Measurement of the ratio of branching fractions $\mathcal{B}(B_c^+\,\to\,J/\psi\tau^+\nu_\tau)$/$\mathcal{B}(B_c^+\,\to\,J/\psi\mu^+\nu_\mu)

• Main Authors: Adinolfi, Marco, Anderlini, Lucio, Baesso, Clarissa, Belyaev, Ivan, Berezhnoy, Alexander, Bertolin, Alessandro, Bordyuzhin, Igor, Calladine, Ryan, Calvi, Marta, Calvo Gomez, Miriam, Camboni, Alessandro, Cardini, Alessandro, Carvalho Akiba, Kazuyoshi, Cattaneo, Marco, Chapman, Matthew George, Chatzikonstantinidis, Georgios, Ciambrone, Paolo, Collins, Paula, Dalseno, Jeremy, De Bruyn, Kristof, De Cian, Michel, De Serio, Marilisa, Eisenhardt, Stephan, Ekelhof, Robert, Fazzini, Davide, Filippov, Sergey, Fitzpatrick, Conor, Franco Lima, Vinicius, Furfaro, Emiliano, Garsed, Philip John, Gavardi, Laura, Gersabeck, Marco, Gianì, Sebastiana, Gotti, Claudio, Graciani Diaz, Ricardo, Griffith, Peter, Hicheur, Adlène, Huard, Zachary, Hutchcroft, David, Kandybei, Sergii, Kosmyntseva, Alena, Kozeiha, Mohamad, Kruse, Florian, Kudryavtsev, Vasily, Lafferty, George, Li, Pei-Rong, Liu, Xuesong, Loh, David, Luppi, Eleonora, Machefert, Frederic, Maciuc, Florin, Marchand, Jean François, Massacrier, Laure Marie, Matteuzzi, Clara, Meadows, Brian, Merk, Marcel, Milanes, Diego Alejandro, Mogini, Andrea, Müller, Janine, Müller, Vanessa, Naik, Paras, Neri, Nicola, Oldeman, Rudolf, Pappagallo, Marco, Petridis, Konstantinos, Petrov, Aleksandr, Petruzzo, Marco, Pinci, Davide, Plo Casasus, Maximo, Pugatch, Valery, Qian, Wenbin, Quintana, Boris, Rodriguez Lopez, Jairo Alexis, Satta, Alessia, Saunders, Daniel Martin, Schael, Stefan, Schreiner, HF, Schwemmer, Rainer, Sergi, Antonino, Silva Coutinho, Rafael, Skidmore, Nicola, Smith, Iwan Thomas, Spradlin, Patrick, Stevens, Holger, Storaci, Barbara, Tellarini, Giulia, Teubert, Frederic, Trisovic, Ana, Tully, Alison, Uwer, Ulrich, Vecchi, Stefania, Van Veghel, Maarten, Velthuis, Jaap, Veneziano, Giovanni, Volkov, Vladimir, Wilkinson, Guy, Wishahi, Julian, Witek, Mariusz, Wotton, Stephen, Zucchelli, Stefano
• Format: Report
• Language: English
• Subjects: B/c+ > > J/psi tau+ neutrino/tau; B/c: branching ratio; B/c: semileptonic decay; branching ratio: ratio: measured; CERN LHC Coll; experimental results; GeV-cms8000 GeV-cms; LHC-B; p p: colliding beams; p p: scattering; tau+ > > muon+ neutrino/mu antineutrino/tau; tau: leptonic decay
• ISSN: 0031-9007; 1092-0145; 1079-7114
• DOI: 10.3204/pubdb-2019-00391

A measurement is reported of the ratio of branching fractions $\mathcal{R}(J/ψ)=B(B_c ^+ → J/ψτ^+ ν_τ )/\mathcal{B}(B_c ^+ → J/ψμ^+ ν_μ )$, where the $τ^+$ lepton is identified in the decay mode $τ^+ → μ^+ ν_μ \bar{ν}_τ$. This analysis uses a sample of proton-proton collision data corresponding to 3.0 fb$^{-1}$ of integrated luminosity recorded with the LHCb experiment at center-of-mass energies of 7 and 8 TeV. A signal is found for the decay $B_c ^+ → J/ψτ^+ ν_τ$ at a significance of 3 standard deviations corrected for systematic uncertainty, and the ratio of the branching fractions is measured to be $\mathcal{R}(J/ψ)=0.71±0.17(stat)±0.18(syst)$. This result lies within 2 standard deviations above the range of central values currently predicted by the standard model.