Test of light-lepton universality in τ decays with the Belle II experiment

Author:

,Adachi I.,Adamczyk K.,Aggarwal L.,Aihara H.,Akopov N.,Aloisio A.,Anh Ky N.,Asner D. M.,Atmacan H.,Aushev V.,Aversano M.,Ayad R.,Babu V.,Bae H.,Bahinipati S.,Bambade P.,Banerjee Sw.,Bansal S.,Barrett M.,Baudot J.,Baur A.,Beaubien A.,Becherer F.,Becker J.,Bennett J. V.,Bernlochner F. U.,Bertacchi V.,Bertemes M.,Bertholet E.,Bessner M.,Bettarini S.,Bianchi F.,Bierwirth L.,Bilka T.,Bilokin S.,Biswas D.,Bobrov A.,Bodrov D.,Bolz A.,Borah J.,Boschetti A.,Bozek A.,Bračko M.,Branchini P.,Browder T. E.,Budano A.,Bussino S.,Campajola M.,Cao L.,Casarosa G.,Cecchi C.,Cerasoli J.,Chang M.-C.,Chang P.,Cheaib R.,Cheema P.,Cheon B. G.,Chilikin K.,Chirapatpimol K.,Cho H.-E.,Cho K.,Cho S.-J.,Choi S.-K.,Choudhury S.,Corona L.,Cui J. X.,Das S.,Dattola F.,De La Cruz-Burelo E.,De La Motte S. A.,de Marino G.,De Nardo G.,De Nuccio M.,De Pietro G.,de Sangro R.,Destefanis M.,Dey S.,Dhamija R.,Di Canto A.,Di Capua F.,Dingfelder J.,Doležal Z.,Domínguez Jiménez I.,Dong T. V.,Dorigo M.,Dorner D.,Dort K.,Dossett D.,Dreyer S.,Dubey S.,Dugic K.,Dujany G.,Ecker P.,Eliachevitch M.,Epifanov D.,Feichtinger P.,Ferber T.,Ferlewicz D.,Fillinger T.,Finck C.,Finocchiaro G.,Fodor A.,Forti F.,Frey A.,Fulsom B. G.,Gabrielli A.,Ganiev E.,Garcia-Hernandez M.,Gaudino G.,Gaur V.,Gaz A.,Gellrich A.,Ghevondyan G.,Ghosh D.,Ghumaryan H.,Giakoustidis G.,Giordano R.,Giri A.,Glazov A.,Gobbo B.,Godang R.,Gogota O.,Goldenzweig P.,Gradl W.,Grammatico T.,Granderath S.,Graziani E.,Greenwald D.,Gruberová Z.,Gu T.,Guan Y.,Gudkova K.,Han Y.,Hara T.,Hayasaka K.,Hayashii H.,Hazra S.,Hearty C.,Hedges M. T.,Heidelbach A.,Heredia de la Cruz I.,Hernández Villanueva M.,Higuchi T.,Hoek M.,Hohmann M.,Horak P.,Hsu C.-L.,Humair T.,Iijima T.,Inami K.,Inguglia G.,Ipsita N.,Ishikawa A.,Itoh R.,Iwasaki M.,Jacobs W. W.,Jaffe D. E.,Jang E.-J.,Ji Q. P.,Jia S.,Jin Y.,Junkerkalefeld H.,Kaleta M.,Kalita D.,Kaliyar A. B.,Kandra J.,Kang S.,Karyan G.,Kawasaki T.,Keil F.,Kiesling C.,Kim C.-H.,Kim D. Y.,Kim K.-H.,Kim Y.-K.,Kindo H.,Kinoshita K.,Kodyš P.,Koga T.,Kohani S.,Kojima K.,Konno T.,Korobov A.,Korpar S.,Kovalenko E.,Kowalewski R.,Kraetzschmar T. M. G.,Križan P.,Krokovny P.,Kuhr T.,Kulii Y.,Kumar J.,Kumar M.,Kumara K.,Kunigo T.,Kuzmin A.,Kwon Y.-J.,Lacaprara S.,Lai Y.-T.,Lalwani K.,Lam T.,Lanceri L.,Lange J. S.,Laurenza M.,Lautenbach K.,Leboucher R.,Le Diberder F. R.,Lee M. J.,Leo P.,Lemettais C.,Levit D.,Lewis P. M.,Li C.,Li L. K.,Li S. X.,Li Y.,Li Y. B.,Libby J.,Liptak Z.,Liu M. H.,Liu Q. Y.,Liu Y.,Liu Z. Q.,Liventsev D.,Longo S.,Lueck T.,Lyu C.,Ma Y.,Maggiora M.,Maharana S. P.,Maiti R.,Maity S.,Mancinelli G.,Manfredi R.,Manoni E.,Mantovano M.,Marcantonio D.,Marcello S.,Marinas C.,Martellini C.,Martini A.,Martinov T.,Massaccesi L.,Masuda M.,Matsuoka K.,Matvienko D.,Maurya S. K.,McKenna J. A.,Mehta R.,Meier F.,Merola M.,Metzner F.,Miller C.,Mirra M.,Mitra S.,Miyabayashi K.,Miyake H.,Mizuk R.,Mohanty G. B.,Mondal S.,Moneta S.,Moser H.-G.,Mrvar M.,Mussa R.,Nakamura I.,Nakamura K. R.,Nakao M.,Nakazawa H.,Nakazawa Y.,Narimani Charan A.,Naruki M.,Narwal D.,Natkaniec Z.,Natochii A.,Nayak L.,Nayak M.,Nazaryan G.,Neu M.,Niebuhr C.,Ninkovic J.,Nishida S.,Novosel A.,Ogawa S.,Onishchuk Y.,Ono H.,Otani F.,Pakhlov P.,Pakhlova G.,Panta A.,Pardi S.,Parham K.,Park H.,Park S.-H.,Paschen B.,Passeri A.,Patra S.,Pedlar T. K.,Peschke R.,Pestotnik R.,Piccolo M.,Piilonen L. E.,Pinna Angioni G.,Podesta-Lerma P. L. M.,Podobnik T.,Pokharel S.,Praz C.,Prell S.,Prencipe E.,Prim M. T.,Prudiiev I.,Purwar H.,Rados P.,Raeuber G.,Raiz S.,Rauls N.,Reif M.,Reiter S.,Remnev M.,Ripp-Baudot I.,Rizzo G.,Robertson S. H.,Roehrken M.,Roney J. M.,Rostomyan A.,Rout N.,Russo G.,Sanders D. A.,Sandilya S.,Santelj L.,Sato Y.,Savinov V.,Scavino B.,Schmitt C.,Schwanda C.,Schwickardi M.,Seino Y.,Selce A.,Senyo K.,Serrano J.,Sevior M. E.,Sfienti C.,Shan W.,Shi X. D.,Shillington T.,Shiu J.-G.,Shtol D.,Shwartz B.,Sibidanov A.,Simon F.,Singh J. B.,Skorupa J.,Sobie R. J.,Sobotzik M.,Soffer A.,Sokolov A.,Solovieva E.,Spataro S.,Spruck B.,Starič M.,Stavroulakis P.,Stefkova S.,Stroili R.,Sue Y.,Sumihama M.,Sumisawa K.,Sutcliffe W.,Suwonjandee N.,Svidras H.,Takahashi M.,Takizawa M.,Tamponi U.,Tanaka S.,Tanida K.,Tenchini F.,Thaller A.,Tittel O.,Tiwary R.,Tonelli D.,Torassa E.,Trabelsi K.,Tsaklidis I.,Uchida M.,Ueda I.,Uglov T.,Unger K.,Unno Y.,Uno K.,Uno S.,Urquijo P.,Ushiroda Y.,Vahsen S. E.,van Tonder R.,Varvell K. E.,Veronesi M.,Vinokurova A.,Vismaya V. S.,Vitale L.,Vobbilisetti V.,Volpe R.,Wach B.,Wakai M.,Wallner S.,Wang E.,Wang M.-Z.,Wang X. L.,Wang Z.,Warburton A.,Watanabe M.,Watanuki S.,Wessel C.,Won E.,Xu X. P.,Yabsley B. D.,Yamada S.,Yan W.,Yang S. B.,Yelton J.,Yin J. H.,Yoshihara K.,Yuan C. Z.,Yusa Y.,Zani L.,Zeng F.,Zhang B.,Zhang Y.,Zhilich V.,Zhou Q. D.,Zhou X. Y.,Zhukova V. I.,Žlebčík R.

Abstract

Abstract We present a measurement of the ratio $$ {R}_{\mu }=\mathcal{B}\left({\tau}^{-}\to {\mu}^{-}{\overline{\nu}}_{\mu }{\nu}_{\tau}\right)/\mathcal{B}\left({\tau}^{-}\to {e}^{-}{\overline{\nu}}_e{\nu}_{\tau}\right) $$ R μ = B τ μ ν ¯ μ ν τ / B τ e ν ¯ e ν τ of branching fractions $$ \mathcal{B} $$ B of the τ lepton decaying to muons or electrons using data collected with the Belle II detector at the SuperKEKB e+e collider. The sample has an integrated luminosity of 362 ± 2 fb1 at a centre-of-mass energy of 10.58 GeV. Using an optimised event selection, a binned maximum likelihood fit is performed using the momentum spectra of the electron and muon candidates. The result, Rμ = 0.9675 ± 0.0007 ± 0.0036, where the first uncertainty is statistical and the second is systematic, is the most precise to date. It provides a stringent test of the light-lepton universality, translating to a ratio of the couplings of the muon and electron to the W boson in τ decays of 0.9974 ± 0.0019, in agreement with the standard model expectation of unity.

Publisher

Springer Science and Business Media LLC

Reference45 articles.

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