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Fusion of 40 Ca + 96 Zr revisited: Transfer couplings and hindrance far below the barrier

By Italy I-35020 Legnaro (Padova) Laboratori Nazionali di Legnaro A.M.INFN Stefanini, Italy) I-35131 Padova Sez. di Padova and INFN Universitá di Padova G.(Dipartimento di Fisica e Astronomia Montagnoli, USA) IL 60439 Argonne Argonne National Laboratory H.(Physics Division Esbensen, Italy) I-35020 Legnaro (Padova) Laboratori Nazionali di Legnaro L.(INFN Corradi, France) F-67037 Strasbourg Cedex 2 Université de Strasbourg CNRS–IN2P3 S.(IPHC Courtin, Italy) I-35131 Padova Sez. di Padova and INFN Universitá di Padova E.(Dipartimento di Fisica e Astronomia Fioretto, France) F-91405 Orsay Campus CNRS/IN2P3 and Université Paris-Sud A.(CSNSM Goasduff, Poland) PL 31-342 Cracow Polish Academy of Sciences J.(Institute of Nuclear Physics Grebosz, France) F-67037 Strasbourg Cedex 2 Université de Strasbourg CNRS–IN2P3 F.(IPHC Haas, Italy) I-35131 Padova Sez. di Padova and INFN Universitá di Padova M.(Dipartimento di Fisica e Astronomia Mazzocco, Italy) I-35131 Padova Sez. di Padova and INFN Universitá di Padova C.(Dipartimento di Fisica e Astronomia Michelagnoli, Croatia) HR-10002 Zagreb T.(Ruđer Bošković Institute Mijatović, Italy) I-35131 Padova Sez. di Padova and INFN Universitá di Padova D.(Dipartimento di Fisica e Astronomia Montanari, Italy) I-35131 Padova Sez. di Padova and INFN Universitá di Padova G.(Dipartimento di Fisica e Astronomia Pasqualato, Italy) I-35131 Padova Sez. di Padova and INFN Universitá di Padova C.(Dipartimento di Fisica e Astronomia Parascandolo, Italy) I-35131 Padova Sez. di Padova and INFN Universitá di Padova F.(Dipartimento di Fisica e Astronomia Scarlassara, Italy) I-35131 Padova Sez. di Padova and INFN Universitá di Padova E.(Dipartimento di Fisica e Astronomia Strano, Croatia) HR-10002 Zagreb S.(Ruđer Bošković Institute Szilner and Italy) I-35131 Padova Sez. di Padova and INFN Universitá di Padova D.(Dipartimento di Fisica e Astronomia Torresi

Abstract

The sub-barrier fusion excitation function of 40 Ca + 96 Zr has been measured down to cross sections ≃2.4 μb, i.e. two orders of magnitude smaller than obtained in a previous experiment, where the sub-barrier fusion of this system was found to be greatly enhanced with respect to 40 Ca + 90 Zr, and the need of coupling to transfer channels was suggested relying on coupled-channels calculations. The purpose of this work has been to investigate the behavior of 40 Ca + 96 Zr fusion far below the barrier, thereby disentangling the elusive interplay of effects due to inelastic couplings, transfer couplings and, possibly, the appearance of the fusion hindrance. The smooth trend of the excitation function has been found to continue, and the logarithmic slope increases very slowly. No indication of hindrance shows up, and a comparison with 48 Ca + 96 Zr is illuminating in this respect. A new CC analysis of the complete excitation function has been performed, including explicitly one- and two-nucleon <math altimg="si1.gif" xmlns="http://www.w3.org/1998/Math/MathML"><mi>Q</mi><mo>&gt;</mo><mn>0</mn></math> transfer channels. Such transfer couplings bring significant cross section enhancements, even at the level of a few μb. Locating the hindrance threshold, if any, in 40 Ca + 96 Zr would require challenging measurements of cross sections in the sub-μb range

Year: 2014
DOI identifier: 10.1016/j.physletb.2013.12.048
OAI identifier: oai:www.openaccessrepository.it:5340

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