The coupled-channel analysis of $D_s$ and $B_s$ mesons

TL;DR

This paper uses a coupled-channel model based on QCD-derived chiral Lagrangian to calculate mass shifts of $D_s$ and $B_s$ mesons, predicting new masses and analyzing state mixing effects.

Contribution

It introduces a parameter-free, QCD-based coupled-channel approach to compute mass shifts of heavy-light mesons, highlighting the role of strong coupling and chiral transitions.

Findings

Mass shifts for $0^+$ and ${1^+}'$ states are significant.

Predicted masses: $B^*_s(0^+)$ at 5710 MeV, $B_s(1^{+'})$ at 5730 MeV.

Experimental width limits constrain mixing angles.

Abstract

In the framework of the coupled channel model the mass shifts of the $P$--wave excitations of $D_s$ and $B_s$ mesons have been calculated. The corresponding coupling to $DK$ and $BK$ channels is provided by the effective chiral Lagrangian which is deduced from QCD and does not contain fitting parameters. The strong mass shifts down for $0^+$ and ${1^+}'$ states have been obtained, while ${1^+}"$ and $2^+$ states remain almost at rest. Two factors are essential for large mass shifts: strong coupling of the $0^+$ and $1^{+'}$ states to the $S$-wave decay channel, containing a Nambu-Goldstone meson, and the chiral flip transitions due to the bispinor structure of both heavy-light mesons. The masses $M(B^*_s(0^+))=5710(15)$ MeV and $M(B_s(1^{+'}))=5730(15)$ MeV are predicted. Experimental limit on the width $\Gamma(D_{s1}(2536))<2.3$ MeV puts strong restrictions on admittable mixing angle between the $1^+$ and $1^{+'}$ states.