Formation of a narrow baryon resonance with positive strangeness in K+ collisions with Xe nuclei

The data on the charge-exchange reaction K +Xe → K 0 pXe′, obtained with the bubble chamber DIANA, are reanalyzed using increased statistics and updated selections. Our previous evidence for formation of a narrow pK 0 resonance with mass near 1538 MeV is confirmed. The statistical significance of the signal reaches some 8 (6) standard deviations when estimated as \( {S \mathord{\left/ {\vphantom {S {\sqrt B \left( {{S \mathord{\left/ {\vphantom {S {\sqrt {B + S} }}} \right. \kern-\nulldelimiterspace} {\sqrt {B + S} }}} \right)}}} \right. \kern-\nulldelimiterspace} {\sqrt B \left( {{S \mathord{\left/ {\vphantom {S {\sqrt {B + S} }}} \right. \kern-\nulldelimiterspace} {\sqrt {B + S} }}} \right)}} \). The mass and intrinsic width of the Θ+ baryon are measured as m = 1538 ± 2 MeV and Γ = 0.39 ± 0.10 MeV.