Transcript 5 - T.Roger – 13-10-08

Probing 11Li halo-neutrons correlations
via (p,t) reaction
with the active target MAYA
T. ROGER (GANIL)
T.Roger – 13-10-08
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State of the art of 11Li (non exhaustive!)
• Matter radius measurement of 11Li (1)
 1st observation of halo phenomenon
• Momentum distribution of core-neutrons (2,3,4)
 Momentum correlations
 Role of s & p-wave mixing
• Coulomb disociation of 11Li (5,6)
 3 body model w.f. with 2n correlations
6He
<r n2>1/2
<r p2>1/2
<r m2> 1/2
rn1

• Charge & matter radii measurements
 Angular correlations of the neutrons
(7,8)
n1
rc2n
r
rn2
rdi-n
rn-n=2rdi-n
n2
(1)
I. Tanihata et. al. (Phys. Rev. Lett. 55, 2676 (1985))
I. Tanihata et. al. (Phys. Lett. B 287, 307 (1992))
(3) I.J. Thompson et. al. (Phys. Rev. C 49, 1904 (1994))
(4) H. Simon et. al. (Phys. Rev. Lett. 83, 496 (1999))
(5) T. Nakamura et. al. (Phys. Rev. Lett. 96, 252502 (2006))
(6) H. Esbensen et. Al. (Nucl. Phys. A542, 310 (1992))
(7) R. Sanchez et. al. (Phys. Rev. Lett. 96, 033002 (2006))
(8) I. Tanihata (Private Communication)
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Method
 Probing halo structure via transfer reaction
 1 nucleon transfer : probes spectroscopy
 2 nucleons transfer : probes strength of correlation
 extraction of angular distributions
+ DWBA analysis
= informations on the structure of the halo
 Study of the 2-neutron transfer reaction on a proton target
Experiment E1055 (2-neutron transfer)
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Experimental system
TISOL source + ISAC II accelerator  up to 5kHz of 11Li @ 5A MeV
 Low energy + Low beam intensity
 Use of Active Target!
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Experimental system
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The active target MAYA
C.E. Demonchy et al. (Nucl. Instrum . Methods A 573, 145 (2007))
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Tracking techinque
Tracking using PADS and Wires
2D angles : Centroïds
observable resolution
2D angle
0.5° - 2°
 angle
1°
Range
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2mm
Reaction plane : e- drift time
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Results of the algorithm
YMAYA (mm)
160
11Li
80
0
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90
180
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Depth (mm)
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Selection of particles
 Selection of the ions : ΔE - E
 2 solid identification stages + 1 gazeous stage
 large dynamic for the selection
CM = 145°
35°
E9Li = 19.1
53.9 MeV
Et = 36.3
1.4 MeV
MeV
<dE/dx>
Rt = 50mm
t = 1.5keV/mm
 11Li mass :
d
p
t
9Li
11Li
• S2n = 386 (20) keV
étage « ΔE » : gaz
Si (700µm)
(5cm)
+ étage « E » : Si
CsI(700µm)
(3cm)
 At least 1 identified particle from 20° CM to 160°CM
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2-neutron transfer : results
• Angular distributions for transitions to 9Li (GS) & 9Li* (2.69 MeV)
p(11Li,9Li)t @ 3A MeV (I.Tanihata)
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p(11Li,9Li)t @ 4.3A MeV (T.Roger)
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CRC Calculations (I.J. Thompson)
Calculations including simultaneous and sequential transfers for ≠ 11Li models
with various s² %
p sequentials
10Li
11Li:
s 2 & p2
s
simultaneous
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9Li
(G.S.)
E11 G.S. Rm rms (s1/2)2 wt (p1/2)2 wt
(MeV)
(fm)
(%)
(%)
P0
-0.33
3.05
3
94
P2
-0.32
3.39
31
64
P3
0.33
3.64
54
51
I.J. Thompson et al. (Phys. Rev. C 49, 1904 (1994))
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CRC Calculations (I.J. Thompson)
• Simultaneous Transfers
• Use 3-body wave functions <p|t> and <9Li|11Li>
• The relative neutron-neutron states must be equal
• One Direct Step
• Need p+11Li and t+9Li Optical Potentials
• Becchetti & Greenlees global optical potential
• Sequential Transfers
• Use 2-body wave functions <p|d> & <d|t>, and <9Li|10Li> & <10Li|11Li>
• Should have complete sets of d* and 10Li* wfs:
d bound state only
10Li* s-wave and p-wave only
• Two successive steps
• Need d+10Li Optical Potential
•Daehnick et al global optical potential
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CRC Calculations (I.J. Thompson)
Simultaneous 2n-transfer
Sequential 2n-transfer
Magnitude varies
• shows s2 strengths in the 11Li w.f.
T.Roger – 13-10-08
Shapes vary
• Shows interference between s- and pwave parts of 10Li.
Note: this interference will diminish if a
complete set of 10Li states included at
same energies.
(May reappear when energies in 10Li*
included properly)
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Results
4.3A MeV
3A MeV
I. Tanihata et al. (Phys. Rev. Lett. 100, 192502 (2008))
 P2 and P3 ~ reproduce the amplitudes
 ... but minimum missed by ~20°
 Not easy to come to a conclusion yet!!
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Perspectives
Use a more realistic optical potential :
 Try to reproduce elastic scattering data
CH89 potential :
 WS > 0 !!
 large radius
JLM potential
 3 parameters (normalisation V, W & data)
 Re-Normalisation of data necessary!!!
 More realistic calculations i.e. include coupling to 1n transfer channel
( like 1H(8He,6He)t : N.Keeley et al. (Phys. Lett. B 646, 222 (2007)) )
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Perspectives
 Do the experiment at higher energy (get rid of compound nucleus effects)
No compound nucleus effect for (p,t) … but strong resonance populated by (p,p)!!
( IAS of 12Li(G.S.)!!)
 20A MeV 11Li beam possible at RCNP (Osaka) ?
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Perspectives
Study the transition to 9Li (2.69) more into details
 Excited core configuration for 11Li (G.S.)???
d3 /2
2+
d5 /2
s1 /2
p1 /2
p3 /2



3
/2

1
/2

2







11
Li
2
n
9
Li
d3 /2
d5 /2
s1 /2
1+
p1 /2
p3 /2



3
/2

1
/2

1







11
Li
9
Li
 To be continued...
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2
n
MAYA@TRIUMF Collaborators
H. Savajols, T. Roger, M. Caamaño, W. Mittig+, and P. Roussel-Chomaz
GANIL, Bd Henri Becquerel, BP 55027, 14076 Caen Cedex 05, France
I. Tanihata*, M. Alcorta**, D. Bandyopadhyay, R. Bieri, L. Buchmann, B. Davids, N. Galinski,
D. Howell, W. Mills, R. Openshaw, E. Padilla-Rodal, G. Ruprecht, G. Sheffer, A. C. Shotter,
M. Subramanian, M. Trinczek, and P. Walden
TRIUMF, 4004 Wesbrook Mall, Vancouver, BC, V6T 2A3, Canada
R. Kanungo and A. Gallant
Saint Mary’s University, 923 Robie St., Halifax, Nova Scotia B3H 3C3, Canada
M. Notani and G. Savard
ANL, 9700 S. Cass Ave., Argonne, IL 60439, USA
I. J. Thompson
LLNL, L-414, P.O. Box 808, Livermore CA 94551, USA
++ MAYA’s Technical Staff as : J.F. Libin, P. Gangnant, C. Spitaels, L. Olivier & G. Lebertre
* RCNP Osaka University
** Institute de Estructura de la Materia, Madrid
+ NSCL MSU
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