21-23 February 2011
Colegio Rector Peset
Europe/Madrid timezone

np pairing in N=Z nuclei studied through 2N transfer reactions

23 Feb 2011, 10:20
Colegio Rector Peset

Colegio Rector Peset


Augusto Macchiavelli (Lawrence Berkeley National Laboratory)


Pairing in exotic nuclei is a subject of active research in nuclear physics. Of particular interest is the competition between isovector (T=1) and isoscalar (T=0) Cooper pairs, expected to occur in N=Z nuclei . Near 40Ca and 56Ni, earlier systematic analyses of two-neutron (L=0) transfer reactions [1,2] found the data consistent with a picture involving configuration mixing induced by simple pairing degrees of freedom of the valence neutrons. While providing evidence for isovector pairing in the form of pairing vibrations [2,3], the question of whether the isoscalar component generates collective modes is still an open one. Direct reactions involving the transfer of an np pair from even-even to the low lying 0+,1+ states in odd-odd self conjugate nuclei could be excellent probes to study np correlations. While absolute cross-section values are always desirable, we note that the ratio σ(0+)/σ(1+) itself provides an almost model independent measure of the pairing collectivity in the respective channels. Thus, the (3He,p) reaction stands out as an ideal tool to study np correlations. Following a short overview of the subject, we will discuss a series of experiments carried out at the Argonne ATLAS facility to study the (3He,p) reaction in reverse kinematics and present results obtained with a beam of 44Ti [4]. We will also speculate on the use of np knockout reactions and conclude by delineating a possible path as we move towards the next generation of rare isotopes facilities. *Supported by The U.S. DOE under contract DE-AC02-05CH11231 1. B. F. Bayman and N. M. Hintz, Phys. Rev . 172, 1113 (1968) 2. D.R.Bes et al. Phys. Rep. 34C, 1 (1977), and references therein. 3. A.O.Macchiavelli et al. Phys. Lett. B480, 1 (2000) 4. A.O.Macchiavelli et al., To be published.


Augusto Macchiavelli (Lawrence Berkeley National Laboratory)

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