36,640 research outputs found
Locating the critical end point using the linear sigma model coupled to quarks
We use the linear sigma model coupled to quarks to compute the effective
potential beyond the mean field approximation, including the contribution of
the ring diagrams at finite temperature and baryon density. We determine the
model couplings and use them to study the phase diagram in the baryon chemical
potential-temperature plane and to locate the Critical End Point.Comment: 8 pages, 2 figures, conference paper from ISMD 201
Flexible Parametrization of Generalized Parton Distributions: The Chiral-Odd Sector
We present a physically motivated parameterization of the chiral-odd
generalized parton distributions. The parametrization is an extension of our
previous one in the chiral-even sector which was based on the reggeized diquark
model. While for chiral even generalized distributions a quantitative fit with
uncertainty estimation can be performed using deep inelastic scattering data,
nucleon electromagnetic, axial and pseudoscalar form factors measurements, and
all available deeply virtual Compton scattering data, the chiral-odd sector is
far less constrained. While awaiting the analysis of measurements on
pseudoscalar mesons exclusive electroproduction which are key for the
extraction of chiral odd GPDs, we worked out a connection between the
chiral-even and chiral-odd reduced helicity amplitudes using Parity
transformations. The connection works for a class of models including
two-components models. This relation allows us to estimate the size of the
various chiral odd contributions and it opens the way for future quantitative
fits.Comment: 35 pages, 18 figures, text changes, corrected typos, added fig.
A phenomenological analysis of azimuthal asymmetries in unpolarized semi-inclusive deep inelastic scattering
We present a phenomenological analysis of the cos-phi and cos-2phi
asymmetries in unpolarized semi-inclusive deep inelastic scattering, based on
the recent multidimensional data released by the COMPASS and HERMES
Collaborations. In the TMD framework, valid at relatively low transverse
momenta, these asymmetries arise from intrinsic transverse momentum and
transverse spin effects, and from their correlations. The role of the Cahn and
Boer-Mulders effects in both azimuthal moments is explored up to order 1/Q. As
the kinematics of the present experiments is dominated by the low-Q^2 region,
higher-twist contributions turn out to be important, affecting the results of
our fits.Comment: 18 pages, 5 figures, one paragraph added at the end of Section IV,
one reference added. PRD versio
A study on the interplay between perturbative QCD and CSS/TMD formalism in SIDIS processes
We study the Semi-Inclusive Deep Inelastic Scattering (SIDIS) cross section
as a function of the transverse momentum, . In order to describe it over a
wide region of , soft gluon resummation has to be performed. Here we will
use the original Collins-Soper-Sterman (CSS) formalism; however, the same
procedure would hold within the improved Transverse Momentum Dependent (TMD)
framework. We study the matching between the region where fixed order
perturbative QCD can successfully be applied and the region where soft gluon
resummation is necessary. We find that the commonly used prescription of
matching through the so-called Y-factor cannot be applied in the SIDIS
kinematical configurations we examine. In particular, the non-perturbative
component of the resummed cross section turns out to play a crucial role and
should not be overlooked even at relatively high energies. Moreover, the
perturbative expansion of the resummed cross section in the matching region is
not as reliable as it is usually believed and its treatment requires special
attention.Comment: Two references and an appendix added, 22 pages, 11 figure
- …