A measurement of$\Lambda _c^ +$ baryon production in proton-proton interactions at$\sqrt s = 62GeV$

Summary

The production of open charm has been studied in proton-proton interactions at$\sqrt s = 62GeV$. We report on the observation of the charmed baryon$\Lambda _c^ +$, in coincidence with an electron from the associated anticharm decay, via the reaction$p + p \to e^ - + \Lambda _c^ + + X$, in the kinematical region defined by |x _F|≅0 andp _t>0.5 GeV/c for the e⁻, and |x _F|>0.35 for the$\Lambda _c^ +$. The longitudinal and transverse momentum distributions of the$\Lambda _c^ +$ have been derived. The cross-section for$\bar D\Lambda _c^ +$ associated production has been estimated extrapolating to the full phase space the observed production distributions. The suppression factor with respect to$\Lambda _s^0$ production, at ISR energies, turns out to be about 1/50 in the high-|x _F| range. The results confirm that the «leading» particle effect dominates baryon production in proton-proton interactions.