M. De Nuccio·G. De Pietro·R. de Sangro·M. Destefanis·S. Dey·A. De Yta-Hernandez·R. Dhamija·A. Di Canto·F. Di Capua·J. Dingfelder·Z. Doležal·I. Domínguez Jiménez·T. V. Dong·M. Dorigo·K. Dort·S. Dreyer·S. Dubey·G. Dujany·P. Ecker·M. Eliachevitch·P. Feichtinger·T. Ferber·D. Ferlewicz·T. Fillinger
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Abstract

We present a measurement of the $\tau$-lepton mass using a sample of about 175 million $e^+e^- \to \tau^+\tau^-$ events collected with the Belle II detector at the SuperKEKB $e^+e^-$ collider at a center-of-mass energy of $10.579\,\mathrm{Ge\kern -0.1em V}$. This sample corresponds to an integrated luminosity of $190\,\mathrm{fb^{-1}}$. We use the kinematic edge of the $\tau $ pseudomass distribution in the decay ${\tau^-\to\pi^-\pi^+\pi^-\nu_\tau}$ and measure the $\tau$ mass to be $1777.09 \pm 0.08 \pm 0.11 \,\mathrm{Me\kern -0.1em V\!/c^2}$, where the first uncertainty is statistical and the second systematic. This result is the most precise to date.

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Belle II Collaboration, I. Adachi, K. Adamczyk, L. Aggarwal, H. Ahmed, H. Aihara, N. Akopov, A. Aloisio, N. Anh Ky, D. M. Asner, H. Atmacan, T. Aushev, V. Aushev, M. Aversano, V. Babu, H. Bae, S. Bahinipati, P. Bambade, Sw. Banerjee, M. Barrett, J. Baudot, M. Bauer, A. Baur, A. Beaubien, F. Becherer, J. Becker, P. K. Behera, J. V. Bennett, F. U. Bernlochner, V. Bertacchi, M. Bertemes, E. Bertholet, M. Bessner, S. Bettarini, B. Bhuyan, F. Bianchi, T. Bilka, D. Biswas, A. Bobrov, D. Bodrov, A. Bolz, A. Bondar, J. Borah, A. Bozek, M. Bračko, P. Branchini, T. E. Browder, A. Budano, S. Bussino, M. Campajola, L. Cao, G. Casarosa, C. Cecchi, J. Cerasoli, M. -C. Chang, P. Chang, R. Cheaib, P. Cheema, V. Chekelian, B. G. Cheon, K. Chilikin, K. Chirapatpimol, H. -E. Cho, K. Cho, S. -J. Cho, S. -K. Choi, S. Choudhury, J. Cochran, L. Corona, L. M. Cremaldi, S. Das, F. Dattola, E. De La Cruz-Burelo, S. A. De La Motte, G. de Marino, G. De Nardo, M. De Nuccio, G. De Pietro, R. de Sangro, M. Destefanis, S. Dey, A. De Yta-Hernandez, R. Dhamija, A. Di Canto, F. Di Capua, J. Dingfelder, Z. Doležal, I. Domínguez Jiménez, T. V. Dong, M. Dorigo, K. Dort, S. Dreyer, S. Dubey, G. Dujany, P. Ecker, M. Eliachevitch, P. Feichtinger, T. Ferber, D. Ferlewicz, T. Fillinger. 2023-05-30. Measurement of the $\tau$-lepton mass with the Belle~II experiment. https://arxiv.org/abs/2305.19116

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