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Jeff Tostevin Department of Physics School of Electronics and Physical Sciences

Reactions using nucleon knockout RISING Workshop Surrey, 29 th -30 th March 2004. Jeff Tostevin Department of Physics School of Electronics and Physical Sciences University of Surrey, UK. A. P 0. P ||. One- and two-nucleon knockout reactions.

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Jeff Tostevin Department of Physics School of Electronics and Physical Sciences

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  1. Reactions using nucleon knockout RISING Workshop Surrey, 29th-30th March 2004 Jeff Tostevin Department of Physics School of Electronics and Physical Sciences University of Surrey, UK RISING Workshop, Surrey, 29th-30th March 2004

  2. A P0 P|| One- and two-nucleon knockout reactions Peripheral collisions (E  50A MeV; MSU, RIKEN, GSI) g heavy mass A residue is detected, with coincident -ray detection A+xN T+xN light target T=9Be,12C Sudden removal of nucleons Target T left in g.s. or excited state Events contributing will be both break-up and stripping both of which leave a mass A residue in the final state RISING Workshop, Surrey, 29th-30th March 2004

  3. One- and two nucleon knockout – to date One-nucleon knockout predominantly – proof of purpose and of accuracy Light nucleus sector – p and sd-shell (Ni looked at but not optimum detection/resolution) Small number of final states and gamma-rays Semi-classical (eikonal) reaction theory seems to work quantitatively. RISING Workshop, Surrey, 29th-30th March 2004

  4. Orientation for magnitudes - extreme sp model Single neutron removal from 23O  [1d5/2]6 [2s1/2] n sp(2s1/2)=64 mb 2s1/2 Sn=2.7 MeV sp(1d5/2)=23 mb 1d5/2 Sn=5.5 MeV -n = 6 sp(1d5/2)+sp(2s1/2) = (138 + 64) = 202 mb typical cross sections 20 – 30 mb RIKEN (PRL 88 (‘02) 142502) 72 MeV/u + 12C target; -n = 233(37)mb RISING Workshop, Surrey, 29th-30th March 2004

  5. Single-neutron knockout from 17C =0,2 admixture =0,2 admixture =2 pure V. Maddalena et al. PRC 63 (2001) 024613 RISING Workshop, Surrey, 29th-30th March 2004

  6. Spectroscopic factor - occupancy of the state Structure – we probe single particle overlaps Nucleon removal from A+1 will leave mass A residue in the ground or an excited state - amplitude for finding nucleon with sp quantum numbers ,j, about core state c in A+1 is Usual to write RISING Workshop, Surrey, 29th-30th March 2004

  7. Experimental v shell model spectroscopic factors Can define reduction factor th Shell model structure plus eikonal reaction More bound systems P.G. Hansen and J.A.Tostevin, ARNPS 53 (2003), 219 RISING Workshop, Surrey, 29th-30th March 2004

  8. Rs factors – deviations from the shell model RISING Workshop, Surrey, 29th-30th March 2004

  9. 30S 28S 26P 28P 24Si 26Si 2n from neutron deficient Two nucleon knockout – go south, or west Z 2p from neutron rich 34Si 32Al 34Al 28Mg 30Mg 32Mg 28Na 30Na 32Na 26Ne 30Ne 28Ne N RISING Workshop, Surrey, 29th-30th March 2004

  10. 2p knockout – production or detailed spectroscopy? reaction mechanism is? production rate R production rate R/1000 30Ne 32Mg could gain x100 rate 2p knockout (~1mb) e.g.Coulex 30Ne D. Bazin et al., PRL 91 (2003) 012501. RISING Workshop, Surrey, 29th-30th March 2004

  11. 40 2s1/2 1d5/2 1p1/2 20 1p3/2 0 2p removal Two nucleon knockout – reaction mechanism 23O  21O 28Mg  26Ne -1n n + 21O -1n 1  22O 2+ 0+ D. Bazin et al., PRL 91 (2003) 012501 RISING Workshop, Surrey, 29th-30th March 2004

  12. 1 2 c A p particles q particles Direct two nucleon knockout – uncorrelated Estimate assuming removal of a pair of uncorrelated nucleons - contribution from direct 2N removal D. Bazin et al., PRL 91 (2003) 012501 RISING Workshop, Surrey, 29th-30th March 2004

  13. 1 2 c A Uncorrelated two proton removal D. Bazin et al., PRL 91 (2003) 012501 28Mg 26Ne(inclusive) with weights 0+: 1.33 to the 26Ne 2+: 1.67 final states 4+: 3.00 RISING Workshop, Surrey, 29th-30th March 2004

  14. 1 2 c A Correlated two proton removal amplitudes of nucleon- pair wave functions about core configurations c. Spin states populated There is now no SF factorisation J.A. Tostevin et al., RNB6 proceedings, in press RISING Workshop, Surrey, 29th-30th March 2004

  15. 28Mg 26Ne(0+) C(2s1/2)2 = – 0.305 C(1d3/2)2 = – 0.301 C(1d5/2)2 = – 1.05 Shell model (sd-shell) 2N amplitudes 28Mg 26Ne(2+) C(1d3/2)2 = – 0.050 C(d5/2,d3/2)= + 0.374 C(1d5/2)2 = – 0.637 C(s1/2,d5/2)= – 0.061 C(s1/2,d3/2)= – 0.139 28Mg 26Ne(4+) C(d5/2,d3/2) = 0.331 C(1d5/2)2 = 1.596 B.A. Brown, private communication RISING Workshop, Surrey, 29th-30th March 2004

  16. SthSexpSthexpth unc. corr. (mb) (mb) 0+ 1.33 2.4(5)1.83 0.70(15) 0.53 2+ 1.67 0.3(5)0.55 0.09(15) 0.16 4+ 3.00 2.0(3)1.79 0.58(9)0.52 2+ - 0.5(3)0.76 0.15(9) 0.22 Inclusive cross section (in mb)1.50(10) 1.43 Cross sections – correlated and uncorrelated 28Mg 26Ne(0+, 2+, 4+) S = (in mb) / 0.29 J.A. Tostevin, G. Podolyák, et al., RNB6 proceedings, in press, and in preparation RISING Workshop, Surrey, 29th-30th March 2004

  17. P0 Nature of the two-nucleon correlations Removed nucleon pair are spatially correlated but no restriction on pair spin S or relative orbital angular momentum in formalism. All contributing pair wave functions are included. Unlike.e.g. (p,t) reaction – where angular momentum selection on the p | t  vertex selects nn pair in S=0, T=1, relative s-state configuration. Can assess by projecting [ T=1, S=0,  =0 ] relative motion component from the pair wave functions  Sth(rel) RISING Workshop, Surrey, 29th-30th March 2004

  18. SthSexpSth rel corr. 0+ 1.60 2.4(5)1.83 2+ 0.14 0.3(5)0.55 4+ 2.00 2.0(3)1.79 2+ 0.46 0.5(3)0.76 Cross sections – relative s-state correlations 28Mg 26Ne(0+, 2+, 4+ ,2+) D. Bazin et al., PRL 91 (2003) 012501 J.A. Tostevin, G. Podolyák, et al., RNB6 proceedings, in press, and in preparation RISING Workshop, Surrey, 29th-30th March 2004

  19. RISING Workshop, Surrey, 29th-30th March 2004

  20. Energy/nucleon 1.05 GeV 250 MeV 2.10 GeV Test case - earlier data from Berkeley (~10%) Kidd et al., Phys Rev C 37 (1988) 2613 2N removal from 12C B.A. Brown, 2N amplitudes J.A. Tostevin et al., RNB6 proceedings, in press and in preparation RISING Workshop, Surrey, 29th-30th March 2004

  21. b Surface localisation of knockout reactions 12Be+9Be  11Be(gs)+X, 80A MeV Eikonal theory: localisation provided by core survival requirement c 12Be v 9Be RISING Workshop, Surrey, 29th-30th March 2004

  22. Skyrme Hartree-Fock radii and densities (1) W.A. Richter and B.A. Brown, Phys. Rev. C67 (2003) 034317 RISING Workshop, Surrey, 29th-30th March 2004

  23. Skyrme Hartree-Fock radii and densities (2) B.A. Brown, S. Typel, and W.A. Richter, Phys. Rev. C65 (2002) 014612 RISING Workshop, Surrey, 29th-30th March 2004

  24. neutron • proton Weakly bound states – with good statistics Reduction Factor Rs P.G. Hansen and J.A.Tostevin, ARNPS 53 (2003), 219 RISING Workshop, Surrey, 29th-30th March 2004

  25. neutron • proton More strongly bound states – deep hole states Reduction Factor Rs inclusive P.G. Hansen and J.A.Tostevin, ARNPS 53 (2003), 219 RISING Workshop, Surrey, 29th-30th March 2004

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