Observation of a resonance in the K$_s$p decay channel at a mass of 1765 MeV/c$^2$

WA89 Collaboration; Adamovich, M. I.; Alexandrov, Yu. A.; Barberis, D.; Beck, M.; Bérat, C.; Beusch, W.; Boss, M.; Brons, S.; Brückner, W.; Buénerd, M.; Busch, C.; Büscher, C.; Charignon, F.; Chauvin, J.; Chudakov, E. A.; Dersch, U.; Dropmann, F.; Engelfried, J.; Faller, F.; Fournier, A.; Gerassimov, S. G.; Godbersen, M.; Grafström, P.; Haller, Th.; Heidrich, M.; Hubbard, E.; Hurst, R. B.; Königsmann, K.; Konorov, I.; Keller, N.; Martens, K.; Martin, Ph.; Masciocchi, S.; Michaels, R.; Müller, U.; Neeb, H.; Newbold, D.; Newsom, C.; Paul, S.; Pochodzalla, J.; Potashnikova, I.; Povh, B.; Ren, Z.; Rey-Campagnolle, M.; Rosner, G.; Rossi, L.; Rudolph, H.; Scheel, C.; Schmitt, L.; Siebert, H. -W.; Simon, A.; Smith, V.; Thilmann, O.; Trombini, A.; Vesin, E.; Volkemer, B.; Vorwalter, K.; Walcher, Th.; Wälder, G.; Werding, R.; Wittmann, E.; Zavertyaev, M. V.

Observation of a resonance in the K$_s$p decay channel at a mass of 1765 MeV/c$^2$

Authors

Description

We report on the observation of a K$_s$p resonance signal at a mass of 1765$\pm$5 MeV/c$^2$, with intrinsic width $Γ= 108\pm 22$ MeV/c$^2$, produced inclusively in $Σ^-$-nucleus interactions at 340 GeV/c in the hyperon beam experiment WA89 at CERN. The signal was observed in the kinematic region $x_F>0.7$, in this region its production cross section rises approximately linearly with $(1-x_F)$, reaching $BR(X\to K_S p)\cdot dσ/dx_F = (5.2\pm 2.3) μb $ per nucleon at $x_F=0.8$. The hard \xf spectrum suggests the presence of a strong leading particle effect in the production and hence the identification as a $Σ^{*+}$ state. No corresponding peaks were observed in the $K^- p$ and $Λπ^{\pm}$ mass spectra.