Study of charmonium and charmonium-like contributions in $B^+ \rightarrow J/\psi \eta K^+$ decays

TL;DR

This paper investigates the decay processes of B+ mesons into J/psi, eta, and K+ particles, revealing evidence for specific charmonium states and their decay modes using data from the LHCb detector.

Contribution

First evidence of the decay of $ ext{psi}_2(3823)$ into J/psi eta and analysis of charmonium contributions in B+ decays.

Findings

Evidence for $B^+ ightarrow ext{psi}_2(3823) K^+$ decay

Evidence for $B^+ ightarrow ext{psi}(4040) K^+$ decay

First observation of $ ext{psi}_2(3823) ightarrow J/ ext{psi} ext{eta}$ decay

Abstract

A study of $B^+ \rightarrow J/\psi \eta K^+$ decays, followed by $J/\psi \rightarrow \mu^+ \mu^-$ and $\eta \rightarrow \gamma \gamma$, is performed using a dataset collected with the LHCb detector in proton-proton collisions at centre-of-mass energies of 7, 8 and 13 TeV, corresponding to an integrated luminosity of 9 fb$^{-1}$. The $J/\psi\eta$ mass spectrum is investigated for contributions from charmonia and charmonium-like states. Evidence is found for the $B^+\rightarrow \left( \psi_2(3823) \rightarrow J/\psi \eta \right) K^+$ and $B^+\rightarrow \left( \psi(4040) \rightarrow J/\psi \eta \right) K^+$ decays with significance of 3.4 and 4.7~standard deviations, respectively. This constitutes the~first~evidence for the $\psi_2(3823) \rightarrow J/\psi \eta$ decay.