Longitudinal-transverse separation of the deuterium (e,e’p) response functions

Abstract

In the four-momentum-transfer range 0.05 <^v 2 < 0.27 (GeV/c) 2 , longitudinal and transverse response functions have been determined by performing a Rosenbluth separation of 2 H(e,e'p) coincidence cross sections measured in parallel kinematics. The results are compared to nonrelativistic calculations that include the effects of final-state interaction, meson-exchange currents, and isobar configurations, and to relativistic calculations that include the effects of final-state interaction. The ratios of the response functions agree with both calculations; the absolute values are (16 ± 3 ± 8)% larger than predicted.PACS numbers: 25.30.Fj, 25.10,+s, The deuteron system plays an essential role in nuclear physics as this bound two-nucleon system contributes to the basis of our understanding of the nucleon-nucleon interaction, being the microscopic input for any fundamental model of heavier nuclei. In the theoretical calculations of the two-nucleon system the state of the art is such that experiments with high precision are important to enable comparisons with theoretical predictions and possibly distinguish between the various calculations. The level of our understanding of the two-nucleon system is illustrated by the reasonable description of many existing electron-scattering data. 1 " 3 Only a limited set of high-precision exclusive experiments exists. In particular, no exclusive experiments aimed at separating individual structure functions of the deuteron in the quasielastic domain have been reported so far. Given its general interest, it is of relevance to obtain such precise exclusive data on the deuterium electrodisintegration process. These data should preferably involve the coincident (e.e'p) reaction as it gives access to four independent observables (if no polarization degrees of freedom are considered).In the past, several inclusive quasielastic (QE) electron-scattering experiments have been performed on the deuteron. Nonrelativistic calculations show good agreement with the separated inclusive longitudinal and transverse response functions 4 in the three-momentumtransfer range between 300 and 500 MeV/c. In exclusive experiments the cross sections are measured over a large missing-momentum range, 5,6 and are rather well reproduced by nonrelativistic calculations. In this paper we present the results of an exclusive 2 H(e,e'p) experiment, in which both the longitudinal and transverse response functions have been determined.The description of the QE (e,e'p) process is generally based on the following assumptions: (i) A simple virtual photon is involved in the knockout process (one-photonexchange approximation); (ii) the energy and momentum that the electron loses in the scattering process are transferred to a single nucleon (quasielastic-scattering process); (iii) for the nucleon current the free-nucleon current is taken, modified for off-shell effects [impulse approximation (IA)]. In order to investigate the validity of these assumptions, experiments have been performed on several nuclei, e.g., 4 He (Refs. ...

Deuteron Electrodisintegration in theΔ-Resonance Region

“…In the unpolarized ͑e, e 0 p͒ reaction, the information on the dynamics of the two-nucleon system is contained in four structure functions: the longitudinal f L , the transverse f T , and the interference terms f LT and f TT . Measurements of the differential cross section and in some cases of the individual structure functions f L , f T , and f LT [3][4][5][6][7][8][9][10][11][12][13][14][15] have provided stringent tests of the existing theoretical models [16][17][18][19]. In particular, the f L and f T data were reproduced by the existing calculations [7,10], while the f LT data pointed to the need for a relativistic form of the current operator [8,[11][12][13][14].…”

Relativistic effects in the electrodisintegration of deuterium

“…The RLT interference structure function originates from the interference between the charge and transverse components of the hadronic current, and as such is known to be especially sensitive to the structure of the current operator [S] . Since RL and RT do not depend on the out-of-plane angle 4, and since RLT 0: cos 4 and Rn LX ~0~24, RLT may be determined by performing measurements at 4 = 0 (proton detected in-plane forward of 4) and 4 = r (proton detected backward of q) :…”

Nucleon Knockout by Intermediate Energy Electrons

“…Separated response functions have been measured for larger momentum transfers by van der Schaar et al (135,136) at NIKHEF. In parallel kinematics, measurements of the ratio for are consistent with PWIA or with a small suppression.…”