nucl-th digest · Mar 6, 2017

Chiral Corrections to Baryon Electromagnetic Form Factors

Corrections motivated by chiral symmetry arguments have long been known to give important contributions to hadronic observables, particularly at low momentum transfer. It is possible to separate these approaches into two broad groups; either the corrections are implemented at the parton level, or at the hadron level. We explore the results of incorporating pion loop corrections at the hadron level to a calculation of electromagnetic form factors in the NJL model. These calculations are compared with the result of an earlier implementation of pion loops at the parton level using the same NJL model formalism. A particular parameter set yields a good description of low energy nucleon properties within both approaches. However, for the

Σ^{-}

there is a remarkable improvement when the chiral corrections are implemented at the hadronic level.

Comments:: 7 pages, 4 figures, 4 tables
Subjects:: Nuclear Theory (nucl-th)
arXiv:: 1703.01032 [pdf]

Few Body Syst.(2018)·2 citations

[Submitted on 3 Mar 2017]

The frozen nucleon approximation in two-particle two-hole response functions

I. Ruiz Simo🇪🇸 · J.E. Amaro🇪🇸 · M.B. Barbaro🇮🇹 · J.A. Caballero🇪🇸 · G.D. Megias🇪🇸 · T.W. Donnelly🇺🇸

We present a fast and efficient method to compute the inclusive two-particle two-hole (2p-2h) electroweak responses in the neutrino and electron quasielastic inclusive cross sections. The method is based on two approximations. The first neglects the motion of the two initial nucleons below the Fermi momentum, which are considered to be at rest. This approximation, which is reasonable for high values of the momentum transfer, turns out also to be quite good for moderate values of the momentum transfer $q ≳ k_{F}$ . The second approximation involves using in the "frozen" meson-exchange currents (MEC) an effective $Δ$ -propagator averaged over the Fermi sea. Within the resulting "frozen nucleon approximation", the inclusive 2p-2h responses are accurately calculated with only a one-dimensional integral over the emission angle of one of the final nucleons, thus drastically simplifying the calculation and reducing the computational time. The latter makes this method especially well-suited for implementation in Monte Carlo neutrino event generators.

Comments:: 8 pages, 5 figures and 1 table
Subjects:: Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
arXiv:: 1703.01186 [pdf]

PLB(2017)·18 citations

Monday·March 6, 2017

Chiral Corrections to Baryon Electromagnetic Form Factors

The frozen nucleon approximation in two-particle two-hole response functions

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