The nuclear dependence for 800 GeV/c proton production of neutron D mesons has been measured near xF=0 in Experiment 789 at Fermilab. D mesons from beryllium and gold targets were detected with a pair spectrometer and a silicon vertex detector via their decay D→Kπ. No nuclear dependence is found, with a measured α=1.02±0.03±0.02. The measured differential cross section, dσ/dxF, for neutral-D-meson production at 〈xF〉=0.031 is 58±3±7 μb/nucleon. The integrated cross section obtained by extrapolation of the measured cross section to all xF is 17.7±0.9±3.4 μb/nucleon and is consistent with previous measurements.
Measurements of the ratio of Drell-Yan yields from an 800 \rm{GeV/c} proton beam incident on liquid hydrogen and deuterium targets are reported. Approximately 360,000 Drell-Yan muon pairs remained after all cuts on the data. From these data, the ratio of anti-down ($\bar{d}$) to anti-up ($\bar{u}$) quark distributions in the proton sea is determined over a wide range in Bjorken-$x$. These results confirm previous measurements by E866 and extend them to lower $x$. From these data, $(\bar{d}-\bar{u})$ and $\int(\bar{d}-\bar{u})dx$ are evaluated for $0.015<x<0.35$. These results are compared with parameterizations of various parton distribution functions, models and experimental results from NA51, NMC, and HERMES.
A precise measurement of the ratio of Drell-Yan yields from an 800 GeV/c proton beam incident on hydrogen and deuterium targets is reported. Over 140,000 Drell-Yan muon pairs with dimuon mass M_{mu+ mu-} >= 4.5 GeV/c^2 were recorded. From these data, the ratio of anti-down (dbar) to anti-up (ubar) quark distributions in the proton sea is determined over a wide range in Bjorken-x. A strong x dependence is observed in the ratio dbar/ubar, showing substantial enhancement of dbar with respect to ubar for x<0.2. This result is in fair agreement with recent parton distribution parameterizations of the sea. For x>0.2, the observed dbar/ubar ratio is much nearer unity than given by the parameterizations.
The inclusive ϱ ° production cross section has been measured in the reaction π − p → π + π − X at 205 GeV/ c . We find σ ( ϱ ° ) = 13.5 ± 3.4 mb, with most of the production occuring in the central region. Assuming σ ( ϱ + ) ≈ σ ( ϱ − ) ≈ σ ( ϱ ° ), it is concluded that approximately one-third of the pions at this energy come from ϱ -decay.
A study of 205-GeV/c π−p interactions has been made with a 48 800-picture exposure in the bare Fermilab 30-inch hydrogen bubble chamber. The average number of charged particles produced per inelastic interaction is 7.99±0.06. The elastic cross section is 3.18±0.13 mb and the total cross section is 24.19±0.44 mb. The inclusive cross sections for neutral-particle production are: σ(γ)=171.3±15.3 mb, σ(KS0)=3.64±0.61 mb (x<0.3), σ(Λ)=1.71±0.34 mb (x<0.3), and σ(Λ¯)=0.59±0.23 mb (x<0.1). The average number of π0's produced per inelastic collision is consistent with a linear rise with the number of charged particles, and about equal to the number of produced π− or π+. The average number of K0's, Λ's, and Λ¯'s is consistent with very little dependence on the number of charged particles. General characteristics of neutral-particle production are presented and compared with other experiments. For each topology the produced neutral energy is ∼13 of the incident energy.
In a 48 000-picture exposure of the Fermilab 30-inch hydrogen bubble chamber to a 205 GeV/ c π − beam, we have measured 169 events of the reaction, π − p → π − π + π − p, with a cross section of 635 ± 61 μ b. This reaction proceeds almost entirely via low mass π − → 3 π and p → p ππ dissociation. Factorization is satisfied for p → pππ dissociation in πp and pp interactions.
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Fermilab experiment 711 has investigated proton-nucleus collisions in which two high-transverse-momentum hadrons are produced forming high-mass ++, +-, and -- charged states, using an 800-GeV/c proton beam on targets of beryllium, aluminum, iron, and tungsten. Our data cover the range in dihadron mass from 6 to 15 GeV/c2. We show here that the dependence of the cross section on atomic weight A can be parametrized as Aα where α=1.043±0.011(stat)±0.025 (syst), and is independent of the charge state of the dihadron system.
Inelastic scattering of 490 GeV μ + from deuterium and xenon nuclei has been studied for x Bj > s .001. The ratio of the xenon/deuterium cross section per nucleon is observed to vary with x Bj , with a depletion in the kinematic range 0.001 < x Bj < 0.025 which exhibits no significant Q 2 dependence. An electromagnetic calorimeter was used to verify the radiative corrections.
We present results on the cross-section ratio for inelastic muon scattering on neutrons and protons as a function of Bjorken chi;. The data extend to χ values two orders of magnitude smaller than in previous measurements, down to 2×10 −5 , for Q 2 >0.01 GeV 2 . The ratio is consistent with unity throughout this new range.
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