Influence of the Dirac sea on proton electromagnetic knockout

Abstract

We use the relativistic distorted-wave impulse approximation (RDWIA) to study the effects of negative-energy components of Dirac wave functions on the left-right asymmetry for (e, e ′ p) reactions on 16 O with 0.2 ≤ Q 2 ≤ 0.8 and 12 C with 0.6 ≤ Q 2 ≤ 1.8 (GeV/c) 2 . Spinor distortion is more important for the bound state than for the ejectile and the net effect decreases with Q 2 . Spinor distortion breaks Gordon equivalence and the data favor the CC2 operator with intermediate coupling to the sea. The left-right asymmetry for Q 2 < ∼ 1.2 (GeV/c) 2 is described well by RDWIA calculations, but at Q 2 = 1.8 (GeV/c) 2 the observed variation with missing momentum is flatter than predicted.

Quasi-elastic neutrino charged-current scattering cross sections on oxygen

“…shells of 12 C(ν µ , µp) and 12 C(ν µ , µn) reactions are shown in Fig. 5 as functions of positive p m values together with Saclay [51], SLAC [42], and JLab [41] data. The data for beam energies The averaged reduced cross sections for the removal of nucleons from the 1p shell in 16 O(ν µ , µp) and 16 O(ν µ , µn) reactions are shown in Fig.…”

“…Furthermore, σ red depends upon initial electron energy due to Coulomb distortion. The RDWIA approach with LEA code was successfully tested against measured 12 C(e, e ′ p) [42], 16 O(e, e ′ p) [43], and 40 Ca(e, e ′ p) [12] differential and reduced cross sections, and the normalization factors S(α)…”

“…The nucleon bound-state functions were calculated by the TIMORA code [40] with the normalization factors S(α) relative to full occupancy of the IPSM orbitals. According the RDWIA analysis of the JLab 12 C(e, e ′ p) data [41,42] S(1p 3/2 ) = 84%, S(1s 1/2 ) = 100% and average factor about ≈ 89%. We use also the following values of normalization factors of 16 O: S(1p 3/2 ) = 66%, S(1p 1/2 ) = 70%, and S(1s 1/2 ) = 100%, that were obtained in the RDWIA analysis of the JLab data [43].…”