INFN –LNS and Sezione di Napoli

1. The XI International Conference NN 2012 Istituto Nazionale di Fisica Nucleare Fragment emission in Ca+Ca reactions at 25 MeV/nucleon Ivano Lombardo (EXOCHIM Collaboration) Dip. di Scienze Fisiche, Università di Napoli “Federico II” INFN – Sezione di Napoli INFN –LNS and Sezione di Napoli E-mail: ivlombardo@na.infn.it ilombardo@lns.infn.it San Antonio, 29/05/2012

2. Frontiers of Nuclear Physics Large densities structure and stability of Neutron Stars Low densities  n-rich cluster formation in Supernovae explosions J.M. Lattimer and M.Prakash, Science 304 (2004) 536  K.Sumiyoshi and G.Ropke, Phys. Rev. C 77 (2008) 055804 • Equation of State (EoS) of asymmetric NM e (r, I) •  topics in nuclear structure and dynamics • relevant role also in astrophysics INFN –LNS and Sezione di Napoli An interdisciplinary topic

3. Competition between reaction mechanisms at semi-central <b> Neutron content of light isotopes inclusively emitted Amplitude of even-odd staggering on Charge and N distributions T P Isospin transport process in peripheral collisions Evaporat. Residue Emission Pre-equilibrium GDR emission Fragment production Pre-equilibrium n/p ratio Pigmy Dipole Resonance How do we probe the (asy)- EoS? INFN –LNS and Sezione di Napoli • Compare reactions having various: • N/Z of projectile • N/Z of target • N/Z of total system • Explore the maximum range available ( RIB) (A)Symmetry Term of Nuclear Equation of State Review: M. Di Toro et al, JoP G 37 (2010)

4. To investigate these topics  limiting experiment … Three reactions @ 25 MeV / nucleon: 40Ca + 40Ca, 40Ca + 48Ca,40Ca + 46Ti (1°) N/Z effects on evaporation residue emission: F. Amorini et al, Phys. Rev. Lett. 102 (2009) I. Lombardo et al, Int. Jour. Mod. Phys. 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) The experiments Limiting & Isospin-1 .. and as an extension  Isospin-1 experiment (1°) N/Z effects on heavy residue emission an the symmetry potential of EOS: I. Lombardo et al, Acta Phys. Pol. B 42 (2011) I. Lombardo et al, submitted to Phys. Rev. C (2°) Light fragments emitted: I. Lombardo et al, Int. Jour. Mod. Phys. E 20 (2011) I. Lombardo et al, Phys. Rev. C 84 (2011) Two reactions @ 25 MeV / nucleon: 48Ca + 48Ca,(48Ca + 40Ca) INFN –LNS and Sezione di Napoli Large range of N/Z involved

5. Details on the Chimera array BEAM 688 TELESCOPES 504 TELESCOPES 40Ca+48Ca 48Ca+48Ca Electronic multiplicity triggerm>3 0.8<Ztot/Zi<1 and ppar_tot>70% INFN –LNS and Sezione di Napoli A. Pagano et al, Nucl. Phys. A 734 (2004) 504

6. In the very n-rich 48Ca+48Ca system  n-rich fragments largely emitted Forward-angle emission: 5.2°<q<15.3° 48Ca+48Ca N/Z=1.4 40Ca+48CaN/Z=1.2 40Ca+40CaN/Z=1.0 Isotopic effects on inclusive emission of fragments INFN –LNS and Sezione di Napoli Large isotopic effects

7. Inclusive emission: staggering N/Z increases N/Z decreases Evenisotopes and isotoneshave largeone particle separation energy P. Napolitani, from Audi & Wapstra M.V. Ricciardi et al, Nucl. Phys. A 749 (2005) 122 min{Es1p,Es1n} keV Inclusive emission of light fragments at forward angles (solid lines qmed=11.5°, dashed lines qmed=16.5°) identifyed by means of DE-E: even-odd effects on Z and N distributions 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) 041602 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) R. Ogul et al, Phys. Rev. C 83 (2011) M. D’Agostino et al, Nucl. Phys. A 861 (2011) 47 P. Napolitani et al, Jour. Phys. G 38 (2011) INFN –LNS and Sezione di Napoli I. Lombardo et al, PRC 84 (2011) De-excitation of highly excited fragments

8. N/Z=1.4 N/Z=1.2 N/Z=1.05 N/Z=1.0 Check system Central collisions: heavy residue emission Central events (mcp≥ 5, 6) with the presence of a fast quasi-projectile(v2 or v3>0.13c) (massive transfer). Mass – velocity correlations of the largets fragment emitted: • The observed phenomenon can not be attributed to mass effects48Ca and 46Ti have similar masses • The N/Z degree of freedom strongly influences the • reaction mechanisms: • Larger N/Z larger heavy residue emission in Incomplete Fusion events • Lower N/Z binary-like, fusion-fission and IMF emission prevail INFN –LNS and Sezione di Napoli N/Z effects in reaction mechanisms

9. Centralcollisions: competitive mechanisms Percentage of HR events by integratingDMnor > 0.4 large N/Z enhan. of HR symmetricsystem  suppr. HR lines in inset  CoMD-II model calculations DMnoranalysis  disentangle the competition of various mechanisms in central collisions: m1 fusion-like large DMnor m2 Binary-like Multi-fragm. Fusion-fission m1 m2 low DMnor • Relative yields ofHR emission in central collisions by means of two gaussian fit of experimental mass spectra: • large N excess HRs increase • N ≈ Z  BL and IMF prevail • This effect can be attributed to the interplay between Coulomb and Symmetry terms  nuclear dynamics INFN –LNS and Sezione di Napoli Submitted to PRC

10. Central collisions: CoMD-II calculations Stiff2  g=1 limiting experiment: We compared experimentalDMnor distributions withCoMD-II (+GEMINI) model calculations  we adopted various form factors of Usym(r/r0) m2<10 m2<10 48Ca+48Ca experiment m2<10 Best agreement Stiff2 option. The GEMINI stage does not change the overall shape of spectra  dynamics INFN –LNS and Sezione di Napoli F. Amorini et al, PRL 102 (2009) M. Papa and G. Giuliani, EPJ A39 (2009)

11. ICF NN (pre-eq.) QP Apparent temperature in ICF events 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) INFN –LNS and Sezione di Napoli Weak effect of N/Z on T

12. INFN – Laboratori Nazionali del Sud – Catania Apparent temperature in ICF events Double isotopic ratio method for apparent temperature estimates S. Albergo et al, Nuovo Cim. A 89 (1985) • For each systems, the obtained apparent temperatures are quite constant as a function of polar emission angle no source mixing • Apparent temperatures are quite similar for the studied systems • Differences of <T> for the three used thermometers due probably to secondary emission + finite size effects • M. B. Tsang et al, PRL 78 (1997) 3836 • A. Kolomiets et al, PRC 54 (1996) 472R • W. Trautmann et al, PRC 76 (2007) 064606 Weak effect of N/Z on T

13. Semi-peripheral collisions: isospin diffusion N/ZQP N/ZMV N/ZMV N/ZMV N/ZMV N/ZQT N/ZQP 48Ca 48Ca 48Ca 48Ca N/ZQT 40Ca 40Ca 40Ca 40Ca N/ZQP N/ZQT N/ZQT N/ZQP INFN –LNS and Sezione di Napoli N/Z of QP and MV source  light isobars

14. Semi-peripheral collisions: isospin diffusion Is the N/Z equilibriumcomplete? 7Li 48Ca+48Ca 7Be 48Ca+48Ca QP:  isospin diffusion MV  neutron enrichment(isospin drift) <b> ≈ 6-7 fm see also I. Lombardo et al, PRC 82 (2010) 7Li and 7Be emission yields by means of multi-component moving source fits. N/Zof QP (and MV)  7Li/7Be INFN –LNS and Sezione di Napoli Incomplete N/Z equilibrium

15. Semi-peripheral collisions: isospin diffusion Following SM, we can assume: and we can estimate (roughly) the degree of N/Z equilibrium Following Keksis et al PRC 81(2010), we can define the fraction of equilibrium as follows: <feq> ≈ 0.63 CoMD-II, Stiff2 At complete charge equilibrium feq=1 The pure systems useful to trace the “equilibrium line” INFN –LNS and Sezione di Napoli

16. Summary and conclusions • N/Z effects on nuclear reactions can be explored by colliding nuclei with large differences in N/Z; in our case 40,48Ca+40,48Ca at 25 MeV/nucleon • Even-odd effects on Z and N distributions  Evaporation stage of excited fragments • 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 dependenceof thesymmetry energy in nuclear EoS at low density • Weak dependence of thermodynamical parameters on the N/Z of entrance channels • Isospin diffusion signals were obtained by looking at light isobar yields emitted by QP source insemi-peripheralcollisions  non complete N/Z equilibrium (preliminary results)  estimate of the fraction of equilibrium reached INFN –LNS and Sezione di Napoli Thank you for the attention !

17. Exochim Collaboration L. Acostaa, C.Agodia, F.Amorinia,c, A.Anzalonea, L. Auditorel, I.Berceanui, M.Buscemia,c, G.Cardellab, S.Cavallaroa,c, M.B.Chatterjeed, E.De Filippob, G.Giulianic, E.Geracib,c, L.Grassib,c, J. Hana, E.La Guidarab,e, G.Lanzalonea,f, I.Lombardom, D.Lorial, C.Maiolinoa, A.Paganob, M.Papab, S.Pirroneb, G.Politib,c, F.Portoa,c, E. Rosatom, F.Rizzoa,c, P.Russottoa,c, A.Trifiròl, M.Trimarchil, G.Verdeb, M. Vigilantem 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 INFN –LNS and Sezione di Napoli

18. Further Slides INFN –LNS and Sezione di Napoli

19. p,d,t emission in coincidence with ER We selected events with Evaporation Residue emission (mER> 0.55mtot) is seen. • Isotopic composition of hydrogensat qcm>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 INFN –LNS and Sezione di Napoli Evaporated LCP  N/Z of the excited source

20. INFN –LNS, Catania and Sezione di Napoli trends are qualitatively reproduced by HIPSE+SIMON calculations p,d,t emission in coincidence with ER We selected events with Evaporation Residue emission (mER> 0.55mtot) is seen. • Isotopic composition of hydrogensat qcm>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

21. Impact parameter selection: mcp v = vproj v ≈ vtarg Gentle collisions v ≈ vproj INFN – Laboratori Nazionali del Sud – Catania vCN < v < vproj Damped collisions v <≈ vproj v ≈ vCN Very-damped collisions 40Ca + 46Ti Velocity correlations of the two largest fragments emitted vp mcp is correlated to the <b>

22. QP N/Z1 MV N/Z2 QT INFN – Laboratori Nazionali del Sud – Catania 40Ca + 48Ca (N/Z=1.2) 40Ca + 46Ti (N/Z=1.05) 40Ca + 40Ca (N/Z=1) Collisioni semi-periferiche: trasporto dell’isospin Nelle collisioni semi-periferiche della reazione 40Ca+48Ca notevole scambio di neutroni tra P e T (“isospin diffusion”) Informazioni sull’N/Zdei sistemi QP e MV (QT soglie) attraverso lo studio dei rapporti isotopici7Li/6Li e 9Be/7Be in funzione della vpar: 0.15< vpar/c < 0.23 emissione QP vpar/c < 0.15 emissione MV Selezione in mcp eventi semi-periferici, trend simile osservato nei dati inclusivi. Il QP acquista neutroni dal QT nella reazione40Ca+48Ca, rispetto alle altre due reazioni Isospin diffusion

23. Staggering, reaction mechanisms and dissipation 40Ca+40Ca <dissipation> qmed=11.5° Kinetic energy of the biggest fragment emitted Does the amplitude of the even-odd effect vary as a function of average dissipation (mLcp)? INFN –LNS and Sezione di Napoli Effect of e* on the staggering amplitude?

24. Symmetry Energy and Symmetry Potential EoS of Asymmetric nuclear matter: (A)Symmetry Energy: various notations… Baran et al, Phys. Rep. (2005) M.F. Rivet, Proc. of Ecole Joliot-Curie (2010) Prakash et al, Phys. Rev. Lett. (1988) INFN –LNS, Catania and Sezione di Napoli Bao An Li et al, Phys. Rep. (2008) g, F(r/r0) e Lsono quantità collegate tra loro attraverso semplici relazioni matematiche  stiffness del potenziale di simmetria A. Carbone et al, PRC 81, 041301(R) (2010) • produzione di cluster (bassa densità) • stabilità delle stelle di neutroni (altissime densità) An open question

25. Central collisions: CoMD-II calculations 48Ca+48Ca experiment As before, good agreement with Stiff2 option (linear) By interpolating the three original options, we find <g> ≈ 1.1 as minimum deviation from experimentalDMnor distributions INFN –LNS and Sezione di Napoli Moderately Stiff form factor

26. QP isoscaling Study of the isoscaling for QP emission (v// > 0.15c) in 40Ca+40Ca and 48Ca+48Ca INFN –LNS and Sezione di Napoli Further analysis to estimate Csym

27. Central collisions: HR emission INFN – Laboratori Nazionali del Sud – Catania Analisi in DMnor vari processi che contribuiscono alle collisioni centrali: emissione di HR per incompleta fusione e presenza di BL e IMF Analisi in DMnor su varie finestre di angolo polare di emissione del frammento m1 HR  emessi preferenzialmente ad angoli in avanti Altri processi  emissione di m1 ad angoli più grandi Similar results also for 48Ca+48Ca

28. n p p Quasi-proiettile n n n n n n n n n a Pre-eq. a a a a ICF INFN –LNS, Catania and Sezione di Napoli Spettri di velocità di m1 fissare le velocità delle sorgenti ICF p p p p p p p p Fit degli spettri con Maxwelliane di volume: Metodo utile per estrarre T apparenti: fit a 3 componenti (QP+NN+ICF) Apparent temperature in ICF events L’N/Z ha influenza sui parametri termodinamici raggiunti dalle sorgenti eccitate prodotte per incompleta fusione?  Selezione eventi m1≥46 (prod. residui)

29. Per eventi centrali, con emissione di ER + particelle leggere (n,p,d,t,3He,a) possiamo ricostruire lo spettro di E* per nucleoneusando lacalorimetria Bisogna fare ipotesi sulla energia e sulla molteplicità dei neutroni (legata all’N/Ztot) che non riveliamo. Scarsa dipendenza della e* dall’N/Z. INFN – Laboratori Nazionali del Sud – Catania Studi di frammentazione di proiettili con differente N/Z hanno mostrato una scarsa dipendenza della curva calorica nucleare dal rapporto N/Z C. Sfienti et al, PRL 102 (2009) Collisioni centrali: stime di energie di eccitazione e* simili per I sistemi studiati

30. Prospettive: uso di Chimera con fasci radioattivi INFN –LNS, Catania and Sezione di Napoli CHIMERA ROOM Production Target Fragment Separator Studio dell’emissione di residui in reazioni nucleari a 25 MeV/nucleone con proiettili di massa media proton rich. Dal trend della sistematicaottenuta finora  ci si può aspettare una notevole soppressione dell’emissione di residui Test di produzione e trasporto a fine Febbraio 2011 alla facility FRIBS dei LNS-INFN Fascio di partenza: 36Ar Target di produzione: 9Be G. Raciti et al, NIM B (2008)

31. Produzione di fasci Ar-like INFN –LNS, Catania and Sezione di Napoli Test di produzione di p-rich nuclei nella regione dell’ Ar alla facility In-flightdi Catania  36Ar (@ 42 MeV/nucleon) +9Be (1.5mm thick, production target)  Ar-like nuclei at ≈ 25 MeV/nucleon • Con alcune semplici migliorie sulla linea (già effettuate) ci si attende: • 37K  100 kHz • 35Ar  70 kHz • 34Cl  >50 kHz Fasci interessanti anche per studi di struttura

32. Effetti dell’N/Z sui parametri termodinamici Approccio termodinamico • Influenza dell’N/Z sulla temperatura limite; Besprosvany & Levit PLB (1990) • Influenza dell’N/Z sulla e* critica; Bohne et al, ZPA 347 (1993) • Influenza dell’N/Z sulla curva calorica nucleare. Sfienti et al, PRL 102 (2009) INFN – Laboratori Nazionali del Sud – Catania DTlim > 1MeV ~ Calcoli di liquid drop model “eccitata” Tlim competizione dei termini coulombiano, superficie e simmetria

33. Isospin-1: check BaF2 g 25 cm particelle cariche neutroni (n,g) INFN – Laboratori Nazionali del Sud – Catania Possibilità di estrarre spettri g e neutroni

34. 48Ca+48Ca m1>54  E.R. m1<40  B.L. m3>12  IMF counts x 1 detector INFN – Laboratori Nazionali del Sud – Catania Spettri gamma di bassa energia Per eventi ben ricostruiti di collisioni 48Ca+48Ca, possiamo selezionare (in ToF-RT) i raggi g; abbiamo anche una calibrazione in energia dei BaF2 con sorgenti 60Co  spettri di energia dei g per vari meccanismi di reazione Sembra che ci sia un yrast-bump più pronunciato nel caso di emissione dei residui q=74° Le pendenze degli spettri g con energia 2 < Eg < 6 MeV cambiano (di poco) al cambiare del meccanismo selezionato preliminary Work in progress  molteplicità g

35. Global behavior of events of reactions Various classes of events their naturev1 , v2 correlations [v1= v(m1) and v2= v(m2)], • cut on the mass of the largest fragment emitted • charged particle multiplicity <b> Masses of the two largest fragments INFN – Laboratori Nazionali del Sud – Catania • We observe mainly events as: • ER emissions (1XL,2S) • Binary-like (2L, 1S) • Ternary (3M), low statistics m1 m2 m3 Typical behavior of reactions near 20-30 MeV/n