12,328 research outputs found
Nucleon Form Factors of the Isovector Axial-Vector Current: Situation of Experiments and Theory
The theoretical and experimental status of the isovector axial-vector current
form factors G_A(q^2) and G_P(q^2) of the nucleon is reviewed. We also describe
a new calculation of these form factors in manifestly Lorentz-invariant chiral
perturbation theory (ChPT) with the inclusion of axial-vector mesons as
explicit degrees of freedom.Comment: 5 pages, 3 figures. Talk given by M. R. Schindler at the
International Workshop "From Parity Violation to Hadronic Structure and
more...", Milos, Greece, May 16-20, 200
Infrared regularization of baryon chiral perturbation theory reformulated
We formulate the infrared regularization of Becher and Leutwyler in a form
analogous to our recently proposed extended on-mass-shell renormalization. In
our formulation, IR regularization can be applied straightforwardly to
multi-loop diagrams with an arbitrary number of particles with arbitrary
masses.Comment: 10 pages, ReVTEX 4, no figure
Deuteron electromagnetic form factors in a renormalizable formulation of chiral effective field theory
We calculate the deuteron electromagnetic form factors in a modified version
of Weinberg's chiral effective field theory approach to the two-nucleon system.
We derive renormalizable integral equations for the deuteron without partial
wave decomposition. Deuteron form factors are extracted by applying the
Lehmann-Symanzik-Zimmermann reduction formalism to the three-point correlation
function of deuteron interpolating fields and the electromagnetic current
operator. Numerical results of a leading-order calculation with removed cutoff
regularization agree well with experimental data.Comment: 9 pages, 2 figure
Improving the ultraviolet behavior in baryon chiral perturbation theory
We introduce a new formulation of baryon chiral perturbation theory which
improves the ultraviolet behavior of propagators and can be interpreted as a
smooth cutoff regularization scheme. It is equivalent to the standard approach,
preserves all symmetries and therefore satisfies the Ward identities. Our
formulation is equally well defined in the vacuum, one- and few-nucleon sectors
of the theory. The equations (Bethe-Salpeter, Lippmann-Schwinger, etc.) for the
scattering amplitudes of the few-nucleon sector are free of divergences in the
new approach. Unlike the usual cutoff regularization, our 'cutoffs' are
parameters of the Lagrangian and do not have to be removed.Comment: 19 pages, 3 figures, REVTeX 4; version to be published in Phys. Rev.
D, additional section on issues of renormalization in few-body sector
include
Chiral expansion of the nucleon mass to order q^6
We present the results of a complete two-loop calculation at order q^6 of the
nucleon mass in manifestly Lorentz-invariant chiral perturbation theory. The
renormalization is performed using the reformulated infrared renormalization,
which allows for the treatment of two-loop integrals while preserving all
relevant symmetries, in particular chiral symmetry.Comment: 6 pages, 2 figures, REVTeX
Axial, induced pseudoscalar, and pion-nucleon form factors in manifestly Lorentz-invariant chiral perturbation theory
We calculate the nucleon form factors G_A and G_P of the isovector
axial-vector current and the pion-nucleon form factor G_piN in manifestly
Lorentz-invariant baryon chiral perturbation theory up to and including order
O(p^4). In addition to the standard treatment including the nucleon and pions,
we also consider the axial-vector meson a_1 as an explicit degree of freedom.
This is achieved by using the reformulated infrared renormalization scheme. We
find that the inclusion of the axial-vector meson effectively results in one
additional low-energy coupling constant that we determine by a fit to the data
for G_A. The inclusion of the axial-vector meson results in an improved
description of the experimental data for G_A, while the contribution to G_P is
small.Comment: 21 pages, 9 figures, REVTeX
Interferometric thermometry of a single sub-Doppler cooled atom
Efficient self-interference of single-photons emitted by a sideband-cooled
Barium ion is demonstrated. First, the technical tools for performing efficient
coupling to the quadrupolar transition of a single Ba ion are
presented. We show efficient Rabi oscillations of the internal state of the ion
using a highly stabilized 1.76 fiber laser resonant with the
S-D transition. We then show sideband cooling of the ion's
motional modes and use it as a means to enhance the interference contrast of
the ion with its mirror-image to up to 90%. Last, we measure the dependence of
the self-interference contrast on the mean phonon number, thereby demonstrating
the potential of the set-up for single-atom thermometry close to the motional
ground state.Comment: 6 pages, 6 figure
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