Evidence for formation of [formula omitted] resonances with masses near 1532, 1578, and 1659 MeV in neutrino interactions with nuclei

Abstract

Three baryon resonances with masses of 1532.2 ± 1.3 , 1577.7 ± 1.9 , and 1658.6 ± 4.4 MeV are observed in invariant mass of the K S 0 p system formed in neutrino and antineutrino collisions with deuterons and neon nuclei. Observed widths of the 1532-MeV and 1578-MeV resonances are consistent with being entirely due to apparatus smearing, and their intrinsic widths are restricted to Γ 12 and 23 MeV, respectively. For the 1659-MeV resonance, the data suggest a nonvanishing intrinsic width of Γ ∼ 20 MeV . Significance levels of the three signals are near 7.1 σ , 5.0 σ , and 4.5 σ , respectively. The Σ + hypothesis for either of these three resonances is disfavored by the data on associated Λ hyperons and on formation of the Λ π system. These resonant states are tentatively interpreted as the recently discovered pentaquark baryon Θ + ( 1530 ) and its spin/isospin partners. The analysis is based on neutrino data collected by past bubble-chamber experiments.