Observation of S=+1 narrow resonances in the system $K^0_sp$ from p+$C_3H_8$ collision at 10 GeV/c

Abstract

The 2m propane bubble chamber experimental data have been analyzed to search for an exotic baryon state, the $\Theta^+$ -baryon, in the $pK^0_s$ decay mode for the reaction p+$C_3H_8$ at 10 GeV/c. The $pK^0_s$ invariant mass spectrum shows resonant structures with $M_{K_s^0 p}$=1540$\pm$8, 1613$\pm$10, 1821$\pm$11 MeV/$c^2$ and $\Gamma_{K_s^0 p}$= 9.2$\pm$1.8, 16.1$\pm$4.1, 28.0$\pm$9.4 MeV/$c^2$. The maximal statistical significance of these peaks have been estimated as 5.5$\sigma$,4.8$\sigma$ and 5.0$\sigma$, respectively.