Final state interactions in electron scattering at high missing energies and momenta

Abstract

Calculations of two-step rescattering and pion emission for the 12 C(e, e ′ p) reaction at very large missing energies and momenta are compared with recent data from TJNAF. For parallel kinematics, final state interactions are strongly reduced by kinematical constraints. A good agreement between calculation and experiment is found for this kinematics when one admits the presence of high momentum components in the nuclear wave function. In recent years, electron scattering experiments have been possible with kinematics that involve large energies and momentum transfered, as for example in studies of nuclear transparency. In this regime, the final state interactions (FSI) for the knock out of a nucleon are usually treated employing Glauber inspired calculations [1,2,3,4]. Such techniques, together with the experience gained in related nuclear structure studies, provide a useful starting point to pursue accurate predictions of neutrino-nucleus interactions at high energy. This was pointed out by various contributions to this conference.At scattering energies of the order of GeV, the leptoninc probe can resolve the high-momentum tail of the spectral function generated by shortrange (central and tensor) correlations (SRC). This represent about 10-20% of the total spectral strength [5,6] and is found along a ridge in the momentum-energy plane (k-E) which spans a region of several hundred MeV/c (MeV) [7,9,8]. This corresponds to large missing momenta (p m ) and energies (E m ) in knock out cross sections. This contribution to the spectral function is also responsible for most of the binding energy of nuclear systems [10]. The main characteristics pre- * Email: C.Barbieri@gsi.de † Present address: Gesellschaft für Schwerionenforshung, Planckstr. 1, 64291, Darmstadt, Germany dicted by these calculations are confirmed by recent experimental data [11,12,13], which will be considered further below. Locating this strength experimentally, at both large E m and p m , is difficult because it is spread over an energy range of several hundred MeV, so the total density of the spectral function is very low. In this energy regime multi-nucleon processes, beyond the direct knock out, are possible [14] and can induce large shifts in the missing energies and momenta, moving strength to regions where the direct signal is much smaller and therefore submerging it. As it will be discussed below, the effects of FSI become larger and less controllable when the transverse structure functions that enter the expression of the (e, e ′ p) cross section dominate the longitudinal one. This trend is predicted by several theoretical studies [14,15,16,17,18]. The issue of how to control FSI in lepton scattering experiments has been discussed in detail in Ref. [19,20] for the particular case of kinematics sensitive to the SRC tail of the nuclear spectral function. A Monte Carlo simulation and kinematical arguments led to the suggestion that the best chance for an identification of SRC occurs in parallel kinematics 3 .3 In this work we refer to 'paralle...

Lepton scattering fromAr40andTi48in the quasielastic peak region

“…For two-body currents and hadron production, Eq. (2) extends non trivially in terms of one-and twobody spectral functions [14,[20][21][22].…”

“…Final-state interactions (FSI) of the struck nucleon can be accounted for using Glauber theory [22][23][24][25][26]. For the inclusive processes discussed here we follow Ref.…”

Self-Consistent Green's Function Theory for Atomic Nuclei

“…A measurement of the charge distribution of 34 Si would require electron scattering on radioactive ions. These experiments are becoming feasible only now [115], with first results on the heavier 132 Xe obtained by the SCRIT collaboration [83]. In the coming years, the case of 34 Si will thus constitute an interesting objective for electron-nucleus scattering facilities.…”

“…where ω represents the energy transfer, M N is the nucleon mass, e(p) the energy of a nucleon with momentum p. The onebody current operators j µ s depend on the spin-isospin degrees of freedom s and S h s (p, E) is the one-body spectral function normalized to the total number of nucleons. For two-body currents and hadron production, Equation (29) extends non trivially in terms of one-and two-body spectral functions [129][130][131][132].…”

Differential cross section measurement of the 12C(e,e’pp)10Beg.s. reaction

“…Similarly, several studies have put in evidence that saturation properties of nuclear systems can also be explained without the need of a strong short-range repulsion among nucleons [13][14][15]. However, a recent experiment on 12 C [16] found direct evidence of high-momentum components, which in parallel kinematics could hardly be ascribed to final-state interactions effects [17,18]. More related investigations, aimed at addressing the nature of the correlations, fol-lowed during the last decade [5,[19][20][21][22].…”