Characteristics of charm particles produced by 800-GeV P-P collisions

This thesis presents the results of Fermilab experiment E743, a study of the production characteristics of the D mesons in 800 GeV proton-proton collisions (√s = 39 GeV), utilizing a high resolution, rapid cycling bubble chamber for vertex detection, and a multiparticle spectrometer for the momentum determination of charged particles. A relatively unbiased measurement of the D meson cross section is accomplished by direct observation of the decay vertices in the bubble chamber, σ(D/D) = 59 -15+22μb. Also measured are the longitudinal and transverse momentum distributions of observed D meson decays. The differential production cross sections are described well by the form 1/σ d2σ/dxFdp2T = (n +1)(b/2) (1-|xF|)ne-bp2T with n = 11.0 -3.6+4.6 and b = 0.66-0.20+0.23 (GeV/C)-2. For |xF| > 0.3 we observe no events, which corresponds to an upper limit of 10 μb at a 95% confidence level. When compared with measurements made at lower energies the results of this study point to a D meson cross section which is slowly rising with center of mass energy. These results are in sharp contrast with the results from a number of experiments performed at the CERN Intersecting Storage Rings (ISR) (√s = 53-62 GeV) which indicated a dramatic rise in the charm particle cross sections with increasing energy. These large cross sections were observed in experiments which were sensitive to production at large xF values (typically sF > 0.3). Unusual mechanisms for charm production invoked to explain these large cross sections do not appear to be necessary below √s = 39 GeV