Observation of ${\tau }^{–}\to {\pi }^{–}{\nu }_{\tau }{e}^{+}{e}^{–}$ and search for ${\tau }^{–}\to {\pi }^{–}{\nu }_{\tau }{\mu }^{+}{\mu }^{–}$

Journal Article · Tue Oct 15 00:00:00 EDT 2019 · Physical Review. D.

DOI:https://doi.org/10.1103/PhysRevD.100.071101· OSTI ID:1570499

Jin, Y. ; Aihara, H.; Epifanov, D.; Adachi, I.; Al Said, S.; Asner, D. M.; Aulchenko, V.; Aushev, T.; Ayad, R.; Babu, V.; Badhrees, I.; Bahinipati, S.; Bansal, V.; Behera, P.; Berger, M.; Bhardwaj, V.; Bilka, T.; Biswal, J.; Bobrov, A.; Bonvicini, G. ; Bozek, A.; Bračko, M.; Campajola, M.; Cao, L.; Červenkov, D.; Chekelian, V.; Chen, A.; Cheon, B. G.; Chilikin, K.; Cho, H. E.; Cho, K.; Choi, Y.; Choudhury, S.; Cinabro, D.; Cunliffe, S.; Di Carlo, S.; Doležal, Z.; Dong, T. V.; Dossett, D.; Eidelman, S.; Fast, J. E.; Ferber, T.; Fulsom, B. G.; Garg, R.; Gaur, V.; Gabyshev, N.; Garmash, A.; Giri, A.; Goldenzweig, P.; Golob, B.; Greenwald, D.; Grzymkowska, O.; Haba, J.; Hayasaka, K.; Hayashii, H.; Hedges, M. T.; Hou, W. -S.; Huang, K.; Iijima, T.; Inami, K.; Inguglia, G.; Ishikawa, A.; Iwasaki, M.; Iwasaki, Y.; Jacobs, W. W.; Jeon, H. B.; Jia, S.; Joffe, D.; Joo, K. K.; Kahn, J.; Kaliyar, A. B.; Karyan, G.; Kawasaki, T.; Kichimi, H.; Kiesling, C.; Kim, D. Y.; Kim, H. J.; Kim, K. T.; Kim, S. H.; Kinoshita, K.; Kodyš, P.; Korpar, S.; Kotchetkov, D.; Križan, P.; Kroeger, R.; Krokovny, P.; Kulasiri, R.; Kumar, R.; Kuzmin, A.; Kwon, Y. -J.; Lalwani, K.; Lange, J. S.; Lee, J. Y.; Lee, S. C.; Li, C. H.; Li, L. K.; Li, Y. B.; Li Gioi, L.; Libby, J.; Lieret, K.; Liptak, Z.; Liventsev, D.; Lu, P. -C.; Luo, T.; MacNaughton, J.; Masuda, M.; Matsuda, T.; Matvienko, D.; Merola, M.; Miyabayashi, K.; Miyata, H.; Mizuk, R.; Mori, T.; Mussa, R.; Nakano, E.; Nakao, M.; Nath, K. J.; Natkaniec, Z.; Nayak, M.; Niiyama, M.; Nisar, N. K.; Nishida, S.; Ogawa, S.; Ono, H.; Onuki, Y.; Pakhlov, P.; Pakhlova, G.; Pal, B.; Pardi, S.; Park, H.; Park, S. -H.; Patra, S.; Paul, S.; Pedlar, T. K.; Pestotnik, R.; Piilonen, L. E.; Popov, V.; Prencipe, E.; Purohit, M. V.; Rostomyan, A.; Russo, G.; Sahoo, D.; Sakai, Y.; Salehi, M.; Sandilya, S.; Santelj, L.; Sanuki, T.; Savinov, V.; Schneider, O.; Schnell, G.; Schueler, J.; Schwanda, C.; Seino, Y.; Senyo, K.; Seon, O.; Sevior, M. E.; Shebalin, V.; Shen, C. P.; Shiu, J. -G.; Shwartz, B.; Simon, F.; Singh, J. B.; Sokolov, A.; Solovieva, E.; Stanič, S.; Starič, M.; Stottler, Z. S.; Strube, J. F.; Sumiyoshi, T.; Takizawa, M.; Tamponi, U.; Tanida, K.; Tenchini, F.; Trabelsi, K.; Uchida, M.; Uglov, T.; Unno, Y.; Uno, S.; Urquijo, P.; Usov, Y.; Van Tonder, R.; Varner, G.; Vinokurova, A.; Vorobyev, V.; Vossen, A.; Wang, B.; Wang, C. H.; Wang, M. -Z.; Wang, P.; Watanuki, S.; Won, E.; Yang, S. B.; Ye, H.; Yin, J. H.; Yuan, C. Z.; Yusa, Y.; Zhang, Z. P.; Zhilich, V.; Zhukova, V.

We present the first measurements of branching fractions of rare tau-lepton decays, τ^– → π^–ν_τℓ⁺ℓ^– (ℓ = e or μ), using a data sample corresponding to 562 fb^–1 collected at a center-of-mass energy of 10.58 GeV with the Belle detector at the KEKB asymmetric-energy e⁺e^– collider. The τ^– → π^–ν_τe⁺e^– decay is observed for the first time with 7.0σ significance. The partial branching fraction determined by the structure-dependent mechanisms mediated by either a vector or an axial-vector current for the mass region M_πee > 1.05 GeV/c² is measured to be B(τ^– → π^–ν_τe⁺e^–)[M_{π^–e⁺e^–} > 1.05 GeV/c²] = (5.90 ± 0.53 ± 0.85 ± 0.11) × 10^–6, where the first uncertainty is statistical, the second is systematic, and the third is due to model dependence. In the full phase space, due to the different detection efficiencies for the structure-dependent mechanisms mediated by axial-vector and vector currents, the branching fraction varies from B_A(τ^– → π^–ν_τe⁺e^–) = (1.46 ± 0.13 ± 0.21) × 10^–5 to B_V(τ^– → π^–ν_τe⁺e^–) = (3.01 ± 0.27 ± 0.43) × 10^–5, respectively. An upper limit is set on the branching fraction of the τ^– → π^–ν_τμ⁺μ^– decay, B(τ^– → π^–ν_τμ⁺μ^–) < 1.14 × 10^–5, at the 90% confidence level.

• Research Organization: Brookhaven National Laboratory (BNL), Upton, NY (United States); Pacific Northwest National Laboratory (PNNL), Richland, WA (United States); Virginia Polytechnic Inst. and State Univ. (Virginia Tech), Blacksburg, VA (United States); Univ. of Hawaii, Honolulu, HI (United States)
• Sponsoring Organization: USDOE Office of Science (SC), High Energy Physics (HEP); National Science Foundation (NSF); USDOE Office of Science (SC), Nuclear Physics (NP)
• Contributing Organization: Belle Collaboration
• Grant/Contract Number: SC0012704; AC05-76RL01830; SC0009973; SC0010504
• OSTI ID: 1570499
• Alternate ID(s): OSTI ID: 1572968; OSTI ID: 1577438; OSTI ID: 1593771
• Report Number(s): BNL-212289-2019-JAAM; PNNL-SA-149804; PRVDAQ; 071101
• Journal Information: Physical Review. D., Journal Name: Physical Review. D. Vol. 100 Journal Issue: 7; ISSN 2470-0010
• Publisher: American Physical Society (APS)
• Country of Publication: United States
• Language: English

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