Center for Nuclear Study,

Study of Astrophysically Important States in ��� Si through Elastic Scattering
with CRIB
J. Chen a , A. Chen a , G. Amadio b , S. Cherubini h , M. La .Cognata h , H. Fujikawa b , S. Hayakawa b ,
N. Iwasaj , J. J. Heb1, D. Kahla , L. H. Khiemb , S. Kubonob , Y. Kurihawab , Y. K. Kwonc ,
J Y. Moonc , M. Niikurab , S. Nishimuraf , A. Odaharae , J. Pearsona , R. Pizzoneh , A. Saitob ,
C. Signorinii , T. Teranishid , Y. Toganog , Y. Wakabayashib , H. Yamaguchib a Department of Physics and Astronomy, McMaster University, Canada
b Center for Nuclear Study, Graduate School of Science, University of Tokyo, Japan
cDepartment of Physics, Chung-Ang University, South Korea
dDepartment of Physics, Kyushu University, Japan
eDepartment of Physics, Nishinippon Institute of Technology, Japan
fRIKEN(The Institute of Physical and Chemical Research)
gDepartment of Physics, Rikkyo University, Japan
hDepartment of Physics, University of Catania and INFN, Italy
iDepartment of Physics, University of Padova and INFN, Italy
jDepartment of Physics, Tohoku University, Japan
1. Introduction
This experiment is for data collection of the elastic scattering
��� Al+ � following up the test experiment performed at
CRIB before [1] and it aims to obtain structure information
of the levels in ��� Si within the Gamow window at nova temperature
to reduce the large uncertainty in the ��� Al( � ,� )��� Si
reaction rate [2, 3, 4, 5]. A thick target method [6, 7] was
used to scan the center-of-mass energy from 0 to 3.38 MeV
with the secondary beam of 3.52 MeV/nucleon ��� Al impinging
on the 6.58 mg/cm� CH � target, which corresponds
to a range of excited states from 5.515 MeV (��� Al+ � threshold)
to about 8.9 MeV.
The secondary ��� Al beam was produced by the reaction
� H(��� Mg,n)��� Al, with the purity of about 50% and intensity
of about 5� 10� pps on target. The particle identification
(PID) for the secondary beam was provided by two PPACs
while PID for the scattered protons by � E-E telescopes as
well as the TOF (time-of-flight) method.
cross-section (a.u.)
Cross Section from 0 degree telescope
0.035
0.03
0.025
0.02
0.015
0.01
0.005
0
1400 1600 1800 2000 2200 2400 2600 2800 3000 3200 3400
Ecm (keV)
Figure 1. Proton spectrum at � � ��� = 0 � in the center of mass frame
with energy loss corrected and background subtracted.
present address:School of Physics, University of Edinburgh, Mayfield
�
Road, EH9 3JZ, Edinburgh, UK
19
2. Data Analysis
When using the thick target method, the energy loss of
the scattered proton traveling through the remaining part of
the target must be taken into account. The total yields of
background protons of different energies from a carbon target
are normalized by the ratio of target thickness per energy
bin and the ratio of the total number of beam events.
Figure 1 shows a final proton spectrum after correcting the
energy loss and subtracting the background protons.
cross-section (a.u.)
Cross Section from 0 degree telescope
0.025
0.02
0.015
0.01
0.005
0
hist_sigma
Entries 128
Mean 1611
RMS 100.1
1450 1500 1550 1600
Ecm (keV)
1650 1700 1750
Figure 2. Breit-Wigner fit for the peak at � ��� =1697keV, corresponding
to the excited state � � =7156keV, ��� =� � . [5]
For preliminary purpose to find the resonant energies, a
Breit-Wiger fit was applied for each single peak in the proton
spectrum. Figure 2, 3, 4 are some sample fits. In the fit,
the dash line represents the coulomb part, the dash-dot line
coulomb-resonance interference and the dot line the pure
resonant part.
An advanced R-Matrix [9] fit for the excitation function
is being performed to extract physical parameters such as
energy levels and proton widths. The analysis is still in
progress.