Search Results (12 total)

We present a measurement of the atomic mass dependence of central Ξ^- and Ξ̅ ⁺ production. It is measured using a sample of 22 459 Ξ^-’s and Ξ̅ ⁺’s produced in collisions between a 250 GeV π^- beam and targets of beryllium, aluminum, copper, and tungsten. The relative cross sections are fit to the two parameter function σ₀A^α, where A is the atomic mass. We measure α=0.924±0.020±0.025, for Feynman x in the range -0.09<x_F<0.15.

We measure the differential cross sections with respect to Feynman x ( x_F) and transverse momentum ( p_T) for π, K, and p-induced charm meson production using fully reconstructed D⁺, D⁰, and D_s decays. The shapes of these cross sections are compared to the theoretical predictions for charm quark production of next-to-leading order perturbative QCD using modern parametrizations of the pion and nucleon parton distributions. We observe the differences expected in production induced by projectiles with different gluon distributions, harder distributions being indicated for mesons than for protons.

We measure forward cross sections for production of D⁺, D⁰, D_s, D^*+, and Λ_c in collisions of π^±, K^±, and p on a nuclear target. Production induced by different beam particles is found to be the same within statistics. Strange and baryonic final states are seen to contribute appreciably to the total charm cross section, which our measurements indicate is larger than but consistent with QCD predictions. The energy dependence mapped out by these and previous measurements is consistent with theory. Leading-particle asymmetry measurements for K and p-induced charm production are also presented.

We report results from Fermilab experiment E769 on the differential cross sections of D^*± charm vector mesons with respect to Feynman-x (x_F) and transverse momentum (P_T), and on the atomic mass dependence of the production. The D^* mesons were produced by a 250 GeV π beam on a target of Be, Al, Cu, and W foils. The dσ / dx_F distribution is fit by the form ((1-x_F)ⁿ) with n=3.5±0.3±0.1, the dσ / dP_T² distribution by exp(-b×P_T²) with b=0.70±0.07±0.04 GeV^-2, and the cross section A dependence by A^α with α=1.00±0.07±0.02. These results are compared to the equivalent parameters for the production of pseudoscalar D⁰ and D^± charm mesons.

A leading charm meson is one with longitudinal momentum fraction, x_F>0, whose light quark (or antiquark) is of the same type as one of the quarks in the beam particles. We report on the production asymmetry, A=[σ(leading-σ(nonleading)]/[σ(leading)+σ(nonleading)] as a function of x_F. The data consist of 1500 fully reconstructed D^± and D^*± decays in Fermilab experiment E 769. We find a significant asymmetry for the production of charm quarks is not expected in perturbative quantum chromodynamics.

We measure the relative cross sections for D mesons produced in interactions of π^- and π⁺ beams with targets of Be, Cu, Al, and W. The measurement is based on 1400 fully reconstructed decays of the types D⁰→K^-π⁺, D⁺→K^-π⁺π⁺, and charge conjugates. We find that the cross section for the production of both neutral and charged D’s by either π^- or π⁺ is well fitted by the form A^α where A is the atomic mass and α=1.00±0.05±0.02, where the errors are statistical and systematic, respectively. There is no significant dependence of α on the transverse or longitudinal momentum of the D meson or on the charge of either the incident pion or the produced D mesons.

We measure the differential cross section with respect to Feynman-x (x_F) and transverse momentum (P_T) for charm meson production using targets of Be, Al, Cu, and W. In the range 0.1<x_F<0.7, dσ/dx_F is well fit by the form (1-x_F)ⁿ with n=3.9±0.3. The difference between n values for D^- and D⁺ is 1.1±0.7. However, we find an asymmetry of 0.18±0.06 favoring the production of D^- compared to D⁺. In the lower P_T range, <2 GeV, dσ/dP_T² is well fit by the form exp(-b×P_T²) with b=1.03±0.06 GeV^-2, while in the higher P_T range, 0.8 to 3.6 GeV, it is well fit by the form exp(-b’×P_T) with b’=2.76±0.08 GeV^-1. The shape of the differential cross section has no significant dependence on atomic mass of the target material.

We report on a study of the inclusive production properties of D / D̅ mesons in pp collisions at 800 GeV/c and compare our results to measurements made at lower energies and to the expectations of the QCD fusion model.

We have established a sensitive upper limit on φφ resonance production by 350-GeV/c protons incident on a beryllium target. The 90%-confidence-level upper limit varies from 1.5×10^-30 cm²/nucleon at M_φφ=2.8 GeV/c² to 6.0×10^-32 cm²/nucleon at M_φφ=3.4 GeV/c². We observe no evidence of the η_c.

We have measured differential cross sections for K^-p→Σ⁺π^- and π^-p→pπ^- at 3.0 and 5.1 GeV/c near the backward direction. At 3.0 GeV/c both have a dip near -u∼0.1 (GeV/c)². At 5.1 GeV/c, dσ / du for π^-p→pπ^- falls exponentially with slope 3.8±0.1 (GeV/c)^-2 whereas du / dσ for K^-p→Σ⁺π^- exhibits a decreasing slope for larger |u|. These data are discussed in terms of SU(3), and the relative importance of the helicity-flip and -non-flip amplitudes is investigated.