Hard breakup of two nucleons from theHe3nucleus

Abstract

We investigate a large angle photodisintegration of two nucleons from the 3 He nucleus within the framework of the hard rescattering model (HRM). In the HRM a quark of one nucleon knocked out by an incoming photon rescatters with a quark of the other nucleon leading to the production of two nucleons with large relative momentum. Assuming the dominance of the quark-interchange mechanism in a hard nucleon-nucleon scattering, the HRM allows the expression of the amplitude of a two-nucleon break-up reaction through the convolution of photon-quark scattering, N N hard scattering amplitude and nuclear spectral function which can be calculated using a nonrelativistic 3 He wave function. The photon-quark scattering amplitude can be explicitly calculated in the high energy regime, whereas for N N scattering one uses the fit of the available experimental data. The HRM predicts several specific features for the hard breakup reaction. First, the cross section will approximately scale as s −11 . Secondly, the s 11 weighted cross section will have the shape of energy dependence similar to that of s 10 weighted N N elastic scattering cross section. Also one predicts an enhancement of the pp breakup relative to the pn breakup cross section as compared to the results from low energy kinematics. Another result is the prediction of different spectator momentum dependencies of pp and pn breakup cross sections. This is due to the fact that samehelicity pp-component is strongly suppressed in the ground state wave function of 3 He. Because of this suppression the HRM predicts significantly different asymmetries for the cross section of polarization transfer N N breakup reactions for circularly polarized photons. For the pp breakup this asymmetry is predicted to be zero while for the pn it is close to 2 3 .

Hard breakup of the deuteron into twoΔisobars

“…Details of the derivation are given in Refs. [16,21]. After the above mentioned factorization is made, the overall invariant amplitude of γd → B 1 B 2 reaction can be expressed as follows:…”

“…angle nucleons are produced through the interaction of the incoming photon with a pre-existing hard two nucleon system in the nucleus [13][14][15]. The second approach is based on the assumption that the two high momentum nucleons are produced through a hard rescattering at the final state of the reaction [16][17][18][19][20][21].…”

HARD PHOTODISINTEGRATION OF3

“…For these reactions, numerical predictions for the cross section differ considerably from one approach to another. Recent experimental data [8] shows a better agreement with HRM calculations [9].…”

“…(5) in accordance with the constituent counting rule [3]. That is dσ dt ∼ s −11 [6], [7], [9], which comes from the s −4 dependence of the φ amplitudes entering Eq.(3). This behavior has already been observed in deuteron photodisintegration [1], [2], and in recent experiments on pp breakup in 3 He [8].…”

“…[9] for details). First, by working in a q + = 0 reference frame, we approximate the struck nucleon's propagator to its on shell component.…”