2024/11/05 by LHCb collaboration, R. Aaij, LHCb Collaboration +2261 · 1 voice · 1 citation
#hep-ex
paper · pdf · doi:10.48550/arxiv.2411.03399
An amplitude analysis of the Ds1(2460)+→ Ds+π+π- transition is performed simultaneously in B0→ D-Ds+π+π-, B+→D0 Ds+π+π-, and B0→ D*-Ds+π+π- decays. The study is based on a data sample of proton-proton collisions recorded with the LHCb detector at centre-of-mass energies of √(s)=7,8, and 13 TeV, corresponding to a total integrated luminosity of 9 \rmfb-1. A clear double-peak structure is observed in the m(π+π-) spectrum of the Ds1(2460)+→ Ds+π+π- decay. The data can be described either with a model including f0(500), f0(980) and f2(1270) resonances, in which the contributions of f0(980) and f2(1270) are unexpectedly large, or with a model including f0(500), a doubly charged open-charm tetraquark state T_cs++ and its isospin partner T_cs0. If the former is considered implausible, the T_cs states are observed with high significance, and the data are consistent with isospin symmetry. When imposing isospin constraints between the two T_cs states, their mass and width are determined to be 2327±13±13 MeV and 96±16 +170-23 MeV, respectively, where the first uncertainty is statistical and the second is systematic. The mass is slightly below the DK threshold, and a spin-parity of 0+ is favoured with high significance.