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

TL;DR

The SVD-2 experiment observed a narrow baryon resonance at 1526 MeV/c^2 in pK^0_s decay mode, providing evidence for the exotic $ heta^+$ pentaquark with a significance of 5.6 sigma in pA interactions at 70 GeV/c.

Contribution

First observation of a narrow baryon resonance consistent with the $ heta^+$ pentaquark in pA interactions at 70 GeV/c, supporting its existence as an exotic baryon state.

Findings

Resonance mass at 1526 MeV/c^2 with width < 24 MeV/c^2

Statistical significance of 5.6 sigma for the resonance

Estimated total cross section for $ heta^+$ production between 30 and 120 μb

Abstract

SVD-2 experiment data have been analyzed to search for an exotic baryon state, the $\Theta^+$-baryon, in a $pK^0_s$ decay mode at $70 GeV/c$ on IHEP accelerator. The reaction $pA \to pK^0_s+X$ with a limited multiplicity was used in the analysis. The $pK^0_s$ invariant mass spectrum shows a resonant structure with $M=1526\pm3(stat.)\pm 3(syst.) MeV/c^2$ and $\Gamma < 24 MeV/c^2$. The statistical significance of this peak was estimated to be of $5.6 \sigma$. The mass and width of the resonance is compatible with the recently reported $\Theta^+$- baryon with positive strangeness which was predicted as an exotic pentaquark ($uudd\bar{s}$) baryon state. The total cross section for $\Theta^+$ production in pN-interactions for $X_F\ge 0$ was estimated to be $(30\div120) \mu b$ and no essential deviation from A-dependence for inelastic events $(\sim A^{0.7})$ was found.