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On the reactions p + p -> p + Lambda + K^+ and p + p -> p + Sigma^0 + K^+ near thresholds
The cross sections for the reactions of the strange production p + p -> p +
Lambda + K^+ and p + p -> p + Sigma^0 + K^+ near thresholds of the final states
p Lambda K^+ and p Sigma^0 K^+ are calculated in the effective Lagrangian
approach. Our approach is based on the dominant contribution of the one-pion
exchange and strong interaction of the colliding protons in the initial state.
The theoretical values of the cross sections agree reasonably well with the
experimental data. The polarization properties of the Lambda and Sigma^0
hyperons are discussed.Comment: 15 pages, 1 Postscript figure, Latex, to appear in Eur. Phys. J
Radiative corrections of order O(alpha E_e/m_N) to Sirlin's radiative corrections of order O(alpha/pi) to neutron lifetime
We calculate the radiative corrections of order O(alpha E_e/m_N) as
next-to-leading order corrections in the large nucleon mass expansion to
Sirlin's radiative corrections of order O(alpha/pi) to the neutron lifetime.
The calculation is carried out within a quantum field theoretic model of strong
low-energy pion--nucleon interactions described by the linear sigma-model (LsM)
with chiral SU(2)xSU(2) symmetry and electroweak hadron-hadron, hadron-lepton
and lepton-lepton interactions for the electron-lepton family with SU(2)_L x
U(1)_Y symmetry of the Standard Electroweak Model (SEM). Such a quantum field
theoretic model is some kind a hadronized version of the Standard Model (SM).
From a gauge invariant set of the Feynman diagrams with one-photon exchanges we
reproduce Sirlin's radiative corrections of order O(alpha/pi), calculated to
leading order in the large nucleon mass expansion, and calculate
next-to-leading corrections of order O(alpha E_e/m_N). This confirms Sirlin's
confidence level of the radiative corrections O(alpha E_e/m_N). The
contributions of the LsM are taken in the limit of the infinite mass of the
scalar isoscalar sigma-meson. In such a limit the LsM reproduces the results of
the current algebra (Weinberg, Phys. Rev. Lett. {\bf 18}, 188 (1967)) in the
form of effective chiral Lagrangians of pion-nucleon interactions with
non--linear realization of chiral SU(2)xSU(2) symmetry. In such a limit the
LM is also equivalent to Gasser-Leutwyler's chiral quantum field theory
or chiral perturbation theory (ChPT) with chiral SU(2)xSU(2)symmetry and the
exponential parametrization of a pion-field (Ecker, Prog. Part. Nucl. Phys.
{\bf 35}, 1 (1995)).Comment: 50 pages, 7 figures. arXiv admin note: text overlap with
arXiv:1805.0970
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