Improved measurement of η/η′ mixing in B s 0 → J / ψ η ′ decays
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13130_2025_Article_27405.pdf
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Author(s)
Aaij, R.
Abdelmotteleb, A. S. W.
Abellan Beteta, C.
Abudinén, F.
Ackernley, T.
Adefisoye, A. A.
Adeva, B.
Adinolfi, M.
Adlarson, P.
Agapopoulou, C.
Date Issued
October 14, 2025
Journal
Journal of High Energy Physics
Publisher
Springer Berlin Heidelberg
Citation
The LHCb collaboration., Aaij, R., Abdelmotteleb, A.S.W. et al. Improved measurement of η/η′ mixing in
B0(s) → J/ψη(′) decays. J. High Energ. Phys. 2025, 113 (2025).
Version
Final published version
Abstract
Branching fraction ratios between the decays B s 0 → J / ψ η ′ are measured using proton-proton collision data collected by the LHCb experiment at centre-of-mass energies of 7, 8 and 13 TeV, corresponding to an integrated luminosity of 9 fb−1. The measured ratios of these branching fractions are B B 0 → J / ψη ′ B B 0 → J / ψη = 0.48 ± 0.06 ± 0.02 ± 0.01 , B B s 0 → J / ψη ′ B B s 0 → J / ψη = 0.80 ± 0.02 ± 0.02 ± 0.01 , where the uncertainties are statistical, systematic and related to the precision of the η(′) branching fractions, respectively. They are used to constrain the η/η′ mixing angle, ϕP, and to probe the presence of a possible glueball component in the η′ meson, described by the gluonic mixing angle ϕG. The obtained results are ϕ P = 41.6 − 1.2 + 1.0 ∘ , ϕ G = 28.1 − 4.0 + 3.9 ∘ , where the uncertainties are statistically dominated. While the value of ϕP is compatible with existing experimental determinations and theoretical calculations, the angle ϕG differs from zero by more than four standard deviations, which points to a substantial glueball component in the η′ meson and/or unexpectedly large contributions from gluon-mediated processes in these decays. The absolute branching fractions are also measured relative to that of the well-established B s 0 → J / ψϕ decay, which serves as the normalisation channel. These results supersede the previous LHCb measurements and are the most precise to date.
MIT Department
Massachusetts Institute of Technology. Laboratory for Nuclear Science
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DOI of Published Version
https://doi.org/10.1007/JHEP10(2025)113
