B.MOUGINOTIPNO

PHD director : F. AZAIEZ, S. FRANCHOO

Search of Giant Pairing Vibration

in nuclei

Ground State 0+

First 0+ excited state A Higher excited 0+

Next M

ajor Shell

Giant Pairing VibrationGPV Mode : Collective Excitation of Pair

in the Next Major Shell

Low-lying 0+ Excitation

How to populate a O+ state in Nuclei ?

>Pairing vibrations : L=0

>Sensitive to Pairing interaction

Giant Pairing Vibrations

GPVGPV is a Collective mode

> Should lie at high excitation energy

> 2 nucleon transfer channel selective for pairing vibration

ex (p,t) reactionKhan, Sandulescu,Van Giai, Grasso PRC69(2004)

QRPA calculation

Mean field calculation

22O

Why revisit (p,t) reactions for GPV?On 208Pb :

>51.9 MeV proton at 8°- 65° : Orihara Phys.Rev. C 9(1974)266

>35 MeV proton at 6° 18° 30° : Lanford Phys.Rev. C 16(1977)988

>40 MeV proton at 7°- 35° : Shepard Nucl.Phys. A 322(1979)

>51.9 MeV proton at 6° 18° 30° : Takahashi Phys.Rev.C 27(1983)

>168 MeV proton at 2°-18° : Gerlic Phys.Rev. C 39(1989)

>120 MeV proton at 7°-34° : Mihailidis Phys.Rev.C 64(2001)

On 120Sn :

>40 MeV proton at 7°- 30° : Bassani Phys.Rev. 139(1965)

>42 MeV proton at 10°- 45° : Crawley et al. Phys.Rev.Let. 39(1977)33

>89MeV proton at 15°- 45° : Crawley et al. Phys.Rev. C 22(1980)

No experiment at the right angle and/or the right energy !!0°or very near 0°& 60 MeV

GPV predicted at 10-20MeV>wrong Excitation Energy Range Observe

At iThemba (South-Africa) :208Pb(p,t)206Pb Q = -5.62 MeV120Sn(p,t)118Sn Q = -7.111 MeV

Proton beam at 60MeV

Spectrometer at 7°( lowest avaible angle)

Our recent Works

Spectrometer at 7°

1 Wire Chamber : position of the light ejectile - triton energy

Proton beamTarget : 208Pb & 120Sn

tritons

1 Paddle : dE/TOF – triton selection

At 60 MeV

Selection of B window (5-7MeV)

thickness 6.4mm

AB

Z

2 Week-ends

B

208Pb (p,t) 206Pb & 120Sn (p,t) 118Sn

Our recent works

Eproton = EexciHeavy + Etriton + Qreaction

Gate on Tritons

Without Gate

triton

deuteron

16O(p,t)

12C(p,t)

208Pb(p,d)207Pb Ground State

5/2-3/2-

13/2+

7/2-

Gate on Deuterons

Exemple for 41MeV setting

TOF

E p

addl

e1

16O(p,t)

12C(p,t)

No gate:

0,996triton gated

triton nongated

N

N

gated on tritons:

0,0019deuton gated

deuton nongated

N

N

Deuterons acceptance ratio :Tritons acceptance ratio :

Exemple for 41MeV setting

TOF

E p

addl

e1

Excitation Spectrum of 206Pb all fields overlapping

(keV)

Excitation Spectrum of 206Pb all fields superimposed

Excited state of 206Pb

14O Ground state

10C Ground state

Excited state of 207Pb

So far no indication of bump or broad structure in the 206Pb spectrum(keV)

Excitation Spectrum of 118Sn all fields overlapping

(keV)

Excitation Spectrum of 118Sn(p,t) :

GPV?Deep hole statesA hint for GPV in 118Sn: observation of cross-section enhancement

(weak bump) at Ex=12MeV?The GPV? If yes, should increase at 0°

Next Move : in SPRING 2009

120Sn(p,t)118Sn & 208Pb(p,t)206Pb

proton beam @ 60 MeV

K600 spectrometer @ 0°

N=70

Futur plans and improvments?

Thank you

iThemba labs

Excitation Spectrum of 1118Sn(p,t) :

GPV?Deep hole states

N=70

A hint for GPV in 120Sn: observation of cross-section enhancement (weak bump) at Ex=12MeV?

The GPV? If yes, should increase at 0°

GPV could be searched for using Pair Transfer Reactions

(t,p) reactions (p,t) reactions

At iThemba :208Pb(p,t)206Pb Q = -5.62 MeV120Sn(p,t)118Sn Q = -7.111 MeV

GPV : L = 0 pairing mode

Spectrometer at 0°

Futur plans and improvments?

Overview of (p,t) reactions

Orihara Phys.Rev. C 9(1974)266

Data recorded at 8°- 65°

51.9MeV protons at Institute of Nuclear Study

Lanford Phys.Rev. C 16(1977)988

35MeV protons at MSU cyclotron :Data recorded at 6° 14° 30°

E* range : 0 - 10 MeV

E* range : 0 - 7 MeV

208Pb (p,t) 206Pb

208Pb (p,t) 206Pb

Position sensitive chamber at the focal plane of the spectrograph

>Data recorded at 7°- 35°

Shepard Nucl.Phys. A 322(1979)

40 MeV protons at Indiana University Cyclotron (IUCF)

Takahashi Phys.Rev.C 27(1983)

51.9 MeV protons at Institute of Nuclear Study Tokyo University

Array of 200 proportional countersat the focal plane of the spectrometer

>Data recorded at 2°- 60°

E* range : 0 - 6 MeV

E* range : 0 - 5 MeV

Mihailidis Phys.Rev.C 64(2001)

Gerlic Phys.Rev. C 39(1989)

168 MeV protons at K220 Orsay Synchrocyclotron

Vertical-wire Drift Chamber at focal plane of K600 spectrometer

Data recorded at 7°- 34°

Data recorded at 2°- 18°

120 MeV protons at IUCF

E* range : 0 - 12 MeV

E* range : 0 - 7 MeV

208Pb (p,t) 206Pb

40 MeV protons at University of Minnesota linear accelerator

Bassani Phys.Rev. 139(1965)

8 Plastic scintillators at the focal plane of the spectrometer

Data recorded at 7°-30°

120Sn (p,t) 118Sn

E* range : 0 - 11 MeV

89MeV protons at IUCF

Crawley et al. Phys.Rev. C 22(1980)

42 MeV protons at Jefferson labresistive-wire proportional counter at focal plane of Enge spectrometer

25000

Crawley et al. Phys.Rev.Lett. 39(1977)33

Data recorded at 10°- 45°

Data recorded at 15°- 45°

E* range : 0 - 50 MeV

E* range : 0 - 20 MeV

120,122Sn (p,t) 118,120Sn