Macroscopic Description of Pairing

A classical description of pairing as vibrations and rotations in the number of particles as a function of the gauge angle is outlined and applied to a calculation of the pair transfer by the pair field in a collision between two superfluid nuclei. I . Surface Vibrations and Rotations The motivation for taking up the subject of a macroscopic description of pairing is the success of the macroscopic or classical description of the excitation of surface vibrations in heavy ion collisions. I t is well-known that one may talk about pairing in much the same way [I]. Fairing vibrations and pairing rotations are excited in two-nucleon transfer reactions, and the question is, whether a similar classical description of these phenomena may also be useful. Most of what I am going, to say will be as well-known to many of you, who have been working In nuclear structure as i t was to Ricardo Broglia who has contributed a great deal to the subject [ Z ] . I shall start out by a short summary of the macroscopic descripLion of surface deformations, where we envisage that the nuclear density 0 can perform vibrations around an equilibrium density 0") The quantity 0") can be parametrized as and surface vibrat~ons can be described by varying the nuclear radius R as function of direction The corresponding change in density is The deformation amplitudes a~~ are the dynamical variables describing the collective modes. A deformation of the density gives rise to a change in the average field Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:1987250