Evidence supporting the existence of $P_c(4380{)}^{\pm }$ from the recent measurements of $B_s\to J/\psi p\bar{p}$

Abstract

Very recently, the LHCb collaboration released the newest measurements of $B_s\to J/\psi p\bar{p}$, where an enhancement structure near 4.34 GeV was observed in the invariant mass spectrum of $J/\psi p$ with the statistical significance of $3.1-3.7$ $\sigma$. In this work, by performing a combined analysis for the three invariant mass spectra of $B_s\to J/\psi p\bar{p}$, we find that this $J/\psi p$ structure near 4.34 GeV can correspond to the contributions from the $P_c(4380{)}^{+}$ state with the assumption of $J^P=3/2^{-}$ together with the reflections of $B_s\to (f_2^{\ast }\to p\bar{p})J/\psi$. Here, $P_c(4380)$ was first observed in ${\Lambda }_b\to J/\psi pK$ but not confirmed in the updated LHCb data in 2019, and $f_2^{\ast }$ means the exciting light isoscalar tensor meson around 2.0 GeV. Thus, this provides a possible evidence to support the existence of the pentaquark $P_c(4380)$. Specifically, the assumed spin parity $J^P=3/2^{-}$ of $P_c(4380)$ is consistent with a prediction of the theoretical explanation of an $S$-wave $\bar{D}{\Sigma }_c^{\ast }$ molecular bound state.

Comments: 8 pages, 2 tables and 3 figures, accepted by Physical Review D