Observation of narrow baryon resonance in $pK^0_s$ mode in $pA$-interactions at $70 GeV/c$ with SVD-2 setup

Abstract

We report on the SVD-2 experiment data analysis aimed to search for an exotic baryon state, the $\Theta^+$-baryon, in a $pK^0_s$ decay mode with IHEP U-70 accelerator proton beam at $70 GeV/c$. A resonant structure with $M=1526\pm3(stat.)\pm 3(syst.)~MeV/c^2$ and $\Gamma < 24 MeV/c^2$ was found in the $pK^0_s$ invariant mass spectrum, with the statistical significance of this peak estimated as $5.6~\sigma$.