8 research outputs found
Coherence Time Effects on J/psi Production and Suppression in Relativistic Heavy Ion Collisions
Using a coherence time extracted from high precision proton-nucleus Drell-Yan
measurements and a nuclear absorption cross section extracted from pA
charmonium production experiments, we study J/psi production and absorption in
nucleus-nucleus collisions. We find that coherence time effects are large
enough to affect the measured J/psi-to-Drell-Yan ratio. The S+U data at 200A
GeV/c measured by NA38 are reproduced quantitatively without the introduction
of any new parameters. However, when compared with recent NA50 measurements for
Pb+Pb at 158A GeV/c, the data is not reproduced in trend or in magnitude.Comment: 8 pages, 2 figure
Search for flavor-changing neutral currents and lepton-family-number violation in two-body D0 decays
Results of a search for the three neutral charm decays, D0 -> mu e, D0 -> mu
mu, and D0 -> e e, are presented. This study was based on data collected in
Experiment 789 at the Fermi National Accelerator Laboratory using 800 GeV/c
proton-Au and proton-Be interactions. No evidence is found for any of the
decays. Upper limits on the branching ratios, at the 90% confidence level, are
obtained.Comment: 28 pages, 18 figures. Submitted to Physical Review
Search for the Proton Decay Mode proton to neutrino K+ in Soudan 2
We have searched for the proton decay mode proton to neutrino K+ using the
one-kiloton Soudan 2 high resolution calorimeter. Contained events obtained
from a 3.56 kiloton-year fiducial exposure through June 1997 are examined for
occurrence of a visible K+ track which decays at rest into mu+ nu or pi+ pi0.
We found one candidate event consistent with background, yielding a limit,
tau/B > 4.3 10^{31} years at 90% CL with no background subtraction.Comment: 13 pages, Latex, 3 tables and 3 figures, Accepted by Physics Letters
Recommended from our members
Production of J/{psi} at Large {ital x}{sub f} in 800 GeV/c {ital p}-Copper and {ital p}-Beryllium Collisions
The Atmospheric neutrino flavor ratio from a 3.9 fiducial kiloton year exposure of Soudan-2
We report a measurement of the atmospheric neutrino flavor ratio, R, using a
sample of quasi-elastic neutrino interactions occurring in an iron medium. The
flavor ratio (tracks/showers) of atmospheric neutrinos in a 3.9 fiducial
kiloton-year exposure of Soudan 2 is 0.64 +- 0.11 (stat.) +- 0.06 (syst.) of
that expected. Important aspects of our main analysis have been checked by
carrying out two independent, alternative analyses; one is based upon automated
scanning, the other uses a multivariate approach for background subtraction.
Similar results are found by all three approaches.Comment: 15 pages, 4 figures. To be published in Physics Letters
Kinematic distributions and nuclear effects of J/ψ production in 920 GeV fixed-target proton-nucleus collisions
Measurement of the atmospheric neutrino flavor composition in Soudan-2
The atmospheric neutrino flavour ratio measured using a 1.52 kton-year
exposure of Soudan 2 is found to be 0.72 +- 0.19 +0.05 -0.07 relative to the
expected value from a Monte Carlo calculation. The possible background of
interactions of neutrons and photons produced in muon interactions in the rock
surrounding the detector has been investigated and is shown not to produce low
values of the ratio.Comment: 18 pages, LaTeX, 3 ps files, and 2 style files. Submitted to Physics
Letter
A Measurement of the to Production Ratio in 920 GeV/c Proton-Nucleus Interactions.
Ratios of the Psi' over the J/psi production cross sections in the dilepton
channel for C, Ti and W targets have been measured in 920 GeV proton-nucleus
interactions with the HERA-B detector at the HERA storage ring. The Psi' and
J/psi states were reconstructed in both the mu+mu- and the e+e- decay modes.
The measurements covered the kinematic range -0.35 < x_F < 0.1 with transverse
momentum p_T < 4.5 GeV/c. The Psi' to J/psi production ratio is almost constant
in the covered x_F range and shows a slow increase with p_T. The angular
dependence of the ratio has been used to measure the difference of the Psi' and
J/psi polarization. All results for the muon and electron decay channels are in
good agreement: their ratio, averaged over all events, is
R_psi'(mu)/R_psi'(e)=1.00+-0.08+-0.04. This result constitutes a new, direct
experimental constraint on the double ratio of branching fractions,
(B'(mu)*B(e))/(B(mu)*B'(e)), of Psi' and J/psi in the two channels.Comment: 20 pages, 9 figure