Photo- and electro-disintegration of {sup 3}He at threshold and pd radiative capture
The present work reports results for: (1) pd radiative capture observables measured at center-of-mass (c.m.) energies in the range 0--100 keV and at 2 MeV by the TUNL and Wisconsin groups, respectively; (2) contributions to the Gerasimov-Drell-Hearn (GDH) integral in {sup 3}He from the two- up to the three-body breakup thresholds, compared to experimental determinations by the TUNL group in this threshold region; (3) longitudinal, transverse, and interference response functions measured in inclusive polarized electron scattering off polarized {sup 3}He at excitation energies below the threshold for breakup into ppn, compared to unpolarized longitudinal and transverse data from the Saskatoon group. The calculations are based on pair-correlated-hyperspherical-harmonics bound and continuum wave functions obtained from a realistic Hamiltonian consisting of the Argonne {upsilon}{sub 18} two-nucleon and Urbana IX three-nucleon interactions. The electromagnetic current operator includes one- and two- body components, leading terms of which are constructed from the Argonne {upsilon}{sub 18} interaction (specifically, its charge-independent part). Two-body currents associated with {Delta}-isobar degrees of freedom are treated non-perturbatively via the transition-correlation-operator method. The theoretical predictions obtained by including only one-body currents are in violent disagreement with data. These differences between theory and experiment are, to a large extent, removed when two-body currents are taken into account, although some rather large discrepancies remain in the c.m. energy range 0--100 keV, particularly for the pd differential cross section {sigma}({theta}) and tensor analyzing power T{sub 20}({theta}) at small angles, and contributions to the GDH integral. A rather detailed analysis indicated that these discrepancies have, in large part, a common origin, and can be traced back to an excess strength obtained in the theoretical calculation of the E{sub 1} reduced matrix element associated with the pd channel having L,S,J = 1, 1/2, 3/2. It is suggested that this lack of E{sub 1} strength observed experimentally might have implications for the nuclear interaction at very low energies. Finally, the validity of the long-wavelength approximation for electric dipole transitions is discussed.
- Research Organization:
- Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States); Univ. of Pisa (IT)
- Sponsoring Organization:
- USDOE Office of Energy Research (ER) (US)
- DOE Contract Number:
- AC05-84ER40150
- OSTI ID:
- 755325
- Report Number(s):
- DOE/ER/40150-1437; JLAB-THY-99-36; nucl-th/9911051; TRN: US0002422
- Journal Information:
- submitted to Phys. Rev. C, Other Information: Submitted to Phys. Rev. C; PBD: 1 Nov 1999
- Country of Publication:
- United States
- Language:
- English
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