1,117,359 research outputs found
Pi pi scattering lengths at O(p^6) revisited
This article completes a former work where part of the O(p^6) low-energy
constants entering in the pi pi scattering were estimated. Some resonance
contributions were missed in former calculations and slight differences
appeared with respect to our outcome. Here, we provide the full results for all
the contributing O(p^6) couplings. We also perform a reanalysis of the hadronic
inputs used for the estimation (resonance masses, widths...). Their reliability
was checked together with the impact of the input uncertainties on the
determinations of the chiral couplings and the scattering lengths a^I_J. Our
outcome is found in agreement with former works though with slightly larger
errors. However, the effect in the final values of the a^I_J is negligible
after combining them with the other uncertainties. Based on this consistency,
we conclude that the previous scattering length determinations seem to be
rather solid and reliable, with the cO(p^6) low-energy constants quite under
control. Nevertheless, the uncertainties found in the present work point out
the limitation on further improvements unless the precision of the O(p^6)
couplings is properly increased.Comment: 19 pages. Improved treatment of the a0 decay width and update of the
numerical outcomes. Final version published in Phys. Rev. D
(10.1103/PhysRevD.79.096006
Thin Ice Target for O(p,p') experiment
A windowless and self-supporting ice target is described. An ice sheet with a
thickness of 29.7 mg/cm cooled by liquid nitrogen was placed at the target
position of a magnetic spectrometer and worked stably in the O
experiment at MeV. Background-free spectra were obtained.Comment: 14 pages, 4 figures, Nucl. Instr. & Meth. A (in press
Nuclear time-reversal violation and the Schiff moment of 225Ra
We present a comprehensive mean-field calculation of the Schiff moment of the
nucleus 225Ra, the quantity which determines the static electric dipole moment
of the corresponding atom if time-reversal (T) invariance is violated in the
nucleus. The calculation breaks all possible intrinsic symmetries of the
nuclear mean field and includes, in particular, both exchange and direct terms
from the full finite-range T-violating nucleon-nucleon interaction, and the
effects of short-range correlations. The resulting Schiff moment, which depends
on three unknown T-violating pion-nucleon coupling constants, is much larger
than in 199Hg, the isotope with the best current experimental limit on its
atomic electric-dipole moment.Comment: 4 pages, 2 figures; this version (references added) to be published
in PR
Corrections to Sirlin's Theorem in Chiral Perturbation Theory
We present the results of the first two-loop calculation of a form factor in
full Chiral Perturbation Theory. We choose a specific
linear combination of and form factors (the one
appearing in Sirlin's theorem) which does not get contributions from order
operators with unknown constants. For the charge radii, the correction to
the previous one-loop result turns out to be significant, but still there is no
agreement with the present data due to large experimental uncertainties in the
kaon charge radii.Comment: 6 pages, Latex, 2 LaTeX figure
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