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Istituto Nazionaledi Fisica Nucleare

E-mail: ivlombardo@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

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

Large densities structure and stability of Neutron StarsNeutron 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

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TP

Compare reactions having various:• N/Z of projectile• N/Z of target• N/Z of total systemExplore 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 <b>

Evaporat.Residue

Emission

Fragmentproduction

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?IN

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The experiments Limiting & Isospin-1

To investigate these topics limiting experiment …

Three reactions @ 2525 MeV / nucleon: 4040Ca + Ca + 4040CaCa, , 4040Ca + Ca + 4848CaCa,, 4040Ca + Ca + 4646TiTi

((1°1°) ) N/Z effects on evaporation residue emission:N/Z effects on evaporation residue emission:F. Amorini et al, Phys. Rev. Lett. 102 (2009)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°2°) ) Influence on thermodynamical parameters:Influence on thermodynamical parameters:I. Lombardo et al, Nucl. Phys. A 834 (2010)I. Lombardo et al, Nucl. Phys. A 834 (2010)

((3°3°) ) Influence on light cluster emission & isospin transport:Influence on light cluster emission & isospin transport: I. Lombardo et al, Phys. Rev. C 82 (2010)I. Lombardo et al, Phys. Rev. C 82 (2010)

.. and as an extension Isospin-1 experiment

(1°) N/Z effects on heavy residue emission an the symmetry potential of EOS: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, Acta Phys. Pol. B 42 (2011)I. Lombardo et al, submitted to Phys. Rev. CI. Lombardo et al, submitted to Phys. Rev. C

(2°) Light fragments emitted:Light fragments emitted:I. Lombardo et al, Int. Jour. Mod. Phys. E 20 (2011)I. Lombardo et al, Int. Jour. Mod. Phys. E 20 (2011)I. Lombardo et al, Phys. Rev. C 84 (2011) I. Lombardo et al, Phys. Rev. C 84 (2011)

Two reactions @ 2525 MeV / nucleon: 4848Ca + Ca + 4848Ca,Ca, ((4848Ca + Ca + 4040Ca)Ca)

Large range of N/Z involved

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A. Pagano et al, Nucl. Phys. A 734 (2004) 504

Details on the Chimera array

688 TELESCOPES504 TELESCOPES

BEAM

48Ca+48Ca

40Ca+48Ca

Exp. technique We measure:

E - E Z (all) e M (up to Z ≈10 or more)

ToF M (fragments stopped in Si)

Fast-Slow on CsI(Tl) Z and M of LCP

Pulse Shape in Si Z (fragments stopped in Si)

Electronic multiplicity trigger m>30.8<Ztot/Zi<1 and ppar_tot>70%

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Isotopic effects on inclusive emission of fragments

1. E+03

1. E+04

1. E+05

1. E+06

1. E+07

0 20 40 60 80q Lab ( deg)

coun

ts/s

r (a

rb.

un.)

6Li

7Li

8Li

1. E+02

1. E+03

1. E+04

1. E+05

1. E+06

1. E+07

0 20 40 60 80q Lab ( deg)

coun

ts/s

r (a

rb.

un.)

9Be

7Be

1. E+02

1. E+03

1. E+04

1. E+05

1. E+06

1. E+07

0 20 40 60 80q Lab ( deg)

coun

ts/s

r (a

rb.

un.)

10B

11B

12B

13B

1. E+03

1. E+04

1. E+05

1. E+06

1. E+07

0 10 20 30 40q Lab ( deg)

coun

ts/s

r (a

rb.

un.)

11C

12C

13C

14C

15C

In the very n-rich 48Ca+48Ca system n-rich fragments largely emitted

Large isotopic effects

0

0. 05

0. 1

0. 15

0. 2

0. 25

0. 3

0. 35

0. 4

0. 45

0. 5

11 12 13 14 15

A of Car bon

rela

tive

yie

lds

48Ca+48Ca

48Ca+40Ca

40Ca+48Ca

40Ca+40Ca

q = 9. 3°

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48Ca+48Ca N/Z=1.4

Forward-angle emission: 5.2°<q<15.3°

40Ca+48Ca N/Z=1.2

40Ca+40Ca N/Z=1.0

Inclusive emission: staggering

Inclusive emission of light fragments at forward angles (solid lines qmed=11.5°, dashed lines qmed=16.5°) identifyed by means of E-E: even-oddeven-odd effects on Z and N distributions

De-excitation of highly excited fragments

N/Z

incr

ease

s N/Z

decreases

I. Lombardo et al, PRC 84 (2011)

Even-odd effects:B. Gatty et al, Nucl. Phys. A 253 (1975) 511C. Beck et al, Zeit. Phys. A 343 (1992)G. Lanzanò et al, Zeit. Phys. A 343 (1992) 429Sl. Cavallaro et al, Phys. Rev. C 57 (1998) 731K. X. Jing et al, Nucl. Phys. A 645 (1999) 203L.B. Yang et al, Phys. Rev. C 60 (1999) 041602E.M. Winchester et al, Phys. Rev. C 63 (2000)E. Geraci et al, Nucl. Phys. A 734 (2004) 524M.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) 47P. Napolitani et al, Jour. Phys. G 38 (2011)

min{Es1p,Es

1n}

keV

Even isotopes and isotones have large one particle separation energy P. Napolitani, from Audi & WapstraM.V. Ricciardi et al, Nucl. Phys. A 749 (2005) 122

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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:

N/Z=1.2

N/Z=1.05 N/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 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

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Central collisions: competitive mechanisms

Submitted to PRC

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Mnor analysis disentangle the competition of various mechanisms in central collisions:

totnor m

mmM 21

m2

m1 fusion-like

m2m1 Binary-likeMulti-fragm.Fusion-fission

large Mnor

low Mnor

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 Mnor > 0.4

large N/Z enhan. of HR

symmetric system suppr. HR

lines in inset CoMD-II model calculations

F. Amorini et al, PRL 102 (2009)M. Papa and G. Giuliani, EPJ A39 (2009)

Best agreement Stiff2 option.The GEMINIGEMINI stage does not change the overall shape of spectra dynamics

Central collisions: CoMD-II calculations

limiting experiment:We compared experimental Mnor

distributions with CoMD-IICoMD-II (+GEMINIGEMINI) model calculations we adopted various form factors of Usym()

Stiff2 =1 m2<10

m2<10

m2<10

020

Stiff

F

0

20

10 12

Stiff

F

00

Soft

Ftot

nor mmm

M 21

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48Ca+48Ca experiment

Apparent temperature in ICF events

ICF

NN (pre-eq.)

QP

ICF sourceApparent T

Pre-equilibriumInverse slope

40Ca + 40Ca 5.3 ± 0.5 MeV 9.3 ± 0.3 MeV40Ca + 46Ti 5.2 ± 0.3 MeV 9.2 ± 0.3 MeV40Ca + 48Ca 5.4 ± 0.4 MeV 9.3 ± 0.3 MeV

Similar results limiting exp. Newlim exp under investigation

inverse slope parameters obtained from the fit are in good agreement with systematicsFuchs e Mohring, Rep. Prog. Phys. 57 (1994)

Weak effect of N/Z on T

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Double isotopic ratio method for apparent temperature estimatesS. 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) 3836A. Kolomiets et al, PRC 54 (1996) 472RW. Trautmann et al, PRC 76 (2007) 064606

CC

LiLi

CLi

YYYY

T

1211

76

//

9.5ln

5.11

HeHe

LiLi

LiHe

YYYY

T

43

76

//

18.2ln

3.13

CC

CC

CC

YYYY

T

1211

1312

//

9.7ln

8.13

Apparent temperature in ICF events

Weak effect of N/Z on T

N/Z of QP and MV source light isobars

Semi-peripheral collisions: isospin diffusion

48Ca

40Ca

48Ca

40Ca

N/ZQP

N/ZMV

N/ZQT

N/ZQP

N/ZQT

N/ZMV

N/ZQP

N/ZQT

N/ZMV

N/ZQT

N/ZQP

N/ZMV

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Incomplete N/Z equilibrium

N/Z of QP (and MV) 7Li/7Be

Semi-peripheral collisions: isospin diffusion

7Li 48Ca+48Ca

7Li and 7Be emission yields by means of multi-component moving source fits.

7Be 48Ca+48Ca

QP: isospin diffusionMV neutron enrichment (isospin drift)<b> ≈ 6-7 fm

see also I. Lombardo et al, PRC 82 (2010)

Is the N/Z equilibrium complete?

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Semi-peripheral collisions: isospin diffusion

Following SM, we can assume:

sourceBe

Li

Z

N

Y

Yexp

7

7

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:

PTOT

PQPeq

ZN

ZN

ZN

ZN

f

At complete charge equilibrium feq=1

The pure systems useful to trace the “equilibrium line”

<feq> ≈ 0.63

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CoMD-II, Stiff2

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 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 !

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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, Italyb) INFN, Sezione di Catania, Catania, Italy

c) Dipartimento di Fisica e Astronomia Università di Catania, Catania, Italyd) Saha Institute of Nuclear Physics, Kolkata, India

e) Centro Siciliano di Fisica Nucleare e Struttura della Materia, Catania, Italyf) Dipartimento di Ingegneria ed Architettura,Università Kore di Enna, Enna, Italy

g) Institut de Physique Nucleaire d'Orsay, CNRS-IN2P3, Orsay Cedex, Franceh) Institute of Physics, University of Silesia, Katowice, Poland

i) Institute for Physics and Nuclear Engineering, Bucharest, Romanial) Dipartimento di Fisica, Università di Messina, Messina, Italy

m) Dipartimento di Fisica, Università di Napoli Federico II, Napoli, Italyand INFN – Sezione di Napoli, Via Cintia, Napoli, Italy

Exochim CollaborationIN

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Further Slides

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p,d,t emission in coincidence with ER

Evaporated LCP N/Z of the excited source

We selected events with Evaporation Residue emission (mER> 0.55mtot) is seen.

Isotopic composition of hydrogens at 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

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ip,d,t emission in coincidence with ER

Evaporated LCP N/Z of the excited source

We selected events with Evaporation Residue emission (mER> 0.55mtot) is seen.

Isotopic composition of hydrogens at 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

trends are qualitatively reproduced by HIPSE+SIMON calculations

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v = vproj

v ≈ vtarg

Gentle collisions

vCN < v < vproj

v ≈ vproj

Damped collisions

Very-damped collisions

v ≈ vCN

v <≈ vproj

Velocity correlations of the two largest fragments emitted

mcp is correlated to the <b>

4040Ca + Ca + 4646TiTi

Impact parameter selection: mcp

vp

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iaCollisioni semi-periferiche: trasporto dell’isospin

N/Z1

N/Z2

QP

QTMV

40Ca + 40Ca(N/Z=1)

40Ca + 46Ti(N/Z=1.05)

40Ca + 48Ca(N/Z=1.2)

Nelle collisioni semi-periferiche della reazione 40Ca+48Ca notevole scambio di neutroni tra P e T (“isospin diffusion”)

Informazioni sull’N/Z dei sistemiQP e MV (QT soglie) attraverso lo studio dei rapporti isotopicirapporti isotopici 7Li/6Li e 9Be/7Be in funzione della vpar:

0.15< vpar/c < 0.23 emissione QPvpar/c < 0.15 emissione MV

Selezione in mcp eventi semi-periferici, trend simile osservato nei dati inclusivi.

Il QP acquista neutroni dal QT nella reazione 40Ca+48Ca, rispetto alle altre due reazioni

Isospin diffusion

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 (mLcp)?

qmed=11.5°

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Kinetic energy of the biggest fragment emitted

<dissipation>

40Ca+40Ca

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iSymmetry Energy and Symmetry Potential

An open question

EoS of Asymmetric nuclear matter:

(A)Symmetry Energy: various notations…

)/(2 0

, FC ps

Baran et al, Phys. Rep. (2005)

Prakash et al, Phys. Rev. Lett. (1988)

Bao An Li et al, Phys. Rep. (2008)

A. C

arbo

ne e

t al

, PR

C 8

1, 0

4130

1(R

) (2

010)

, F(0) e L sono quantità collegate tra loro

attraverso semplici relazioni matematiche stiffness del potenziale di simmetria

• produzione di cluster cluster (bassa densità)• stabilità delle stelle di neutronistelle di neutroni (altissime densità)

M.F

. Rivet, P

roc. of Ecole Joliot-C

urie (2010)

48Ca+48Ca experiment

As before, good agreement with Stiff2 option (linear)

By interpolating the three original options, we find <> ≈ 1.1 as minimum deviation from experimental Mnor distributions

Moderately Stiff form factor

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Central collisions: CoMD-II calculations

QP isoscaling

Study of the isoscaling for QP emission (v// > 0.15c) in 40Ca+40Ca and 48Ca+48Ca

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Further analysis to estimate Csym

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Similar results also for 48Ca+48Ca

Analisi in Mnor vari processi che contribuiscono alle collisioni centrali: emissione di HR per incompleta fusione e presenza di BL e IMF

totnor m

mmM 21

Analisi in Mnor su varie finestre di angolo polare di emissione del frammento m1

HR emessi preferenzialmente ad angoli in avantiAltri processi emissione di m1 ad angoli più grandi

Central collisions: HR emission

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L’N/Z ha influenza sui parametri termodinamici raggiunti dalle sorgenti eccitate prodotte per incompleta fusione? Selezione eventi m1≥46 (prod. residui)

Spettri di velocità di m1 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

pp

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

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iaCollisioni centrali: stime di energie di eccitazione

Per eventi centrali, con emissione di ER + particelle leggere (n,p,d,t,3He,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/Ztot) 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/ZC. Sfienti et al, PRL 102 (2009)

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iProspettive: 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: 36ArTarget di produzione: 9Be

Production Target

Fragment Separator

CHIMERA ROOM

G. Raciti et al, NIM B (2008)

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iProduzione di fasci Ar-like

Test di produzione di p-rich nuclei nella regione dell’ Ar alla facility In-flight di 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

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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

Tlim > 1MeV~

Calcoli di liquid drop model “eccitata”Tlim competizione dei termini coulombiano, superficie e simmetria

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iaIsospin-1: check BaF2

neu

tron

i (n

,) particelle cariche

Possibilità di estrarre spettri e neutroni

25 cm

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iaSpettri gamma di bassa energia

m1>54 E.R.

m1<40 B.L.

m3>12 IMF

cou

nts

x 1

dete

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48Ca+48Ca

Per eventi ben ricostruiti di collisioni 48Ca+48Ca, possiamo selezionare (in ToF-RT) i raggi raggi ; abbiamo anche una calibrazione in energia dei BaF2 con sorgenti 60Co 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

q=74°

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m1m2

m3

We observe mainly events as: • ER emissions (1XL,2S) • Binary-like (2L, 1S)• Ternary (3M), low statistics

Various classes of eventstheir nature v1 , v2 correlations[v1= v(m1) and v2= v(m2)],

• cut on the mass of the largest fragment emitted

• charged particle multiplicity <b>

Typical behavior of reactions near 20-30 MeV/n

Masses of the two largest fragments