152 research outputs found
Influence of working environments on fatigue crack propagation in high nitrogen steels
The characteristic parameters dependence under cyclic deformation in hydrogen,
chloride environments and the subsequent selective dissolution has been studied. For high
nitrogen steels and welded joints it has been established that mechanical stresses accelerate
general dissolution of an alloy in different ways and lead to the formation of a surface layer
morphology which is different from the original one. Welded joints characterized by a higher
corrosion fatigue resistance in all investigated solutions, except saturated cupper chloride
solution
Baryon stopping and saturation physics in relativistic collisions
We investigate baryon transport in relativistic heavy-ion collisions at
energies reached at the CERN Super Proton Synchrotron, BNL Relativistic
Heavy-Ion Collider (RHIC), and CERN LHC in the model of saturation. An
analytical scaling law is derived within the color glass condensate framework
based on small-coupling QCD. Transverse momentum spectra, net-baryon rapidity
distributions and their energy, mass and centrality dependences are well
described. In a comparison with RHIC data in Au + Au collisions at sqrt (s_NN)
= 62.4 GeV and 200 GeV, the gradual approach to the gluon saturation regime is
investigated, and limits for the saturation-scale exponent are determined.
Predictions for net-baryon rapidity spectra and the mean rapidity loss in
central Pb + Pb collisions at LHC energies of sqrt (s_NN) = 5.52 TeV are made.Comment: 11 pages, 10 Figures; improved figure inscriptions, corrected typos,
minor changes in text/titl
Baryon Stopping as a new Probe of Geometric Scaling
We suggest to use net-baryon rapidity distributions in central relativistic
heavy-ion collisions at SPS, RHIC and LHC energies in order to probe saturation
physics. Within the color glass condensate framework based on small-coupling
QCD, net-baryon rapidity distributions are shown to exhibit geometric scaling.
In a comparison with RHIC data in Au + Au collisions at sqrt(s_NN) = 62.4 GeV
and 200 GeV the gradual approach to the gluon saturation regime is
investigated. Predictions for net-baryon rapidity spectra and the mean rapidity
loss in central Pb + Pb collisions at LHC energies of sqrt (s_NN) = 5.5 TeV are
made.Comment: 4 pages 3 figures; calculation and figures now for net baryons
instead of net protons; modified conclusion
Strong Bootstrap Conditions
We reformulate the so-called ``strong bootstrap'' conditions for the gluon
Reggeization in the next-to-leading approximation (NLA), firstly suggested by
Braun and Vacca, using a different approach, which is not based on properties
of the eigenstates of the NLA octet BFKL kernel. We write the second strong
bootstrap condition for the NLA octet impact factors in a form which makes
clear their dependence on the process. According to this condition, the NLA
octet impact factors must be given by the product of the corresponding Reggeon
interaction vertices with a universal coefficient function. This function can
be used also in the formulation of the first strong bootstrap condition for the
NLA BFKL kernel in the octet state.Comment: 10 page
The Interest of Large-t Elastic Scattering
Existing data for large- elastic-scattering differential
cross-sections are energy-independent and behave as . This has been
explained in terms of triple-gluon exchange, or alternatively through
triple-singlet exchange. A discussion is given of the problems raised by each
of these explanations, and of the possibility that at RHIC or LHC energies the
exchange of three BFKL pomerons might result in a rapid rise with energy.Comment: 6 pages, plain tex, 3 figures embedded with eps
Geometric scaling as traveling waves
We show the relevance of the nonlinear Fisher and Kolmogorov-Petrovsky-
Piscounov (KPP) equation to the problem of high energy evolution of the QCD
amplitudes. We explain how the traveling wave solutions of this equation are
related to geometric scaling, a phenomenon observed in deep-inelastic
scattering experiments. Geometric scaling is for the first time shown to result
from an exact solution of nonlinear QCD evolution equations. Using general
results on the KPP equation, we compute the velocity of the wave front, which
gives the full high energy dependence of the saturation scale.Comment: 4 pages, 1 figure. v2: references adde
Elastic scattering and the proton form factor
We compute the differential and the total cross sections for scattering
using the QCD pomeron model proposed by Landshoff and Nachtmann. This model is
quite dependent on the experimental electromagnetic form factor, and it is not
totally clear why this form factor gives good results even at moderate
transferred momentum. We exchange the eletromagnetic form factor by the
asymptotic QCD proton form factor determined by Brodsky and Lepage (BL) plus a
prescription for its low energy behavior dictated by the existence of a
dynamically generated gluon mass. We fit the data with this QCD inspired form
factor and a value for the dynamical gluon mass consistent with the ones
determined in the literature. Our results also provide a new determination of
the proton wave function at the origin, which appears in the BL form factor.Comment: 10 pages, 2 figures. Submitted to Physics Letters B. Submitted to
Phys. Lett.
Evaluation of Multiloop Diagrams via Lightcone Integration
We present a systematic method to determine the dominant regions of internal
momenta contributing to any two-body high-energy near-forward scattering
diagram. Such a knowledge is used to evaluate leading high-energy dependences
of loop diagrams. It also gives a good idea where dominant multiparticle cross
sections occur.Comment: 14 pages with eight postscript figures; composed in the Revtex
widetext format. This is an expanded and a completely rewritten version
replacing the previous on
Color mixing in high-energy hadron collisions
The color mixing of mesons propagating in a nucleus is studied with the help
of a color-octet Pomeron partner present in the two-gluon model of the Pomeron.
For a simple model with four meson-nucleon channels, color mixings are found to
be absent for pointlike mesons and very small for small mesons. These results
seem to validate the absorption model with two independent color components
used in recent analyses of the nuclear absorption of mesons produced
in nuclear reactions.Comment: 3 journal-style page
Ultrahigh energy neutrinos and non-linear QCD dynamics
The ultrahigh energy neutrino-nucleon cross sections are computed taking into
account different phenomenological implementations of the non-linear QCD
dynamic s. Based on the color dipole framework, the results for the saturation
model supplemented by DGLAP evolution as well as for the BFKL formalism in the
geometric scaling regime are presented. They are contrasted with recent
calculations using NLO DGLAP and unified BFKL-DGLAP formalisms.Comment: 5 pages, 2 figures. Version to be published in Physical Review
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