Spin polarization ofAl34fragments produced by nucleon pickup at intermediate energies

Abstract

The polarization of 34 Al fragments, produced by single neutron pickup from a 9 Be target by a 36 S projectile at 77.5 MeV/nucleon, have been observed at GANIL via the detection of resonantly destroyed β-asymmetry. The reaction-induced polarization is deduced using a tentative spin/parity assignment for the 34 Al ground state. A positive polarization was measured near the peak of the 34 Al yield curve. A kinematical model based on the spectator-participant model for projectile fragmentation reactions has been extended in order to take into account the features of pickup reactions, i.e., the picked-up nucleon having an average momentum equal to the Fermi momentum and aligned along the incident beam direction. The trend-line in the observed spin-orientation is very well reproduced by this model.

Spin-orbit coupling and the up-down differential transverse flow in intermediate-energy heavy-ion collisions

“…So far polarized rare isotope beams can already be produced with nucleon removal or pickup reactions at RIKEN [35], GSI [36], NSCL [37], and GANIL [38], and the spin polarization of projectile fragments can be measured through the angular distribution of their β or γ decays. In addition, at AGS or RHIC energy people are measuring the analyzing power denoting the chiral asymmetry as well as spin flip probability in elastic pp or pA collisions, see, e.g., [39,40].…”

Dynamical effects of spin-dependent interactions in low- and intermediate-energy heavy-ion reactions

“…Although the detailed experimental status will be presented in another topic review of this issue, here we'd like to briefly mention two related experiments that might be relevant in analyzing the probes discussed above. One of them is the spin-polarized beam which can be produced through pick-up or removal reactions at Rikagaku Kenkyusho (RIKEN) [90,91], Gesellschaft für Schwerionenforschung mbH (GSI) [92], the National Superconducting Cyclotron Laboratory (NSCL) [93], and the Grand Accélérateur National d'Ions Lourds (GANIL) [94][95][96]. It is expected that the effects of spin dynamics with spin-polarized beam will be much enhanced, providing a better system for extracting the information of the spin-dependent nuclear force, especially the nuclear tensor force.…”

Precise nuclear moments of extremely proton-rich nuclus 23 Al

“…However, the statistics was insufficient to discuss further details of the nuclear structure because of very small production rate of 23 Al nuclei. In the present work, by using the pick-upfragmentation process [3,4] to produce polarized 23 Al nuclei, we succeeded to gain the production rate by around ten times larger. Therefore, we have measured the electric quadrupole coupling constant eqQ/ h of 23 Al in an Al 2 O 3 single crystal using the β-ray detecting nuclear quadrupole resonance in the strong external field (β-NQR) for the first time.…”

“…The polarized 23 Al nuclei were produced through the pick-up and fragmentation process of the intermediate-energy nuclear collisions of 100-AMeV 24 Mg 12+ ions and 9 Be atoms in a 2.5-mm-thick production target [3,4]. The production cross section of the pick-up fragmentation is about ten times larger than that of the pure fragmentation process, 28 Si + 9 Be, which was utilized in the previous work [2].…”