Relativity versus exchange currents in O 16 (e,e′p)

Janina Grineviciute , D. Halderson


Background: The O16(e,e′p) reaction in the quasielastic region has been studied in several experiments to determine spectroscopic factors, hence, the degree to which O16 looks like a closed shell. By varying the kinematics, experimentalists are able to extract response functions which comprise the cross section. However, analysis of the response functions separately produces very different spectroscopic factors. Two calculations led to different conclusions as to whether exchange currents can eliminate the discrepancies. Neither calculation considered relativistic corrections. Purpose: The purpose of the article is to investigate the disagreement as to whether exchange currents are the solution to obtaining consistent spectroscopic factors and to show that relativistic corrections have a much greater influence on providing this consistency. Methods: This calculation employs the recoil corrected continuum shell model, a model that uses a realistic interaction and produces nonspurious scattering states that are solutions to the coupled-channel problems. Pionic and pair contributions to the exchange currents were calculated as developed by Dubach et al. [Nucl. Phys. A 271, 279 (1976)10.1016/0375-9474(76)90246-3]. Relativistic effects are included by use of the direct Pauli reduction. Results: Contributions of the exchange currents are shown to be insufficient to provide consistent spectroscopic factors. However, the inclusion of relativistic corrections produces spectroscopic factors from the different responses and cross sections which are very similar for both the p1/2 and the p3/2 states and both the (|q|,ω)=(460MeV/c,100MeV) and (|q|,ω)=(570MeV/c,172MeV) data. The influence of channel coupling is also shown to be significant. Tests of current conservation show that inclusion of the direct Pauli reduction produces small increases in its violation. Conclusions: Results are model dependent. Meson-exchange current contributions are not sufficient. Relativistic corrections can be large and lead to more consistent spectroscopic factors. Contributions from channels other than the outgoing channels can be significant. Response functions which depend on the transverse current are sensitive to the lower component of relativistic wave functions and, hence, would provide a measure of the appropriateness of any relativistic model. © 2016 American Physical Society.
Author Janina Grineviciute (FP / NPD)
Janina Grineviciute,,
- Nuclear Physics Division
, D. Halderson
D. Halderson,,
Journal seriesPhysical Review C, ISSN 0556-2813
Issue year2016
Publication size in sheets0.5
Languageen angielski
Score (nominal)45
ScoreMinisterial score = 35.0, 28-11-2017, ArticleFromJournal
Ministerial score (2013-2016) = 45.0, 28-11-2017, ArticleFromJournal
Publication indicators WoS Impact Factor: 2014 = 3.733 (2) - 2014=3.439 (5)
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