Observation of the open-charm tetraquark candidate $T_{cs 0}^{*}(2870)^0$ in the $B^- \rightarrow D^- D^0 K_\mathrm{S}^0$ decay

TL;DR

This paper reports the observation of a new open-charm tetraquark candidate, $T_{cs 0}^{*}(2870)^0$, in $B^-$ decays, confirming its existence in a different decay mode with detailed amplitude analysis and significance assessment.

Contribution

The study provides the first observation of the $T_{cs 0}^{*}(2870)^0$ in the $B^- ightarrow D^- D^0 K_ ext{S}^0$ decay mode, expanding understanding of open-charm tetraquarks.

Findings

Resonant structure with 5.3 sigma significance observed in $D^0 K_ ext{S}^0$ spectrum.

Mass and width of the state measured as $2883 ext{ MeV}/c^2$ and $87 ext{ MeV}$.

No evidence found for the $T_{cs1}^{*}(2900)^0$ state in this decay mode.

Abstract

An amplitude analysis of $B^-\rightarrow D^- D^0 K_\mathrm{S}^0$ decays is performed using proton-proton collision data, corresponding to an integrated luminosity of $9\,\text{fb}^{-1}$, collected with the LHCb detector at center-of-mass energies of 7, 8, and 13$\mathrm{\,Te\kern -0.1em V}$. A resonant structure of spin-parity $0^+$ is observed in the $D^0 K_\mathrm{S}^0$ invariant-mass spectrum with a significance of $5.3\,\sigma$. The mass and width of the state, modeled with a Breit$-$Wigner lineshape, are determined to be $2883\pm11\pm8\mathrm{\,Me\kern -0.1em V\!/}c^2$ and $87_{-47}^{+22}\pm17\mathrm{\,Me\kern -0.1em V}$ respectively, where the first uncertainties are statistical and the second systematic. These properties and the quark content are consistent with those of the open-charm tetraquark candidate $T_{cs 0}^{*}(2870)^0$ observed previously in the $D^+ K^-$ final state of the $B^-\rightarrow D^- D^+ K^-$ decay. This result confirms the existence of the $T_{cs 0}^{*}(2870)^0$ state in a new decay mode. The $T_{cs1}^{*}(2900)^0$ state, reported in the $B^-\rightarrow D^- D^+ K^-$ decay, is also searched for in the $D^0 K_\mathrm{S}^0$ invariant-mass spectrum of the $B^- \rightarrow D^- D^0 K_\mathrm{S}^0$ decay, without finding evidence for it.