Separated structure functions for the proton-knockout reactionO16(e,e’p)

Abstract

Three structure functions have been determined in the reaction O(e, e'p) N at Q = 0.20 (GeV/c) for 1p~l2 and 1psI2 knockout and for the excitation of the (5/2+, 1/2+) doublet at E = 5.3 MeV in N. The longitudinal-transverse interference structure function WL,~is enhanced by a factor 2.05 + 0.06 + 0.12 for 1p3/z knockout and by a factor 1.50 + 0.10 + 0.08 for 1pq/q knockout with respect to a calculation that gives a proper account of data taken in parallel kinematics. The longitudinal structure function Wl. is also enhanced, albeit less with respect to these calculations. PACS number(s): 25.30. Fj, 27.20.+n ExperiInents involving the electron-induced protonknockout reaction are commonly used to study proton momentum distributions in atomic nuclei [1, 2]. In most cases these experiments comprise cross-section measurements only. More information on various aspects of the (e, e'p) reaction, such as the basic electron-proton coupling or the final-state interaction, can be obtained by studying the four structure functions that are contained in the (e, e p) cross section. By combining cross sections measured under difFerent kinematical conditions one can isolate these structure functions, and thus reveal efFects that may not be easily observable in the cross section. A few experiments involving a separation of the longitu-I dinal and transverse structure functions have been performed in kinematics with the recoil proton and virtualphoton momentum vectors parallel [3]. For transitions to final states below the two-particle emission threshold these experiments generally confirm the validity of the impulse approximation. In this paper we present the results of an (e, e'p) experiment on 0, in which all three in-plane structure functions have been measured. In previous sO(e, e'p) experiments [4, 5] not all in-plane structure functions have been extracted. In the one-photon-exchange approximation the cross section for the (e, e'p) reaction is expressed as follows [6]: 0 -It oMott (vLWL + vTWT + vLTWLT cos p + vTTWTT cos 2cjk),where IVI"WT, RI,T, and WTT represent the longitudinal, transverse, and interference structure functions, and the electron kinematical factors are given by vL, --$, vT = tan'e. /2 -~' "vLT =~tan'0. /2 -$, and vTT --», with 0, the electron-scattering an-@2 2+2 1 gle, q and u the momentum and energy transfer, and I Q = toq . In Eq. (1), K =~z , is a kinematical factor and 0M tt is the cross section for elastic scattering ofF a point charge. Finally, P represents the angle between the electron-scattering plane and the plane defined by the momentum transfer q and the outgoing proton momentum p . If these planes coincide, the kinematics is labeled "in plane. " The structure functions can be separated by "Present address:The Netherlands.performing measurements with difFerent kinematical factors v and/or values of P, while keeping q and to constant. For the separation of t/VL, T in an in-plane experiment, two measurements at constant p =~0 & -0~~a re required: one at 0&I ( 0~corresponding to P = 0' and the o...

Short-Range Correlations in Semi-exclusive Electron Scattering Experiments

“…16 we compare the results of our calculations with the empirical values of the electromagnetic responses given in Ref. [41]. These calculations have been done with the S3 input and using the Scwhandt et al optical potential [38].…”

Influence of the Dirac sea on proton electromagnetic knockout

“…Figure 4 surveys the Q 2 dependence of A LT for 16 O(e, e ′ p). The data for Q 2 = 0.2 are from Spaltro et al [24] while those for Q 2 = 0.3 (GeV/c) 2 are from Chinitz et al [25]. These calculations use NLSH wave functions, EDAD1 optical potential, CC2 current operator, and Coulomb gauge.…”

Dynamics of the quasielasticO16(e,e′p)reaction atFissum1, Liang2, Anderson3 et al. 2004Phys. Rev. C

“…The knockout of 1p-shell protons in 16 O(e, e ′ p) was studied by Bernheim et al [11] and Chinitz et al [12] at Saclay, Spaltro et al [13] and Leuschner et al [14] at NIKHEF, and Blomqvist et al [15] at Mainz at Q 2 < 0.4 (GeV/c) 2 . In these experiments, cross-section data for the lowest-lying fragments of each shell were measured as a function of p miss , and normalization factors (relating how much lower the measured cross-section data were than predicted) were extracted.…”