2,990 research outputs found
Hadron tomography for pion and its gravitational form factors
Generalized parton distributions (GPDs) are three-dimensional structure
functions of hadrons, and they can reveal the orbital-angular-momentum
contributions to the nucleon spin. Therefore, GPDs are important for solving
the proton spin puzzle. The generalized distribution amplitudes (GDAs) are the
- crossed quantities of the GPDs, and the GDAs can be investigated in
two-photon process () which is accessible at KEKB.
The pion GDAs were obtained by analyzing the Belle measurements for production in the collision. From the obtained GDAs, the form
factors of energy-momentum tenor were calculated for pion in the timelike
region. In order to study the gravitational radii for the pion, the form
factors of energy-momentum tenor were obtained in the spacelike region by using
the dispersion relation. Then, the mass radius was calculated as 0.32
0.39 fm and the mechanical radius was also estimated for the pion as 0.82
0.88 fm by using the spacelike form factors. This is the first finding
on gravitational form factors and radii of hadrons from actual experimental
measurements. In the near future we can expect more precise measurements of
as the Belle II started data taking by the higher
luminosity Super KEKB, so that the GDAs of other hadrons could be studied as
well.Comment: 4 pages, 4 figures, Proceedings of Eighth International Conference on
Quarks and Nuclear Physics (QNP2018), November 13-17, 2018, Tsukuba, Japa
Novel relations for twist-3 tensor-polarized fragmentation functions in spin-1 hadrons
There are three types of fragmentation functions (FFs) which are used to
describe the twist-3 cross sections of the hard semi-inclusive processes under
QCD collinear factorization, and they are called intrinsic, kinematical, and
dynamical FFs. In this work, we investigate the theoretical relations among
these FFs for a tensor-polarized spin-1 hadron. Three Lorentz-invariance
relations (LIRs) are derived by using the identities between the nonlocal
quark-quark and quark-gluon-quark operators, which guarantee the frame
independence of the twist-3 spin observables. The QCD equation of motion
(e.o.m.) relations are also presented for the tensor-polarized FFs. In
addition, we also show that the intrinsic and kinematical twist-3 FFs can be
decomposed into the contributions of twist-2 FFs and twist-3 three-parton FFs,
and the latter are also called dynamical FFs. If one neglects the dynamical
FFs, we can obtain relations which are analogous to the Wandzura-Wilczek (WW)
relation. Then, the intrinsic and kinematical twist-3 FFs are expressed in
terms of the leading-twist ones. Since the FFs of a spin-1 hadron can be
measured at various experimental facilities in the near future, these
theoretical relations will play an important role in the analysis of the
collinear tensor-polarized FFs.Comment: 10 page
3D structure of hadrons by generalized distribution amplitudes and gravitational form factors
Generalized distribution amplitudes (GDAs) are one type of three-dimensional
structure functions, and they are related to the generalized distribution
functions (GPDs) by the - crossing of the Mandelstam variables. The GDA
studies provide information on three-dimensional tomography of hadrons. The
GDAs can be investigated by the two-photon process , and the GPDs are studied by the deeply virtual Compton scattering . The GDA studies had been pure theoretical topics, although the
GPDs have been experimentally investigated, because there was no available
experimental measurement. Recently, the Belle collaboration reported their
measurements on the differential cross
section, so that it became possible to find the GDAs from their measurements.
Here, we report our analysis of the Belle data for determining the pion GDAs.
From the GDAs, the timelike gravitational form factors and
can be calculated, which are mechanical (pressure, shear force)
and mass (energy) form factors, respectively. They are converted to the
spacelike form factors by using the dispersion relation, and then gravitational
radii are evaluated for the pion. The mass and mechanical radii are obtained
from and as fm and fm, whereas the experimental charge radius is fm for the charged pion. Future
developments are expected in this new field to explore gravitational physics in
the quark and gluon level.Comment: 6 pages, LaTeX, 1 style file, 8 figure files, Proceedings of the XXV
International Workshop on Deep-Inelastic Scattering and Related Subjects,
April 3-7, 2017, University of Birmingham, U
and : Candidates for charmed-strange mesons
Newly observed two charmed-strange resonances, and
, are investigated by calculating their Okubo-Zweig-Iizuka
allowed strong decays, which shows that they are suitable candidates for the
and states in the charmed-strange meson family. Our study
also predicts other main decay modes of and ,
which can be accessible at the future experiment. In addition, the decay
behaviors of the spin partners of and , i.e.,
and , are predicted in this work, which are still
missing at present. Experimental search for the missing and
charmed-strange mesons is an intriguing and challenging task
for further experiment.Comment: 8 pages, 3 figures and 4 tables. More discussions added and typos
corrected. Accepted by Eur. Phys. J.
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