Transcript Diapositive 1

Reaction cross section and strong absorption radius
measurements of neutron-rich exotic nuclei
in the vicinity of closed shells
N=20 and N=28
Abdenbi KHOUAJA
I.N.F.N
Laboratorio Nazionale del Sud
Catania
Available data of the reaction cross-section
A.C.C.Villari et al. en 1991
Ca35 Ca36 Ca37 Ca38 Ca39 Ca40 Ca41 Ca42 Ca43 Ca44 Ca45 Ca46 Ca47 Ca48 Ca49 Ca50 Ca51 Ca52 Ca53
I.Licot et al en 1997
K35 K36 K37 K38 K39 K40 K41 K42 K43 K44 K45 K46 K47 K48 K49 K50 K51 K52
Ar31 Ar32 Ar33 Ar34 Ar35 Ar36 Ar37 Ar38 Ar39 Ar40 Ar41 Ar42 Ar43 Ar44 Ar45 Ar46 Ar47 Ar48 Ar49 Ar50 Ar41
N.Aissaoui et al en 1999
Chulkov, Suzuki, Ozawa et al. en 2001
Cl31 Cl32 Cl33 Cl34 Cl35 Cl36 Cl37 Cl38 Cl39 Cl40 Cl41 Cl42 Cl43 Cl44 Cl45 Cl46 Cl47 Cl48 Cl49
S27 S28 S29 S30 S31 S32 S33 S34 S35 S36 S37 S38 S39 S40 S41 S42 S43 S44 S45 S46 S47 S48
Y.H.Zhang et al. en 2002
P26 P27 P28 P29 P30 P31 P32 P33 P34 P35 P36 P37 P38 P39 P40 P41 P42 P43 P44 P45 P46
Si22 Si23 Si24 Si25 Si26 Si27 Si28 Si29 Si30 Si31 Si32 Si33 Si34 Si35 Si36 Si37 Si38 Si39 Si40 Si41 Si42
Al22 Al23 Al24 Al25 Al26 Al27 Al28 Al29 Al30 Al31 Al32 Al33 Al34 Al35 Al36 Al37 Al38 Al39
Mg20Mg21Mg22Mg23Mg24Mg25Mg26Mg27Mg28Mg29Mg30Mg31Mg32Mg33Mg34Mg35Mg36
28
26
Na20 Na21 Na22 Na23 Na24 Na25 Na26 Na27 Na28 Na29 Na30 Na31 Na32 Na33 Na34 Na35
Ne17 Ne18 Ne19 Ne20 Ne21 Ne22 Ne23 Ne24 Ne25 Ne26 Ne27 Ne28 Ne29 Ne30 Ne31 Ne32
F17 F18 F19 F20 F21 F22 F23 F24 F25 F26 F27
F29
18
20
O13 O14 O15 O16 O17 O18 O19 O20 O21 O22 O23 O24
24
22
N12 N13 N14 N15 N16 N17 N18 N19 N20 N21 N22 N23
C9 C10 C11 C12 C13 C14 C15 C16 C17 C18 C19 C20
B8
B10 B11 B12 B13 B14 B15
Be7
Be9 Be10 Be11 Be12
Li6
He3 He4
2
Li7
Li8
Li9
He6
He8
4
6
Li11
8
Be14
B17
B19
12
14
C22
16
10
Goal of the experience
Experiment Details
Secondary
beam
Primary
beam
Production target
181Ta
47Cl
45S
44P
43Si
Degrader
41Al
9Be
with thickness of 25µm
38Mg
35Na
32Ne
29F
22C
11Li
23N
21C
17B
14Be
Energy=60.3A MeV
48Ca
Intensity=4000nAe
L. Bianchi et al., Nucl. Instr. and Meth. A276 (1989) 509.
W. Mittig et al., Bormio, Italy 1986
A. Gillibert et al., Phys. Lett. B176(1986)317.
SPEG-GANIL
Spectromètre
Alpha
SISSI
 Long flight path = 82m
 Time of flight ~ 700ns - 1.2 ms
Dm/m ~ 10-4
NaI
beam
B= M V/Q
M = Q B/L.Tvol
dE1
dE2
NaI
Silicon Telescope
Ebar
E
Reaction cross-section
Direct method developed by A.C.C.Villari
(which is a variant of the known transmission method)
NaI
NaI
Reaction target
In this method, the stack of Silicon detectors is used as both :
Detection system
R


E max
0
 R E dR / dEdE

R max
0
dR

A ln1  PR 
d N A Rmax
Reaction probability PR
Spectrum obtained directly
from the silicon detectors
Spectrum in coincidence with
emitted gammas
Masse (MeV)~Etot.Tvol2
Typical mass spectra as a function of the total energy (~ET2) for 25F (E= 45.5A MeV).
Energy resolution ~ 0.23%. Effective resolution Q=2.58MeV
Spectra (a) :
Spectra (b) :
PR 
N rea
Ni
N 
N rea
 corr
 corr   coinc 
Nrea  N
PR 
Ni
reaction probability
Parametrization of S.Kox
Reduced strong absorption radius :

AP1/ 3 At1/ 3
2
1/ 3
1/ 3



 R   r0  ( AP  At  a 1/ 3

C
E
1/ 3
AP  At


 cste ln(1  PR )
2

V 
1  b 
Ecm 

CE  0.31  0.014E / AP
Results
 More than 70 radii are measured
19 radii are measured for the
first time:
27F, 27, 30Ne, 33Na, 28, 34-35Mg,
36-38Al, 38-40Si, 41-42P, 42-44S, 45Cl.
Parametrization of the reduced strong absorption radii:
r02  0.06( N  Z )  1
Z≤13 : evolution according to :
W.Mittig et al., Phys. Rev. Lett. 59, 1889 (1987)
r02  ( N  Z ) / 30  32 / 30
Z≥13 : evolution according to:
N.Aissaoui et al., Phys. Rev. C60, 034614 (1999)
r02
8≤Z≤18 and 12≤A≤46 :
A.Khouaja et al (ENAM04)
r02
stability
A.Khouaja et al (EXON04)
r02
TZ/A
 0.282
 4.628 2
r  1.164 
Tz   2 Tz
 A 
 A 
2
0
New parametrization
27P
22N
17F
23Al
23O
24F
29Ne
44S
33Na
35Mg
45Ar
45Cl
41Ar




Strong influence of the isospin is revealed for each isobar,
New parametrization permits :
To study the evolution of the matter distribution : efficiently reproduces the skin effect
To give a fast indication on the existence of abnormal structures: deformation, halo…
for these nuclei: 23N, 29Ne, 33Na, 35Mg, 44S, 45Cl, and 45Ar
Glauber Model
permits us to deduce:

The effective nuclear matter radii “RMS”

The effective density distributions
Coulomb-modified Glauber Model:
R

VC
 2 (1 
)  b db1  (b)
Ecm 0
Transparency function :
T (b)  exp(
NN
tot
 (b))

NN
tot

Z P Z C pp  N P N C nn  N P Z C np  Z P N C pn
:
AP AC
 (b)   d 2 b1  d 2 b2 f ( b1  b2 )  zC (b1 )  zP ( b2  b )
Thickness density :

P, C
z

(b)   dz  P, C ( b 2  z 2 )

Profile function :
f (b) 
1
2
4  NN
exp(
 NN  0.996 exp( 
R.M. Devries et al., Phys. Rev. C22, 1055 (1980)
b2
2
2  NN
)
E
)  0.089
106 .679
T. ZHENG et al., Nucl. Phys. A709, 103 (2002)
Standard Glauber model
Coulomb-modified
Glauber model
 Matter distribution: using 2pF density distribution
k , 0
k , 2 pF (r ) 
3k

4Rk3, 2 pF
  2ak2, 2 pF
1  2

Rk , 2 pF





1
Rk , 2 pF  r2 pF Z1/ 3 (or N1/ 3 )
k , 0
r  Rk , 2 pF
1  exp
ak , 2 pF
where: k=Z or N
2 2
3 2  7 a n, 2 pF
 r  n  Rn, 2 pF 1 
5
3Rn2, 2 pF




 7 2 a 2p , 2 pF
3 2
 r  p  R p , 2 pF 1 
5
3R p2, 2 pF




2
2
Skin effect
DR  r 2 1n/ 2   r 2 1p/ 2
Two free parameters
Matter radii: Radius Mean Square
 r m  (Z / A)  r  p  ( N / A)  r n
2
2
2
The results of T.Suzuki (Phys. Rev. Lett. 75, 3244 (1995))
Absence of data at intermediate energy:
Rp, 2 pF ( ANa)  Rn, 2 pF ( 23Na)  3.114 fm
T.Suzuki et al.,
.
an, 2 pF ( ANa)  a p, 2 pF ( ANa)  0.401 fm
Phys. Rev. Lett. 75, 3244 (1995)
Actual work
Presence of data at intermediate energy :
We disentangle:
Rp, 2 pF  rp Z 1/ 3, Rn, 2 pF  rn N1/ 3
and
ap
,
an
Si-target
protons
neutrons
C-target
Matter Radii Mean Square
L.S. Geng et al, Nucl. Phys. A 730(2004)80
Conclusion
In the same setup, more than 70 reaction cross sections are measured
 The measurements , for the first time, of 19 new reaction cross sections
 New phenomenological parametrization is suggested for the nuclear radii in the region
of closed shells N=8 and N=28, which permits :

to reproduce the skin effect far from stability

to give a current indications on the existence of abnormal structure: 23N, 29Ne, 33Na,
35Mg, 44S, 45Cl, and 45Ar
 We disentangle the effect of nuclear size and surface diffusivity of matter distribution
using Glauber model.
Collaborators:
D.Hirata
Open University, U.K
A.C.C.Villari
GANIL, Caen, France
M.Benjelloun LPTN, El jadida, Morocco
A.Khouaja
LNS-INFN, Catania, Italy
Participants:
H.SAVAJOLS1, W.MITTIG1, P.ROUSSEL-CHOMAZ1, N.ORR2, S. PITAE1, C.E.DEMONCHY1, L.GIOT1,
M.CHARTIER3, A.GILLIBERT4, D. BAIBORODIN5, Y. PENIONZHKEVICH6, W.CATFORD7, A.LÉPINE-SZILY8,
Z.DLOUHY6
1GANIL (IN2P3/CNRS – DSM/CEA), B.P. 55027 14076 Caen Cedex 5 France
2LPC, ISMRA et Université de Caen, F-6704 Caen, France
3University of Liverpool, Dept. of Physics, Liverpool, L69 7ZE, UK
4SPHN (DAPNIA/CEA), CEN Saclay, F-91191 Gif-sur Yvette, France
5FLNR, JINR, Dubna, P.O.Box 79, 101000 Moscow, Russia
6Nucl.Phys.Ins., ASCR, 25068 Rez, Czech Republic
7University of Surrey, Stoy Fill, Nuclear Physics Dept, Guilford, GU27XH, UK
8University of São-Paulo, IFUSP, C.P.66318, 05315-970 São –Paulo, Brazil
Great thanks to MAGNEX’s group:
A.Cunsolo, F.Cappuzzelo, J.S.Winfield,
C.Nocifiro, A.Khouaja, A.Foti, S.
E.A.Orrigo, M.Cavallaro
MERCI DE VOTRE ATTENTION
profile function :
1  i
b
f (b) 
exp(

)
2
2
4  NN
2  NN
f (b) 
2
1
4 
2
NN
exp(
 NN  0.996 exp( 
b2
2
2
NN
)
E
)  0.089
106 .679
T. ZHENG et al., Nucl. Phys. A709, 103 (2002)
S.K Charagi et al., Phys. Rev. C41, 1610 (1990)
 np  70.67  18.18 /   25.26 /  2  113.85

NN
tot
 pp   nn  13.73  15.04 /   8.76 /  2  68.67 4
avec
  v/c
R.M. Devries et al., Phys. Rev. C22, 1055 (1980)



NN
2
2
C
P
 R (b)  2  b db 1  exp   tot
d
b
d
b
f
(
b

b
)

(
b
)

 1  2 1 2 z 1 z ( b2  b ) finite range



NN
2
C
P
 R (b)  2  b db 1  exp   tot
d
b

(
b
)

( b1  b )
1
z
1
z

zero range
Discovery of a new magic number, N=16 :
Possible existence of one-neutron halo
structure : 22N, 23O, 24F
Magic
number
A.Ozawa et al., Phys. Rev. Lett. 84, 5493(2000)
Appearance of a
new magic number N=16
Matter distribution far from stability
Halo structure
I.Tanihata et al, Phys.Lett. B206, 592 (1988)
14Be
17B
11Li
11Be
8He
6He
Skin structure
 RMF: 1n-halo nuclei:
33Na, 34Na and 35Mg
T.Suzuki et al, Nucl. Phys. A616, 286c (1997)
J.S.Wang et al., Nucl. Phys. A691, 618(2001)
Noyaux
a2pF
Rp, 2pF
Rn, 2pF
 r 2 1p/ 2
 r 2 1n/ 2
DR
 r 2 1m/ 2 T.Suzuki
31Mg
0.370
3.17
3.70
2.810.04
3.180. 05
0.36
3.04  0.03
3.12  0.13
30Mg
0.415
3.03
3.47
2.810.03
3.100.03
0.29
2.99  0.02
3.08  0.08
29Mg
0.400
3.01
3.38
2.770. 06
3.010. 06
0.25
2.91  0.05
3.01  0.10
29Na
0.440
2.88
3.40
2.770.03
3.100.03
0.33
2.98  0.02
3.06  0.06
28Na
0.385
3.01
3.48
2.740.03
3.050.03
0.32
2.93  0.02
3.04  0.03
27Na
0.270
3.16
3.58
2.650.05
2.950. 05
0.30
2.83  0.04
2.96  0.05
26Ne
0.47
2.59
3.02
2.660.02
2.920.03
0.26
2.82  0.02
2.86  0.05
25Ne
0.370
2.81
3.22
2.580.04
2.850.04
0.27
2.74  0.03
2.82  0.04
24Ne
0.247
2.97
3.33
2.480.04
2.740. 04
0.26
2.63  0.03
2.79  0.13
Our results are slightly small to the results of T.Suzuki
The precision of different results are ameliorated
As a preliminary results, the skin effect is revealed in the structure of these nuclei