Observation and investigation of the $T_{c\bar{c}1}(4430{)}^{+}$ structure in $B^{+}\to \ddot{I}ˆ(2S)K_{\text{S}}^0\ddot{I}{€}^{+}$ decays

Abstract

The first four-dimensional amplitude analysis of the $B^{+}\to \ddot{I}ˆ(2S)K_{\text{S}}^0\ddot{I}{€}^{+}$ decay is performed with proton-proton collision data collected by the LHCb experiment at $\sqrt{s}=13\mathrm{TeV}$, corresponding to an integrated luminosity of $5.4\mathrm{f}{\mathrm{b}}^{-1}$. The data cannot be fully explained by $B^{+}\to \ddot{I}ˆ(2S)K^{\ast +}$ contributions alone. A significantly better description of the data is obtained by adding a $T_{c\bar{c}}^{+}$ contribution decaying to $\ddot{I}ˆ(2S)\ddot{I}{€}^{+}$. The properties of the $T_{c\bar{c}}^{+}$ structure are consistent with the exotic state $T_{c\bar{c}1}(4430{)}^{+}$ reported in the isospin-related ${\bar{B}}^0\to \ddot{I}ˆ(2S)K^{-}\ddot{I}{€}^{+}$ decay. Effects of a possible $T_{c\bar{c}1}(4430{)}^{+}\to {\bar{D}}_1^{\ast }(2600{)}^0{D}^{+}$ decay mode on the $T_{c\bar{c}1}(4430{)}^{+}\to \ddot{I}ˆ(2S)\ddot{I}{€}^{+}$ mass distribution are investigated through a Flatté parametrization, providing constraints on the relative decay strength. A description of the $T_{c\bar{c}1}(4430{)}^{+}$ structure using the triangle singularity mechanism is studied and also found to be consistent with the data.

All figures and tables, along with machine-readable versions and any supplementary material and additional information, are available at https://lbfence.cern.ch/alcm/public/analysis/full-details/3755/ (LHCb public pages)