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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