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

TL;DR

This paper reports the observation and measurement of mass differences and production rates of $oldsymbol{ ext{Sigma}_c^0}$ and $ extbf{ ext{Sigma}_c^{++}}$ baryons in 500 GeV $oldsymbol{ ext{pi}^-}$-N interactions, providing insights into charmed baryon production.

Contribution

First measurement of $ ext{Sigma}_c$ mass differences and production rates in high-energy pion-nucleon interactions.

Findings

Mass differences: $(167.38 ext{ MeV}, 167.76 ext{ MeV})$ for $ ext{Sigma}_c^0$ and $ ext{Sigma}_c^{++}$.

Production rate of $ ext{Lambda}_c^+$ from $ ext{Sigma}_c$ decays is about 22%.

No significant baryon-antibaryon asymmetry observed.

Abstract

From a sample of $2722 \pm 78$ $\Lambda_c^+$ decaying to the $pK^-\pi^+$ 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 $(167.76\pm 0.29\pm0.15) {MeV}$. 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.