Nuclear Physics in Astrophysics - V

Nuclear Physics in Astrophysics - V
Contribution ID : 50
Astrophysical factor for the
4He(3He,g)7Be reaction measured at
central mass energies of 900-2800 keV
Tuesday 05 Apr 2011 at 18:10 (00h00')
Content :
The rate of the 4He(3He, g)7Be reaction plays an important role in determining the
primordial 7Li abundance from the consequent beta disintegration of 7Be.
Furthermore, the high energy solar neutrino flux depends strongly on the 8B abundance
due to 7Be proton capture. Reaction cross sections of astrophysical interest drop
rapidly with decreasing energy making a direct measurement at the energy of interest,
i.e. at the Gamow peak (around 22 keV), impossible. The astrophysical S(E) factor is
defined as:
σ=1/E•S(E)•e^(-2πη(E))
where sigma is cross section at energy E and eta is the sommerfield parameter. The
S(E) gives the nuclear dependence of the cross section and the theoretical models for
7Li abundance and solar neutrino calculations use the extrapolated experimental value
of the S34(E) at zero energy. Presently, there are serious discrepancies between the
existing measurements carried out using different methods, particularly in the energy
range of 2 MeV to 3 MeV, where only data from Ref. [1] in 1963 and Ref [2] in 2009
exist. This results in an error contribution that is largest among the nuclear inputs
to the solar neutrino calculations.
New independent measurements would help to constrain the S34(E) factor at
high energies and thus improve the extrapolation to the S34(0). We report here on an
experiment performed at the Centro de Microanálisis de Materiales (CMAM) [3], a 5
MeV Tandem accelerator in Madrid using the activation method utilizing the same
experimental setup as was used at Weizmann Institute[4].
The 3He beam with laboratory energies between 2.3 MeV and 5.3MeV was impinging on a
4He gas target of 55 torr pressure. The recoiling 7Be atoms were collected onto Cu
catchers, and the subsequent beta delayed gamma radiation was measured off-line using
a low-background HPGe gamma detection station [5].
Results obtained in the experiment for the S34(E) values and an analysis with
calculations using a new approach will be presented. These results will help to
resolve the discrepancies between previous measurements.
[1] P. Parker and R. Kavanagh, Phys. Rev. 131, 2578 (1963).
[2] A. Di Leva et al. Phys. Rev. Lett. 102, 232502 (2009).
[3] http://www.cmam.uam.es/
[4]B. S. Nara Singh et al, Phys. Rev. Lett. 93, 262503 (2004)
[5] Soreq Research Centre, Yavne, Israel
Primary authors : Mr. CARMONA GALLARDO, Mariano (Instituto de Estructura de la Materia
(CSIC))
Co-authors : Prof. TENGBLAD, Olof Erik (Instituto de Estructura de la Materia (CSIC)) ; Mr.
CUBERO CAMPOS, Mario (Instituto de Estructura de la Materia (CSIC)) ; Mr. CRUZ DE
LA TORRE, Carlos (Instituto de Estructura de la Materia (CSIC)) ; Mr. DOMINGUEZ
REYES, Ricardo (Instituto de Estructura de la Materia (CSIC)) ; Dr. FYNBO, Hans (Aarhus
University) ; Dr. GORDILLO, Nuria (Centro de Microanálisis de Materiales) ; Dr. KUMAR,
Vivek (Weizmann Institute of Sicence) ; Dr. MAIRA VIDAL, Arantza (Centro de
Microanálisis de Materiales) ; Dr. MUÑOZ MARTIN, Angel (Centro de Microanálisis de
Materiales) ; Mr. PEREA MARTÍNEZ, Ángel (Instituto de Estructura de la Materia (CSIC)) ;
Dr. NARA SINGH, B. S. (University of York) ; Prof. HASS, Michael (Weizmann Institute of
Sicence) ; Dr. NIR-EL, Y. (Soreq Research Center) ; Dr. HAQUIN, G. (Soreq Research
Center) ; Dr. YUNGREIS, Z. (Soreq Research Center) ; Dr. ALCORTA, Martín (Argonne
National Laboratory) ; Prof. GARCÍA BORGE, Mª José (Instituto de Estructura de la
Materia (CSIC)) ; Mr. BRIZ MONAGO, José Antonio (Instituto de Estructura de la Materia
(CSIC))
Presenter : Mr. CARMONA GALLARDO, Mariano (Instituto de Estructura de la Materia (CSIC))
Session classification : Poster Session
Track classification : --not yet classified-Type : Poster