Proton and neutron knockout from36Ca

Abstract

The cross sections for single-nucleon knockout from 36 Ca on a 9 Be target at 70 MeV/nucleon were measured to be σ exp (−p) = 51.1 ± 2.6 mb for proton knockout and σ exp (−n) = 5.03 ± 0.46 mb for neutron knockout. The spectroscopic factors and orbital angular momenta of the neutrons and protons removed from 36 Ca, leading to bound A = 35 residues, were deduced by comparison of the experimental cross sections and longitudinal-momentum distributions to those calculated in an eikonal reaction theory, and found to be S(p, 1d 3/2 ) = 0.79 ± 0.04 and S(n, 2s 1/2 ) = 0.23 ± 0.02 (relative to independent-particle-model values and only including experimental contributions to the uncertainties). As found in previous knockout studies, the spectroscopic factor deduced for the deeply bound neutron was significantly reduced relative to shell-model calculations, a result at variance with dispersive optical model (DOM) extrapolations, which suggest a spectroscopic factor closer to 60% of the independent-particle-model value.

Direct Reaction Probes of Single-Particle States and Correlations

“…The figure is adapted from [12] and includes two new data points deduced from neutron removal measurements from the very neutron-rich carbon isotopes 19 C and 20 C, with ∆S < −25 MeV, made at RIKEN at 240 MeV per nucleon [13] (extreme left). The shaded vertical bars and associate data points show the positions of additional data points for both neutron and proton removal from 36 Ca, with |∆S| = 16.6 MeV, made at the NSCL, also presented at this meeting [14], and which are also consistent also with the systematics shown.…”

Isospin dependence of nucleon correlations in ground-state nuclei

“…A recent knockout experiment on 36 Ca suggests reduction factors of 0.75 and 0.22 for the majority proton d 3/2 and minority neutron s 1/2 orbits, respectively [34]. DOM extrapolations for 36 Ca generate 0.70 and 0.65 for the proton and neutron orbit, respectively.…”

Experimental study of the knockout reaction mechanism usingO14at 60 MeV/nucleon

“…Thus the one-neutron removal cross section could not be obtained from this measurement. On the other hand, because of the similar beam energy and reaction mechanism, the one-neutron removal cross section should be almost the same with that measured at 53 MeV/u on a 9 Be target, which is 14(1) mb [10]. The measured 2pn-removal cross section of 60(9) mb is much larger than that of one-neutron removal from 14 O, which may be attributed to the core excitations or other complicated reaction processes.…”

“…However, the trends of reduction factors with asymmetric nuclei from these two methods are not consistent. A significant dependence on ∆S was found for R s from knockout reactions taken at energies lower than 100 MeV/nucleon with a light composite target ( 9 Be or 12 C), which are close to unity for loosely-bound nucleons but are as small as 0.24 for deeply-bound nucleons [2,8,9]. In contrast, R s from transfer reactions show a weak dependence on ∆S [3].…”

“…Background: For the deeply-bound one-nucleon removal at intermediate energies using a 9 Be or 12 C target, a strong reduction of cross section was observed relative to the prediction of eikonal theoretical model. The large disagreement has not been explained and the systematic trend is inconsistent with results from transfer reactions.…”