1,172 research outputs found
Dilepton Production at Fermilab and RHIC
Some recent results from several fixed-target dimuon production experiments
at Fermilab are presented. In particular, we discuss the use of Drell-Yan data
to determine the flavor structure of the nucleon sea, as well as to deduce the
energy-loss of partons traversing nuclear medium. Future dilepton experiments
at RHIC could shed more light on the flavor asymmetry and possible
charge-symmetry-violation of the nucleon sea. Clear evidence for scaling
violation in the Drell-Yan process could also be revealed at RHIC.Comment: 5 pages, talk presented at the RIKEN-BNL Workshop on 'Hard Parton
Physics in Nucleus-Nucleus collisions, March 199
Suppression of Quarkonium Production in Heavy Ion Collisions at RHIC and LHC
A model for the production of quarkonium states in the midrapidity region at
RHIC and LHC energy range is presented which explores well understood
properties of QCD only. An increase of the quarkonium hadronisation time with
the initial energy leads to a gradual change of the most important phenomena
from fixed target- to collider-energies. We evaluate nuclear effects in the
quarkonium production due to medium modification of the momentum distribution
of the heavy quarks produced in the hard interactions, i.e. due to the
broadening of the transverse momentum distribution. Other nuclear effects, i.e.
nuclear shadowing and parton energy loss, are also evaluated.Comment: 5 pages, 1 table, 1 figure, Contribution to the Proceedings of the V
International Conference on Strangeness in Quark Matter July 20-25, 2000
Berkeley, Californi
Jet Tomography of Hot and Cold Nuclear Matter
Medium modification of parton fragmentation functions induced by multiple
scattering and gluon bremsstrahlung is shown to describe the recent HERMES data
in deeply inelastic scattering (DIS) very well, providing the first evidence of
-dependence of the modification. The energy loss is found to be
GeV/fm for a 10-GeV quark in a nucleus. Including
the effect of expansion, analysis of the spectra in central
collisions at GeV yields an averaged energy loss equivalent to
GeV/fm in a static medium. Predictions for central
collisions at GeV are also given.Comment: 4 pages in RevTex with 3 ps figures, final version published in Phys.
Rev. Letter
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Seniors and Information Technology: A MIS-Fit?
The “digital divide” between the haves and have-nots in society continues to draw attention in traditional media outlets as well as academic research. Those yearning to join the computer revolution comprise several groups defined by wealth, ethnicity, country (even regions of countries), and age. While there has been research into the digital divide in all of these areas, the focus of this paper is Information Technology (IT) use by the elderly, or our senior citizens. Our interest in this group stems from the dynamic interaction of two forces: 1) senior populations are growing in percentage and sheer number both in the United States and internationally; and 2) as a group, the elderly have more disposable income to spend on IT than their younger counterparts. In order to coordinate our research agenda, the current investigation presents a framework that delineates scholarly inquiry into this topic by the elements of the framework. We look at what has been done, and what we feel needs to be done, in order to incorporate an important demographic group into the mainstream of computing society: our seniors
Open and Hidden Charm Production in Heavy Ion Collisions at Ultrarelativistic Energies
We consider the production of the open charm and J/psi mesons in heavy ion
collisions at BNL RHIC. We discuss several recently developed pictures for
J/psi production and argue that a measurement at RHIC energies is crucial for
disentangling these different descriptions.Comment: 19 pages, Latex, 5 PS-figures. v3: Fig.6 is adde
Partonic Energy Loss and the Drell-Yan Process
We examine the current status of the extraction of the rate of partonic
energy loss in nuclei from A dependent data. The advantages and difficulties of
using the Drell-Yan process to measure the energy loss of a parton traversing a
cold nuclear medium are discussed. The prospects of using relatively low energy
proton beams for a definitive measurement of partonic energy loss are
presented.Comment: 12 pages, 2 figure
Coherence Time in High Energy Proton-Nucleus Collisions
Precisely measured Drell-Yan cross sections for 800 GeV protons incident on a
variety of nuclear targets exhibit a deviation from linear scaling in the
atomic number A. We show that this deviation can be accounted for by energy
degradation of the proton as it passes through the nucleus if account is taken
of the time delay of particle production due to quantum coherence. We infer an
average proper coherence time of 0.4 +- 0.1 fm/c, corresponding to a coherence
path length of 8 +- 2 fm in the rest frame of the nucleus.Comment: 11 pages in LaTeX. Includes 6 eps figures. Uses epsf.st
Geometric Parameterization of Absorption in Heavy Ion Collisions
We calculate the survival probability of particles in various
colliding systems using a Glauber model. An analysis of recent data has
reported a -nucleon breakup cross section of 6.20.7 mb derived
from an exponential fit to the ratio of to Drell-Yan yields as a
function of a simple, linearly-averaged mean path length through the nuclear
medium. Our calculations indicate that, due to the nature of the calculation,
this approach yields an apparent breakup cross section which is systematically
lower than the actual value.Comment: LaTex, 7 pages, 2 figure
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