189 research outputs found
A unified description of initial and final state interactions in heavy ion collisions
We have investigated the gauge field of a fast moving projectile passing
through a dense medium. We provide a simple and unified derivation, in light
cone gauge, of the gluon production cross-section in proton-nucleus (initial
state interactions), and the radiative gluon spectrum of a hard parton produced
in a nucleus-nucleus collision (final state interactions). Finally, we discuss
the validity of the eikonal approximation in proton-nucleus collisions at RHIC
energies.Comment: 8 pages, 2 figures. talk given at International Conference on Strong
and Electroweak Matter (SEWM 2006), Upton, New York, 10-13 May 200
Adiabatic times for Markov chains and applications
We state and prove a generalized adiabatic theorem for Markov chains and
provide examples and applications related to Glauber dynamics of Ising model
over Z^d/nZ^d. The theorems derived in this paper describe a type of adiabatic
dynamics for l^1(R_+^n) norm preserving, time inhomogeneous Markov
transformations, while quantum adiabatic theorems deal with l^2(C^n) norm
preserving ones, i.e. gradually changing unitary dynamics in C^n
Forward Quark Jets from Protons Shattering the Colored Glass
We consider the single-inclusive minijet cross section in pA at forward
rapidity within the Color Glass Condensate model of high energy collisions. We
show that the nucleus appears black to the incident quarks except for very
large impact parameters. A markedly flatter p_t distribution as compared to QCD
in the dilute perturbative limit is predicted for transverse momenta about the
saturation scale, which could be as large as Q_s^2 ~ 10 GeV^2 for a gold
nucleus boosted to rapidity ~10 (as at the BNL-RHIC).Comment: 9 pages, no figure
Comparing AdS/CFT Calculations to HERA F_2 Data
We show that HERA data for the inclusive structure function F_2(x,Q^2) at
small Bjorken-x and Q^2 can be reasonably well described by a color-dipole
model with an AdS/CFT-inspired dipole-proton cross section. The model contains
only three free parameters fitted to data. In our AdS/CFT-based
parameterization the saturation scale varies in the range of 1-3 GeV becoming
independent of energy/Bjorken-x at very small x. This leads to the prediction
of x-independence of the F_2 and F_L structure functions at very small x. We
provide predictions for F_2 and F_L in the kinematic regions of future
experiments. We discuss the limitations of our approach and its applicability
region, and argue that our AdS/CFT-based model of non-perturbative physics
could be viewed as complimentary to the perturbative description of data based
on saturation/Color Glass Condensate physics.Comment: 23 pages, 10 figures; v3: new plots added showing our model
predictions for charm and longitudinal structure functions and
photoproduction cross-section, discussion extended. The version to appear in
PR
R-Current DIS on a Shock Wave: Beyond the Eikonal Approximation
We find the DIS structure functions at strong coupling by calculating
R-current correlators on a finite-size shock wave using AdS/CFT correspondence.
We improve on the existing results in the literature by going beyond the
eikonal approximation for the two lowest orders in graviton exchanges. We argue
that since the eikonal approximation at strong coupling resums integer powers
of 1/x (with x the Bjorken-x variable), the non-eikonal corrections bringing in
positive integer powers of x can not be neglected in the small-x limit, as the
non-eikonal order-x correction to the (n+1)st term in the eikonal series is of
the same order in x as the nth eikonal term in that series. We demonstrate
that, in qualitative agreement with the earlier DIS analysis based on
calculation of the expectation value of the Wilson loop in the shock wave
background using AdS/CFT, after inclusion of non-eikonal corrections DIS
structure functions are described by two momentum scales: Q_1^2 ~ \Lambda^2 \,
A^{1/3}/x and Q_2^2 ~ \Lambda^2 \, A^{2/3}, where \Lambda is the typical
transverse momentum in the shock wave and A is the atomic number if the shock
wave represents a nucleus. We discuss possible physical meanings of the scales
Q_1 and Q_2.Comment: 44 pages, 3 figures; v2: typos corrected, refs added, discussion
extende
Genuine collective flow from Lee-Yang zeroes
We propose to use the theory of phase transitions of Lee and Yang as a
practical tool to analyze long-range correlations in a finite-size system. We
apply it to the analysis of anisotropic flow in nucleus-nucleus collisions, and
show that this method is more reliable than any other used so far.Comment: 5 pages, 3 eps figures, RevTeX. v2: overall presentation modifie
Directed flow at RHIC from Lee-Yang zeroes
Directed flow in ultrarelativistic nucleus-nucleus collisions is analyzed
using the reaction plane from elliptic flow, which reduces the bias from
nonflow effects. We combine this method with the determination of elliptic flow
from Lee-Yang zeroes. The resulting method is more consistent and somewhat
easier to implement than the previously used method based on three-particle
cumulants, and is also less biased by nonflow correlations. Error terms from
residual nonflow correlations are carefully estimated, as well as statistical
errors. We discuss the application of the method at RHIC and LHC.Comment: 10 pages. Final version, to appear in Nucl. Phys.
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
Cronin Effect and High-p_T Suppression in pA Collisions
We review the predictions of the theory of Color Glass Condensate for gluon
production cross section in p(d)A collisions. We demonstrate that at moderate
energies, when the gluon production cross section can be calculated in the
framework of McLerran-Venugopalan model, it has only partonic level Cronin
effect in it. At higher energies/rapidities corresponding to smaller values of
Bjorken x quantum evolution becomes important. The effect of quantum evolution
at higher energies/rapidities is to introduce suppression of high-p_T gluons
slightly decreasing the Cronin enhancement. At still higher energies/rapidities
quantum evolution leads to suppression of produced gluons at all values of p_T.Comment: 32 pages, 8 figures, v2: extended and improved discussion, references
adde
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