Smith Da

Comparison of the double giant-dipole states observed in (. pi. sup minus ,. pi. sup + ) and (. pi. sup + ,. pi. sup minus ) reactions on sup 40 Ca and sup 27 Al

The double isovector giant-dipolar state has been observed in the ({pi}{sup {minus}},{pi}{sup +}) {Delta}{ital T}{sub {ital z}}=+2 and ({pi}{sup +},{pi}{sup {minus}}) {Delta}{ital T}{sub {ital z}}={minus}2 double-charge-exchange reactions on {sup 40}Ca and {sup 27}Al. The resonances observed in the ({pi}{sup {minus}},{pi}{sup +}) reaction are closely related via Coulomb energy and isospin symmetry to the resonances measured in the inverse ({pi}{sup +},{pi}{sup {minus}}) reaction on the same nuclei. The new observations provide strong support for the identification of the double giant-dipole state in nuclei. The differences between the self-conjugate and non-self-conjugate cases are outlined.

Pion elastic scattering from polarized 13C in the energy region of the P33 resonance.

Analyzing powers [ital A][sub [ital y]] were measured for [pi][sup +] and [pi][sup [minus]] elastic scattering from polarized [sup 13]C at incident pion energies [ital T][sub [pi]] near the [ital P][sub 33] [pi]-nucleon resonance. At [ital T][sub [pi]]=130 MeV, the values of [ital A][sub [ital y]] are significantly different from zero for [pi][sup [minus]] scattering. For [pi][sup +] at [ital T][sub [pi]]=130 MeV and for both [pi][sup [minus]] and [pi][sup +] at all other energies, the [ital A][sub [ital y]] are mostly consistent with zero. Elastic differential cross sections were measured using an unpolarized [sup 13]C target. Both the analyzing-power and cross-section data were compared with predictions using a variety of nuclear structure and reaction models. The analyzing power was found to be strongly sensitive to the quadrupole spin-flip part of the transition. The data of this work complement measurements of the magnetic form factor by electron scattering. The pion [ital A][sub [ital y]] data are not reproduced by calculations using wave functions that fit the magnetic form factor at low momentum transfers.

Pion elastic scattering from polarized [sup 13]C in the energy region of the [ital P][sub 33] resonance

Analyzing powers [ital A][sub [ital y]] were measured for [pi][sup +] and [pi][sup [minus]] elastic scattering from polarized [sup 13]C at incident pion energies [ital T][sub [pi]] near the [ital P][sub 33] [pi]-nucleon resonance. At [ital T][sub [pi]]=130 MeV, the values of [ital A][sub [ital y]] are significantly different from zero for [pi][sup [minus]] scattering. For [pi][sup +] at [ital T][sub [pi]]=130 MeV and for both [pi][sup [minus]] and [pi][sup +] at all other energies, the [ital A][sub [ital y]] are mostly consistent with zero. Elastic differential cross sections were measured using an unpolarized [sup 13]C target. Both the analyzing-power and cross-section data were compared with predictions using a variety of nuclear structure and reaction models. The analyzing power was found to be strongly sensitive to the quadrupole spin-flip part of the transition. The data of this work complement measurements of the magnetic form factor by electron scattering. The pion [ital A][sub [ital y]] data are not reproduced by calculations using wave functions that fit the magnetic form factor at low momentum transfers.

Pion double charge exchange onO16atTπ=300–500 MeV

Measurements of small-angle cross sections for the pion double-charge-exchange (DCX) reaction [sup 16]O([pi][sup +],[pi][sup [minus]])[sup 16]Ne (g.s.) at incident energies of 300--500 MeV are reported. These are the first measurements of DCX cross sections on a [ital T]=0 nucleus in this energy region. The behavior of the cross sections is similar to that of analog transitions, but they are smaller by more than an order of magnitude. This suggests sequential charge-exchange scattering as the dominant process, but suppressed by a mechanism not yet identified.

Pion double charge exchange on [sup 16]O at [ital T][sub [pi]]=300--500 MeV

Measurements of small-angle cross sections for the pion double-charge-exchange (DCX) reaction [sup 16]O([pi][sup +],[pi][sup [minus]])[sup 16]Ne (g.s.) at incident energies of 300--500 MeV are reported. These are the first measurements of DCX cross sections on a [ital T]=0 nucleus in this energy region. The behavior of the cross sections is similar to that of analog transitions, but they are smaller by more than an order of magnitude. This suggests sequential charge-exchange scattering as the dominant process, but suppressed by a mechanism not yet identified.

Pion double charge exchange on O 16 at T π =300–500 MeV

Measurements of small-angle cross sections for the pion double-charge-exchange (DCX) reaction [sup 16]O([pi][sup +],[pi][sup [minus]])[sup 16]Ne (g.s.) at incident energies of 300--500 MeV are reported. These are the first measurements of DCX cross sections on a [ital T]=0 nucleus in this energy region. The behavior of the cross sections is similar to that of analog transitions, but they are smaller by more than an order of magnitude. This suggests sequential charge-exchange scattering as the dominant process, but suppressed by a mechanism not yet identified.