Probing 11 Li halo-neutrons correlations via (p,t) reaction with the active target MAYA
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Transcript of Probing 11 Li halo-neutrons correlations via (p,t) reaction with the active target MAYA
- 1 -T.Roger – 13-10-08 - ENST Workshop Saclay -
Probing 11Li halo-neutrons correlationsvia (p,t) reaction
with the active target MAYA
T. ROGER (GANIL)
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(1) I. Tanihata et. al. (Phys. Rev. Lett. 55, 2676 (1985))(2) 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)
• 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
• Charge & matter radii measurements (7,8)
Angular correlations of the neutrons
State of the art of 11Li (non exhaustive!)
<rn2>1/2
<rp2>1/2
r rc2n
<rm2>1/2
n1
n2
rdi-n
rn-n=2rdi-n
rn1
rn2
6He
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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
Method
Experiment E1055 (2-neutron transfer)
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TISOL source + ISAC II accelerator up to 5kHz of 11Li @ 5A MeV
Low energy + Low beam intensity
Use of Active Target!
Experimental system
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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
Reaction plane : e- drift time
resolutionobservable
2mmRange
1° angle
0.5° - 2°2D angle
2D angles : Centroïds
Tracking using PADS and Wires
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Results of the algorithm
YMAYA (mm)
0
80
160
Depth (mm)90 180
11Li
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CM = 145°
E9Li = 19.1 MeV
Et = 36.3 MeV
<dE/dx>t = 1.5keV/mm
pd t
étage « ΔE » : Si (700µm)
+ étage « E » : CsI (3cm)
Selection of the ions : ΔE - E
2 solid identification stages + 1 gazeous stage
large dynamic for the selection
Selection of particles
CM = 35°
E9Li = 53.9 MeV
Et = 1.4 MeV
Rt = 50mm
11Li9Li
étage « ΔE » : gaz (5cm)
+ étage « E » : Si (700µm)
At least 1 identified particle from 20° CM to 160°CM
11Li mass :
• S2n = 386 (20) keV
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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) p(11Li,9Li)t @ 4.3A MeV (T.Roger)
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I.J. Thompson et al. (Phys. Rev. C 49, 1904 (1994))
Calculations including simultaneous and sequential transfers for ≠ 11Li modelswith various s² %
11Li: s2 & p2
10Li9Li (G.S.)
s
sequentials
simultaneous
p
51543.640.33P3
64313.39-0.32P2
9433.05-0.33P0
(%)(%)(fm)(MeV)
(p1/2)2 wt(s1/2)2 wtRm rmsE11 G.S.
CRC Calculations (I.J. Thompson)
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• 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 only10Li* s-wave and p-wave only
• Two successive steps
• Need d+10Li Optical Potential
•Daehnick et al global optical potential
CRC Calculations (I.J. Thompson)
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Magnitude varies
• shows s2 strengths in the 11Li w.f.
Shapes vary• Shows interference between s- and p-
wave 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)
Simultaneous 2n-transfer Sequential 2n-transfer
CRC Calculations (I.J. Thompson)
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Results
I. Tanihata et al. (Phys. Rev. Lett. 100, 192502 (2008))
3A MeV 4.3A MeV
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
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)) )
CH89 potential : WS > 0 !!
large radius
JLM potential 3 parameters (normalisation V, W & data) Re-Normalisation of data necessary!!!
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Perspectives
Do the experiment at higher energy (get rid of compound nucleus effects)
20A MeV 11Li beam possible at RCNP (Osaka) ?
No compound nucleus effect for (p,t) … but strong resonance populated by (p,p)!!
( IAS of 12Li(G.S.)!!)
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Perspectives
Study the transition to 9Li (2.69) more into details
Excited core configuration for 11Li (G.S.)???
To be continued...
p3/2/2
p1/2/2
s1/2/2
d5/2/2
d3/2/22++
p3/2/2
p1/2/2
s1/2/2
d5/2/2
d3/2/2
1++
nLiLi 2
22/12/3
911
nLiLi 2
12/12/3
911
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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
* RCNP Osaka University** Institute de Estructura de la Materia, Madrid+ NSCL MSU
++ MAYA’s Technical Staff as : J.F. Libin, P. Gangnant, C. Spitaels, L. Olivier & G. Lebertre