2,609 research outputs found
The baryon-decuplet in the chiral dynamics of Lambda-hyperons in nuclear matter
We study the long range part of the -hyperon optical potential in
nuclei using Quantum Many Body techniques and flavor-SU(3) Chiral Lagrangians
as starting point. More precisely, we study the contributions to the
-hyperon optical potential due to the long-range two-pion exchange,
with and baryons in the internal baryonic lines and
considering Nh and h excitations. We also consider the contribution to
the spin-orbit potentials that comes out from these terms. Our results support
a natural explanation of the smallness of the -nuclear spin-orbit
interaction and shows the importance of the and degrees of
freedom for the hyperon-nucleus interactions.Comment: 8 pages, 5 figure
Properties of the ground-state baryons in chiral perturbation theory
We review recent progress in the understanding of low-energy baryon structure
by means of chiral perturbation theory. In particular, we discuss the
application of this formalism to the description of various properties such as
the baryon-octet magnetic moments, the electromagnetic structure of decuplet
resonances and the hyperon vector coupling . Moreover, we present the
results on the chiral extrapolation of recent lattice QCD results on the
lowest-lying baryon masses and we predict the corresponding baryonic
sigma-terms.Comment: 6 pages; shortened version to appear in the proceedings of QCD1
The lowest-lying baryon masses in covariant SU(3)-flavor chiral perturbation theory
We present an analysis of the baryon-octet and -decuplet masses using
covariant SU(3)-flavor chiral perturbation theory up to next-to-leading order.
Besides the description of the physical masses we address the problem of the
lattice QCD extrapolation. Using the PACS-CS collaboration data we show that a
good description of the lattice points can be achieved at next-to-leading order
with the covariant loop amplitudes and phenomenologically determined values for
the meson-baryon couplings. Moreover, the extrapolation to the physical point
up to this order is found to be better than the linear one given at
leading-order by the Gell-Mann-Okubo approach. The importance that a reliable
combination of lattice QCD and chiral perturbation theory may have for hadron
phenomenology is emphasized with the prediction of the pion-baryon and
strange-baryon sigma terms.Comment: Typos in formulas correcte
Phenomenology of an model with lepton-flavour non-universality
We investigate a gauge extension of the Standard Model in light of the
observed hints of lepton universality violation in and decays at BaBar, Belle and LHCb. The model consists of an
extended gauge group which breaks spontaneously around the TeV scale to the
electroweak gauge group. Fermion mixing effects with vector-like fermions give
rise to potentially large new physics contributions in flavour transitions
mediated by and bosons. This model can ease tensions
in -physics data while satisfying stringent bounds from flavour physics, tau
decays, and electroweak precision data. Possible ways to test the proposed new
physics scenario with upcoming experimental measurements are discussed. Among
other predictions, the lepton flavour violating ratios , with , are found to be reduced with respect to the Standard Model expectation
.Comment: 46 pages, 11 figures. v2: version published in JHE
Non-abelian gauge extensions for B-decay anomalies
We study the generic features of minimal gauge extensions of the Standard
Model in view of recent hints of lepton-flavor non-universality in
semi-leptonic and decays. We
classify the possible models according to the symmetry-breaking pattern and the
source of flavor non-universality. We find that in viable models the
factor is embedded non-trivially in the extended gauge
group, and that gauge couplings should be universal, hinting to the presence of
new degrees of freedom sourcing non-universality. Finally, we provide an
explicit model that can explain the -decay anomalies in a coherent way and
confront it with the relevant phenomenological constraints.Comment: 8 pages, 2 figures; discussion improved, a figure and references
added; conclusions unchange
Masses and magnetic moments of ground-state baryons in covariant baryon chiral perturbation theory
We report on some recent developments in our understanding of the light-quark
mass dependence and the SU(3) flavor symmetry breaking corrections to the
magnetic moments of the ground-state baryons in a covariant formulation of
baryon chiral perturbation theory, the so-called EOMS formulation. We show that
this covariant ChPT exhibits some promising features compared to its
heavy-baryon and infrared counterparts.Comment: 8 pages, 3 figures; plenary talk delivered by LSG at the 14th
national conference on nuclear structure, April 12nd - 16th, 2012, Huzhou,
Chin
Chiral perturbation theory study of the axial transition
We have performed a theoretical study of the axial Nucleon to Delta(1232)
() transition form factors up to one-loop order in covariant baryon
chiral perturbation theory within a formalism in which the unphysical spin-1/2
components of the fields are decoupled.Comment: 4 page
Leading SU(3)-breaking corrections to the baryon magnetic moments in Chiral Perturbation Theory
We calculate the baryon magnetic moments using covariant Chiral Perturbation
Theory (PT) within the Extended-on-mass-shell (EOMS) renormalization
scheme. By fitting the two available low-energy constants (LECs), we improve
the Coleman-Glashow description of the data when we include the leading SU(3)
breaking effects coming from the lowest-order loops. This success is in
dramatic contrast with previous attempts at the same order using Heavy Baryon
(HB) PT and covariant Infrared (IR) PT. We also analyze the source
of this improvement with particular attention on the comparison between the
covariant results.Comment: 4 pages, 2 figures, accepted for publication in PR
- …