Observation Of The Cabibbo-suppressed Decay ξc+ π K- π+

We report the first observation of the Cabihbo-suppressed charm baryon decay ξc+ → pK- π+. We observe 150 ± 22 ± 5 events for the signal. The data were accumulated using the SELEX spectrometer during the 1996-1997 fixed target run at Fermilab, chiefly from a 600 GeV/c Σ- beam. The branching fractions of the decay relative to the Cabibbo-favored ξc+ → Σ + K- π and ξ+ →c+ →- ξ+ π+ π+ are measured to he B(ξc+ → pK- π+)/B(ξc+ → Σ- π+ K π+) = 0.22 ± 0.06 ± 0.03 and B(ξc+ → ξ π+π+pK- π+)/B(ξc+ →- π+ π+) = 0.20 ± 0.04 ± 0.02, respectively.84918571861Körner, J.G., Krämer, M., (1992) Z. Phys. C, 55, p. 659Bauer, M., Stech, B., Wirbel, M., (1987) Z. Phys. C, 34, p. 103Alexander, J.P., (1996) Phys. Rev. D, 53, pp. R1013Frabetti, P.L., (1993) Phys. Lett. B, 314, p. 477Russ, J.S., Proceedings of the 29th International Conference on High Energy Physics, 1998, 2, p. 1259. , edited by A. Astbury et al. (World Scientific, Singapore, 1998), hep-ex/9812031Engelfried, J., (1999) Nucl. Instrum. Methods Phys. Res., Sect. A, 431, p. 53Caso, C., (1998) Eur. Phys. J., C3, p. 1Bergfeld, T., (1996) Phys. Lett. B, 365, p. 43