Recently developed chiral effective field theory models provide excellent descriptions of the bulk characteristics of finite nuclei, but have not been tested with other observables. In this work, densities from both relativistic point-coupling models and mean-field meson models are used in the analysis of meson-nucleus scattering at medium energies. Elastic scattering observables for 790 MeV/c π ± on 208 Pb are calculated in a relativistic impulse approximation, using the Kemmer-Duffin-Petiau formalism to calculate the π ± nucleus optical potential.PACS number(s): 25.80. Dj, 24.10.Jv, 24.10.Ht, The concepts and methods of effective field theory (EFT) [1][2][3] have recently elucidated the successful nuclear phenomenology of relativistic field theories of hadrons, called quantum hadrodynamics (QHD) [4][5][6][7]. The EFT framework shows how QHD models can be consistent with the symmetries of quantum chromodynamics (QCD) and can be extended to accurately reproduce its low-energy features. The EFT perspective accounts for the success of relativistic mean-field models and provides an expansion scheme at the mean-field level and for going beyond it [6,8].A practical outcome of these EFT studies has been new sets of relativistic mean-field models, with parameters determined by global fits to bulk nuclear observables. Here we make the first independent tests of densities from these models by using them as inputs to relativistic impulse approximation (RIA) calculations of elastic π ± nucleus scattering. At energies above the ∆ resonance we expect the impulse approximation to reproduce experiment at forward angles, since the elementary amplitudes incorporate the dominant effects of intermediate ∆'s while medium modifications due to the ∆ should be small.In Ref.[6], an effective hadronic lagrangian consistent with the symmetries of QCD and intended for application to finite density systems was constructed. The goal was to test a systematic expansion for low-energy observables, which included the effects of hadron compositeness and the constraints of chiral symmetry. The degrees of freedom are (valence) nucleons, pions, and the low-lying non-Goldstone bosons. A scalar-isoscalar field with a mass of roughly 500 MeV was also included to simulate the exchange between nucleons of two correlated pions in this channel. The lagrangian was expanded in powers of the fields and their derivatives, with the terms organized using Georgi's "naive dimensional analysis" [9,2,10].The result is a faithful representation of low-energy, non-strange QCD, as long as all nonredundant terms consistent with symmetries are included. In addition, the mean-field framework provides a means of approximately including higher-order many-body and loop effects, since the scalar and vector meson fields play the role of auxiliary KohnSham potentials in relativistic density functional theory [7]. Fits to nuclear properties at the mean-field level showed that the effective lagrangian could be truncated at the first few powers of the fields and their derivatives...
The 5-dimensional spin-0 form of the Kemmer-Duffin-Petiau (KDP) equation is used to calculate scattering observables [elastic differential cross sections (dσ/dΩ), total cross sections (σ Tot ), and reaction cross sections (σ Reac )] and to deduce σ Tot and σ Reac from transmission data for K + + 6 Li, 12 C, 28 Si, and 40 Ca at several momenta in the range 488 − 714 MeV/c. Realistic uncertainties are generated for the theoretical predictions. These errors, mainly due to uncertainties associated with the elementary K + + nucleon amplitudes, are large, so that the disagreement that has been noted between experimental and theoretical σ Tot and σ Reac is not surprising. The results suggest that the K + + nucleon amplitudes need to be much better determined before unconventional medium effects are invoked to explain the data. 24.10Jv,25.80NvTypeset using REVT E X Recent K + +A transmission cross section data were analyzed using the relativistic KDP-RIA model. The model-dependence in the deduced, experimental total and reaction cross sections was discussed, and the uncertainties in the corresponding theoretical predictions owing to uncertainties in the elementary K + N amplitudes were calculated. Our experimental σ Tot and σ Reac cross sections are consistent with those found in Ref. [13]. Although the theoretical predictions underestimate the experimental quantities, improved knowledge of the K + N amplitudes is required before studies of possible K + -nucleus medium effects can meaningfully be pursued.
Pion-nucleus elastic scattering at energies above the ∆(1232) resonance is studied using both π + and π − beams on 12 C, 40 Ca, 90 Zr, and 208 Pb. The present data provide an opportunity to study the interaction of pions with nuclei at energies where second-order corrections to impulse approximation calculations should be small. The results are compared with other data sets at similar energies, and with four different first-order impulse approximation calculations. Significant disagreement exists between the calculations and the data from this experiment. 25.80.Dj, Typeset using REVT E X 2
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.