Observation of a J/ψΛ Resonance Consistent with a Strange Pentaquark Candidate in B- → J/ψΛ(p)over-bar Decays

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.; 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.; Aslanides, E.

来源：Physical Review Letters, 2023, 131(3): 031901.

DOI：10.1103/PhysRevLett.131.031901

An amplitude analysis of B- -> J/psi Lambda(p) over bar decays is performed using 4400 signal candidates selected on a data sample of pp collisions recorded at center-of-mass energies of 7, 8, and 13 TeV with the LHCb detector, corresponding to an integrated luminosity of 9 fb(-1). A narrow resonance in the J/psi Lambda system, consistent with a pentaquark candidate with strangeness, is observed with high significance. The mass and the width of this new state are measured to be 4338.2 +/- 0.7 +/- 0.4 MeV and 7.0 +/- 1.2 +/- 1.3 MeV, where the first uncertainty is statistical and the second systematic. The spin is determined to be 1/2 and negative parity is preferred. Because of the small Q-value of the reaction, the most precise single measurement of the B- mass to date, 5279.44 +/- 0.05 +/- 0.07 MeV, is obtained.