- 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)

- 2 -T.Roger – 13-10-08 - ENST Workshop Saclay -

(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

- 3 -T.Roger – 13-10-08 - ENST Workshop Saclay -

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)

- 4 -T.Roger – 13-10-08 - ENST Workshop Saclay -

TISOL source + ISAC II accelerator up to 5kHz of 11Li @ 5A MeV

Low energy + Low beam intensity

Use of Active Target!

Experimental system

- 5 -T.Roger – 13-10-08 - ENST Workshop Saclay -

Experimental system

- 6 -T.Roger – 13-10-08 - ENST Workshop Saclay -

The active target MAYA

C.E. Demonchy et al. (Nucl. Instrum . Methods A 573, 145 (2007))

- 7 -T.Roger – 13-10-08 - ENST Workshop Saclay -

Tracking techinque

Reaction plane : e- drift time

resolutionobservable

2mmRange

1° angle

0.5° - 2°2D angle

2D angles : Centroïds

Tracking using PADS and Wires

- 8 -T.Roger – 13-10-08 - ENST Workshop Saclay -

Results of the algorithm

YMAYA (mm)

0

80

160

Depth (mm)90 180

11Li

- 9 -T.Roger – 13-10-08 - ENST Workshop Saclay -

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

- 10 -T.Roger – 13-10-08 - ENST Workshop Saclay -

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)

- 11 -T.Roger – 13-10-08 - ENST Workshop Saclay -

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)

- 12 -T.Roger – 13-10-08 - ENST Workshop Saclay -

• 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)

- 13 -T.Roger – 13-10-08 - ENST Workshop Saclay -

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)

- 14 -T.Roger – 13-10-08 - ENST Workshop Saclay -

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!!

- 15 -T.Roger – 13-10-08 - ENST Workshop Saclay -

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!!!

- 16 -T.Roger – 13-10-08 - ENST Workshop Saclay -

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.)!!)

- 17 -T.Roger – 13-10-08 - ENST Workshop Saclay -

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

- 18 -T.Roger – 13-10-08 - ENST Workshop Saclay -

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