451 research outputs found
Vector potential versus colour charge density in low-x evolution
We reconsider the evolution equations for multigluon correlators derived in
hep-ph/9709432. We show how to derive these equations directly in terms of
vector potentials (or colour field strength) avoiding the introduction of the
concept of colour charge density in the intermediate steps. The two step
procedure of deriving the evolution of the charge density correlators followed
by the solution of classical equations for the vector potentials is shown to be
consistent with direct derivation of evolution for vector potentials. In the
process we correct some computational errors of hep-ph/9709432 and present the
corrected evolution equations which have a somewhat simpler appearance.Comment: 15 pages, 1 figure, changes made referee report, to be published in
Phys. Rev
Saturation physics and angular correlations at RHIC and LHC
We investigate the angular correlation between pions and photons produced in
deuteron-gold collisions at RHIC and proton-lead collisions at LHC using the
Color Glass Condensate formalism and make predictions for the dependence of the
production cross section on the angle between the pion and photon at different
rapidities and transverse momenta. Measuring this dependence would shed further
light on the role of high gluon density and saturation dynamics at RHIC and
LHC.Comment: 2-column EPJ C format, requires svjour.cls and svepj.clo; 4 pages, 4
figure
Shadowing of gluons in perturbative QCD: A comparison of different models
We investigate the different perturbative QCD-based models for nuclear
shadowing of gluons. We show that in the kinematic region appropriate to RHIC
experiment, all models give similar estimates for the magnitude of gluon
shadowing. At scales relevant to LHC, there is a sizable difference between
predictions of the different models.Comment: 11 pages, 4 figure
Non-Gaussian Correlations in the McLerran-Venugopalan Model
We argue that the statistical weight function W[rho] appearing in the
McLerran-Venugopalan model of a large nucleus is intrinsically non-Gaussian,
even if we neglect quantum corrections. Based on the picture where the nucleus
of radius R consists of a collection of color-neutral nucleons, each of radius
a<<R, we show that to leading order in alpha_s and a/R only the Gaussian part
of W[rho] enters into the final expression for the gluon number density. Thus,
the existing results in the literature which assume a Gaussian weight remain
valid.Comment: 21 pages with 4 figures (revtex
Dilepton production from the Color Glass Condensate
We consider dilepton production in high energy proton-nucleus (and very
forward nucleus-nucleus) collisions. Treating the target nucleus as a Color
Glass Condensate and describing the projectile proton (nucleus) as a collection
of quarks and gluons as in the parton model, we calculate the differential
cross section for dilepton production in quark-nucleus scattering and show that
it is very sensitive to the saturation scale characterizing the target nucleus.Comment: 9 pages LaTeX document, 1 postscript figur
The initial energy density of gluons produced in very high energy nuclear collisions
In very high energy nuclear collisions, the initial energy of produced gluons
per unit area per unit rapidity, , is equal to , where is proportional to the gluon density per unit
area of the colliding nuclei. For an SU(2) gauge theory, we perform a
non--perturbative numerical computation of the function . It
decreases rapidly for small but varies only by %, from
to , for a wide range 35.36--296.98 in , including the range relevant for collisions at RHIC and LHC. Extrapolating
to SU(3), we estimate the initial energy per unit rapidity for Au-Au collisions
in the central region at RHIC and LHC.Comment: 11 pages, Latex, 3 figures; revised version-includes additional
numerical data; reference adde
Prompt photons at RHIC
We calculate the inclusive cross section for prompt photon production in
heavy-ion collisions at RHIC energies ( GeV and
GeV) in the central rapidity region including next-to-leading order,
, radiative corrections, initial state nuclear
shadowing and parton energy loss effects. We show that there is a significant
suppression of the nuclear cross section, up to at
GeV, due to shadowing and medium induced parton energy loss effects. We find
that the next-to-leading order contributions are large and have a strong
dependence.Comment: 9 pages, 5 figures, expanded discussion of the K facto
Eikonal Evolution and Gluon Radiation
We give a simple quantum mechanical formulation of the eikonal propagation
approximation, which has been heavily used in recent years in problems
involving hadronic interactions at high energy. This provides a unified
framework for several approaches existing in the literature. We illustrate this
scheme by calculating the total, elastic, inelastic and diffractive DIS cross
sections, as well as gluon production in high energy hadronic collisions. From
the q-qbar-g-component of the DIS cross sections, we straightforwardly derive
low x evolution equations for inelastic and diffractive DIS distribution
functions. In all calculations, we provide all order 1/N corrections to the
results existing in the literature.Comment: 40 pages, LaTeX, 3 eps-figures, typos corrected, to be published in
PR
Physical and mechanical properties of Oak (Quercus Persica) fruits
This research was conducted over one Iranian variety of Oak (Quercus Persica) with 70 observations. Physical and mechanical properties of oak are necessary for equipment used in activities such as transportation, storage, grading, packing etc. Properties which were measured include fruit dimensions, mass, volume, projected area, fruit density, geometric mean diameter, sphericity and surface area. Bulk density, porosity and also packing coefficient were measured. Experiments were carried out at Results showed that average mass and volume were 12.95 g and 10.27 mL, respectively. Dimensions increased from 41.85 to 61.09 mm in length, 14.45 to 25.02 mm in width and 14.42 to 24.38 mm in thickness. The mean projected area perpendicular to length, width and thickness obtained 433.91, 1085.48 and 1115.46 mm2, respectively. The geometric mean diameter and surface area were calculated as 27.638 mm and 2423.82 mm2, respectively, while sphericity was measured 51.78%. Elasticity modulus (E), maximum force which fruit can support (Fmax) and work which performed to this force have been determined
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