We present results on the production of hadrons in collisions of 400-GeV/c protons with beryllium, copper, and tungsten nuclei. The data cover the region from 5.6 to 8.0 GeV/c in the transverse momentum of the final-state hadron and from 73° to 102° in the proton-nucleon center-of-momentum frame production angle theta*. The restriction of the data to values of xT (xT=2pT/ √s ) greater than 0.4 enriches the sample with hard collisions of valence quarks. Asymmetries about theta*=90° reflect the presence of neutrons in the target nuclei. The variation of the atomic-weight dependence parameter α with production angle is discussed in the context of the phenomenology of nucleonic structure within nuclei. We also extrapolate our measurements to a ‘‘deuteron’’ target to minimize nuclear effects and compare the result to QCD calculations.
A measurement of continuum dimuon production in proton-copper collisions at 800-GeV incident energy is presented. The dimuons observed in this experiment cover the mass range from 6.5 to 18 GeV near y=0 in the proton-nucleon center-of-momentum frame. Scaling forms of the cross section for the continuum are compared with the results of other experiments in the context of the parton model and quantum chromodynamics. The present limitations of such scaling comparisons are discussed.
Experimental results on the production of dimuons by 800-GeV protons incident on a copper target are presented. The results include measurements of both the continuum of dimuons and the dimuon decays of the three lowest-mass ϒ S states. A description of the apparatus, data acquisition, and analysis techniques is included. A comparison of the results with data taken at lower incident energies indicates a scaling behavior of the continuum dimuon yields.
Results of high-transverse-momentum charged-hadron production in 400-GeV/c proton-proton and proton-deuteron collisions and 800-GeV/c proton-proton collisions are presented. The transverse-momentum range of the data is from 5.2 to 9.0 GeV/c for the 400-GeV/c collisions and from 3.6 to 11.0 GeV/c for the 800-GeV/c collisions; the data are centered around 90° in the proton-nucleon center-of-momentum system. Single-pion invariant cross sections and particle ratios were measured at both energies. The results are compared to previous experiments and the Lund model.
We report measurements of the ratios K+π+, pπ+, K−π−, p¯π−, π−π+, K−K+, and p¯p for hadrons with 0.19<xt<0.62 produced in p−Be and p−W collisions at s=38.8 GeV. The K+π+ ratio at high xt gives the fragmentation-function ratio DuK+Duπ+ at high z. The high-xt K−π− ratio gives an upper limit for DdK−Ddπ− at high z. The pt dependence of pπ+ suggests that scattered constituent diquarks are the primary source of protons with pt<6 GeV/c. We also present species correlations in high-mass h+h− pairs. Strong K+K− and pp¯ correlations were observed.
Measurements of correlations of nearly back-to-back hadrons produced at a large transverse momentum in s=38.8 GeV proton-proton collisions are presented and compared to previous results with a beryllium target. The correlations of identified unlike-sign hadron pairs in ratio to the correlation for all unlike-sign pairs are compared with predictions of the Lund model. These predictions differ from the data.
Measurements of the cross section for production of massive dihadrons by 800-GeV protons incident on a tungsten target are presented. These are compared with measurements taken at lower and higher s and with perturbative-QCD predictions. Scaling and A-dependence behaviors observed at lower energies are confirmed, and good agreement with QCD is obtained. Model dependences of earlier measurements are discussed.
We present an analysis of 800-GeV proton-induced Drell-Yan production data from isoscalar targets 2H and C, and from W, which has a large neutron excess. The ratio of cross sections per nucleon, R-σW/σIS, is sensitive to the difference between the d¯(x) and u¯(x) structure functions of the proton. We find that R is close to unity in the range 0.04≤x≤0.27, allowing upper limits to be set on the d¯-u¯ asymmetry. Additionally, the shape of the differential cross section m3 d2σ/dxF dm for 2H at xF≊0 shows no evidence of an asymmetric sea in the proton. We examine the implications of these data for various models of the violation of the Gottfried sum rule in deep-inelastic lepton scattering.
A precise measurement of the atomic-mass dependence of dimuon production induced by 800-GeV protons is reported. Over 450 000 muon pairs with dimuon mass M≥4 GeV were recorded from targets of H2, C, Ca, Fe, and W. The ratio of dimuon yield per nucleon for nuclei versus H2, R=YA/Y2H, is sensitive to modifications of the antiquark sea in nuclei. No nuclear dependence of this ratio is observed over the range of target-quark momentum fraction 0.1<xt<0.3. For xt<0.1 the ratio is slightly less than unity for the heavy nuclei. These results are compared with predictions of models of the European Muon Collaboration effect.
Using a silicon-microstrip detector array to identify secondary vertices occurring downstream of a short platinum target, we have searched for the decay D0→μ+μ−. Normalized relative to the J/ψ→μ+μ− signal observed in the same data sample, for a 3.25-mm minimum decay distance our branching-ratio sensitivity is (4.8±1.4)×10−6 per event, and after background subtraction we observe -4.1±4.8 events. Using the statistical approach advocated by the Particle Data Group, we obtain a limit B(D0→μ+μ−)<3.1×10−5 at 90% confidence, confirming with a different technique the limit previously obtained by Louis et al. The interpretation of the upper limit involves complex statistical issues; we present another approach which is more suitable for combining the results of different experiments.
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