3,688 research outputs found
The Temperature Dependence of the QCD Running Coupling
We study the running of the QCD coupling with the momentum squared ()
and the temperature scales in the high temperature limit (), 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 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 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 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.
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 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 and are shown
Standard map in magnetized relativistic systems: fixed points and regular acceleration
We investigate the concept of a standard map for the interaction of
relativistic particles and electrostatic waves of arbitrary amplitudes, under
the action of external magnetic fields. The map is adequate for physical
settings where waves and particles interact impulsively, and allows for a
series of analytical result to be exactly obtained. Unlike the traditional form
of the standard map, the present map is nonlinear in the wave amplitude and
displays a series of peculiar properties. Among these properties we discuss the
relation involving fixed points of the maps and accelerator regimes.Comment: Work to appear in Phys. Rev. E. 2 figure
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