Mass Splitting and Production of ${\Sigma }_c^0$ and ${\Sigma }_c^{++}$ Measured in $500GeV$ ${\pi }^{-}-$N Interactions

Abstract

From a sample of $2722\pm 78$ ${\Lambda }_c^{+}$ decaying to the $p{K}^{-}{\pi }^{+}$ final state, we have observed, in the hadroproduction experiment E791 at Fermilab, $143\pm 20$ ${\Sigma }_c^0$ and $122\pm 18$ ${\Sigma }_c^{++}$ through their decays to ${\Lambda }_c^{+}{\pi }^{\pm }$. The mass difference $M({\Sigma }_c^0)-M({\Lambda }_c^{+}$) is measured to be $(167.38\pm 0.29\pm 0.15)MeV$; for $M({\Sigma }_c^{++})-M({\Lambda }_c^{+})$, we find $(167.76\pm 0.29\pm 0.15)MeV$. The rate of ${\Lambda }_c^{+}$ production from decays of the ${\Sigma }_c$ triplet is $(22\pm 2\pm 3) {%}$ of the total ${\Lambda }_c^{+}$ production assuming equal rate of production from all three, as measured for ${\Sigma }_c^0$ and ${\Sigma }_c^{++}$. We do not observe a statistically significant ${\Sigma }_c$ baryon-antibaryon production asymmetry. The $x_F$ and $p_t^2$ spectra of ${\Lambda }_c^{+}$ from ${\Sigma }_c$ decays are observed to be similar to those for all ${\Lambda }_c^{+}$'s produced.

15 pages, uuencoded postscript 3 figures uuencoded, tar-compressed file