The Nu-SNS proposal - ORNL Physics Division - Oak Ridge ...

neutrino-nucleus interactions on nearby heavy stable nuclei would be invaluable as a gauge
of the accuracy of nuclear structure and reaction predictions.
3.4 Supernova Neutrino Astronomy
Observations of supernova neutrino luminosities are only as accurate as knowledge of neutrino
interaction rates.
The twenty neutrino events detected by IMB and Kamiokande from SN1987A confirmed a
central tenant of supernova theory—that core collapse supernovae mark the formation of a protoneutron
star and release of the liberated binding energy in the form of neutrinos—and signaled
the birth of extra-Solar-System neutrino astronomy. For a Galactic supernova, thousands of
events will be seen by Super-Kamiokande [73], SNO [74], and KamLAND, which for the first
time will give us detailed neutrino “light curves” and provide volumes of information about the
deepest regions in the explosion. In turn, these light curves can be used to test and improve
supernova models, thereby improving predictions about the explosion and resultant
nucleosynthesis as well as the behavior of matter at super-nuclear densities. Moreover, from
these detailed neutrino light curves and an understanding of the effects of neutrino oscillations,
interesting insight could be gained about the density structure of the supernova progenitor. To
achieve this will require an accurate normalization of the neutrino flux in a supernova neutrino
detector and knowledge of the cross sections and by-products of neutrino interactions in the
detector material. For a galactic supernova, variants of the Baade-Wesselink method will likely
provide distances to the supernova with uncertainties of 10% or less [86,87], making 10% or
smaller uncertainties for the neutrino-nucleus cross sections desirable. From deuterium to lead, a
number of nuclei have been proposed and, in some cases, used as supernova detector materials.
In all cases, accurate neutrino-nucleus cross sections are essential and currently not
available. Among the neutrino-nucleus interactions most relevant for supernova neutrino
detection are neutrino interactions on 2 H, C, O, Fe and Pb.
While the occurrence of a Galactic supernova is a rare event, Beacom and Vagins [75] have
recently suggested a modification of Super-Kamiokande that would allow detection of the
diffuse supernova neutrino background, i.e., the flux from all supernovae that have occurred in
the history of the universe, at the rate of 2-6 events per year. In just a few years, the yield from
SN 1987A could be exceeded, allowing improved tests of numerical supernova models through
the measured flux and spectral shape. In addition, this modification should also allow neutrino
observations of pre-supernova massive stars within 1 kpc [76]. These possibilities open the
opportunity to expand our knowledge of supernovae (and their progenitors) on an ongoing basis
while we await a nearby event.
3.4.1 Oxygen
In water Cherenkov detectors like the Sudbury Neutrino Observatory (SNO) and Super-
Kamiokande, the charged-current reaction 16 O(ν e ,e - ) 16 F is the principal channel for electron
neutrino interactions for thermal sources in the range T ν ≥ 4-5 MeV. Its rate exceeds that of
neutrino-electron scattering by an order of magnitude for T ν ≥ 7-9 MeV [77]. Moreover, the
electron angular distribution is strongly correlated with the electron neutrino energy [78],
providing a way to measure the incident neutrino energy.
ν-SNS Proposal 30 8/4/2005