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

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Abstract

An amplitude analysis of B−→J/ψΛ¯p 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/ψΛ 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.
Original languageEnglish
Article number031901
Number of pages11
JournalPhysical Review Letters
Volume131
Issue number3
DOIs
Publication statusPublished - 17 Jul 2023

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