138 research outputs found
Study of Stability of a Charged Topological Soliton in the System of Two Interacting Scalar Fields
An analytical-numerical analysis of the singular self-adjoint spectral
problem for a system of three linear ordinary second-order differential
equations defined on the entire real exis is presented. This problem comes to
existence in the nonlinear field theory. The dependence of the differential
equations on the spectral parameter is nonlinear, which results in a quadratic
operator Hermitian pencil.Comment: 22 pages, 2 figure
Dispersive and absorptive corrections to the pion-deuteron scattering length
We present a parameter--free calculation of the dispersive and absorptive
contributions to the pion--deuteron scattering length based on chiral
perturbation theory. We show that once all diagrams contributing to leading
order to this process are included, their net effect provides a small
correction to the real part of the pion--deuteron scattering length.
At the same time the sizable imaginary part of the pion--deuteron scattering
length is reproduced accurately.Comment: Numerical error corrected. Results for dispersive corrections changed
- conclusions unchanged. Version as accepted by Phys. Lett.
Role of the Delta(1232) in pion-deuteron scattering at threshold within chiral effective field theory
We investigate the role of the delta isobar in the reaction
at threshold in chiral effective field theory. We discuss the corresponding
power counting and argue that this calculation completes the evaluation of
diagrams up to the order (m_pi/M_N)^(3/2), with m_pi (M_N) for the pion
(nucleon) mass. The net effect of all delta contributions at this order to the
pion-deuteron scattering length is (2.4 +/- 0.4)x 10^(-3) m_pi^{-1}.Comment: 11 page
Anatomy of relativistic pion loop corrections to the electromagnetic nucleon coupling
We present a relativistic formulation of pion loop corrections to the coupling of photons with nucleons on the light front. Vertex and wave function renormalization constants are computed to lowest order in the pion field, including their nonanalytic behavior in the chiral limit, and studied numerically as a function of the ultraviolet cutoff. Particular care is taken to explicitly verify gauge invariance and Ward-Takahashi identity constraints to all orders in the mπ expansion. The results are used to compute the chiral corrections to matrix elements of local operators, related to moments of deep-inelastic structure functions. Finally, comparison of results for pseudovector and pseudoscalar coupling allows the resolution of a longstanding puzzle in the computation of pion cloud corrections to structure function moments.Chueng-Ryong Ji, W. Melnitchouk, and A.W. Thoma
Precision calculation of the pi^- deuteron scattering length and its impact on threshold pi-N scattering
We present a calculation of the pi^- d scattering length with an accuracy of
a few percent using chiral perturbation theory. For the first time
isospin-violating corrections are included consistently. Using data on pionic
deuterium and pionic hydrogen atoms, we extract the isoscalar and isovector
pion-nucleon scattering lengths and obtain a^+=(7.6 +/- 3.1) x 10^{-3} mpi^{-1}
and a^-=(86.1 +/- 0.9) x 10^{-3} mpi^{-1}. Via the Goldberger-Miyazawa-Oehme
sum rule, this leads to a charged-pion-nucleon coupling constant g_c^2/4 pi =
13.69 +/- 0.20.Comment: 6 pages, 2 figures. Discussion of several points expanded, references
added in this version, which will appear in Physics Letters
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