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

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

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

On the Gluon Regge Trajectory in O(αs2)O(\alpha_s^2)

We recalculate the gluon Regge trajectory in next-to-leading order to clarify a discrepancy between two results in the literature on the constant part. We confirm the result obtained by Fadin et al.~\cite{FFK}. The effects on the anomalous dimension and on the $s^{\omega}$ behavior of inclusive cross sections are also discussed.Comment: 8 pages Latex + 1 style file all compressed by uufile

The Color Dipole Picture of low-x DIS: Model-Independent and Model-Dependent Results

We present a detailed examination of the color-dipole picture (CDP) of low-$x$ deep inelastic scattering. We discriminate model-independent results, not depending on a specific parameterization of the dipole cross section, from model-dependent ones. The model-independent results include the ratio of the longitudinal to the transverse photoabsorption cross section at large $Q^2$, or equivalently the ratio of the longitudinal to the unpolarized proton structure function, $F_L (x,Q^2)=0.27 F_2 (x, Q^2)$, as well as the low-$x$ scaling behavior of the total photoabsorption cross section $\sigma_{\gamma^*p} (W^2, Q^2)=\sigma_{\gamma^*p} (\eta (W^2, Q^2))$ as $\log (1 / \eta (W^2, Q^2))$ for $\eta (W^2, Q^2) <1$, and as $1/\eta (W^2, Q^2)$ for $\eta (W^2, Q^2) \gg 1$. Here, $\eta (W^2, Q^2)$ denotes the low-$x$ scaling variable, $\eta (W^2, Q^2)=(Q^2 + m^2_0) / \Lambda^2_{sat} (W^2)$ with $\Lambda^2_{sat} (W^2)$ being the saturation scale. The model-independent analysis also implies $\lim\limits_{W^2\rightarrow\infty, Q^2 {\rm fixed}} \sigma_{\gamma^*p} (W^2, Q^2) / \sigma_{\gamma p} (W^2) \rightarrow 1$ at any $Q^2$ for asymptotically large energy, $W$. Consistency with pQCD evolution determines the underlying gluon distribution and the numerical value of $C_2 = 0.29$ in the expression for the saturation scale, $\Lambda^2 (W^2) \sim (W^2)^{C_2}$. In the model-dependent analysis, by restricting the mass of the actively contributing $q \bar q$ fluctuations by an energy-dependent upper bound, we extend the validity of the color-dipole picture to $x \cong Q^2 / W^2 \le 0.1$. The theoretical results agree with the world data on DIS for $0.036 {\rm GeV}^2 \le Q^2 \le 316 {\rm GeV}^2$.Comment: 77 pages, 30 figure

Probing QCD dynamics in two-photon interactions at high energies

In this paper the two-photon interactions at high energies are investigated considering different approaches for the QCD dynamics. In particular, we calculate the $\gamma^* \gamma^*$ total cross section in different theoretical approches and present a comparison among the predictions of the BFKL dynamics at leading and next-to-leading order with those from saturation physics. We analyze the possibility that the future linear colliders could discriminate between these different approaches.Comment: 14 pages, 2 figures. Version to be published in Journal of Physics G: Nuclear and Particle Physic

Geometric Scaling in Inclusive Charm Production

We show that the cross section for inclusive charm production exhibits geometric scaling in a large range of photon virtualities. In the HERA kinematic domain the saturation momentum $Q_{sat}^2(x)$ stays below the hard scale $\mu_c^2=4m_c^2$, implying charm production probing mostly the color transparency regime and unitarization effects being almost negligible. We derive our results considering two saturation models which are able to describe the DESY ep collider HERA data for the proton structure function at small values of the Bjorken variable $x$. A striking feature is the scaling on $\tau=Q_2^2/Q_{sat}^2(x)$ above saturation limit, corroborating recent theoretical studies.Comment: 4 pages, 2 figures. Version to be published in Physical Review Letter

Non-forward NLO BFKL Kernel

Details of the calculation of the non-forward BFKL kernel at next-to-leading order (NLO) are offered. Specifically we show the calculation of the two-gluon production contribution. This contribution was the last missing part of the kernel. Together with the NLO gluon Regge trajectory, the NLO contribution of one-gluon production and the contribution of quark-antiquark production which were found before it defines the kernel completely for any colour state in the $t$-channel, in particular the Pomeron kernel presented recently.Comment: 31 page