Measurement of CP asymmetries in B0 → ϕKs0 decays with Belle II

• Published in: Physical review. D 2023-10, Vol.108 (7)
• Main Authors: Adachi, I., Adamczyk, K., Aggarwal, L., Ahmed, H., Aihara, H., Akopov, N., Aloisio, A., Anh Ky, N., Asner, D. M., Atmacan, H., Aushev, T., Aushev, V., Aversano, M., Babu, V., Bae, H., Bahinipati, S., Bambade, P., Banerjee, Sw, Barrett, M., Baudot, J., Bauer, M., Baur, A., Beaubien, A., Becherer, F., Becker, J., Behera, P. K., Bennett, J. V., Bertacchi, V., Bertemes, M., Bertholet, E., Bessner, M., Bettarini, S., Bhuyan, B., Bianchi, F., Bilka, T., Biswas, D., Bobrov, A., Bodrov, D., Bolz, A., Bondar, A., Borah, J., Bozek, A., Bračko, M., Branchini, P., Briere, R. A., Browder, T. E., Budano, A., Bussino, S., Campajola, M., Cao, L., Casarosa, G., Cecchi, C., Cerasoli, J., Chang, M. -C., Chang, P., Cheema, P., Chekelian, V., Chen, C., Cheon, B. G., Chilikin, K., Chirapatpimol, K., Cho, H. -E., Cho, K., Cho, S. -J., Choi, S. -K., Choudhury, S., Cochran, J., Corona, L., Cremaldi, L. M., Das, S., Dattola, F., De La Cruz-Burelo, E., de la Motte, S. A., De Nardo, G., de Nuccio, M., de Pietro, G., de Sangro, R., Destefanis, M., Dey, S., de Yta-Hernandez, A., Dhamija, R., Di Canto, A., Di Capua, F., Dingfelder, J., Doležal, Z., Domínguez Jiménez, I., Dong, T. V., Dorigo, M., Dort, K., Dreyer, S., Dubey, S., Dujany, G., Ecker, P., Eliachevitch, M., Feichtinger, P., Ferber, T., Ferlewicz, D., Fillinger, T., Finck, C., Finocchiaro, G.
• Format: Article
• Language: English
• Subjects: Physics
• ISSN: 2470-0010; 2470-0029
• DOI: 10.1103/PhysRevD.108.072012

We present a measurement of time-dependent rate asymmetries in $B^0\to \phi K^0_S$ decays to search for non-standard-model physics in $b\to q \overline{q}s$ transitions. The data sample is collected with the Belle II detector at the SuperKEKB asymmetric-energy $e^{+}e^{-}$ collider in 2019-2022 and contains $(387\pm 6)\times 10^6$ bottom-antibottom mesons from $\Upsilon(4S)$ resonance decays. We reconstruct $162\pm17$ signal events and extract the charge-parity ($CP$) violating parameters from a fit to the distribution of the proper-decay-time difference of the two $B$ mesons. The measured direct and mixing-induced $CP$ asymmetries are $A=0.31\pm0.20\pm0.05$ and $S=0.54\pm0.26^{+0.06}_{-0.08}$, respectively, where the first uncertainties are statistical and the second are systematic. The results are compatible with the $CP$ asymmetries observed in $b\to c\overline{c} s$ transitions.