1,022 research outputs found
Parton model versus color dipole formulation of the Drell-Yan process
In the kinematical region where the center of mass energy is much larger than
all other scales, the Drell-Yan process can be formulated in the target rest
frame in terms of the same color dipole cross section as low Bjorken-x deep
inelastic scattering. Since the mechanisms for heavy dilepton production appear
very different in the dipole approach and in the conventional parton model, one
may wonder whether these two formulations really represent the same physics. We
perform a comparison of numerical calculations in the color dipole approach
with calculations in the next-to-leading order parton model. For proton-proton
scattering, the results are very similar at low x_2 from fixed target to RHIC
energies, confirming the close connection between these two very different
approaches. We also compare the transverse momentum distributions of Drell-Yan
dileptons predicted in both formulations. The range of applicability of the
dipole formulation and the impact of future Drell-Yan data from RHIC for
determining the color dipole cross section are discussed. A detailed derivation
of the dipole formulation of the Drell-Yan process is also included.Comment: 20 pages, 5 figure
Energy loss of fast quarks in nuclei
We report an analysis of the nuclear dependence of the yield of Drell-Yan
dimuons from the 800 GeV/c proton bombardment of , C, Ca, Fe, and W
targets. Employing a new formulation of the Drell-Yan process in the rest frame
of the nucleus, this analysis examines the effect of initial-state energy loss
and shadowing on the nuclear-dependence ratios versus the incident proton's
momentum fraction and dimuon effective mass. The resulting energy loss per unit
path length is GeV/fm. This is the first
observation of a nonzero energy loss of partons traveling in nuclear
environment.Comment: 5 pages, including 4 figure
Thermal conductivity of one-dimensional lattices with self-consistent heat baths: a heuristic derivation
We derive the thermal conductivities of one-dimensional harmonic and
anharmonic lattices with self-consistent heat baths (BRV lattice) from the
Single-Mode Relaxation Time (SMRT) approximation. For harmonic lattice, we
obtain the same result as previous works. However, our approach is heuristic
and reveals phonon picture explicitly within the heat transport process. The
results for harmonic and anharmonic lattices are compared with numerical
calculations from Green-Kubo formula. The consistency between derivation and
simulation strongly supports that effective (renormalized) phonons are energy
carriers in anharmonic lattices although there exist some other excitations
such as solitons and breathers.Comment: 4 pages, 3 figures. accepted for publication in JPS
1950: Abilene Christian College Bible Lectures - Full Text
Introduction
We offer with interest and pleasure another volume of a great series of discourses delivered at Abilene Christian College. The following were given in February, 1950. The first of these Lectureships was held in the year 1919, and was published by the Firm Foundation Publishing House in book form. With little exception they have appeared each year since that time. The printing was done by others a few times. Those who are fortunate enough to have a complete set of these fine gospel sermons are possessed of a treasure in religious literature. Only a few of the later years can now be supplied. The rest are numbered among the “rare books” and we frequently have calls for them, but of course cannot supply them. Any reader having a copy for sale is requested to write the office of the Firm Foundation at Austin, Texas. The “Lectureship” of Abilene Christian College has become a great annual affair to the churches of Christ; thousands are in attendance, many of them coming from Canada and other countries besides all over the United States. This annual “mass meeting” must not be understood to be a “Convention” of the churches of Christ. We have no such conventions and do not endorse them. The Lectureship is simply a feature in the work of Abilene Christian College, a series of gospel sermons to which friends and patrons of the school and others are invited. It is our hope that the contents of this book may enrich the life, and strengthen the faith of the reader.
G. H. F. SHOWALTER
Austin, Texas August 20, 195
Parton energy loss limits and shadowing in Drell-Yan dimuon production
A precise measurement of the ratios of the Drell-Yan cross section per
nucleon for an 800 GeV/c proton beam incident on Be, Fe and W targets is
reported. The behavior of the Drell-Yan ratios at small target parton momentum
fraction is well described by an existing fit to the shadowing observed in
deep-inelastic scattering. The cross section ratios as a function of the
incident parton momentum fraction set tight limits on the energy loss of quarks
passing through a cold nucleus
Rapidity Distributions of Dileptons from a Hadronizing Quark-Gluon Plasma
It has been predicted that dilepton production may be used as a quark-gluon
plasma probe. We calculate the rapidity distributions of thermal dileptons
produced by an evolving quark-gluon plasma assuming a longitudinal scaling
expansion with initial conditions locally determined from the hadronic rapidity
density. These distributions are compared with Drell-Yan production and
semileptonic charm decays at invariant mass , 4, and 6 GeV.Comment: 17 pages (standard LaTeX), 6 figures (available as topdraw files or
printed versions upon request), GSI-93-6
Massive Lepton Pairs as a Prompt Photon Surrogate
We discuss the transverse momentum distribution for the production of massive
lepton-pairs in hadron reactions at fixed target and collider energies within
the context of next-to-leading order perturbative quantum chromodynamics. For
values of the transverse momentum greater than the pair mass , , we show that the differential cross section is dominated by subprocesses
initiated by incident gluons. Massive lepton-pair differential cross sections
are an advantageous source of constraints on the gluon density, free from the
experimental and theoretical complications of photon isolation that beset
studies of prompt photon production. We compare calculations with data and
provide predictions for the differential cross section as a function of
in proton-antiproton reactions at center-of-mass energies of 1.8 TeV, and in
proton-nucleon reactions at fixed target and LHC energies.Comment: 36 pages, RevTeX, including 16 ps files of figures; minor changes in
wording; one reference added. Version to appear in Phys Rev
Measurement of the Light Antiquark Flavor Asymmetry in the Nucleon Sea
A precise measurement of the ratio of Drell-Yan yields from an 800 GeV/c
proton beam incident on hydrogen and deuterium targets is reported. Over
140,000 Drell-Yan muon pairs with dimuon mass M_{mu+ mu-} >= 4.5 GeV/c^2 were
recorded. From these data, the ratio of anti-down (dbar) to anti-up (ubar)
quark distributions in the proton sea is determined over a wide range in
Bjorken-x. A strong x dependence is observed in the ratio dbar/ubar, showing
substantial enhancement of dbar with respect to ubar for x<0.2. This result is
in fair agreement with recent parton distribution parameterizations of the sea.
For x>0.2, the observed dbar/ubar ratio is much nearer unity than given by the
parameterizations.Comment: REVTeX, to be published in Phys. Rev. Let
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