Observation of the Anomalous Shape of X (1840) in J/? ??3 (?+?-) Indicating a Second Resonance Near p p ¯ Threshold

Using a sample of (10087±44)×106 J/? events, which is about 45 times larger than that was previously analyzed, a further investigation on the J/???3(?+?-) decay is performed. A significant distortion at 1.84 GeV/c2 in the line shape of the 3(?+?-) invariant mass spectrum is observed for the first time, which could be resolved by two overlapping resonant structures, X(1840) and X(1880). The new state X(1880) is observed with a statistical significance larger than 10?. The mass and width of X(1880) are determined to be 1882.1±1.7±0.7 MeV/c2 and 30.7±5.5±2.4 MeV, respectively, which indicates the existence of a pp¯ bound state. © 2024 authors. Published by the American Physical Society. Published by the American Physical Society under the terms of the "https://creativecommons.org/licenses/by/4.0/"Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI. Funded by SCOAP3.