60 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
Electromagnetic properties of baryons
We discuss the chiral behavior of nucleon and Delta(1232) electromagnetic
properties within the framework of a SU(2) covariant baryon chiral perturbation
theory. Our one-loop calculation is complete to the order p^3 and p^4/Delta
with Delta as the Delta(1232)-nucleon energy gap. We show that the magnetic
moment of a resonance can be defined through the linear energy shift only when
an additional relation between the involved masses and the applied magnetic
field strength is fulfilled. Singularities and cusps in the pion mass
dependence of the Delta(1232) electromagnetic moments reflect a
non-fulfillment. We show results for the pion mass dependence of the nucleon
iso-vector electromagnetic quantities and present results for finite volume
effects on the iso-vector anomalous magnetic moment.Comment: 4 pages, 3 figures, prepared for Proceedings of the International
Conference on the Structure of Baryons (BARYONS'10), Osaka, Japan, Dec. 7-11,
201
Electric properties of the baryon anti-decuplet in the SU(3) chiral quark-soliton model
We investigate the electric form factors and charge radii of the pentaquark
baryons within the framework of the chiral quark-soliton model. We consider the
rotational and linear corrections, assuming isospin symmetry and
employing the symmetry-conserving quantization. The flavor-decomposed charge
densities of the are presented. The electric form factors and charge
radii of the charged pentaquark baryons turn out to be very similar to those of
the corresponding octet baryons. The charge radii of the neutral pentaquark
baryons are obtained to be very tiny and positive. The strange electric form
factor of the pentaquark proton is shown to be larger than the corresponding
one of the proton by around 20%. We also present the charge radii of the baryon
decuplet for comparison.Comment: 11 pages, 7 figure
Octet-baryon axial-vector charges and SU(3)-breaking effects in the semileptonic hyperon decays
The octet-baryon axial-vector charges and the g(1)/f(1) ratios measured in the semileptonic hyperon decays are studied up to O(p(3)) using the covariant baryon chiral perturbation theory with explicit decuplet contributions. We clarify the role of different low-energy constants and find a good convergence for the chiral expansion of the axial-vector charges of the baryon octet, g(1)(0), with O(p(3)) corrections typically around 20% of the leading ones. This is a consequence of strong cancellations between different next-to-leading- order terms. We show that considering only nonanalytic terms is not enough and that analytic terms appearing at the same chiral order play an important role in this description. The same effects still hold for the chiral extrapolation of the axial-vector charges and result in a rather mild quark-mass dependence. As a result, we report a determination of the leading-order chiral couplings, D = 0.623(61)(17) and F = 0.441(47)(2), as obtained from a completely consistent chiral analysis up to O(p(3)). Furthermore, we note that the appearance of an unknown low-energy constant precludes the extraction of the proton octet charge from semileptonic decay data alone, which is relevant for an analysis of the composition of the proton spin
Large-N-c naturalness in coupled-channel meson-meson scattering
The analysis of hadronic interactions with effective field theory techniques is complicated by the appearance of a large number of low-energy constants, which are usually fitted to data. On the other hand, the large-Nc limit helps to impose natural short-distance constraints on these low-energy constants, providing a parameter reduction. A Bayesian interpretation of the expected 1/Nc accuracy allows for an easy and efficient implementation of these constraints, using an augmented χ2. We apply this approach to the analysis of meson-meson scattering, in conjunction with chiral perturbation theory to one loop and coupled-channel unitarity, and show that it helps to largely reduce the many existing ambiguities and simultaneously provide an acceptable description of the available phase shifts
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