Investigating the link between proton reaction cross sections and the quenching of proton spectroscopic factors in 48Ca

Abstract

The nucleon self-energies of 40 Ca and 48 Ca are determined using a nonlocal dispersive optical model (DOM). By enforcing the dispersion relation connecting the real and imaginary part of the self-energy, scattering and structure data are used to constrain these self-energies. The ability to calculate both bound and scattering states simultaneously puts these selfenergies in a unique position to consistently describe exclusive knockout reactions such as (e, e p). The present analysis reveals the importance of high-energy proton reaction cross-section data in constraining spectroscopic factors required for the description of the (e, e p) cross sections. In particular, it is imperative that high-energy proton reaction cross-section data are measured for 48 Ca in the near future so that the quenching of the spectroscopic factors in the 48 Ca(e, e p) 47 K reaction can be unambiguously constrained using the DOM. Measurements of proton reaction cross sections in inverse kinematics employing rare isotope beams with large neutron excess will provide corresponding constraints on proton spectroscopic factors for exotic nuclei. Moreover, DOM generated spectral functions indicate that the quenching of spectroscopic factors compared to 40 Ca is not only due to long-range correlation, but also partly due to the increase in high-momentum protons in 48 Ca on account of the strong neutron-proton interaction. Single-particle momentum distributions of protons and neutrons in 48 Ca calculated from these spectral functions confirm that neutron excess causes a higher fraction of high-momentum protons than neutrons.

Nucleon-Nucleon Short-Ranged Correlations, $β$ Decay and the Unitarity of the CKM Matrix

“…Their result is the SRC contribution amounts to 22% ± 8% and the LRC contribution to δ = 14% ± 10%. This is in accordance with expectations [18][19][20][21]29] and with the results of [48][49][50][51]. In the following we argue that, in analogy with the (e, e ′ p) and (d, 3 He) reactions, the superallowed beta decay measurements are impacted by the short-ranged correlations that reduce the spectroscopic strength by about 20%.…”

“…The missing strength of 30%-40% implies the existence of collective effects (long-range correlations) and short-range correlations in nuclei. See also the substantial theoretical analyses [48][49][50][51] that used detailed many-body evaluations to find that including the effects of both long and short-range correlations must be included to reproduce the results of experiments that measure spectroscopic factors.…”

Dispersive optical model analysis of Pb208 generating a neutron-skin prediction beyond the mean field

“…The latter results increased the canonical values of proton spectroscopic factors for double closed-shell nuclei [18] by about 0.05 due to the use of nonlocal potentials to describe the proton distorted waves. The coincidence cross sections of the valence transitions in the 48 Ca(e, e p) 47 K reaction are also accurately described, provided proper care is taken of the proton reaction cross sections in the DOM analysis [19]. The resulting N − Z trend of the spectroscopic strength near the Fermi energy demonstrates an increased reduction of the proton removal strength with a slope that is not as large as in Ref.…”

An overview of symmetric nuclear matter properties from chiral interactions up to fourth order of the chiral expansion

“…These quantities, which can be dramatically different from model to model -as has been known for decades -are not observable. The SRC probabilities and highmomentum distributions in nuclei, which have been and are being extracted from hard electron scattering experiments [64][65][66][67][68][69][70][71][72][73][74][75][76] are equally non-observable, although highmomentum information can be extracted from data in a scale and scheme dependent way [93]. The recent comprehensive analysis from Ref.…”

“…Claims that momentum distributions in nuclei, with particularly emphasis on SRC, can be measured have stimulated considerable interest in the subject. These are not new discussions, but they have recently resurfaced in conjunction with inclusive or exclusive high-momentum transfer electron scattering experiments [64][65][66][67][68][69][70][71][72][73][74][75][76]. We will include a brief discussion of the issue.…”