Observation of the Bs0 ?x (3872)? Decay

Abstract

Using a data sample of proton-proton collisions at s=13 TeV, corresponding to an integrated luminosity of 140 fb-1 collected by the CMS experiment in 2016-2018, the Bs0?X(3872)? decay is observed. Decays into J/?+?- and K+K- are used to reconstruct, respectively, the X(3872) and ?. The ratio of the product of branching fractions B[Bs0?X(3872)?]B[X(3872)?J/?+?-] to the product B[Bs0?(2S)?]B[?(2S)?J/?+?-] is measured to be [2.21�0.29(stat)�0.17(syst)]%. The ratio B[Bs0?X(3872)?]/B[B0?X(3872)K0] is found to be consistent with one, while the ratio B[Bs0?X(3872)?]/B[B+?X(3872)K+] is two times smaller. This suggests a difference in the production dynamics of the X(3872) in B0 and Bs0 meson decays compared to B+. The reported observation may shed new light on the nature of the X(3872) particle. � 2020 CERN.