N/Z effects on 40,48 Ca+ 40,48 Ca reactions at 25 MeV/nucleon

Transcription

1 IWM 2011 Int. Work. Multifrag. Rel. Topics Istituto Nazionale di Fisica Nucleare N/Z effects on 40,48 Ca+ 40,48 Ca reactions at 25 MeV/nucleon Ivano Lombardo (EXOCHIM Collaboration) Dip. di Scienze Fisiche, Università di Napoli Federico II INFN Sezione di Napoli Caen, 3/11/

2 N/Z effects on nuclear reactions at MeV/nucleon Competition between reaction mechanisms at semi-central <b> Neck emission and isospin drift phenomena Evaporat. Residue Emission Fragment production Neutron content of light isotopes inclusively emitted P T Compare reactions having various: N/Z of projectile N/Z of target N/Z of total system Explore the maximum range available ( RIB) Amplitude of evenodd staggering on Charge and N distributions Pre-equilibrium GDR emission Isospin diffusion process in peripheral collisions (A)Symmetry Term of Nuclear Equation of State Review: M. Di Toro et al, JoP G 37 (2010)

3 To investigate these topics limiting experiment The experiments Limiting & Isospin-1 Three 25 MeV / nucleon: 40 (1 ) N/Z effects on evaporation residue emission: F. Amorini et al, Phys. Rev. Lett (2009) I. Lombardo et al, Int. Jour. Mod. Phys. P E 19 (2010) (2 ) Influence on thermodynamical parameters: I. Lombardo et al, Nucl.. Phys. A 834 (2010) (3 ) Influence on light cluster emission & isospin transport: I. Lombardo et al, Phys. Rev. C 82 (2010).. and as an extension Isospin-1 experiment Two 25 MeV / nucleon: Ca + 40 Ca, 40 Ca + 48 Ca, 40 Ca + 46 Ti (1 ) N/Z effects on evaporation residue emission an the symmetry potential of EOS: I. Lombardo et al, Acta Phys. Pol. B 42 (2011) I. Lombardo et al, to be submitted (2 ) Light fragments emitted: I. Lombardo et al, Int. Jour. Mod. Phys. E 20 (2011) I. Lombardo et al, Phys. Rev. C 84 (2011) 48 Ca + 48 Ca, ( 48 Ca + 40 Ca) 48 Ca Large range of N/Z involved

4 The Chimera multi-detector array Exp. technique We measure: BEAM 48 Ca+ 48 Ca E - E ToF Fast-Slow on CsI(Tl) Pulse Shape in Si Electronic multiplicity trigger m>3 0.8<Z tot /Z i <1 and ppar_tot>70% Z (all) e M (up to Z 10 or more) M (fragments stopped in Si) Z and M of LCP Z (fragments stopped in Si) 688 TELESCOPES 504 TELESCOPES 40 Ca+ 48 Ca A. Pagano et al, Nucl. Phys. A 734 (2004) 504

5 Inclusive emission: staggering Inclusive emission of light fragments at forward angles (solid lines θ med =11.5, dashed lines θ med =16.5 ) identifyed by means of E-E: even-odd effects on Z and N distributions N/Z increases I. Lombardo et al, PRC 84 (2011) See also M. D Agostino s M. La Commara s talks N/Z decreases Even-odd effects: B. Gatty et al, Nucl. Phys. A 253 (1975) 511 C. Beck et al, Zeit. Phys. A 343 (1992) G. Lanzanò et al, Zeit. Phys. A 343 (1992) 429 Sl. Cavallaro et al, Phys. Rev. C 57 (1998) 731 K. X. Jing et al, Nucl. Phys. A 645 (1999) 203 L.B. Yang et al, Phys. Rev. C 60 (1999) E.M. Winchester et al, Phys. Rev. C 63 (2000) E. Geraci et al, Nucl. Phys. A 734 (2004) 524 M.V. Ricciardi et al, Nucl. Phys. A 749 (2005) Jun Su et al, Phys. Rev. C 83 (2011) G. Ademard et al, Phys. Rev. C 83 (2011) S. Pirrone et al, EPJ Web Conf. 17 (2011) min{e 1p R. Ogul et al, Phys. Rev. s,e 1n C 83 (2011) s } M. D Agostino et al, Nucl. Phys. A 861 (2011) 47 P. Napolitani et al, Jour. Phys. G 38 (2011) Even isotopes and isotones have large one particle separation energy P. Napolitani, from Audi & Wapstra M.V. Ricciardi et al, Nucl. Phys. A 749 (2005) 122 kev De-excitation of highly excited fragments

6 θ med =11.5 Staggering, reaction mechanisms and dissipation Does the amplitude of the even-odd effect vary as a function of reaction mechanisms (m 1 ) or dissipation (m Lcp )? M. D Agostino et al, NPA 861 (2011) preliminary results ER selection staggering is suppressed High m Lcp high dissipation staggering is suppressed Low m Lcp or BL selection staggering is enhanced preliminary results importance of reaction mechanisms Effects of temperature, density asymmetry term?

7 Semi-central collisions: evaporation residue emission Central events (m cp 5, 6) with the presence of a fast quasi-projectile (v 2 or v 3 >0.13c) (massive transfer). Mass velocity correlations of the largets fragment emitted: N/Z=1.4 N/Z=1.05 Check system N/Z=1.2 N/Z=1.0 The observed phenomenon can not be attributed to mass effects 48 Ca and 46 Ti have similar masses The N/Z degree of freedom strongly influences the reaction mechanisms: Larger N/Z larger evaporation residue emission in Incomplete Fusion events Lower N/Z binary-like, fusion-fission and IMF emission prevail N/Z effects in reaction mechanisms

8 Stiff2 γ=1 m 2 <10 Semi-central collisions: CoMD-II calculations limiting experiment: m1 m2 Mnor mtot ρ F ρ 0 ρ Stiff2 0 Best agreement Stiff2 option. The GEMINI stage does not change the overall shape of spectra dynamics F. Amorini et al, PRL 102 (2009) M. Papa and G. Giuliani, EPJ A39 (2009) = ρ ρ F ρ 0 ρ F ρ Soft m 2 <10 m 2 <10 = 0 1 Stiff1 ρ ρ 0 ( ρ ρ ) 2 0 = + ρ ρ 2 0 We compared experimental M nor distributions with CoMD-II (+GEMINI) model calculations we adopted various form factors of U sym (ρ/ρ ) 0 isospin-1 ( 48 Ca+ 48 Ca) experiment: Best agreement Stiff2 option again

9 p,d,t emission in coincidence with ER We selected events with Evaporation Residue emission (m ER > 0.55m tot ) is seen. Isotopic composition of hydrogens at θ cm >40 LCP evaporated by ICF sources d/p, t/p and t/d ratios are strongly connected with the N/Z of the entrance channels the ICF sources have N/Z contents that reflect very well the initial N/Z rank pre-equilibrium does not modify the original N/Z rank Evaporated LCP N/Z of the excited source

10 Apparent temperature in ICF events 40 Ca + 40 Ca 40 Ca + 46 Ti 40 Ca + 48 Ca Similar results limiting exp. Newlim exp under investigation inverse slope parameters obtained from the fit are in good agreement with systematics Fuchs e Mohring, Rep. Prog. Phys. 57 (1994) ICF source Apparent T 5.3 ± 0.5 MeV 5.2 ± 0.3 MeV 5.4 ± 0.4 MeV ICF NN (pre-eq.) QP Pre-equilibrium Inverse slope 9.3 ± 0.3 MeV 9.2 ± 0.3 MeV 9.3 ± 0.3 MeV Weak effect of N/Z on T

11 Semi-peripheral collisions: isospin diffusion N/Z QP 48 Ca N/Z MV 40 Ca 48 Ca 40 Ca N/Z QT N/Z QP N/Z MV N/Z QT N/Z QP N/Z QT N/Z QT N/Z MV N/Z QP N/Z MV N/Z of QP and MV source light isobars

12 Semi-peripheral collisions: isospin diffusion N/Z of QP (and MV) 7 Li/ 7 Be Is the N/Z equilibrium complete? 7 Be 48 Ca+ 48 Ca 7 Li 48 Ca+ 48 Ca 7 Li and 7 Be emission yields by means of multi-component moving source fits. (preliminary results) QP: 40 Ca+ 48 Ca isospin diffusion MV neutron enrichment (isospin drift) I. Lombardo et al, PRC 82 (2010) Incomplete N/Z equilibrium

13 Summary and conclusions N/Z effects on nuclear reactions can be explored by colliding nuclei with large differences in N/Z; in our case 40,48 Ca+ 40,48 Ca at 25 MeV/nucleon (at fragmentation threshold) Even-odd effects on Z and N distributions Evaporation stage of excited fragments effects of reaction mechanisms on staggering amplitude Nuclear dynamics seems to strongly depend on N/Z values of entrance channels. The balance between ER and other mechanisms in semi-central events depends strongly on the neutron richness of entrance channels. Dynamical calculations (CoMD-II model) reproduce the experimental mass spectra, and indicate a stiff dependence of the symmetry energy in nuclear EoS at low density Isospin diffusion signals were obtained by looking at light isobar yields emitted by QP source in semi-peripheral collisions non complete N/Z equilibrium (preliminary results) Thank you for the attention!

14 Exochim Collaboration L. Acosta a, C.Agodi a, F.Amorini a,c, A.Anzalone a, L. Auditore l, I.Berceanu i, M.Buscemi a,c, G.Cardella b, S.Cavallaro a,c, M.B.Chatterjee d, E.De Filippo b, G.Giuliani c, E.Geraci b,c, L.Grassi b,c, J. Han a, E.La Guidara b,e, G.Lanzalone a,f, I.Lombardo m, D.Loria l, C.Maiolino a, A.Pagano b, M.Papa b, S.Pirrone b, G.Politi b,c, F.Porto a,c, E. Rosato m, F.Rizzo a,c, P.Russotto a,c, A.Trifirò l, M.Trimarchi l, G.Verde b, M. Vigilante m a) INFN Laboratori Nazionali del Sud, Catania, Italy b) INFN, Sezione di Catania, Catania, Italy c) Dipartimento di Fisica e Astronomia Università di Catania, Catania, Italy d) Saha Institute of Nuclear Physics, Kolkata, India e) Centro Siciliano di Fisica Nucleare e Struttura della Materia, Catania, Italy f) Dipartimento di Ingegneria ed Architettura,Università Kore di Enna, Enna, Italy g) Institut de Physique Nucleaire d'orsay, CNRS-IN2P3, Orsay Cedex, France h) Institute of Physics, University of Silesia, Katowice, Poland i) Institute for Physics and Nuclear Engineering, Bucharest, Romania l) Dipartimento di Fisica, Università di Messina, Messina, Italy m) Dipartimento di Fisica, Università di Napoli Federico II, Napoli, Italy and INFN Sezione di Napoli, Via Cintia, Napoli, Italy