Szczegóły publikacji

An amplitude analysis of the Ds1(2460)+→Ds+π+π−Ds1​(2460)+→Ds+​π+π− transition is performed simultaneously in B0→D−Ds+π+π−B0→D−Ds+​π+π−, B+→Dˉ0Ds+π+π−B+→Dˉ0Ds+​π+π−, and B0→D∗−Ds+π+π−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 13TeV, corresponding to a total integrated luminosity of 9 fb−19fb−1. A clear double-peak structure is observed in the m(π+π−)m(π+π−) spectrum of the Ds1(2460)+→Ds+π+π−Ds1​(2460)+→Ds+​π+π− decay. The data can be described either with a model including f0(500)f0​(500), f0(980)f0​(980) and f2(1270)f2​(1270) resonances, in which the contributions of f0(980)f0​(980) and f2(1270)f2​(1270) are unexpectedly large, or with a model including f0(500)f0​(500), a doubly charged open-charm tetraquark state Tcsˉ++Tcsˉ++​ and its isospin partner Tcsˉ0Tcsˉ0​. If the former is considered implausible, the TcsˉTcsˉ​ states are observed with high significance, and the data are consistent with isospin symmetry. When imposing isospin constraints between the two TcsˉTcsˉ​ states, their mass and width are determined to be 2327±13±13 2327±13±13MeV and 96±16 −23+170 96±16−23+170​MeV, respectively, where the first uncertainty is statistical and the second is systematic. The mass is slightly below the DKDK threshold, and a spin-parity of 0+0+ is favoured with high significance.