The Temperature Dependence of the QCD Running Coupling

We study the running of the QCD coupling with the momentum squared ($Q^2$) and the temperature scales in the high temperature limit ($T > T_{c}$), using a mass dependent renormalization scheme to build the Renormalization Group Equations. The approach used guaranty gauge invariance, through the use of the Hard Thermal Loop approximation, and independence of the vertex chosen to renormalize the coupling. In general, the dependence of the coupling with the temperature is not logarithmical, although in the region $Q^2 \sim T^2$ the logarithm approximation is reasonable. Finally, as known from Debye screening, color charge is screened in the coupling. The number of flavors, however, is anti-screened.Comment: 5 pages, 2 figure

New Approaches to Target Mass Corrections

We analyze different prescriptions for the inclusion of target mass effects in the extraction of parton distributions from the measured structure functions. As a main result, the problem of defining parton distributions in the presence of mass is an open problem.Comment: 4 pages. Presented at HiX2010, Jlab, October 201

Target mass corrections revisited

We propose a new implementation of target mass corrections to nucleon structure functions which, unlike existing treatments, has the correct kinematic threshold behavior at finite Q^2 in the x -> 1 limit. We illustrate the differences between the new approach and existing prescriptions by considering specific examples for the F_2 and F_L structure functions, and discuss the broader implications of our results, which call into question the notion of universal parton distribution at finite Q^2.Comment: 11 pages, 5 figure

Vibrational Aspects of the SU(2) Skyrmion

We treat the Skyrme model with the breathing mode in a situation involving two quartic terms. It is seen that there is a new limit for large $e$ due to the breathing mode not found in the usual rotating hedgehog.Comment: 15 pages, ADP-93-206/T12

On the Interpretation of the NA51 Experiment

We study the $p-n$ Drell-Yan asymmetry, recently measured by the NA51 collaboration, and conclude that the value quoted by their experiment only sets a lower limit on the asymmetry of the proton sea. In particular, we notice that charge symmetry breaking between the proton and the neutron may produce corrections which should be taken into account.Comment: To appear in Phys. Lett.

Meson Cloud and SU(3) Symmetry Breaking in Parton Distributions

We apply the Meson Cloud Model to the calculation of nonsinglet parton distributions in the nucleon sea, including the octet and the decuplet cloud baryon contributions. We give special attention to the differences between nonstrange and strange sea quarks, trying to identify possible sources of SU(3) flavor breaking. A analysis in terms of the $\kappa$ parameter is presented, and we find that the existing SU(3) flavor asymmetry in the nucleon sea can be quantitatively explained by the meson cloud. We also consider the $\Sigma^+$ baryon, finding similar conclusions.Comment: 17 pages, LaTeX, 8 figures in .ps file

Local Duality and Charge Symmetry Violation in Quark Distributions

We use local quark-hadron duality to calculate the nucleon structure function as seen by neutrino and muon beams. Our result indicates a possible signal of charge symmetry violation at the parton level in the very large x region.Comment: 4 pages, 2 figures. Modified version to appear on PRD. A dicussion on the experimental errors of the form factors was adde

A Constraint on the x Dependence of the Light Antiquarks Ratio

We perform a careful study on the effect of the Pauli blocking to the light antiquark structure of the proton sea. We develop the formal expressions for the antiquark distributions, highlighting the role played by quark statistics and the vacuum structure. Ratios involving the antiquarks are calculated. In particular, it is found that $\Delta\bar{d}(x)/\Delta\bar{u}(x)$ should be negative and x independent

Heavy Quarks in Polarized Structure Functions

Quark mass effects are included in the calculation of polarized structure functions. In particular, the validity of fixed order perturbation theory and of massless evolution is studied in the framework of heavy quarks structure functions. The polarized version of the ACOT and MRRS interpolating schemes for the evolution of massive quarks distributions is also developed and studied. The different behaviours of the various approaches in $x$ and $Q^2$ are shown