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STUDY OF QUASI-FREE SCATTERING OF PROTON BY CLUSTERS OF 6 He HALO NUCLEUS

First Workshop on. State of the Art in Nuclear Cluster Physics. Strasbourg, May 13 -May 16, 2008. STUDY OF QUASI-FREE SCATTERING OF PROTON BY CLUSTERS OF 6 He HALO NUCLEUS. G. Belovitsky 1 , E. Konobeevski 1 , A. Stepanov 1 , V. Zavarzina 1 , S. Zuyev 1 ,

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STUDY OF QUASI-FREE SCATTERING OF PROTON BY CLUSTERS OF 6 He HALO NUCLEUS

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  1. First Workshop on State of the Art in Nuclear Cluster Physics Strasbourg, May 13 -May 16, 2008 STUDY OF QUASI-FREE SCATTERING OF PROTON BY CLUSTERS OF 6He HALO NUCLEUS G. Belovitsky1, E. Konobeevski1, A. Stepanov1, V. Zavarzina1, S. Zuyev1, N. Polukhina2, A.Rusetsky2, N. Starkov2, S. Lukyanov3, and Yu. Sobolev3 1 Institute for Nuclear Research, RAS, 117312 Moscow, Russia 2 P.N.Lebedev Physical Institute, RAS, 117924 Moscow, Russia 3 Flerov Laboratory of Nuclear Reactions, JINR, 141980 Dubna, Russia SOTANCP: May 13 - 16, 2008

  2. 13 14 15 16 17 18 19 20 21 22 23 24 12 13 14 15 16 17 18 19 20 21 22 23 9 10 11 12 13 14 15 16 17 18 19 20 22 8 10 11 12 13 14 15 17 19 7 9 10 11 12 14 6 7 8 9 11 3 4 6 8 2 3 n Two-neutron halo nuclei – Borromean nuclei Two neutron halo – Borromean nuclei core+n+n – boundcore+nn+n - unbound Halo Nuclei SOTANCP: May 13 - 16, 2008

  3. 100 100 10-1 10-1 10-2 10-2 8He matter 11Li matter 4He 9Li ρm(r) [fm-3] ρm(r) [fm-3] 10-3 10-3 10-4 10-4 8He core 11Li core 10-5 10-5 0 2 4 6 8 10 0 2 4 6 8 10 r [fm] r [fm] Nuclear Matter Density Distribution Compact core and extended tail: halo SOTANCP: May 13 - 16, 2008

  4. Weak Binding of Halo Neutrons Small neutron separation energy SOTANCP: May 13 - 16, 2008

  5. 6He Halo Nucleus RNBT collaboration Two-neutron transfer cross-section G.M.Ter-Akopian et al. Yu.Ts.Oganessian et al. 6He E=151 MeV; 4He and 1H targets “…dineutron configura- tion of the 6He nucleus gives the dominant contribution to the two-neutron transfer cross-section.” Quasi-free capture E.Sauvan, et al. 6He E=240MeV; 1H target “…non-observation of capture on a dineutron indicates… that cigar-like configuration is the dominant configura-tion present in 6Hegs.” Study of spatial conigu- ration of halo neutrons by the technique of intensity interferometry Marques et al., 2000. Large R(n-n) ~6-7 fm found for 6He Cigar-like R(n-n) ≈ 6 fm R(nn-core) ≈ 1 fm Dineutron R(n-n) ≈ 2 fm R(nn-core) ≈ 3 fm SOTANCP: May 13 - 16, 2008

  6. 6He S g Q Q’ t p P’ V=0 V=0 V=V0 V=V0 V=V0 Quasi-Free Scattering in Inverse Kinematics: 6He Quasi-free scattering 6He S QFS of proton by dineutron – direct kinematics 4He-spectator stay at rest p 6He S QFS of proton by dineutron – inverse kinematics 4He-spectator conserves its momentum in 6He p 1/Rnn» qtr»1/Rh or Rh»p»Rnn ħ=1 Rnn=2fm Rh=3fm =0.7 fm @ Ep=40 MeV SOTANCP: May 13 - 16, 2008

  7. Study of Reactions Induced by Halo-Nuclei in Nuclear Photoemulsion REACTIONS – NEUTRON TRANSFER, QUASI-FREE SCATTERING BEAM – HALO-NUCLEI (6,8He,11Li,14Be) ENERGY – 3 < Eint <15 Mev/nucleon TARGET – PHOTOMULSION (H,C,O,N,Br,Ag) SOTANCP: May 13 - 16, 2008

  8. Irradiation of Stack of Photoemulsions by 6He Beam Flerov Laboratory of Nuclear Reaction (JINR, Dubna) E0 (MeV) 42 23 0 60 6He beam PE stack 6He-beam with energy of 60 MeV Width of PE stack ~ 1600 m Interaction energy - 15-60 MeV Target nuclei– H, C, N, 0 Angular resolution ~ 1º Energy resolution ~ 2-5% p 6He 4He SOTANCP: May 13 - 16, 2008

  9. Determination of Particle Trajectories Three-dimensional scanning of PE is performed at automated setup PAVIKOM at P.N. Lebedev Physical Institute The images of consecutive (with step of several m) PE layers are obtained and transferred to the computer In each layer we select darkening areas (globes) with characteristics inherent for tracks of given charged particle Coordinates (x, y) of centers of mass of all globes in each layer (z-coordinate) are determined and stored Then, the particle trajectories Xi(z) and Yi(z) are determined by center-of-mass coordinates in consecutive layers of PE SOTANCP: May 13 - 16, 2008

  10. Determination of Trajectory Parameters Eint, E1, E2,1,2 Eint=f(E0,R0) E1=f(R1) E2=f(R2) The characteristic trajectory corresponding to the given reaction consists of the track of primary particle (6He), interaction point (IP), and trajectories of secondary particles emitting from the interaction point. Then the program determines range (energy) of the primary particle at the interaction point, anglesof emission of secondary particles, and ranges (energies) of the secondary particles. SOTANCP: May 13 - 16, 2008

  11. X p - =9º; E=3.8 MeV 6He Eint=21 MeV 4He - =0.5º; E=15.6 MeV Z Y Z Interaction of 6He with 1H in Photoemulsionat Energy of 16 – 23 MeV Reactions – QFS of proton on 6He Secondary particles: 4He, p Comparable ranges Trajectory - three-pronged star (6He,4He,p) with 4He track emitting from the interaction point at close to zero angle SOTANCP: May 13 - 16, 2008

  12. 6He S S p QFS of Proton by the Constituents of 6He Halo projectile 6He is considered as a system - claster (C) and spectator (S) Then QFS may be denoted as S+C(1H,1H)C+S where C = 5He4He2n1n S = 1n2n 4He5He Condition I - Spectator conserves direction of motion of projectile QFS Condition I I - Spectator conserves its momentum in the projectile SOTANCP: May 13 - 16, 2008

  13. Ep/E0 Ep/E0 EHe/E0 EHe/E0 Tree-Body Kinematical Calculations: 6He+p→p+4He+2nE0= 16 - 23 MeV, p ≤ 10ºProton-Dineutron Scattering – Dalitz Plot Condition I - 4He=0±1º Condition II - q4He≈4/6 q6He Condition I - 4He=0±1º SOTANCP: May 13 - 16, 2008

  14. Ep/E0 Ep/E0 EHe/E0 EHe/E0 Tree-Body Kinematical Calculations: 6He+p→p+4He+n+nE0= 16 - 23 MeV, p ≤ 10ºProton-Neutron Scattering – Dalitz Plot Condition I - 5He=0±1º Condition II - q5He≈5/6 q6He Condition I - 4He=0±1º SOTANCP: May 13 - 16, 2008

  15. Preliminary Experimental Data on QFS: 6He+pE0= 16 - 23 MeV, 4He= 0 ± 1º , p ≤ 10º Experiment Experiment and Calculations (Condition I) p2n-Scattering pn-Scattering SOTANCP: May 13 - 16, 2008

  16. 1/Rnn >>q>>1/Rh Comparison of Experimental Data and Three-Body Kinematics of QFS Condition I - Spectator conserves direction of motion of projectile Condition I I - Spectator conserves its momentum in the projectile Etr≈4 MeV qtr≈0.5 fm-1 p2n-QFS @ Rnn=2 fm Rh =3 fm 1/Rnn≥ q≥1/Rh pn-QFS SOTANCP: May 13 - 16, 2008

  17. Ep/E0 EHe/E0 Three-Body Kinematics of QFS: 8He+pE0= 24 - 32 MeV, 4,6He= 0 ± 1º , p ≤ 10º Condition I - Spectator conserves direction of motion of projectile Condition I I - Spectator conserves its momentum in the projectile p2n-QFS p4n-QFS pn-QFS SOTANCP: May 13 - 16, 2008

  18. Conclusions • Irradiation ofPEshas been performed using 6He beam at 60 MeV • Systematic processing of irradiated PEs with goal of obtaining data on QFS of proton by the constituents of halo-nucleus 6He is started • Preliminary data on 6He-p interaction at energy of 16-23 MeV are compared with three-body kinematical calculations for QFS • A part of data does not contradict with simplified kinematical calculations of QFS of proton by dineutron claster of 6He • QFS of proton at low energies may provide useful information on the cluster structure of neutron halo SOTANCP: May 13 - 16, 2008

  19. Thank you! SOTANCP: May 13 - 16, 2008

  20. SOTANCP: May 13 - 16, 2008

  21. SOTANCP: May 13 - 16, 2008

  22. 11Li dineutron halo neutron halo core 8He 4He+n+n+n+n 4He+4n 6He+2n 4He+2n+2n Structure of Neutron Halo SOTANCP: May 13 - 16, 2008

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