Nuclear excitations in nucleon removal processes SPES 2014 Second International Workshop Legnaro, Italy, May 26-28, 2014 Nuclear excitations in nucleon removal processes José Benlliure Universidad de Santiago de Compostela Spain

Nucleon-removal processes Interplay between fragmentation and nuclear structure Production of neutron-rich nuclei Structural properties The puzzling quenching of deeply bound nucleons Access to unbound systems José Benlliure, SPES 2014 Legnaro, Italy,, May 2014 2

Experimental approach Inverse kinematics GSI José Benlliure, SPES 2014 Legnaro, Italy, May 2014

Experimental approach Inverse kinematics GSI More than 1000 fission fragments identified in the reaction 238U(1 A GeV)+d José Benlliure, SPES 2014 Legnaro, Italy, May 2014

Multinucleon-removal reactions Isospin fluctuations the abrasion process is isospin independent: hot pre-fragments prefragments with large N/Z fluctuations most of the prefragments do not survive because of the excitation energy gained cold final-residues - nature of final fragments governed by neutron-proton evaporation: N/Z fluctuations are reduced José Benlliure, SPES 2014 Legnaro, Italy, May 2014

Producing nuclei far from stability Nuclei far from stability in nucleon-removal/fragmentation reactions Fragmentation is an optimum reaction mechanism for exploring the nuclide chart: neutron-deficient nuclei are highly populated up to the drip-line the in-flight fragmentation of heavy nuclei leading to fission produces medium-mass neutron-rich nuclei the large fluctuation in isospin (abrasion) and excitation energy (ablation) give access to cold fragmentation processes where neutron-rich nuclei are produced. José Benlliure, SPES 2014 Legnaro, Italy, May 2014 6

Producing nuclei far from stability Heavy neutron-rich nuclei 238U + Be @ 1 A GeV 208Pb + Be @ 1 A GeV José Benlliure, SPES 2014 Legnaro, Italy, May 2014 7

Producing nuclei far from stability Heavy neutron-rich nuclei 238U+Be 1000 A MeV H. Alvarez et al., PRC 82, 041602 ( 2010) 208Pb+Be 1000 A MeV T. Kurtukian et al., PRC 89, 024616 ( 2014) J. Kurcewicz et al., PLB 717, 371 ( 2012) 238U+Be 1000 A MeV H. Alvarez et al., PRC 82, 041602 ( 2010) 238U+Be 1000 A MeV H. Alvarez et al., PRC 82, 041602 ( 2010) 208Pb+Be 1000 A MeV T. Kurtukian et al., PRC 89, 024616( 2014) 126 new heavy neutron-rich nuclei fragmenting beams of 238U and 208Pb José Benlliure, SPES 2014 Legnaro, Italy,, May 2014 8

Production of heavy neutron-rich nuclei Predicted cross sections with ABRASION/ABLATION models www.usc.es/genp/cofra The measured cross sections are only reproduced when highly excited remnants are considered. On average the remnant gains 27 MeV per abraded nucleon. - EPAX - COFRA José Benlliure, SPES 2014 T. Kurtukian et al., PRC 89, 024616 (2014) Legnaro, Italy, May 2014

The puzzling quenching of the spectroscopic factors Knock-out versus transfer A. Gade et al., PRC 77, 044306 (2008) F. Flavigny et al., PRL 110, 122503 (2013) “The disagreement of the two systematic trends from knockout and transfer calls for a better description of so-called direct reaction mechanisms in order that a consistent picture of nuclear structure emerges from measurements at different incident energies.” José Benlliure, SPES 2014 Legnaro, Italy, May 2014

Nuclear excitations in proton knock-out Model description: Glauber model Adiabatic and inert-core approximations core survival probability 1-N removal probability       Explicit treatment of core excitations was suggested for the 1-N quenching puzzle A-1X core A-2X core A. Bonaccorso C. Louchart et al., PRC 83, 011601 (2011) evaporation José Benlliure, SPES 2014 Legnaro, Italy, May 2014 11

Nuclear excitations in proton knock-out Proton knock-out at FRS/GSI José Benlliure, SPES 2014 Legnaro, Italy, May 2014 12

Nuclear excitations in proton knock-out Measurements at FRS/GSI José Benlliure, SPES 2014 Legnaro, Italy,, May 2014 13

Nuclear excitations in proton knock-out Model description: abrasion-ablation The probability for nucleon removal processes is defined by the geometrical overlap between projectile and target nuclei Remnants survive when excited below the neutron evaporation threshold (Sn). Excitations of the residual nuclei are considered from the holes created in the Fermi distribution of single-particle levels. José Benlliure, SPES 2014 Legnaro, Italy,, May 2014 14

Nuclear excitations in proton knock-out Data interpretation Excitation energy gained by the remnants seems to be larger than expected from particle-hole excitations K.-H. Schmidt et al., PLB 300, 313 (1993) José Benlliure, SPES 2014 Legnaro, Italy, May 2014 15

Nuclear excitations in proton knock-out Data interpretation The persistence of this effect should be checked with lighter projectiles and as a function of the neutron excess. José Benlliure, SPES 2014 Legnaro, Italy, May 2014 16

Nucleon excitations in proton knock-out Isospin dependence of the nucleon-removal process Sn 106 107 108 109 110 In 115 125 124 123 122 121 120 119 118 117 116 114 113 112 111 Sb Te 126 Sn 132 238U beam D. Pérez et al., PLB 703 (2011) 552 José Benlliure, SPES 2014 Legnaro, Italy, May 2014 17

Nucleon excitations in proton knock-out Isospin dependence of the proton-removal process Calculations validated with stable beams underestimate the survival probability of proton knock-out residues obtained with neutron-deficient beams. José Benlliure, SPES 2014 Legnaro, Italy, May 2014 18

Nucleon excitations in proton knock-out Isospin dependence of the nucleon-removal process The excitation energy induced by nucleon removal seems to be enhanced for the deficient species in systems with large neutron-proton asymmetries. José Benlliure, SPES 2014 Legnaro, Italy, May 2014 19

Nucleon excitations in proton knock-out Isospin dependence of the nucleon-removal process Protons and neutrons exchange their role in neutron-rich and proton-rich nuclei. José Benlliure, SPES 2014 Legnaro, Italy, May 2014 20

Nucleon excitations in proton knock-out Isospin dependence of the nucleon-removal process Sn > Sp Vn > Vp Sn = Sp Vn > Vp Sn < Sp Vn < Vp José Benlliure, SPES 2014 Legnaro, Italy, May 2014 21

Nucleon excitations in proton knock-out Isospin dependence of the nucleon-removal process Sn > Sp Vn > Vp Sn = Sp Vn > Vp Sn < Sp Vn < Vp José Benlliure, SPES 2014 Legnaro, Italy, May 2014 22

Nucleon excitations in proton knock-out Isospin dependence of the proton-removal process Sn > Sp Vn > Vp Sn = Sp Vn > Vp Sn < Sp Vn < Vp José Benlliure, SPES 2014 Legnaro, Italy, May 2014 23

Conclusions Multinucleon-removal reactions play a key role in the production of nuclei far from stability because of the large fluctuations in isospin and excitation energy gained in these processes. According to abrasion-ablation model calculations, the production cross sections of nucleon knock-out process can only be described when remnant excitations are considered. This isospin dependence of the excitation could be related to the quenching of the spectroscopic factors in nucleon knock-out. However, more realistic model calculations and transfer data in similar systems should be used for a final interpretation. Collaborators: U. Santiago de Compostela: J. Vargas, J.L. Rodríguez, Y. Ayyad, S. Beceiro, D. Cortina, P. Díaz, M. Mostazo, C. Paradela GSI: T. Aumann, J. Atkinson, K. Boretzky, A. Estrade, H. Geissel, A. Kelic, Y. Litvinov, S. Pietri, A. Prochazka, M. Takechi, J. Winfield CEA/DAM: A. Chatillon, J. Taieb José Benlliure, SPES 2014 Legnaro, Italy, May 2014 24