INFN –LNS and Sezione di Napoli Istituto Nazionale di Fisica Nucleare The XI International.

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1 INFN –LNS and Sezione di Napoli Istituto Nazionale di Fisica Nucleare E-mail: ivlombardo@na.infn.itivlombardo@na.infn.it ilombardo@lns.infn.it The XI International Conference NN 2012 San Antonio, 29/05/2012 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

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

3 T P 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 Neutron content of light isotopes inclusively emitted Competition between reaction mechanisms at semi-central Evaporat. Residue Emission Fragment production Pre-equilibrium GDR emission Review: M. Di Toro et al, JoP G 37 (2010) Amplitude of even-odd staggering on Charge and N distributions Isospin transport process in peripheral collisions Pre-equilibrium n/p ratio Pigmy Dipole Resonance How do we probe the (asy)- EoS? INFN –LNS and Sezione di Napoli

4 The experiments Limiting & Isospin-1 To investigate these topics  limiting experiment … 25 Three reactions @ 25 MeV / nucleon: 40 Ca + 40 Ca, 40 Ca + 48 Ca, 40 Ca + 46 Ti (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) I. Lombardo et al, Int. Jour. Mod. Phys. E 19 (2010) (2°) Influence on thermodynamical parameters: (2°) Influence on thermodynamical parameters: I. Lombardo et al, Nucl. Phys. A 834 (2010) (3°) Influence on light cluster emission & isospin transport: (3°) Influence on light cluster emission & isospin transport: I. Lombardo et al, Phys. Rev. C 82 (2010).. and as an extension  Isospin-1 experiment N/Z effects on heavy residue emission an the symmetry potential of EOS: (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 Light fragments emitted: (2°) Light fragments emitted: I. Lombardo et al, Int. Jour. Mod. Phys. E 20 (2011) I. Lombardo et al, Phys. Rev. C 84 (2011) 25 Two reactions @ 25 MeV / nucleon: 48 Ca + 48 Ca, ( 48 Ca + 40 Ca) Large range of N/Z involved INFN –LNS and Sezione di Napoli

5 A. Pagano et al, Nucl. Phys. A 734 (2004) 504 Details on the Chimera array 688 TELESCOPES 504 TELESCOPES BEAM 48 Ca+ 48 Ca 40 Ca+ 48 Ca Exp. technique We measure:  E - E Z (all) e M (up to Z ≈10 or more) ToFM (fragments stopped in Si) Fast-Slow on CsI(Tl)Z and M of LCP Pulse Shape in SiZ (fragments stopped in Si) Electronic multiplicity trigger m>3 0.8 70% INFN –LNS and Sezione di Napoli

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

7 Inclusive emission: staggering even-odd Inclusive emission of light fragments at forward angles (solid lines  med =11.5°, dashed lines  med =16.5°) identifyed by means of  E-E: even-odd effects on Z and N distributions De-excitation of highly excited fragments N/Z increases N/Z decreases I. Lombardo et al, PRC 84 (2011) 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) min{E s 1p,E s 1n } keV 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 INFN –LNS and Sezione di Napoli

8 Central collisions: heavy 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=1.2 N/Z=1.05N/Z=1.0 N/Z=1.4 N/Z effects in reaction mechanisms Check system 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 heavy residue emission in Incomplete Fusion events Lower N/Z  binary-like, fusion-fission and IMF emission prevail INFN –LNS and Sezione di Napoli

9 Central collisions: competitive mechanisms Submitted to PRC INFN –LNS and Sezione di Napoli  M nor analysis  disentangle the competition of various mechanisms in central collisions: m2m2 m1m1 fusion-like m2m2 m1m1 Binary-like Multi-fragm. Fusion-fission large  M nor low  M nor Relative yields of HR 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 Percentage of HR events by integrating  M nor > 0.4 large N/Z  enhan. of HR symmetric system  suppr. HR lines in inset  CoMD-II model calculations

10 F. Amorini et al, PRL 102 (2009) M. Papa and G. Giuliani, EPJ A39 (2009) Best agreement  Stiff2 option. GEMINI The GEMINI stage does not change the overall shape of spectra  dynamics Central collisions: CoMD-II calculations limiting experiment: CoMD-II GEMINI We compared experimental  M nor distributions with CoMD-II ( +GEMINI ) model calculations  we adopted various form factors of U sym (   ) Stiff2   =1 m 2 <10 INFN –LNS and Sezione di Napoli 48 Ca+ 48 Ca experiment

11 Apparent temperature in ICF events ICF NN (pre-eq.) QP ICF source Apparent T Pre-equilibrium Inverse slope 40 Ca + 40 Ca5.3 ± 0.5 MeV9.3 ± 0.3 MeV 40 Ca + 46 Ti5.2 ± 0.3 MeV9.2 ± 0.3 MeV 40 Ca + 48 Ca5.4 ± 0.4 MeV9.3 ± 0.3 MeV 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) Weak effect of N/Z on T INFN –LNS and Sezione di Napoli

12 INFN – Laboratori Nazionali del Sud – Catania 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 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 Apparent temperature in ICF events Weak effect of N/Z on T

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

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

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: At complete charge equilibrium  f eq =1 The pure systems  useful to trace the “equilibrium line” ≈ 0.63 INFN –LNS and Sezione di Napoli CoMD-II, Stiff2

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 40,48 Ca+ 40,48 Ca 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 dependence of the symmetry 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 in semi-peripheral collisions  non complete N/Z equilibrium (preliminary results)  estimate of the fraction of equilibrium reached Thank you for the attention ! INFN –LNS and Sezione di Napoli

17 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 Exochim Collaboration INFN –LNS and Sezione di Napoli

18 Further Slides INFN –LNS and Sezione di Napoli

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

20 INFN –LNS, Catania and Sezione di Napoli p,d,t emission in coincidence with ER Evaporated LCP  N/Z of the excited source We selected events with Evaporation Residue emission (m ER > 0.55m tot ) is seen. Isotopic composition of hydrogens at  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 trends are qualitatively reproduced by HIPSE+SIMON calculations

21 INFN – Laboratori Nazionali del Sud – Catania v = v proj v ≈ v targ Gentle collisions v CN < v < v proj v ≈ v proj Damped collisions Very-damped collisions v ≈ v CN v <≈ v proj Velocity correlations of the two largest fragments emitted m cp is correlated to the 40 Ca + 46 Ti Impact parameter selection: m cp vpvp

22 INFN – Laboratori Nazionali del Sud – Catania Collisioni semi-periferiche: trasporto dell’isospin N/Z 1 N/Z 2 QP QT MV 40 Ca + 40 Ca (N/Z=1) 40 Ca + 46 Ti (N/Z=1.05) 40 Ca + 48 Ca (N/Z=1.2) Nelle collisioni semi-periferiche della reazione 40 Ca+ 48 Ca  notevole scambio di neutroni tra P e T (“isospin diffusion”) Informazioni sull’N/Z dei sistemi rapporti isotopici QP e MV (QT  soglie) attraverso lo studio dei rapporti isotopici 7 Li/ 6 Li e 9 Be/ 7 Be in funzione della v par : 0.15< v par /c < 0.23 emissione QP v par /c < 0.15 emissione MV Selezione in m cp  eventi semi- periferici, trend simile osservato nei dati inclusivi. Il QP acquista neutroni dal QT nella reazione 40 Ca+ 48 Ca, rispetto alle altre due reazioni Isospin diffusion

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

24 INFN –LNS, Catania and Sezione di Napoli Symmetry Energy and Symmetry Potential An open question EoS of Asymmetric nuclear matter: (A)Symmetry Energy: various notations… Baran et al, Phys. Rep. (2005) Prakash et al, Phys. Rev. Lett. (1988) Bao An Li et al, Phys. Rep. (2008) A. Carbone et al, PRC 81, 041301(R) (2010) , F(  0 ) e L sono quantità collegate tra loro attraverso semplici relazioni matematiche  stiffness del potenziale di simmetria cluster produzione di cluster (bassa densità) stelle di neutroni stabilità delle stelle di neutroni (altissime densità) M.F. Rivet, Proc. of Ecole Joliot-Curie (2010)

25 48 Ca+ 48 Ca experiment As before, good agreement with Stiff2 option (linear) By interpolating the three original options, we find ≈ 1.1 as minimum deviation from experimental  M nor distributions Moderately Stiff form factor INFN –LNS and Sezione di Napoli Central collisions: CoMD-II calculations

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

27 INFN – Laboratori Nazionali del Sud – Catania Similar results also for 48 Ca+ 48 Ca Analisi in  M nor  vari processi che contribuiscono alle collisioni centrali: emissione di HR per incompleta fusione e presenza di BL e IMF Analisi in  M nor su varie finestre di angolo polare di emissione del frammento m 1 HR  emessi preferenzialmente ad angoli in avanti Altri processi  emissione di m 1 ad angoli più grandi Central collisions: HR emission

28 INFN –LNS, Catania and Sezione di Napoli L’N/Z ha influenza sui parametri termodinamici raggiunti dalle sorgenti eccitate prodotte per incompleta fusione?  Selezione eventi m 1 ≥46 (prod. residui) Spettri di velocità di m 1  fissare le velocità delle sorgenti ICF n  p p p p n n n  ICF n p p n  Quasi-proiettile n Pre-eq. n  p p p p n n  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

29 INFN – Laboratori Nazionali del Sud – Catania Collisioni centrali: stime di energie di eccitazione Per eventi centrali, con emissione di ER + particelle leggere (n,p,d,t, 3 He,a) possiamo ricostruire lo spettro di E* per nucleone usando la calorimetria Bisogna fare ipotesi sulla energia e sulla molteplicità dei neutroni (legata all’N/Z tot ) che non riveliamo. Scarsa dipendenza della  * dall’N/Z.  * simili per I sistemi studiati 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)

30 INFN –LNS, Catania and Sezione di Napoli Prospettive: uso di Chimera con fasci radioattivi Studio dell’emissione di residui in reazioni nucleari a 25 MeV/nucleone con proiettili di massa media proton rich. Dal trend della sistematica ottenuta 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: 36 Ar Target di produzione: 9 Be Production Target Fragment Separator CHIMERA ROOM G. Raciti et al, NIM B (2008)

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

32 INFN – Laboratori Nazionali del Sud – Catania Approccio termodinamico Influenza dell’N/Z sulla temperatura limite; Besprosvany & Levit PLB (1990) Influenza dell’N/Z sulla  * critica; Bohne et al, ZPA 347 (1993) Influenza dell’N/Z sulla curva calorica nucleare. Sfienti et al, PRL 102 (2009) Effetti dell’N/Z sui parametri termodinamici  T lim > 1MeV ~ Calcoli di liquid drop model “eccitata” T lim  competizione dei termini coulombiano, superficie e simmetria

33 INFN – Laboratori Nazionali del Sud – Catania Isospin-1: check BaF 2  neutroni (n,  ) particelle cariche Possibilità di estrarre spettri  e neutroni 25 cm

34 INFN – Laboratori Nazionali del Sud – Catania Spettri gamma di bassa energia m 1 >54  E.R. m 1 <40  B.L. m 3 >12  IMF counts x 1 detector 48 Ca+ 48 Ca raggi  Per eventi ben ricostruiti di collisioni 48 Ca+ 48 Ca, possiamo selezionare (in ToF-RT) i raggi  ; abbiamo anche una calibrazione in energia dei BaF 2 con sorgenti 60 Co  spettri di energia dei  per vari meccanismi di reazione Work in progress  molteplicità  Sembra che ci sia un yrast-bump più pronunciato nel caso di emissione dei residui Le pendenze degli spettri  con energia 2 < E  < 6 MeV cambiano (di poco) al cambiare del meccanismo selezionato  =74°

35 INFN – Laboratori Nazionali del Sud – Catania Global behavior of events of reactions m1m1 m2m2 m3m3 We observe mainly events as: ER emissions (1XL,2S) Binary-like (2L, 1S) Ternary (3M), low statistics Various classes of events their nature  v 1, v 2 correlations [v 1 = v(m 1 ) and v 2 = v(m 2 )], cut on the mass of the largest fragment emitted charged particle multiplicity  Typical behavior of reactions near 20-30 MeV/n Masses of the two largest fragments