/ Experiment-HEP hep-ex/0401024

Observation of narrow baryon resonance decaying into p K0(S) in pA interactions at 70-GeV/c with SVD-2 setup

Aleev, A. ; Amaglobeli, N. ; Ardashev, E. ; Balandin, V. ; Basiladze, S. ; Berezhnev, S. ; Bogdanova, G. ; Boguslavsky, M. ; Egorov, N. ; Ejov, V. ; Ermakov, G. ; Ermolov, P. ; Furmanec, N. ; Golovnia, S. ; Golubkov, S. ; Gorkov, A. ; Gorokhov, S. ; Gramenitsky, I.M. ; Grishin, N. ; Grishkevich, Ya. ; Karmanov, D. ; Kholodenko, A. ; Kiriakov, A. ; Kosarev, I. ; Kouzmine, N.

Year: 2005 / 2005
Vol.: 68 / 68
Page No: 974-981 / 1012-1019
Pages: 8

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.

Keyword(s): baryon hadronic decay ; proton-nucleus reactions ; strange particles ; mass formulae ; meson mass ; baryon mass

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