23 research outputs found
Background field approach to electromagnetic properties of baryons
We investigate the self-energies of particles in an external magnetic field
. The dependence is generally of the type with a
polynomial in and the participating masses. The non-analytic point depends
on the mass and charge constellations, is unproblematic for stable particles
but constrains the linear energy shift approximation for resonances. We
calculate the dependent self-energies of the nucleon and
-isobar in the SU(2) covariant chiral perturbation theory and
outline a way to obtain finite volume corrections to the nucleon anomalous
magnetic moment without using the three point function method. We show that
finite volume corrections might explain present discrepancies of lattice QCD
and chiral perturbation theory results in the small pion mass region.Comment: revised, Refs adde
A dispersion relation for the pion-mass dependence of hadron properties
We present a dispersion relation in the pion-mass squared, which static
quantities (nucleon mass, magnetic moment, etc.) obey under the assumption of
analyticity in the entire complex plane modulo a cut at negative
associated with pion production. The relation is verified here in a
number of examples of nucleon and -isobar properties computed in chiral
perturbation theory up to order . We outline a method to obtain relations
for other mass-dependencies, and illustrate it on a two-loop example.Comment: 8 pages, 4 fig
Tensor properties of the nucleon
We report in the present talk recent results of the tensor properties of the
nucleon within the framework of the chiral quark-soliton model. The tensor and
anomalous tensor magnetic form factors are calculated for the momentum transfer
up to and at a renormalization scale of
. The main results are summarized as follows: the
flavor tensor charges of the nucleon are yielded as , , , while the up and down anomalous tensor magnetic
moments are evaluated as and ,
respectively. The strange anomalous tensor magnetic moment turns out to be
, compatible with zero. We discuss their physical
implications, comparing them in particular with those from the lattice QCD.Comment: 4 pages. 4 figures. A talk given at International Conference on the
structure of baryons, BARYONS 2010, Dec. 7-11, 2010, Osaka, Japa
Threshold Neutral Pion Photoproduction on the Proton
The neutral pion photoproduction on the proton near threshold has a very
small scattering cross section when compared to the charged channels, which in
ChPT is explained by strong cancellations between the lowest order pieces.
Therefore it is very sensitive to higher-order corrections of chiral
perturbation theory. We perform a fully covariant calculation up to chiral
order p^3 and we investigate the effect of the inclusion of the Delta(1232)
resonance as an explicit degree of freedom. We show that the convergence
improves, leading to a much better agreement with data at a wide range of
energies.Comment: Proceedings to the NSTAR2015 conference, which will be published in
JPS conference proceeding
Hyperon forward spin polarizability gamma0 in baryon chiral perturbation theory
We present the calculation of the hyperon forward spin polarizability gamma0
using manifestly Lorentz covariant baryon chiral perturbation theory including
the intermediate contribution of the spin 3/2 states. As at the considered
order the extraction of gamma0 is a pure prediction of chiral perturbation
theory, the obtained values are a good test for this theory. After including
explicitly the decuplet states, our SU(2) results have a very good agreement
with the experimental data and we extend our framework to SU(3) to give
predictions to the hyperons' gamma0 values. Prominent are the Sigma^- and Xi^-
baryons as their photon transition to the decuplet is forbidden in SU(3)
symmetry and therefore they are not sensitive to the explicit inclusion of the
decuplet in the theory
Semileptonic hyperon decays in the self-consistent SU(3) chiral quark-soliton model
We investigate the semileptonic hyperon decays within the framework of the
self-consistent SU(3) chiral quark-soliton model (QSM). We take linear
rotational as well as linear corrections into account and apply
the symmetry conserving quantization. We present the results for the form
factors , and in addition to the semileptonic
decay constants of hyperons. We also have calculated the radii and dipole
masses of these form factors for all relevant strangeness-conserving and
strangeness-changing transitions.Comment: 29 pages, 6 figure
Transverse strange quark spin structure of the nucleon
We investigate the transverse quark spin densities of the nucleon with the
lowest moment within the framework of the SU(3) chiral quark-soliton model,
emphasizing the strange quark spin density. Based on previous results of the
vector and tensor form factors, we are able to determine the impact-parameter
dependent probability densities of transversely polarized quarks in an
unpolarized nucleon as well as those of unpolarized quarks in a transversely
polarized nucleon. We find that the present numerical results for the
transverse spin densities of the up and down quarks are in good agreement with
those of the lattice calculation. We predict the transvere spin densities of
the strange quark. It turns out that the polarized strange quark is noticeably
distorted in an unpolarized proton.Comment: 10 pages. 16 figures. Submitted to Physical Review