Possibilities for Nuclear Physics at the Madrid

Tandem

Hans O. U. FynboDepartment of Physics and AstronomyUniversity of Aarhus, Denmark

•Nuclear physics and astrophysics of light nuclei A=9 and A=12•Studies at CERN of the CSIC group•What could be done at a tandem?

Nuclear chart

N = Z

?

A=9 and A=12 Nuclei

– “Exact” A-body calculations possible for A12 (soon)

• Shell-model states• Molecular-cluster states

– Break-up mechanism not fixed by kinematics

• How does three particles tunnel?

• Fundamental QM problem

– Crucial for bridging the • A=5 and A=8 gaps in Big Bang

and Stellar nuclear synthesis.

Ab-initio Monte-Carlo calculations for A12

Model Predictions (eff. Int.)

The triple- reaction rate

Break-up to Multi-particle Final States

Initial state X : Some (nuclear) stateFinal state Y : Three (or more) particles

E,

X Y : a+b+c

En

erg

y

(ab) + cDirect

(ab) + c

Sequential

12C* 8Begs+31Cl* 30S+p 29P+2p

(ab) + c

?

12C* 8Be(2+)+

a+(bc)

9B 8Be+p, 5Li+ p

Questions E,

•E, ? -Often difficult to Measure

•Spin-parity? - Selection rules

•The structure of the state? -Cluster states -Many-body states

•The mechanism of the break-up? -Sequential or direct? -Importance of different channels

•Relation to state structure

What is :

•Assymptotic Spectra-Observable-Energy and angular correlations

0,2+

8Be+

0+

3-

1-

2-

10.27

9.641

10.3

10.84

11.83

7.6542

12.71 1+

14.08

13.35

15.11

2-

4+

1+

7.377

15.9572

12C

11B+p

0+

2+

7.285

++7.285

Width Decay Structure

Elevel /MeV J level 8Be (0+)

8Be (2+)

7.6542(15)

0+ 8.5(1.0) eV >96% <4%

9.641(5) 3- 34(5) keV >96% <4%

10.3(3) 0+ 3.0(7) MeV >90% <10%

10.849(25)

1- 315(25)keV Strong Yes

11.828(16)

2- 260(25)keV No Yes

12.710(6) 1+ 18.1(2.8) eV No Yes

13.352(17)

2- 375(40)keV No Yes

14.083(15)

4+ 258(15)keV 17(4)%

83(4)%

15.110(3) 1+ 43.6(1.3) eV No Yes

ISOLDE @ CERN

– Modern segmented Si-Detectors

• Large Solid Angle– detect all particles

• High Segmentation– no summing

Previous studies using this setup31Ar 2p Nucl. Phys. A677 (2000) 389C 2p Nucl. Phys. A692 (2001) 42712N 3 Under analysis

R.R.Betts IL NOUVO CIMENTO 110A (1997) 975

ISOL beam• Low energy isotope

separated beam• Can be stopped in C-foil • Well-defined source

– Modern segmented Si-Detectors

• Large Solid Angle– detect all particles

• High Segmentation– no summing

L. Fraile

12C from the -decay of 12B

Latest evaluation 1990

Region probed by

-decay 0+, 1+ ,2+

Region probed by delayed -emission

Dalitz plot for 3

E1

E2 E3

Dalitz plot

= E/Q= (E+2 E)/Q

Q

Simultaneous stepwise

Data

The 12.71MeV state: Dalitz plots

Phase space

E1

E2 E3

Dalitz plot

Stepwise

Simultaneous

T

-8Be

-

8Be

Coulomb interaction between 1st and 2nd emitted s neglected !!!!

PRL 20 (1968) 1178

• Classical calculation• No ang.mom. Included• Need unphysical S

Towards the Astrophysical Region

0+ state

2+ state

0+ state includinginterference with ghost anomaly

The triple- reaction rate

-decay summary

• Selection rules pick out specific states among possibly many (spin + isospin)• Particles from breakup of unbound states fed in the decay emitted from rest• Point source • Thin host -> reduced energy loss

• Certain states cannot be produced• Time structure of events can be very peaked• Yield is often very limited• Very restricted access to beam

10B(3He,p3)

Peaks in p-spectrum State in 12CPeaks in -spectrum State in 9B

10B(3He,p3)

10Be(3He,n3)...

E

Ep

Ep1966

6Li(6Li,3)

• Reaction mechanism• FSI Coulomb effects

E

E

1968

9Be (3He,3)

• Reaction mechanism• FSI Coulomb effects

8Be (0+)

E

E

1965

13C(3He,4)

Also : 7Li (d,n), 10Be(3He,n), 6Li (3He,p)

E

E

1965

Summary• To study exotic short lived nuclei new effective detector arrays have been developed• New analysis methods

• A number of reactions suitable for tandems exist which were last visited >30 years ago.

• Huge potential for extracting interesting and very relevant information on light nuclei.