| The goal of this work is the study of the differential cross sections of the J/ψ particle decaying into dimuons. It is based on the data from the first year of dimuon production at the HERA-B spectrometer in the DESY synchrotron in Hamburg, Germany. This dissertation presents results from approximately 150 hours of running during 2000.; HERA-B utilizes a 920 GeV/c proton beam on several fixed target wires ( = 41.6 GeV). It exercised a dilepton trigger to collect 0.6 million dimuon events in 2000. 3,000 J/ψs are recorded from a carbon target, and 1,000 have been discovered on a titanium wire. The HERA-B collaboration collected J/ψs with a transverse momentum (pT) up to 3.75 GeV/c and with a Feynman x (xF) between −0.275 and 0.075. In experiments studying J/ψ via pN collisions, HERA-B has the highest energy of any fixed target experiment, titanium has never before been exploited as a nuclear target, and the experiments' reach in negative xF is unparalleled by all other experiments reporting their xF spectrum.; This dissertation concentrates on the shape of the differential cross section in pT and xF. The characteristic shape parameters are the average transverse momentum ⟨ pT⟩ and the slope of the xF distribution, designated by c in dσ/ dxF ∝ (1 − |xF|) c. For carbon and titanium, we find that ⟨p T⟩ = 1.220 ± 0.021(stat) GeV/c and 1.256 ± 0.036(stat) GeV/c respectively, and that c = 6.28 ± 0.36(stat) ± 0.36(syst) and 5.42 ± 0.62(stat) ± 0.31(syst) respectively. No sizable systematic error has yet been found for the measurements of ⟨pT⟩. The values are found to be consistent with data from other experiments and theoretical predictions. |
