"The Structure of 12C and Stellar Helium Burning ∗"
Moshe Gai, Laboratory for Nuclear Science at Avery Point University of Connecticut, 1084 Shennecossett Rd, Grot
(id #51)
Seminar: NoPoster: No
Invited talk: Yes
Moshe Gai for the UConn-Yale-Duke-Weizmann-PTB-UCL Collaboration:
The observation of the second 2+ state in 12C, predicted to be between 9-10 MeV, is a subject of continuing interest and debate. Such a state may reveal the structure of the Hoyle 0+ state at 7.6542 MeV in 12C [1]. On one hand there has been a long standing search for the proposed 2+ member of the rotational band built on the (deformed) Hoyle state and on the other hand within the context of the small N limit of Bose-Einstein alpha-condensate [2] such a band is not predicted. An inclusion of the predicted 2+_2 at 9.11 MeV with a Gamma Width = 0.2 eV increase (by up to a factor of 15) the production of 12C during stellar helium burning at high temperatures (above 3 GK) [3]. Such a dramatic deviation (at high temperatures) will be the first hint of a significant deviation from the prediction of carbon formation based on the Hoyle state alone.
The search for the 2+_2 via the beta decay of 12B and 12N yielded null result [4] with a significantly small upper limit on the non-observed bete-deacy branching-ratio to a 2+ state between 9.0 and 10.0 MeV (with very large log ft value). Alpha scattering, 12C(a ,a ′) experiment [5] and more recently proton scattering 12C(p,p′) data [6], reveal a broad 2+ state (Width = 600 keV) at 9.6 MeV.
We have used an Optical Readout Time Projection Chamber (O-TPC) detector [7] placed at the gamma beam at the HIgS facility of the TUNL at Duke University [8] to study the 12C(g,3a) reaction. The detector system and the HIgS facility will be discussed. Data taken at E = 9.363, 9.556 and 9.771 MeV reveal direct evidence for the 2+_2 in 12C with angular distributions of a pure E2 transition. Our data also allow us to measure the gamma-width of this state. Data analysis is in progress and up to date results will be discussed.
* Work Supported by the Yale-Weizmann Collaboration of the ACWIS, N.Y., and USDOE Grant No DE-FG02-94ER40870, and DE-FG02-97ER41033.
1. M. Chernykh et al.; Phys. Rev. Lett. 98(2007)032501.
2. Y. Funaki et al.; Phys. Rev. C 80(2009)064326 and references therein.
3. C. Angulo et al.; Nucl. Phys. A656(1999)3.
4. S. Hyldegaard et al.; Phys. Let. B678(2009)459 and references therein.
5. M. Itoh et al.; Nucl. Phys. A738(2004)268.
6. M. Freer et al.; Phys. Rev. C 80(2009)041303(R).
7. M. Gai, M.W. Ahmed, A. Breskin, B. Bromberger, R. Chechik, V. Dangendorf, Th. Delbar, R.H. France III, S.S. Henshaw, C.R. Howell, T.J. Kading, P.P. Martel, J.E.R. McDonald, P.-N. Seo, S.C. Stave, K. Tittelmeier, H.R.Weller, A.H. Young, andW.R. Zimmerman;
to be published.
8. H.R. Weller, M.W. Ahmed, H. Gao, W. Tornow, Y. Wu, M. Gai, R. Miskimen;
Prog. Part. Nucl. Phys. 62(2009)257.
The observation of the second 2+ state in 12C, predicted to be between 9-10 MeV, is a subject of continuing interest and debate. Such a state may reveal the structure of the Hoyle 0+ state at 7.6542 MeV in 12C [1]. On one hand there has been a long standing search for the proposed 2+ member of the rotational band built on the (deformed) Hoyle state and on the other hand within the context of the small N limit of Bose-Einstein alpha-condensate [2] such a band is not predicted. An inclusion of the predicted 2+_2 at 9.11 MeV with a Gamma Width = 0.2 eV increase (by up to a factor of 15) the production of 12C during stellar helium burning at high temperatures (above 3 GK) [3]. Such a dramatic deviation (at high temperatures) will be the first hint of a significant deviation from the prediction of carbon formation based on the Hoyle state alone.
The search for the 2+_2 via the beta decay of 12B and 12N yielded null result [4] with a significantly small upper limit on the non-observed bete-deacy branching-ratio to a 2+ state between 9.0 and 10.0 MeV (with very large log ft value). Alpha scattering, 12C(a ,a ′) experiment [5] and more recently proton scattering 12C(p,p′) data [6], reveal a broad 2+ state (Width = 600 keV) at 9.6 MeV.
We have used an Optical Readout Time Projection Chamber (O-TPC) detector [7] placed at the gamma beam at the HIgS facility of the TUNL at Duke University [8] to study the 12C(g,3a) reaction. The detector system and the HIgS facility will be discussed. Data taken at E = 9.363, 9.556 and 9.771 MeV reveal direct evidence for the 2+_2 in 12C with angular distributions of a pure E2 transition. Our data also allow us to measure the gamma-width of this state. Data analysis is in progress and up to date results will be discussed.
* Work Supported by the Yale-Weizmann Collaboration of the ACWIS, N.Y., and USDOE Grant No DE-FG02-94ER40870, and DE-FG02-97ER41033.
1. M. Chernykh et al.; Phys. Rev. Lett. 98(2007)032501.
2. Y. Funaki et al.; Phys. Rev. C 80(2009)064326 and references therein.
3. C. Angulo et al.; Nucl. Phys. A656(1999)3.
4. S. Hyldegaard et al.; Phys. Let. B678(2009)459 and references therein.
5. M. Itoh et al.; Nucl. Phys. A738(2004)268.
6. M. Freer et al.; Phys. Rev. C 80(2009)041303(R).
7. M. Gai, M.W. Ahmed, A. Breskin, B. Bromberger, R. Chechik, V. Dangendorf, Th. Delbar, R.H. France III, S.S. Henshaw, C.R. Howell, T.J. Kading, P.P. Martel, J.E.R. McDonald, P.-N. Seo, S.C. Stave, K. Tittelmeier, H.R.Weller, A.H. Young, andW.R. Zimmerman;
to be published.
8. H.R. Weller, M.W. Ahmed, H. Gao, W. Tornow, Y. Wu, M. Gai, R. Miskimen;
Prog. Part. Nucl. Phys. 62(2009)257.
