27 research outputs found
Charged particle production in the Pb+Pb system at 158 GeV/c per nucleon
Charged particle multiplicities from high multiplicity central interactions
of 158 GeV/nucleon Pb ions with Pb target nuclei have been measured in the
central and far forward projectile spectator regions using emulsion chambers.
Multiplicities are significantly lower than predicted by Monte Carlo
simulations. We examine the shape of the pseudorapidity distribution and its
dependence on centrality in detail.Comment: 17 pages text plus 12 figures in postscript 12/23/99 -- Add TeX
version of sourc
Observation of Scaling Violations in Scaled Momentum Distributions at HERA
Charged particle production has been measured in deep inelastic scattering
(DIS) events over a large range of and using the ZEUS detector. The
evolution of the scaled momentum, , with in the range 10 to 1280
, has been investigated in the current fragmentation region of the Breit
frame. The results show clear evidence, in a single experiment, for scaling
violations in scaled momenta as a function of .Comment: 21 pages including 4 figures, to be published in Physics Letters B.
Two references adde
Projectile stopping in nucleus-nucleus and hadron-nucleus collisions at 4.2 and 10 GeV/c per nucleon
Rapidity and transverse momentum structure inπ + andK + collisions with Al and Au nuclei at 250 GeV/c
Proton distributions in the target fragmentation region in proton - nucleus and nucleus-nucleus collisions at high-energies
We present measurements of the rapidity and transverse-momentum distributions of the protons emitted in S + W, O + W, and p + W reactions at 200 GeV/A around the target rapidity (y = 1). The rapidity density rises linearly with the transverse energy for all three systems, but the slope for p + W is much steeper than for O + W and S + W. The rapidity density for p + W is much higher than predicted by summing single nucleon-nucleon collisions without any nuclear effects, indicating substantial rescattering of the produced particles. The predictions of the VENUS 3 model, including rescattering, show reasonable agreement with the data for all three systems. We do not have evidence for a strong collective flow of the outgoing particles
Measurement of deeply virtual Compton scattering at HERA
The cross section for deeply virtual Compton scattering in the reaction ep ->
e gamma p has been measured with the ZEUS detector at HERA using integrated
luminosities of 95.0 pb-1 of e+p and 16.7 pb-1 of e-p collisions. Differential
cross sections are presented as a function of the exchanged-photon virtuality,
Q2, and the centre-of-mass energy, W, of the gamma*p system in the region 5 <
Q2 < 100 GeV2 and 40 < W < 140 GeV. The measured cross sections rise steeply
with increasing W. The measurements are compared to QCD-based calculations.Comment: 23 pages, 6 figures, 3 tables. Minor wording and changes to
reference
Measurement of the E**2(T,jet) / Q**2 dependence of forward jet production at HERA
The forward-jet cross section in deep inelastic ep scattering has been
measured using the ZEUS detector at HERA with an integrated luminosity of 6.36
pb^-1. The jet cross section is presented as a function of jet transverse
energy squared, E(T,jet)^2, and Q^2 in the kinematic ranges
10^-2<E(T,jet)^2/Q^2<10^2 and 2.5 10^-4<x<8.0 10^-2. Since the perturbative QCD
predictions for this cross section are sensitive to the treatment of the
log(E_T/Q)^2 terms, this measurement provides an important test. The measured
cross section is compared to the predictions of a next-to-leading order pQCD
calculation as well as to various leading-order Monte Carlo models. Whereas the
predictions of all models agree with the measured cross section in the region
of small E(T,Jet)^2/Q^2, only one model, which includes a resolved photon
component, describes the data over the whole kinematic range.Comment: 8 pages including 3 figure