possibilities for nuclear physics at the madrid tandem hans o. u. fynbo department of physics and...

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.