Dynamics of the quasielasticO16(e,e′p)reaction at

Kevin Fissum¹,

M. Liang²,

B. D. Anderson³

et al.

Abstract

The physics program in Hall A at Jefferson Lab commenced in the summer of 1997 with a detailed investigation of the 16 O(e, e ′ p) reaction in quasielastic, constant (q, ω) kinematics at Q 2 ≈ 0.8 (GeV/c) 2 , q ≈ 1 GeV/c, and ω ≈ 445 MeV. Use of a self-calibrating, self-normalizing, thin-film waterfall target enabled a systematically rigorous measurement. Five-fold differential cross-section data for the removal of protons from the 1p-shell have been obtained for 0 < pmiss < 350 MeV/c. Six-fold differential cross-section data for 0 < Emiss < 120 MeV were obtained for 0 < pmiss < 340 MeV/c. These results have been used to extract the ALT asymmetry and the RL, RT , RLT , and RL+T T effective response functions over a large range of Emiss and pmiss. Detailed comparisons of the 1p-shell data with Relativistic Distorted-Wave Impulse Approximation (rdwia), Relativistic Optical-Model Eikonal Approximation (romea), and Relativistic Multiple-Scattering Glauber Approximation (rmsga) calculations indicate that two-body currents stemming from Meson-Exchange Currents (MEC) and Isobar Currents (IC) are not needed to explain the data at this Q 2 . Further, dynamical relativistic effects are strongly indicated by the observed structure in ALT at pmiss ≈ 300 MeV/c. For 25 < Emiss < 50 MeV and pmiss ≈ 50 MeV/c, proton knockout from the 1s 1/2 -state dominates, and romea calculations do an excellent job of explaining the data. However, as pmiss increases, the single-particle behavior of the reaction is increasingly hidden by more complicated processes, and for 280 < pmiss < 340 MeV/c, romea calculations together with two-body currents stemming from MEC and IC account for the shape and transverse nature of the data, but only about half the magnitude of the measured cross section. For 50 < Emiss < 120 MeV and 145 < pmiss < 340 MeV/c, (e, e ′ pN ) calculations which include the contributions of central and tensor correlations (two-nucleon correlations) together with MEC and IC (two-nucleon currents) account for only about half of the measured cross section. The kinematic consistency of the 1p-shell normalization factors extracted from these data with respect to all available 16 O(e, e ′ p) data is also examined in detail. Finally, the Q 2 -dependence of the normalization factors is discussed.

Nucleon-nucleon correlations, short-lived excitations, and the quarks within

“…meson coupling, QMC) used the MIT bag model to represent the three confined quarks in the proton (Guichon, 1988;Guichon et al, 1996;Stone et al, 2016). Later work used the QMC model with more general confinement mechanisms (Blunden and Miller, 1996), the covariant NJL model (Cloet et al, 2009a(Cloet et al, , 2006(Cloet et al, , 2016 and the chiral quark soliton model (Diakonov et al, 1996;Smith and Miller, 2003, 2004. In these models the attraction needed to produce a bound state is generated by the exchange of scalar quantum numbers (either by a scalar meson (Guichon, 1988;Guichon et al, 1996;Stone et al, 2016) or by pairs of pions (Smith and Miller, 2003, 2004) and the repulsion needed to obtain nuclear saturation is caused by exchange of vector mesons.…”

Quasi-elastic neutrino charged-current scattering off medium-heavy nuclei:40Ca and40Ar

“…data for electron scattering off 12 C and 16 O [46,47] and we adopted this program for neutrino reaction [33].…”

Neutron knockout in neutral-current neutrino-oxygen interactions

“…Nucleon knockout experiments, while confirming the validity of the shell model, have unambiguously shown its limitations. Owing to strong correlations, nucleons are excited to states of higher energy and the occupation of the shell-model states is reduced to values sizably less than 1 [43][44][45]. Moreover, their energy distribution acquires finite widths, reflecting the finite lifetime of singleparticle states [46,47].…”