Improved measurement of η/η′ mixing in B₍ₛ₎⁰→ J/ψ η( ) decays

A bstract Branching fraction ratios between the decays B₍ₛ₎⁰→ J/ψ η( ) 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 $$ { {array}{c}{B({B}^0→ J/{ψ η}^{})}{B({B}^0→ J/ψ η )}=0.48± 0.06± 0.02± 0.01,\\ {}{B({B}_s^0→ J/{ψ η}^{})}{B({B}_s^0→ J/ψ η )}=0.80± 0.02± 0.02± 0.01,{array}} $$ 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, ϕ P , and to probe the presence of a possible glueball component in the η ′ meson, described by the gluonic mixing angle ϕ G . The obtained results are arraycφP=(41.6-1.2+1.0)∘,\\ φG=(28.1-4.0+3.9)∘,array ϕ P = 41.6 − 1.2 + 1.0