News on C12 from -decay and reaction

studies

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

• Why study 12C ? • New results from -decay studies• Conclusions

York, April 19, 2006

Historic Introduction1953 Hoyle predicts 7.6MeV state from abundances of He, C and O and finds it experimentally1956 Morinaga interprets 7.6MeV state and predicts 2+

state near 9MeV1957 Fowler determines J of 7.6MeV state and finds

a very broad state near 10MeV1966 Morinaga interprets 10MeV state as his 2+ state

0

4.4

7.6

10

E in MeV0+

2+

0+

0+/2+

Hoyle

Fowler Morinaga

3

12C

B2FH 1956

Hoyle

Fowler

Burbridge

Burbridge

Suggested most elements above helium were formed in stars and not in B.B.

Morinaga’s Idea for rotational bands in n nuclei

2+ ?2+ ?10.3

Bold conjecture shortly after work of Aa.Bohr on rotational motion

Ongoing theoretical interest :

•Ab-initio Pieper, NP A751 (2005) 516.•AMD Kanada En’yo, PRL 81 (1998) 5291•FMD Feldmeier•SM Navratil, Vary & Barrett, PRL 84 (2000) 5728•U(+1) group Bijker & Iachello, PRC61 (2000) 67305•Cluster too many to do justice

S.Courtin’s talkCharissa collab.

The rate(s) of the 3 process

Nacre assumes 2+ state at 9MeVCaughlan & Fowler do not

Current situation

++

11.2

(0/2+)

0+

(2+)

(2+)15.3

3-

1-

2-

9.64110.3

10.84

11.83

7.65

12.71 1+

14.08

13.35

15.11

(2-, 4-)4+

1+

7.275

4.4389

0

2+

0+

8Be+

10.27

2+

7.377 0+ 7.275

Levels according to TUNL

Why it isn’t all known

”Standard” approach :12C+ 12C*+’

E=9.8(4) MeV 0+E=11.46 MeV 2+

Texas A&M (2003)E=10.0(3) MeV 0+

E=9.9(3) MeV 2+

RCNP (2004)

13C 16O?16O

-decay approach

(11.5)

0,2+

0+

10.3

7.6542

12.71 1+

15.11 1+

7.275

(2+)

(2+)(15.3)

4.4389

0

2+

0+

0.972(3)

0.0125(5)

0.015(3)

0.0008(2)

0.94

6(6)

0.01

90(3

)0.

027(

4)

0.00

46(1

5)

0.0031(12)0.000044(15)

-decay measured:

•1950 by Alvarez 12N

•1957 by Fowler et al. 12B

•1963 by Wilkinson et al.12B/12N

•1966 by Schwalm 12B/12N

Before introduction of solid state detectors and multi-channel analyzers

A ghosts enters..

-decay

nucleus

€

"Breit − Wigner"=(Γ /2)2

(E − E res)2 + (Γ /2)2

€

Γ→ Γ(E)Amy Bartlett’s talk

Since 1963 no one has seen or heard of this ghost ?

One of first uses of solid state detectors and multi-channel analyzers

Illustrations from I. Gergely Ph.D. thesis

How to measure -decay?

Previous

12N/12B+X

ISOL

12N/12B

12N/12B+X

IGISOL @ JYFL

ISOLDE @ CERN

2001: 12N @ IGISOL2002: 12B @ ISOLDE

ISOL beams of 12N and 12B in Europe

CERNConseil Européen pour la Recherche Nucléaire

1GeV p

Experiments 2001-2002

12N/12B

Bergmann, Fynbo & Tengblad NIMA515 (2003) 657.Tengblad, Bergmann, Fraile, Fynbo & Walsh, NIMA525 (2004) 458.

Reduced dead-layer

The -decay of 12N

12N decay to 12C - 3 events

8Be s

1

The -decay of 12B

12B decay to 12C - 3 events

C. Diget PhD

Interpretation of results

Combined fit of 12B and 12N

1. Select 8Be 0+ channel2. Divide by different detection efficiency3. Divide by different -phase space4. Normalize

Result of combined fit

473 d.o.f.

Work performed by F.C. Barker

Relative contribution of “Ghost” and higher state varies with channel radius “a”(no absolute normalization)

4.36(17)4.2(2)

C. Diget et al. NPA760 (2005) 3.

E(2+) = 13.7(1) MeVΓ(2+) = 1.9(3) MeV

E(0+) = 10.73(3) MeVΓ(0+) = 1.72(2) MeV

New experiments

• What is the nature of the high energy state ?

• Decays via 8Be (2+) ?

• Measure branch to 7.65MeV state

Relative contribution of “ghost” and “10MeV” state ?

• Is the correction for detection efficiency correctly done ?

• Branching ratios and Gamow-Teller strength ?

• New ISOL experiment 2004• Experiment by implantation method 2006

0

4.4

7.6

10

0+

2+

0+

0+

3

12C

Ghost

New ISOL experiment 2004 12N & 12B @ IGISOL

Experiment 2004

12N/12BL.M. Fraile & J.Äystö, NIMA513 (2003) 287.

• Sensitive to 8Be 2+ channel

12N 200112N 2004

2004 data

C. Diget PhD

12B 200212B 2004

2004 data

B.R. ~ 3 . 10-6

C. Diget PhD

8Be 0+

8Be 2+

Select 8Be channel

Divide by different -phase space

Same detection eff.

Normalize

Compare 12N and 12B in new data

New - not in “old” data

As in “old” data

Spin-determination by 8Be (2+) ?12C(0 1 2) 8Be(2+)+ 3

~10% of breakupAlso Dalitz plot for correlations

2-2.5MeV 2-2.5MeV

7.5-8MeV7.5-8MeV

l=2l=0,2

KVI Groningen

• Measure branch to 7.65MeV state Relative contribution of “ghost” and “10MeV” state ?

• Is the correction for detection efficiency correctly done ?

• Branching ratios and Gamow-Teller strength ?

• What is the nature of the high energy state ?

0

4.4

7.6

10

0+

2+

0+

0+/2+

3

12C

Ghost

Method

12N/12B+X

12N/12B+X

ISOL

12N/12B

12N/12B

-Inv.kin.-Separator-Implantationp/d

12C/11B

p/d

12C/11B

Setup

• 4848 strip DSSD• 1616mm2 size• KU-Leuven (R.Raabe)

Data from the week before Easter

Data from the week before Easter

First results

0.53(3)

0.106(5)

2.95(15)10-4

1.26(6)

0.52(3)

0.119(6)

98.16(4) 96.20(10)

What have we learned ?

• There is no low energy 2+ state in 12C populated in the 12B and 12N -decays.

• The “Ghost” of the 7.6MeV state is needed to understand the “10 MeV” state, which has spin 0+.

• The “10 MeV” state mainly decays to the 8Be ground state and its “ghost”, but also to 8Be 2+.

• There is a new (2+) state above 14MeV in12C populated in the 12N (and 12B) -decays.

• The branching ratios are now much better known.

The 3-rate

C. Diget

Interpretation three peaks

8Be

3.1MeV

2+

0.93MeV 0+

Breakup of the 12.71 MeV state in 12C

Phys. Rev. C10 (1974) 975 Sov. J. Nucl. Phys. 52 (1990) 827

R-matrix based Sequential breakup

Hyper spherical Harmonics expansion.

Phys Rev C16 (1977) 529

Faddeev equationsIn momentum space

Sequentialwithout Interference

Sequentialwith Interference

Direct

Fynbo et al. PRL 91 (2003) 82502.

12.71 MeV 1+ state - breakup

B.Blank’s talk

data from April 2005New data March 2006

10B+3Hep+12C* + 8BeCMAM Madrid

Monte-CarloData

Collaborators• C. Aa. Diget, H. Fynbo, H. Jeppesen, S.G. Pedersen, K. Riisager, Department of Physics and Astronomy, Århus University, Denmark

• U.C. Bergmann, J. Cederkäll, L.M. Fraile, S. Franchoo, L. Weissman ISOLDE, EP-Division, CERN, Geneva, Switzerland

• B. Jonson, M. Meister, T. Nilsson, G. Nyman, K. Wilhelmsen, Fundamental Physics, Chalmers University of Technology, Gothenburg, Sweden• T. Eronen, W. Huang, J. Huikari, A. Jokinen, P. Jones, A. Kankainen, I. Moore, A. Nieminen, H. Penttilä, S. Rinta-Anttila, Y. Wang, J. Äystö, A. Saatamoinen, K. Perajärvi, Department of Physics, University of Jyväskylä, Finland

• B. Fulton, S.Fox

University of York, United Kingdom.

• M. Alcorta, R. Boutami, M.J.G. Borge, M. Madurga Flores, O. Tengblad, M. Turrion, Instituto Estructura de la Materia, CSIC, Madrid, Spain + CMAM operators

Thank you for your attention !• F.C. Barker Australian National University

• K. Jungmann, S. Brandenburg, H. Wilschut, P. Dendooven, A. Rogachevskiy, G. Onderwater, E. Traykov, M. Sohani, KVI, Groningen, The Netherlands

• R. Raabe, J. Bücherer, Piet van Duppen, Mark Huyse, IKS, Leuven, Belgium