Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Open Questions in Stellar Helium Burning Addressed With Real Photons   The outcome of helium burning is the formation of the two elements, carbon
and oxygen. The ratio of carbon to oxygen at the end of helium burning is
crucial for understanding the final fate of a progenitor star and the
nucleosynthesis of heavy elements in Type II supernova, with oxygen rich star
predicted to collapse to a black hole, and a carbon rich star to a neutron
star. Type Ia supernovae (SNeIa) are used as standard candles for measuring
cosmological distances with the use of an empirical light curve-luminosity
stretching factor. It is essential to understand helium burning that yields the
carbon/oxygen white dwarf and thus the initial stage of SNeIa. Since the triple
alpha-particle capture reaction, $^{8}Be(\alpha,\gamma)^{12}C$, the first
burning stage in helium burning, is well understood, one must extract the cross
section of the $^{12}C(\alpha,\gamma)^{16}O$ reaction at the Gamow window (300
keV) with high accuracy of approximately 10% or better. This goal has not been
achieved despite repeated strong statements that appeared in the literature. In
particular constraint from the beta-delayed alpha-particle emission of $^{16}N$
were shown to not sufficiently restrict the p-wave cross section factor; e.g. a
low value of $S_{E1}(300)$ can not be ruled out. Measurements at low energies,
are thus mandatory for determining the elusive cross section factor for the
$^{12}C(\alpha,\gamma)^{16}O$ reaction. We are constructing a Time Projection
Chamber (TPC) for use with high intensity photon beams extracted from the
HI$\gamma$S/TUNL facility at Duke University to study the
$^{16}O(\gamma,\alpha)^{12}C$ reaction, and thus the direct reaction at
energies as low as 0.7 MeV. This work is in progress.

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The categories of this paper are: eess
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The categories of this paper are: comp-gas
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The categories of this paper are: acc-phys
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The categories of this paper are: q-fin
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The categories of this paper are: q-alg
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The categories of this paper are: gr-qc
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The categories of this paper are: patt-sol
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The categories of this paper are: alg-geom
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The categories of this paper are: hep-th
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The categories of this paper are: q-bio
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The categories of this paper are: quant-ph
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The categories of this paper are: physics
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The categories of this paper are: chao-dyn
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The categories of this paper are: solv-int
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The categories of this paper are: hep-ex
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The categories of this paper are: bayes-an