25,262 research outputs found
D-instantons and multiparticle production in N=4 SYM
N=4 Super-symmetric Yang-Mills theory (N=4 SYM) in the strong coupling regime
has been successfully applied (through the AdS/CFT correspondence) to the
description of strongly coupled plasma which is a multiparticle state. Yet, the
high-energy scattering in the strong coupling limit of N=4 SYM is purely
elastic, so this multiparticle final state can never be produced: this is
because in this limit the theory is dual to weak supergravity, and the dominant
interaction is the elastic graviton exchange. Here we propose a resolution of
this dilemma by considering the contribution of D-instantons in bulk
space to the scattering amplitude. We argue that D-instantons coupled to
dilatons and axions are responsible for multiparticle production in strongly
coupled N=4 SYM, and the corresponding cross section increases with energy. We
evaluate the intercept and the slope of the corresponding Pomeron trajectory in
terms of the typical size of the D-instanton, and argue that the resulting
physical picture may resemble the real world.Comment: 22 pp and 11 figures in the eps forma
Gluon saturation effects on J/Psi production in heavy ion collisions
We consider a novel mechanism for J/Psi production in nuclear collisions
arising due to the high density of gluons. We calculate the resulting J/Psi
production cross section as a function of rapidity and centrality. We evaluate
the nuclear modification factor and show that the rapidity distribution of the
produced J/Psi's is significantly more narrow in AA collisions due to the gluon
saturation effects. Our results indicate that gluon saturation in the colliding
nuclei is a significant source of J/Psi suppression that can be disentangled
from the quark-gluon plasma effects.Comment: 5 pages, 3 figures; v2: typos corrected; presentation improve
Hadron multiplicity in pp and AA collisions at LHC from the Color Glass Condensate
We provide quantitative predictions for the rapidity, centrality and energy
dependencies of inclusive charged-hadron productions for the forthcoming LHC
measurements in nucleus-nucleus collisions based on the idea of gluon
saturation in the color-glass condensate framework. Our formulation gives very
good descriptions of the first data from the LHC for the inclusive
charged-hadron production in proton-proton collisions, the deep inelastic
scattering at HERA at small Bjorken-x, and the hadron multiplicities in
nucleus-nucleus collisions at RHIC.Comment: 7 pages, 8 figures; v3: minor changes, one reference added, results
unchanged, the version to appear in Phys. Rev.
Production of q bar-q Pairs in Proton-Nucleus Collisions at High Energies
We calculate production of quark-antiquark pairs in high energy
proton-nucleus collisions both in the quasi-classical approximation of
McLerran-Venugopalan model and including quantum small- evolution. The
resulting production cross section is explicitly expressed in terms of
Glauber-Mueller multiple rescatterings in the classical case and in terms of
dipole-nucleus scattering amplitude in the quantum evolution case. We
generalize the result of one of us (K.T.) beyond the aligned jet
configurations. We expand on the earlier results of Blaizot, Gelis and
Venugopalan by deriving quark production cross section including quantum
evolution corrections in rapidity intervals both between the quarks and the
target and between the quarks and the projectile.Comment: 18 pages, 3 figures; typos corrected, discussion extende
Accelerated Detectors and Temperature in (Anti) de Sitter Spaces
We show, in complete accord with the usual Rindler picture, that detectors
with constant acceleration in de Sitter (dS) and Anti de Sitter (AdS)
spaces with cosmological constants measure temperatures , the detector "5-acceleration" in the
embedding flat 5-space. For dS, this recovers a known result; in AdS, where
is negative, the temperature is well defined down to the critical
value , again in accord with the underlying kinematics. The existence
of a thermal spectrum is also demonstrated for a variety of candidate wave
functions in AdS backgrounds.Comment: Latex +2 Fi
Giant microwave-induced -periodic magnetoresistance oscillations in a two-dimensional electron gas with a bridged-gate tunnel point contact
We have studied the magnetoresistance of the quantum point contact fabricated
on the high mobility two-dimensional electron gas (2DEG) exposed to microwave
irradiation. The resistance reveals giant -periodic oscillations with the
relative amplitude of up to \% resulting from the propagation
and interference of the edge magnetoplasmons (EMPs) in the sample. This giant
photoconductance is attributed to the considerably large local electron density
modulation in the vicinity of the point contact. We have also analyzed the
oscillation periods of the resistance oscillations and, comparing
the data with the EMP theory, extracted the EMP interference length . We
have found that the length substantially exceeds the distance between the
contact leads but rather corresponds to the distance between metallic contact
pads measured along the edge of the 2DEG. This resolves existing controversy in
the literature and should help to properly design highly sensitive microwave
and terahertz spectrometers based on the discussed effect.Comment: 5 pages, 5 figure
Measuring the saturation scale in nuclei
The saturation momentum seeing in the nuclear infinite momentum frame is
directly related to transverse momentum broadening of partons propagating
through the medium in the nuclear rest frame. Calculation of broadening within
the color dipole approach including the effects of saturation in the nucleus,
gives rise to an equation which describes well data on broadening in Drell-Yan
reaction and heavy quarkonium production.Comment: 11 pages, 5 figures, based on the talk presented by B.K. at the INT
workshop "Physics at a High Energy Electron Ion Collider", Seattle, October
200
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