Study of the decay and production properties of $D_{s1}(2536)$ and $D_{s2}^*(2573)$

TL;DR

This study measures decay branching fractions and cross sections of $D_{s1}(2536)$ and $D_{s2}^*(2573)$, revealing new resonant structures around 4.6 and 4.75 GeV, challenging existing theoretical models.

Contribution

First measurement of absolute branching fractions for $D_{s1}(2536)$ and $D_{s2}^*(2573)$ decays, and observation of a new resonance near 4.6 GeV in $e^+e^-$ collisions.

Findings

Branching fractions: $(35.9 ext{--}4.8 ext{--}3.5)\%$ and $(37.4 ext{--}3.1 ext{--}4.6)\%$

Resonant structure at 4.6 GeV with 50 MeV width, significance $15\sigma$

Evidence for a structure at 4.75 GeV in both processes

Abstract

The $e^+e^-\rightarrow D_s^+D_{s1}(2536)^-$ and $e^+e^-\rightarrow D_s^+D^*_{s2}(2573)^-$ processes are studied using data samples collected with the BESIII detector at center-of-mass energies from 4.530 to 4.946~GeV. The absolute branching fractions of $D_{s1}(2536)^- \rightarrow \bar{D}^{*0}K^-$ and $D_{s2}^*(2573)^- \rightarrow \bar{D}^0K^-$ are measured for the first time to be $(35.9\pm 4.8\pm 3.5)\%$ and $(37.4\pm 3.1\pm 4.6)\%$, respectively. The measurements are in tension with predictions based on the assumption that the $D_{s1}(2536)$ and $D_{s2}^*(2573)$ are dominated by a bare $c\bar{s}$ component. The $e^+e^-\rightarrow D_s^+D_{s1}(2536)^-$ and $e^+e^-\rightarrow D_s^+D^*_{s2}(2573)^-$ cross sections are measured, and a resonant structure at around 4.6~GeV with a width of 50~MeV is observed for the first time with a statistical significance of $15\sigma$ in the $e^+e^-\rightarrow D_s^+D^*_{s2}(2573)^-$ process. It could be the $Y(4626)$ found by the Belle collaboration in the $D_s^+D_{s1}(2536)^{-}$ final state, since they have similar masses and widths. There is also evidence for a structure at around 4.75~GeV in both processes.