103 research outputs found
Regularization dependence of pion generalised parton distributions
Pion generalised parton distributions are calculated within the framework of
the Nambu--Jona-Lasinio model using different regularization schemes, including
the proper time regularization scheme, the three dimensional momentum cutoff
scheme, the four dimensional momentum cutoff scheme, and the Pauli-Villars
regularization scheme. Furthermore, we check the theoretical constraints of
pion generalised parton distributions required by the symmetries of quantum
chromodynamics in different regularization schemes. The diagrams of pion parton
distribution functions are plotted, in addition, we evaluate the Mellin moments
of generalised parton distributions, which related to the electromagnetic and
gravitational form factors of pion. Pion generalised parton distributions are
continuous but not differential at , when considering the effect
of D-term, generalised parton distributions become not continuous at in all the four regularization schemes. Generalised parton distributions
in impact parameter space are considered, the width distribution of quark
in the pion and the mean-squared
are calculated. The light-front transverse-spin distributions are studied, when
quark polarized in the light-front-transverse direction, the
transverse-spin density is no longer symmetric around , the
peaks shift to , we compare the average transverse shift
and in
different regularization schemes. The light-cone energy radius and
the light-cone charge radius are also evaluated, we find that in the
proper time regularization scheme the values of these quantities are the
largest, in the three dimensional momentum cutoff scheme they are the smallest.Comment: 34 pages, 39 figure
Which Constituent Quark Model Is Better?
A comparative study has been done by calculating the effective baryon-baryon
interactions of the 64 lowest channels consisting of octet and decuplet baryons
with three constituent quark models: the extended quark gluon exchange model,
the Goldstone boson exchange model and the quark gluon meson exchange hybrid
model. We find that these three models give similar results for 44 channels.
Further tests of these models are discussed.Comment: 6pp., 3 figs., Asia-Pacific Few-Body Conf. II (Shanghai, Aug.25-30
2002), to appear in MPLA; references adde
Study of pentaquark system in the Chiral Quark Model
With the discovery of some hidden-charm pentaquark resonances by the LHCb
Collaboration, investigations of pentaquark states containing heavy quarks have
aroused the interest of theorists. We study herein ( or
, or ) pentaquark system, in the framework of the chiral quark
model. In consequence, some charmed and bottomed pentaquarks are considered to
exist by five-body dynamical calculations. In the charm sector,
and are
possible candidates of and , respectively.
Besides, two high-spin states, and
, are also found in the energy region of GeV. In the bottom sector, ,
could be candidates of
and , respectively. And
and are found in the energy region of GeV. and are expected as
compact states, while , , and
are expected as molecular states.Comment: 11 pages, 1 figur
Contact interaction analysis of pion GTMDs
A contact interaction is used to calculate an array of pion twist-two, -three
and -four generalised transverse light-front momentum dependent parton
distribution functions (GTMDs). Despite the interaction's simplicity, many of
the results are physically relevant, amongst them a statement that GTMD size
and shape are largely prescribed by the scale of emergent hadronic mass.
Moreover, proceeding from GTMDs to generalised parton distributions (GPDs), it
is found that the pion's mass distribution form factor is harder than its
electromagnetic form factor, which is harder than the gravitational pressure
distribution form factor; the pressure in the neighbourhood of the pion's core
is commensurate with that at the centre of a neutron star; the shear pressure
is maximal when confinement forces become dominant within the pion; and the
spatial distribution of transversely polarised quarks within the pion is
asymmetric. Regarding transverse momentum dependent distribution functions
(TMDs), their magnitude and domain of support decrease with increasing twist.
The simplest Wigner distribution associated with the pion's twist-two
dressed-quark GTMD is sharply peaked on the kinematic domain associated with
valence-quark dominance; has a domain of negative support; and broadens as the
transverse position variable increases in magnitude.Comment: 20 pages, 12 figures, 1 tabl
- …