We report the first measurement of the Michel parameter ζ′ in the τ-→μ-ν¯μντ decay with a new method proposed just recently. The measurement is based on the reconstruction of the τ-→μ-ν¯μντ events with subsequent muon decay in flight in the Belle central drift chamber. The analyzed data sample of 988 fb-1 collected by the Belle detector corresponds to approximately 912×106 τ+τ- pairs. We measure ζ′=0.22±0.94(stat)±0.42(syst), which is in agreement with the standard model prediction of ζ′=1. Statistical uncertainty dominates in this study, being a limiting factor, while systematic uncertainty is well under control. Our analysis proved the practicability of this promising method and its prospects for further precise measurement in future experiments.
First measurement of the Michel parameter ζ' in the τ- →μ- ν ν decay at Belle / Bodrov, D.; Pakhlov, P.; Adachi, I.; Aihara, H.; Al Said, S.; Asner, D. M.; Atmacan, H.; Aushev, T.; Ayad, R.; Babu, V.; Banerjee, Sw.; Behera, P.; Belous, K.; Bennett, J.; Bessner, M.; Bhuyan, B.; Bilka, T.; Biswas, D.; Bobrov, A.; Bondar, A.; Borah, J.; Bozek, A.; Bračko, M.; Branchini, P.; Browder, T. E.; Budano, A.; Campajola, M.; Červenkov, D.; Chang, M. -C.; Cheon, B. G.; Chilikin, K.; Cho, H. E.; Cho, K.; Cho, S. -J.; Choi, S. -K.; Choi, Y.; Choudhury, S.; Cinabro, D.; Das, S.; De Nardo, G.; De Pietro, G.; Dhamija, R.; Di Capua, F.; Dingfelder, J.; Doležal, Z.; Dong, T. V.; Epifanov, D.; Ferber, T.; Ferlewicz, D.; Fulsom, B. G.; Gaur, V.; Garmash, A.; Giri, A.; Goldenzweig, P.; Graziani, E.; Greenwald, D.; Gu, T.; Guan, Y.; Gudkova, K.; Hadjivasiliou, C.; Halder, S.; Hayasaka, K.; Hayashii, H.; Hedges, M. T.; Herrmann, D.; Hou, W. -S.; Hsu, C. -L.; Iijima, T.; Inami, K.; Ipsita, N.; Ishikawa, A.; Itoh, R.; Iwasaki, M.; Jacobs, W. W.; Jang, E. -J.; Ji, Q. P.; Jia, S.; Jin, Y.; Joo, K. K.; Kalita, D.; Kaliyar, A. B.; Kawasaki, T.; Kiesling, C.; Kim, C. H.; Kim, D. Y.; Kim, K. -H.; Kim, Y. -K.; Kindo, H.; Kinoshita, K.; Kodyš, P.; Korpar, S.; Križan, P.; Krokovny, P.; Kuhr, T.; Kumar, M.; Kumar, R.; Kumara, K.; Kwon, Y. -J.; Lange, J. S.; Lee, S. C.; Li, J.; Li, L. K.; Libby, J.; Lieret, K.; Lin, Y. -R.; Liventsev, D.; Luo, T.; Ma, Y.; Masuda, M.; Matsuda, T.; Maurya, S. K.; Meier, F.; Merola, M.; Metzner, F.; Miyabayashi, K.; Mizuk, R.; Mohanty, G. B.; Mussa, R.; Nakao, M.; Narwal, D.; Natkaniec, Z.; Natochii, A.; Nayak, L.; Nayak, M.; Nisar, N. K.; Nishida, S.; Ogawa, S.; Oskin, P.; Pakhlova, G.; Pardi, S.; Park, H.; Park, J.; Park, S. -H.; Passeri, A.; Patra, S.; Paul, S.; Pestotnik, R.; Piilonen, L. E.; Podobnik, T.; Prencipe, E.; Prim, M. T.; Rabusov, A.; Rout, N.; Russo, G.; Sandilya, S.; Sangal, A.; Santelj, L.; Savinov, V.; Schnell, G.; Schwanda, C.; Seino, Y.; Senyo, K.; Shan, W.; Shapkin, M.; Sharma, C.; Shiu, J. -G.; Singh, J. B.; Sokolov, A.; Solovieva, E.; Starič, M.; Stottler, Z. S.; Sumihama, M.; Takizawa, M.; Tamponi, U.; Tanida, K.; Tenchini, F.; Tiwary, R.; Trabelsi, K.; Uchida, M.; Uglov, T.; Unno, Y.; Uno, K.; Uno, S.; Vahsen, S. E.; Varner, G.; Vinokurova, A.; Vossen, A.; Wang, D.; Wang, E.; Wang, M. -Z.; Watanuki, S.; Werbycka, O.; Xu, X.; Yabsley, B. D.; Yan, W.; Yang, S. B.; Yelton, J.; Yin, J. H.; Yuan, C. Z.; Yusa, Y.; Zhang, Z. P.; Zhilich, V.; Zhukova, V.. - In: PHYSICAL REVIEW LETTERS. - ISSN 1092-0145. - (2023). [10.1103/PhysRevLett.131.021801]
First measurement of the Michel parameter ζ' in the τ- →μ- ν ν decay at Belle
M. CampajolaMembro del Collaboration Group
;G. De NardoMembro del Collaboration Group
;F. Di CapuaMembro del Collaboration Group
;M. MerolaMembro del Collaboration Group
;G. RussoMembro del Collaboration Group
;
2023
Abstract
We report the first measurement of the Michel parameter ζ′ in the τ-→μ-ν¯μντ decay with a new method proposed just recently. The measurement is based on the reconstruction of the τ-→μ-ν¯μντ events with subsequent muon decay in flight in the Belle central drift chamber. The analyzed data sample of 988 fb-1 collected by the Belle detector corresponds to approximately 912×106 τ+τ- pairs. We measure ζ′=0.22±0.94(stat)±0.42(syst), which is in agreement with the standard model prediction of ζ′=1. Statistical uncertainty dominates in this study, being a limiting factor, while systematic uncertainty is well under control. Our analysis proved the practicability of this promising method and its prospects for further precise measurement in future experiments.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
