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

Understand

The data on the charge-exchange reaction K^+Xe --> K^0 p Xe, 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 and reinforced.
• The statistical significance of the signal reaches some 8\sigma (6\sigma) when estimated as S/\sqrt{B} (S/\sqrt{B+S}).
• The mass and intrinsic width of the \Theta^+ baryon are measured as m = (1538+-2) MeV and \Gamma = (0.39+-0.10) MeV.