First observation of an excited charm baryon decaying to omega charm baryon at the BABAR experiment.

摘要

We have carried out a search for a charmed baryon W*c decaying to W0c and a gamma where Oc candidates are reconstructed using decay modes O-pi +(c1), O-pi+ pi0(c2), O-pi +pi-pi+(c3) and xi -K-pi+pi +(c4). This search is performed by analyzing integrated luminosity of 230.7 fb-1 data collected by the BABAR detector at the Stanford Linear Accelerator Center. In decay channel W*c→W0 c&parl0;W-p+&parr0; g (C1), we observe a signal yield of 39.2+9.8-9.1 (stat) +/- 6.0(syst) events with a significance of 4.2 standard deviations. In decay channels W*c→W0 c&parl0;W-p+p 0&parr0;g (C2) and W*c→W0 c&parl0;X-K-p+ p+&parr0;g (C4), we observe signal yields of 55.216.1-15.2 +/- 5.6 and 20.2+9.3-8.5 +/- 3.1 with significances of 3.4 and 2.0 sigma, respectively. As for the W*c→W0 c&parl0;W-p+p -p+&parr0;g (C3) decay channel , we observe signal yields of -5.1+5.3.8-4.7 +/- 1.0 without a positive significance. We assume the same production mechanism for the four decay channels of W*c studied. By combining these four channels, the fit results in a signal yield of 105.3+21.2-20.5 +/- 6.0 events with a significance of 5.2 sigma. We report the mass difference W*c-W0c (deltam) of the singly charmed baryon W*c to be 70.8+1.0-1.0 +/- 1.1 MeV. Finally, the ratios of production cross sections are calculated: se+e-→ C1se+ e-→c1 = 0.71+0.19-0.18 +/- 0.11, se+e-→ C2se+ e-→c2 = 1.76+0.71-0.69 +/- 0.19, se+e-→ C3se+ e-→c3 = -0.66+0.74-0.66 +/-{09}0.13, se+e-→ C4se+ e-→c4 = 1.70+1.0-1.0 +/- 0.27 and se+e-→ W*ccombined se+ e-→W0c combined = 1.0+0.23-0.22 +/- 0.11.