132 research outputs found
Partonic quasi-distributions of the pion in chiral quark models
The evaluation of partonic distributions presents a challenge for QCD, and in
particular for its Euclidean lattice realization. Recently, objects called
quasi-distributions (which become standard distributions in a limit of the
longitudinal momentum of the target hadron going to infinity) have been
proposed. We present a non-perturbative, dynamical evaluation of the quark
quasi-distribution amplitude (QDA) of the pion in the framework of chiral quark
models (the Nambu--Jona-Lasinio model and the spectral quark model). We arrive
at simple but nontrivial analytic expressions, where the dependence on the
longitudinal momentum, the momentum fraction, or the transverse-momentum (for
the unintegrated objects) can be explicitly assessed. For the parton
distribution amplitude (PDA), we carry out the necessary QCD evolution from the
constituent quark model scale to higher scales accessible on the lattice, and
compare favorably to the LaMET data.Comment: 6 pages, talk presented by WB at XVII International Conference on
Hadron Spectroscopy and Structure - Hadron2017, Salamanca, 25-29 September
201
Dimension-2 condensates, zeta-regularization and large-Nc Regge Models
Dimension-2 and -4 gluon condensates are re-analyzed in large-Nc Regge models
with the zeta-function regularization which preserves the spectrum in any q
qbar channel separately. We demonstrate that the signs and magnitudes of both
condensates can be properly described within the framework.Comment: 3 pages, 1 figure. Talk given at 4th International Conference on
Quarks and Nuclear Physics (QNP06), Madrid, Spain, 5-10 Jun 2006. (typos
corrected. References added
Nonperturbative partonic quasidistributions of the pion from chiral quark models
We evaluate nonperturbatively the quark quasidistribution amplitude and the
valence quark quasidistribution function of the pion in the framework of chiral
quark models, namely the Nambu--Jona-Lasinio model and the Spectral Quark
Model. We arrive at simple analytic expressions, where the nonperturbative
dependence on the longitudinal momentum of the pion can be explicitly assessed.
The model results for the quark quasidistribution amplitude of the pion compare
favorably to the data obtained from the Euclidean lattice simulations. The
quark distribution amplitude, arising in the limit of infinite longitudinal
momentum of the pion, agrees, after suitable QCD evolution, to the recent data
extracted from Euclidean lattices, as well as to the old data from transverse
lattice simulations.Comment: references added, 7 pages, 3 figure
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