G. Crawford et al., OBSERVATION OF THE CHARMED BARYON-SIGMA(C)+ AND MEASUREMENT OF THE ISOSPIN MASS SPLITTINGS OF THE SIGMA(C), Physical review letters, 71(20), 1993, pp. 3259-3262
We observe the SIGMA(c)+ baryon decaying to LAMBDA(c)+pi0 and measure
the mass difference M(SIGMA(c)+) - M(LAMBDA(c)+) to be 168.5 +/- 0.4 /- 0.2 MeV/c2. We also measure the mass differences M(SIGMA(c)++) - M(
LAMBDA(c)+) and M(SIGMA(c)0) - M(LAMBDA(c)+) with improved precision a
nd determine the isospin mass splittings M(SIGMA(c)++) - M(SIGMA(c)0)
and M(SIGMA(c)+) - M(SIGMA(c)0) to be 1.1 +/- 0.4 +/- 0.1 MeV/c2 and 1
.4 +/- 0.5 +/- 0.3 MeV/c2, respectively. Our results indicate that the
light quark mass difference does not dominate the isospin mass splitt
ing in SIGMA(c).