The FARCOS project
Collaboration: INFN (CT, LNS, MI, NA; Italy),
GANIL (France), Un. Huelva (Spain)
Synergies: Fazia, Neutron detectors,
Spectrometers, …
Physics case: dynamics and spectroscopy
1. Imaging in heavy-ion collisions
2. Spectroscopy of exotic nuclei:
– In heavy-ion collisions
MPCS: Multi-Particle Correlation Spectroscopy
– Direct reactions
FARCOS: Femtoscope ARray for
COrrelations and Spectroscopy
Double-sided Silicon Strip
6.4 x 6.4 cm2
1500 m
300 m
CsI(Tl) + D
32 x 32
32 x 32
Angular resolution: ~0.2o at d=60 cm
Farcos as a modular correlator
Correlations
Event characterization (4)
Coupling to 4 detectors for dynamics studies
(LNS, GANIL, NSCL-MSU, …)
Chimera @ INFN LNS
Beam
TARGET
30°
176°
1°
1m
1192 Si-CsI(Tl) Telescopes
Particle identification (as in Chimera)
PSD in CsI(Tl)
ΔE(Si)-E(CsI)
Z and A for light charged particles
Charge Z for particles
punching throught the Si
detector
Be
HI
t
a
V(t)
3He
t
slow
d
fast
p
CsI(Tl)
Si
~300 μm
3-12 cm
ΔE(Si)-ToF
Mass for particles
stopping in the Si
detector
E(Si)-Rise time
ΔE(Si)-E(CsI)
Charge Z and A for light
ions (Z<9) punching
throught the Si detector
Li
Charge Z for
particle
stopping in Si
detectors
(NEW)
Farcos array features
• High angular resolution (<0.5o):
• Flexibility: allow coupling to
– 4 detectors, magnetic spectrometers, other correlators
– Neutron detectors for n-p correlations (future)
• Low thresholds for low energy experiments at
Spiral2 and Spes
– pulse-shape on silicon and digitalization (future,
interface to Fazia project)
Density dependence of the
asymmetry term in nuclear EoS
E(, )  E ,  0 Esym ()  
B.A. Li et al., Phys. Rep. 464, 113 (2008)
2

n   p 
     

n
p
???
Many approaches…
large uncertainties
Microscopic many-body,
phenomenological, variational
Symmetry Energy: who cares?
Lassa @ MSU
Imbalance ratios
skins
halos
FOPI @ GSI
Elliptic flow
resonances
GDR & PYGMY RESONANCE
Chimera @ LNS
Competitiion Inc. Fusion / DIC
Supernovae,
neutron stars
Producing density gradients
Large N/Z to enhance effects of Esym()
124Sn+124Sn
(N/Z=1.48), 48Ca+48Ca (N/Z=1.4), 197Au+197Au (N/Z=1.49)
Sec. decays!
Radioactive beams…

n
p
Ebeam<100 MeV

Pre-equilibrium n,p
• n/p energy spectra and angular
distributions
Expansion
Multifragmentation
• Isospin diffusion, fractionation,
isoscaling phenomena…
• p-p, n-n and n-p correlation functions Chimera@INFN, Indra@GANIL,
Lassa@MSU, …
Heavy-ion collisions: open issues
• Pre-equilibrium neutron/proton emissions: the
most sensitive probes of Esym()
– n/p relative energy spectra
– p-p, n-p, n-n two-particle correlation functions
• Space-time characterization: different particles
emitted by several sources & over different
time scales
– Need space-time probes to disentangle sources
t as short as 10-22 sec
r as small as 1 fm “femtoscopy”
Correlation femtoscopy in HIC
Femtoscope
1  R(q)  k 

p1
Ycoin p1, p2 
qrel
Yevt.mixing p1, p2 

q

p2
Sensitive to space-time properties

a
d
p
1+R(q)
p2
1+R(q)
p1
6Li
p
proton-proton
deuteron-alpha
q (MeV/c)
q (MeV/c)
Low q (qrel)
measurements
Resonances
High angular resolution required!
Imaging correlations, “Femtoscopy”
G. Verde et al., PRC65,
069604 (2002)
R(q)  4  dr  r 2  S(r)  K(r,q)
14N+197Au
E/A=75 MeV
Fast simultaneous emitting
sources (pre-equilibium)
Slow sequential
emissions (evap.)
Source size
Space-time images
q
e
Source function: Spatial distribution of proton emitting source in
HIC: “femtoscopy” - measuring sizes r~1 fm and times t~10-21s
Farcos for complex particle correlations
6Li-a
p-p
1+R(E*)
d-a
S(r)
Images
d-a
a-6Li
p-p
E*(MeV)
r (fm)
Different particles emitted by different sources and at different
times (hierarchy)
Event characterization required ! ==> Coupling to 4 mandatory
Multi-Particle Correlation
Spectroscopy (MPCS)
Not only EoS…
10C*
Several unbound species in
just one single experiment!
Expansion
HIC and correlations as a spectroscopic tool
MPCS: 8B and 12C
8B
 p+7Be
12C
 aaa

12C
 aBe  aa

3-alpha correlation function
Spin of
8B
states
12C
states:
sequential decay
C+Mg, E=53 MeV/u
Indra data
F. Grenier et al., NPA 2008
LASSA data
W.Tan, PRC 2004
J=1+
Event mixing
Modified event mixing
Accessing spins and branching ratios (sequential decay paths)
Multi-a correlations: Hoyle and Boson condensate states
2a-2p correlations: states in 10C*
10C
p-p-aa four-particle correlations
1+R(Ek)
F. Grenier, A. Chbihi, G. Verde et al.,
Nucl. Phys. A811 (2008) 233
2
4
6
8
10
12
14
6Be
9B
8Be
10C
 6Be+a (2p+a)a
10C
 8Be+p  (a+a)p
10C
 9B+p  (a+ap)p
Ek (MeV)
Disentangle sequential decay paths
Symmetry energy and pp, nn and np
correlations
Symmetry potential
52Ca+48Ca
Asy-stiff
7
Asy-soft
E/A=80 MeV
neutron-neutron
5
3
1
1+R(q)
1.5
pp Sources
Asy-stiff: more
localized source
1.0
0.5
0.0
4
proton-proton
proton-neutron
3
2
1
q (MeV/c)
Future perspectives: pp, nn, np correlations!
Coupling to neutron detectors
Neutron-proton correlation expts
Ghetti et al, PRC 69 (2004) 031605
Protons
neutron-proton
Neutrons
Emission chronology sensitive to Asy-EOS
…difficult experiments
n/p experiments @ MSU
112Sn+112Sn
vs
E/A=50 MeV
124Sn+124Sn
M. Famiano et al., PRL97, 052701 (2006)
n detectors
Liquid scintillators
p detectors
DE-E (Lassa)
M.B. Tsang et al., PRL102, 122701 (2009)
 
Esym (  )   
 0 

n/p spectra ==>   0.7
Spectroscopy: “stand-alone” mode
Shell structure close to drip lines
Must2 expts
Example:
8He
beam @ Spiral (GANIL)
E/A=15.4 MeV
8H
+ p  7He + d
8H
+ p  6He + t
Similar experiments at LNS (FRIBS) or at LNL(SPES)
Spes: low energies (Pulse shape on 1st Silicon)
Spectroscopy: “coupling” mode
FRIBS beams at the LNS of Catania
Correlator
34Ar+p33Ar+d
Chimera (d)
(33Ar residue)
d
34Ar
33Ar
Day-1 experiment at the INFN-LNS
Correlator
• Heavy core: Magnex at ~ 0o
• Scattered d with Correlator
• Spiral/Spiral2, Spes, …
Imaging correlations at low energies
• Perspectives at Spiral2 and Spes:
Imaging in fusion, fission, DIC, N/Z effects on limiting
temperatures and reaction mechanisms, particle emission
chronology
Requires low identification thresholds: pulse-shaping
techniques on silicon detectors
• Chimera solution, Fazia implementation
(digitalization of silicon signals)
• Future issue: Pulse-shape capabilities in integrated
electronics (ASIC, etc.)
Workshop in 2011
• Catania, probably spring or early fall 2011
– Integrated electronics for silicon detectors, new
solutions, pulse-shape in integrated solutions,
coupling to different detectors (also neutrons,
gammas, spectrometers, …), others
You are all very welcome:
need to build up synergies