First Observation of a Doubly Charged Tetraquark and Its Neutral Partner

作者：Aaij, R.; Abdelmotteleb, A. S. W.; Beteta, C. Abellan; Abudinen, F.; Ackernley, T.; Adeva, B.; Adinolfi, M.; Adlarson, P.; Afsharnia, H.; Agapopoulou, C.; Aidala, C. A.; Aiola, S.; Ajaltouni, Z.; Akar, S.; Akiba, K.; Albrecht, J.; Alessio, F.; Alexander, M.; Alfonso Albero, A.; Aliouche, Z.; Cartelle, P. Alvarez; Amalric, R.; Amato, S.; Amey, J. L.; Amhis, Y.; An, L.; Anderlini, L.; Andersson, M.; Andreianov, A.; Andreotti, M.; Andreou, D.; Ao, D.; Archilli, F.; Artamonov, A.; Artuso, M.

来源：Physical Review Letters, 2023, 131(4): 041902.

DOI：10.1103/PhysRevLett.131.041902

A combined amplitude analysis is performed for the decays B0-+ D0D thorn s & pi;- and B thorn -+ D-D thorn s & pi; thorn , which are related by isospin symmetry. The analysis is based on data collected by the LHCb detector in proton -proton collisions at center-of-mass energies of 7, 8, and 13 TeV. The full data sample corresponds to an integrated luminosity of 9 fb-1. Two new resonant states with masses of 2.908 ? 0.011 ? 0.020 GeV and widths of 0.136 ? 0.023 ? 0.013 GeV are observed, which decay to D thorn s & pi; thorn and D thorn s & pi;- respectively. The former state indicates the first observation of a doubly charged open-charm tetraquark state with minimal quark content 1/2cs over bar ud over bar ?, and the latter state is a neutral tetraquark composed of 1/2cs over bar u over bar d ? quarks. Both states are found to have spin-parity of 0 thorn , and their resonant parameters are consistent with each other, which suggests that they belong to an isospin triplet.