"Discovery of a Novel Subatomic Particle Confirmed"

The BESIII collaboration has observed an anomalous line shape around the ppbar mass threshold in the J/ψ→γ3(π+π-) decay, indicating the existence of a ppbar bound state, with a new resonance X(1880) discovered near the ppbar mass threshold. The mass and width of X(1880) were determined to be 1882.1±1.7±0.7 MeV/c2 and 30.7±5.5±2.4 MeV/c, respectively, supporting the existence of a ppbar bound state. This result was published in Physical Review Letters and selected as "Featured in Physics."