Production of the SIGMA(0)(C) and SIGMA(++)(C) by High Energy Neutrons.
Abstract
We present the first observation of hadroproduction of the Sigma_sp{c}{++ } and Sigma_sp{c }{0}, decaying into Lambda _{c}pi. The daughter Lambda_{c} is observed in the decay modes pKpi and pK _{s}pipi. The Experiment was conducted at a broadband neutron beam in the Proton East area of the Fermi National Accelerator Laboratory. A twomagnet multiparticle spectrometer equipped with proportional wire chambers and a high resolution MWPC vertex detector was used to momentum analyze charged particles produced in the interactions of neutrons on targets of beryllium, silicon and tungsten. Particles were identified using three Cerenkov counters. The beam energy for each event was reconstructed using hadronic and electromagnetic calorimetry. The mass differences delta m_ {Sigma_sp{c}{++} Lambda_{c}}, delta m_{Sigma_sp{c }{0}Lambda_{c}} and delta m_{Sigma _sp{c}{++}Sigma_sp {c}{0}} are measured and found to be 166.4 +/.3 +/ 2.0 MeV/c^2, 178.5 +/.3 +/ 2.5MeV/c ^2 and 12.1 +/ .4 +/ 2.8MeV/c^2 . This last value is larger in magnitude than the predictions of most theoretical calculations. We also report measurements of particle to antiparticle ratios, x_{f} dependence, A dependence, and p_{t} dependence of the production cross sections. The total production cross sections of the Sigma_sp{c} {0} and Sigma_sp {c}{++} are calculated, assuming {dsigmaover dx_{f }} ~ (1 x)^4, linear atomic weight dependence, B(Lambda_{c} to pKpi) =.022, and symmetric production of particle and antiparticle. From this, and the value of sigma cdot B( Lambda_{c} to pK_sp{s}{0} pipi), calculated under the same assumptions, we calculate the ratio of branching fractions {B(Lambda_{c} to p K^{0}pipi)}over {B(Lambda_{c}to pKpi) }. We conclude that the level of charm production indicated by our measurements is substantially higher than that predicted by first order gluongluon fusion.
 Publication:

Ph.D. Thesis
 Pub Date:
 1988
 Bibcode:
 1988PhDT........79L
 Keywords:

 Physics: Elementary Particles and High Energy