V. Chahar | Searcharxiv

arXiv2026

Field-theoretical description of the deuteron breakup in the clothed particle representation

We present a field-theoretical description of the deuteron electrodisintegration reaction d(e,e'p)n induced by unpolarized and polarized electrons. The approach combines the Lehmann-Symanzik-Zimmermann in(out) formalism with the clothed particle representation in the instant form of relativistic dynamics, providing a fully relativistic and gauge-independent framework based on the Fock-Weyl criterion. Within the method of unitary clothing transformations, one and the same transformation that generates the relativistic nucleon-nucleon interaction (the Kharkiv potential) also induces a fresh family of electromagnetic current operators. As a result, one-body and two-body (meson-exchange) currents emerge on a common footing. We compute differential cross sections and polarization observables with the inclusion of final-state interaction effects and meson-exchange current contributions, and compare the results with Saclay and Jefferson Lab data as well as with earlier theoretical predictions. The role of relativistic ingredients (one- and two-body currents, Fermi-motion effects, etc.) and the interplay between them are analyzed in several kinematic regimes of the experiments at Saclay and Jefferson Lab.

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arXiv2026

Comparison of Relativistic and Non-relativistic Faddeev calculations for Proton-Deuteron Elastic Scattering

This investigation compares non-relativistic and relativistic nucleon-nucleon potentials in the context of proton-deuteron scattering. Conventional NN potentials (e.g., CDBonn, AV18, Nijmegen) rely on the nonrelativistic Schroedinger equation, whereas the Kharkiv potential is intrinsically relativistic. We employ the Coester-Pieper-Serduke (CPS) and Kamada-Gloeckle (KG) conversion methods to construct a phenomenological-relativistic potential (PRP) from a realistic NN potential, preserving the deuteron binding energy and phase shifts. Focusing on relativistic effects and not including Coulomb forces to avoid complexity, the solutions are compared by solving relativistic and nonrelativistic Faddeev equations. Calculations of the differential cross section using the relativistic Faddeev equation show that relativistic effects - particularly the deviation at the backward angle - become pronounced at 135 MeV. The differences in the forward angle were attributed to the characteristics of the Kharkiv potential itself. The reverse transformation of the Kharkiv potential into a pseudo-nonrelativistic potential (PNRP) confirms that the backward-angle relativistic effect increases with energy in the range from 100 MeV to 400 MeV. Comparisons of the polarization observables indicate that relativistic effects, as well as the discrepancy between the CPS and KG transformations, become significant above 300 MeV. However, for polarization observations below 300 MeV, the nonrelativistic results from PNRP do not deviate significantly from relativistic calculations.

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