Journal Article

Updated measurement of CP violation and polarisation in $$ {B}_s^0\\to J/\\psi {\\overline{K}}^{\\ast }{(892)}^0 $$ decays

Baladron Rodriguez, P., Blake, T., Battista, P. B., Akiba, K., Bediaga, I. B., Barsuk, S., Ajaltouni, Z., Benane, G., Aaij, R., Belov, I., Anderlini, L., Belin, S., Bachmayer, M., Balagura, V., Bieker, M. S., Barlow, R. J., Anelli, A., Becker, M., Balzani, L., Bacher, D., Bernet Andres, S., Bedeschi, F., Belous, K., Biesuz, N. V., Atzeni, M., Abellan Beteta, C., Ao, D., Amalric, R., Adeva, B., Barbosa, I. R., Bencivenni, G., Baptista de Souza Leite, J., Albicocco, P., Bhom, J., Aleksiejunas, R., Barter, W., Blanc, F., Adefisoye, A. A., Adinolfi, M., Aslanides, E., Bao, H., Bashir, S., Abdelmotteleb, A. S. W., Andreotti, M., Betti, F., Akar, S., Barnyakov, M., Bezshyiko, Ia, Albrecht, J., Behling, N. A., Ackernley, T., Billoir, P., Bezshyyko, O., Areg, Z, Amhis, Y., Back, J. J., Balboni, A., Barbetti, M., Belyaev, I., Baldini, W., Berezhnoy, A., Authier, J. A., Andres Estrada, S., Argenton, M., Ataíde Da Silva, R., Bachmann, S., Bishop, F. C. R., Audurier, B., Blank, J. E., Artuso, M., Bernet, R., An, L., Adlarson, P., Artamonov, A., Aliouche, Z., Archilli, F., Aidala, C. A., Birch, M., Batsukh, B., Beck, A., Betancourt, C., Arguedas Cuendis, S.

2025

Overview

A time-integrated angular analysis of the decay $$ {B}_s^0\\to J/\\psi {\\overline{K}}^{\\ast }{(892)}^0 $$ B s 0 → J / ψ K ¯ ∗ 892 0 , with J / ψ → μ + μ − and $$ {\\overline{K}}^{\\ast }{(892)}^0\\to {K}^{-}{\\pi}^{+} $$ K ¯ ∗ 892 0 → K − π + , is presented. The analysis employs a sample of proton-proton collision data collected by the LHCb experiment during 2015–2018 at a centre-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 6 fb − 1 . A simultaneous maximum-likelihood fit is performed to the angular distributions in bins of the K − π + mass. This fit yields measurements of the CP -averaged polarisation fractions and CP asymmetries for the P-wave component of the K − π + system. The longitudinal and parallel polarisation fractions are determined to be f 0 = 0.534 ± 0.012 ± 0.009 and f || = 0.211 ± 0.014 ± 0.005, respectively, where the first uncertainty is statistical and the second is systematic. The CP asymmetries are measured with 3–7% precision and are found to be consistent with zero. These measurements, along with an updated determination of the branching fraction relative to the B 0 → J / ψK *0 decay, are combined with previous LHCb results, providing the most precise values for these observables to date.