Deuteron Electrodisintegration in theΔ-Resonance Region

Abstract

The differential cross section and the transverse-transverse interference structure function for the reaction 2 H͑e, e 0 p͒n have been determined at an np invariant mass of 2.16 GeV. The data, covering a 40 ± range in the proton emission angle, indicate that D excitation and subsequent ND interaction is the dominant reaction mechanism. Calculations performed within an ND coupled-channel approach reproduce the cross section data, but underestimate the f TT results by 30 to 40 percent.[S0031-9007(97)03090-1] PACS numbers: 25.10. + s, 13.60. Rj, 13.75.Cs, 25.30.Rw Deuteron electrodisintegration in the D-resonance region offers an excellent probe to investigate the dynamics of the D isobar in a nuclear system. While at low energy transfer the deuteron response is reproduced by microscopic calculations based on realistic NN potentials, at higher energy transfer the first nucleon resonance, the D or P 33 baryon, plays an important role. This has been illustrated in several theoretical studies [1,2].Many electron scattering experiments have been devoted to deuteron disintegration in quasifree kinematics. Of these, the exclusive ͑e, e 0 p͒ measurements have provided the most detailed information on the deuteron structure. 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]. The measurement of f TT is more difficult, since it requires the detection of protons outside of the electron scattering plane. Hitherto, only one measurement [6] has been reported, at very low transferred energy and momentum ͑v, jqj͒ ͑18 MeV, 160 MeV͞c͒; the f TT results were not significantly different from zero.Although the effects of D isobar currents (IC) are small in quasifree kinematics, they are expected to become important at higher excitation energies. In the Dresonance region, which corresponds to an np invariant mass W np of about 2.17 GeV, one has to treat the D isobar and the nucleon degrees of freedom in a coupledchannel (CC) approach, as was shown for NN scattering in Ref. [20], and for electromagnetic deuteron break-up first in Ref.[21] and more recently in improved calculations in Refs. [22,23]. These models predict that the 2 H͑e, e 0 p͒n reaction in the D-resonance region is almost purely transverse in character and therefore the structure functions f T and f TT essentially generate the entire cross section. These structure functions in turn are predicted to have the characteristic features of a dominant M1 multipo...

General survey of polarization observables in deuteron electrodisintegration

“…With this we will close the discussion of our results. We will not compare to experimental data on the exclusive reaction [61][62][63][64][65][66][67][68][69][70][71][72][73][74][75] because they have already been compared to our approach and thus nothing new can be said.…”

Meson retardation in deuteron electrodisintegration

“…This is demonstrated in Figs. 5 and 6 for the kinematics of a more recent experiment by Pellegrino et al [18] with E np = 280 MeV and q 2 = 2.47 fm −2 . The effects of retardation on f L anf f LT in Fig.…”

Few-nucleon systems (theory)

“…This is illustrated in fig. 10 for a suitable kinematics in the ∆-region which has been studied at NIKHEF [27]. It turns out that especially the recoil charge contribution (right panel in fig.…”

“…Results for deuteron electrodisintegration taken from [15]. Left panel: the structure functions fL, fT , fLT and fT T for the kinematics of the NIKHEF experiment [27], i.e. Enp = 280 MeV, q 2 = 2.47 fm −2 .…”