Evidence for formation of a narrow pKshort resonance with mass near 1533 MeV in neutrino interactions

TL;DR

This paper reports the observation of a narrow resonance near 1533 MeV in neutrino interactions, likely indicating the production of the  pentaquark baryon, based on data from multiple bubble chamber experiments.

Contribution

First evidence of a narrow pentaquark resonance at 1533 MeV in neutrino interactions, suggesting a new baryonic state not matching known  states.

Findings

Resonance mass estimated at 1533b15 MeV

Width less than 20 MeV, compatible with experimental resolution

Statistical significance near 6.7 sigma

Abstract

A narrow baryon resonance is observed in invariant mass of the pKshort system formed in neutrino and antineutrino collisions with nuclei. The mass of the resonance is estimated as (1533+-5)MeV. The observed width is less than 20 MeV, and is compatible with being entirely due to experimental resolution. The statistical significance of the signal is near 6.7 standard deviations. As the position of the observed resonance does not match the mass of any known \Sigma^{*+} state, we believe that it arises from neutrino production of the \Theta^+ pentaquark baryon. The analysis is based on the data obtained in past neutrino experiments with big bubble chambers: WA21, WA25, WA59, E180 and E632.