Resolving the low mass puzzle of $\Lambda_c(2940)^+$

TL;DR

This paper proposes an unquenched model to explain the low mass of $\Lambda_c(2940)^+$, showing that channel contributions can reconcile theoretical predictions with experimental data and predicting a distinctive mass inversion pattern.

Contribution

It introduces an unquenched approach to resolve the low mass puzzle and predicts a novel mass inversion relation for $\Lambda_c^+$ states, offering a testable criterion.

Findings

Mass of $\Lambda_c(2P,3/2^-)$ can be lowered to match experimental data.

Narrow width of $\Lambda_c(2940)^+$ explained semi-quantitatively.

Predicted mass inversion relation for $\Lambda_c^+$ states as a test for unquenched models.

Abstract

For the long standing low mass puzzle of $\Lambda_c(2940)^+$, we propose an unquenched picture. Our calculation explicitly shows that the mass of the $\Lambda_c(2P,3/2^-)$ state can be lowered down to be consistent with the experimental data of $\Lambda_c(2940)^+$ by introducing the $D^*N$ channel contribution. Additionally, we give a semi-quantitative analysis to illustrate why the $\Lambda_c(2940)^+$ state has a narrow width. It means that the low mass puzzle of $\Lambda_c(2940)^+$ can be solved. What is more important is that we predict a mass inversion relation for the $2P$ $\Lambda_{c}^+$ states, i.e., the $\Lambda_c(2P,1/2^-)$ state is higher than the $\Lambda_c(2P,3/2^-)$, which is totally different from the result of conventional quenched quark model. It provides a criterion to test such an unquenched scenario for $\Lambda_c(2940)^+$. We expect the future experimental progress from the LHCb and Belle II.