  We propose the addition of scintillator to the existing MiniBooNE detector to
allow a test of the neutral-current/charged-current (NC/CC) nature of the
MiniBooNE low-energy excess. Scintillator will enable the reconstruction of 2.2
MeV $\gamma$s from neutron-capture on protons following neutrino interactions.
Low-energy CC interactions where the oscillation excess is observed should have
associated neutrons with less than a 10% probability. This is in contrast to
the NC backgrounds that should have associated neutrons in approximately 50% of
events. We will measure these neutron fractions with $\nu_\mu$ CC and NC events
to eliminate that systematic uncertainty. This neutron-fraction measurement
requires $6.5\times10^{20}$ protons on target delivered to MiniBooNE with
scintillator added in order to increase the significance of an oscillation
excess to over $5\sigma$.
  This new phase of MiniBooNE will also enable additional important studies
such as the spin structure of nucleon ($\Delta s$) via NC elastic scattering, a
low-energy measurement of the neutrino flux via $\numu ^{12}C \rightarrow
\mu^{-} ^{12}N_\textrm{g.s.}$ scattering, and a test of the quasielastic
assumption in neutrino energy reconstruction. These topics will yield
important, highly-cited results over the next 5 years for a modest cost, and
will help to train Ph.D. students and postdocs. This enterprise offers
complementary information to that from the upcoming liquid Argon based
MicroBooNE experiment. In addition, MicroBooNE is scheduled to receive
neutrinos in early 2014, and there is minimal additional cost to also deliver
beam to MiniBooNE.

High Energy Physics - Experiment