43 research outputs found
The Role of the Running Coupling Constant in the Unveiling of The Hadronic Structure
peer reviewe
First glances at the transversity parton distribution through dihadron fragmentation functions
We present first observations of the transversity parton distribution based
on an analysis of pion-pair production in deep inelastic scattering off
transversely polarized targets. The extraction of transversity relies on the
knowledge of dihadron fragmentation functions, which we take from
electron-positron annihilation measurements. This is the first attempt to
determine the transversity distribution in the framework of collinear
factorization.Comment: Minor changes in text and reference
First extraction of Interference Fragmentation Functions from e+e- data
We report on the first extraction of interference fragmentation functions
from the semi-inclusive production of two hadron pairs in back-to-back jets in
e+e- annihilation. A nonzero asymmetry in the correlation of azimuthal
orientations of opposite \pi+\pi- pairs is related to the transverse
polarization of fragmenting quarks through a significant polarized dihadron
fragmentation function. Extraction of the latter requires the knowledge of its
unpolarized counterpart, the probability density for a quark to fragment in a
\pi+\pi- pair. Since data for the unpolarized cross section are missing, we
extract the unpolarized dihadron fragmentation function from a Monte Carlo
simulation of the cross section.Comment: 17 pages, 7 (multiple) figures, 15 tables, RevTeX format; refined
version of the fit, conclusions unchanged; added referenc
Pion nucleus Drell-Yan process and parton transverse momentum in the pion
We present a thorough analysis of unpolarized Drell-Yan (DY) pair production
in pion-nucleus scattering. On the nucleus side, we use nuclear parton
distributions along with parametrisations of the nucleon partonic transverse
distribution available in the literature. Partonic longitudinal and transverse
distributions of the pion are those obtained in a recent calculation in a
Nambu-Jona Lasinio (NJL) framework, with Pauli-Villars regularization. The
scale of the NJL model is fixed by a comparison between NLO predictions based
on NJL evolved pion distributions and rapidity differential DY cross sections
data. The resulting distributions are then used to describe, up to
next-to-leading logarithmic accuracy, the transverse momentum spectrum of
dilepton pairs up to a transverse momentum of 2 GeV. With no additional
parameters, fair agreement is found with available pion-nucleus data,
confirming the virtues of the NJL description of pion parton structure. We find
sizable evolution effects on the shape of the distributions and on the
generated average transverse momentum of the dilepton pair. We discuss the
possibility of extracting details on pion unpolarized transverse momentum
dependent parton distribution from pion nucleus DY data. In this respect, the
region of low invariant mass of the lepton pair appears to be favored to
discriminate between different descriptions of the non-perturbative pion
transverse structure.Comment: 13 pages, 8 figure