We report the multiplicity and angular distributions of the low energy target-associated particles from 32S and 16O induced reactions at 200 GeV/nucleon and 16O induced reactions at 60 GeV/nucleon in emulsion. The results are compared with the Monte-Carlo Code VENUS.
We compute the multifractal moments Gq in terms of a new scaled variable X suggested by Bialas and Gazdzicki to study the dynamical fluctuations of particles produced in the interactions of Au197 at 10.6A GeV with nuclear emulsion. An asymptotic power-law dependence of the moments on the bin size δX has been observed in pseudorapidity (η), azimuthal (φ), and η-φ phase spaces. The dynamical values of the generalized dimensions are determined in all the phase spaces. The dynamical properties of the produced particles are mapped onto smooth multifractal spectra f(Δαq) by excluding the statistical contribution. The Au197 results are compared with a Si28 ion at 14.5A GeV and a S32 beam at 200A GeV.
Partial production cross sections of projectile alpha fragments produced in high-energy interactions of 16 O and 32 S at 200 GeV/n and 16 O at 60 GeV/n in emulsion are studied. Evidence of multiplicity scaling of such produced fragments is presented in the energy range 2–200 GeV/n for various projectiles.
Pseudorapidity-interval dependence of multiplicity distributions of shower particles produced in high energy interactions of protons at 800 GeV, 4 He at ≈ 11 A GeV, and 28 Si at 14.5 A GeV in nuclear emulsions have been investigated. The multiplicity distributions and correlated moments are parametrised successfully in terms of a negative binomial distribution (NBD). The heavy-ion data for NBD agree well with the predictions of the multistring Monte Carlo code VENUS.
We present a systematic analysis on the helium projectile fragments produced from 10.6 A GeV197Auemulsion interactions in an experiment conducted at the Brookhaven AGS. Total charge changing and partial production cross-sections are measured experimentally on the basis of helium multiplicity. The multiplicity distribution of helium fragments which are produced collectively obey a KNO scaling. The transverse momentum distribution of these particles indicates that they are produced from two different independent sources.
Multiplicity and angular distributions of shower, grey, and black particles produced in the interactions of S32 at 200A GeV, O16 at 200 and 60A GeV, and He4 at ∼140A GeV in emulsion are compared with the predictions of a Monte Carlo code which takes into account the internuclear cascading. The correlations between the various parameters belonging to the same or to the different kinds of particles are discussed. The data on shower and grey particles from all the beams are well described by the code. However, the black prong data show a significant departure from this model.
We have studied the properties of hadron production in photon-photon scattering with tagged photons at the e + e − storage ring PETRA. A tail in the p T distribution of particles consistent with p T −4 has been observed. We show that this tail cannot be due to the hadronic part of the photon. Selected events with high p T particles are found to be consistent with a two-jet structure as expected from a point-like coupling of the photons to quarks. The lowest-order cross section predicted for γγ → q q , σ = 3 Σ e q 4 · σ γγ → μμ , is approached from above by the data at large transverse momenta.
J/psi production has been measured in proton-proton collisions at sqrt(s)= 200 GeV over a wide rapidity and transverse momentum range by the PHENIX experiment at RHIC. Distributions of the rapidity and transverse momentum, along with measurements of the mean transverse momentum and total production cross section are presented and compared to available theoretical calculations. The total J/psi cross section is 3.99 +/- 0.61(stat) +/- 0.58(sys) +/- 0.40(abs) micro barns. The mean transverse momentum is 1.80 +/- 0.23(stat) +/- 0.16(sys) GeV/c.
Using a silicon-microstrip detector array to identify secondary vertices, we have observed b→J/ψ→μ+μ− decays in 800GeV/c proton-gold interactions. The doubly differential cross section for J/ψ mesons originating from b-quark decays, assuming linear dependence on nucleon number, is d2σ/dxFdpT2=107±28±19[pb/(GeV/c)2]/nucleon at xF=0.05 and pT=1GeV/c. This measurement is compared to next-to-leading-order QCD predictions. The integrated b-quark production cross section, obtained by extrapolation over all xF and pT, is σ(pN→bb¯+X)=5.7±1.5±1.3 nb/nucleon.
With a data sample containing 1.1×105 J/ψ→μ+μ− decays reconstructed with 16 MeV/c2 rms mass resolution, we have measured the differential cross sections versus Feynman-x, rapidity, and pT for the production of J/ψ and ψ’ in 800 GeV/c p-Au collisions. Our results are compared with leading-order QCD predictions and with previous measurements. While the shapes of the cross sections are in qualitative agreement with QCD predictions, the magnitudes disagree by factors of 7 (J/ψ) and 25 (ψ’). Assuming an appropriate form for the differential cross sections in regions not measured we derive a total J/ψ production cross section σ(p+N→J/ψ+X)=442±2±88 nb/nucleon and a (model-dependent) total ψ’ cross secton σ(p+N→ψ’+X)=75±5±22 nb/nucleon. For J/ψ produced at central rapidity, dσ(p+N→J/ψ+X)/dy‖y=0=230±5±46 nb/nucleon.
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