MINERvA and the Global Program in Neutrino Oscillations

The discovery of neutrino masses and mixings from observations of solar
and atmospheric neutrinos has set in motion an ambitious new program of
neutrino measurements. This program consists of three stages: (I)
precise measurements of leading flavor transitions (including MINOS at
FNAL), (II) establishing "sub-dominant" flavor transitions and
determining the neutrino mass hierarchy (including NOvA at FNAL) and
(III) searching for CP violation (future accelerator and detector
upgrades under discussion at FNAL and elsewhere). The scientific goals
of all three stages require measurements from long-baseline
accelerator-based neutrino beams with energies from 700MeV to several
GeV.

***MINERvA improves current and future oscillation experiments by
accurately measuring both the signal and background processes that these
experiments will observe.*** Two of the many processes MINERvA will
measure, along with the current state of our knowledge, are shown in the
figures below. While independent measurements of the quasi-elastic cross
section differ by 30-40%, MINERvA will provide an accurate measurement
at the 5% level across a broad energy range (Figure 1). Quasi-elastic
interactions provide at least half of the expected signal for future
oscillation experiments. For coherent neutrino-nucleus interactions,
which are among the least understood backgrounds in future oscillation
experiments, MINERvA will again provide unprecedented precision. Figure
2 shows the expected MINERvA precision for the charged current channel.
MINERvA's dramatic improvements in precision are largely due to the very
high flux and tunable energy of the NuMI beam as well as a choice of
detector technology that ensures good identification of exclusive
reactions with a multi-ton detector fiducial mass.

![](media/image1.jpeg){width="6.922916666666667in"
height="3.213888888888889in"}

Figure 1 shows the current world's data on the quasi-elastic cross
section (faded colors) and the expected accuracy of the MINERvA
measurement of the same channel (red points with error bars).

Figure 2 shows MINERvA's expected precision (in red) of the measurement
of coherent pion production cross sections on carbon.

![](media/image2.jpeg){width="3.8444444444444446in" height="3.3in"}

By making precise measurements of interactions, MINERvA helps NOvA to
accurately predict the background level and correctly translate an
excess above background to a measurement of sub-dominant oscillations.
By simultaneously studying interactions on carbon, iron, and lead,
MINERvA will be able to measure the neutrino-nuclear effects which must
be incorporated when translating from a measured energy in a detector to
neutrino energy. This is currently the dominant systematic uncertainty
in the MINOS mass splitting measurement, which depends on measuring an
oscillation probability as a function of neutrino energy.

The figure below shows the effective running time in years that would be
saved by the inclusion of the MINERvA neutrino-nucleus interaction
results to reduce the total systematic errors associated with the MINOS
(Stage I) and NOvA (Stage II) primary measurements. ***For the NOvA and
MINOS experiments, after 5 years of data taking for each, MINERvA will
provide the equivalent of an extra 6 and 1.5 years of running time,
respectively.***

![](media/image3.jpeg){width="4.55in" height="2.6666666666666665in"}Just
as MINERvA plays a larger role for NOvA than for MINOS because of NOvA's
higher requirements for statistical precision, the importance of the
MINERvA measurements will be larger still as the field moves into the
third stage of the program outlined above. For measurements of the
difference between neutrino and anti-neutrino oscillation probabilities,
the experiments will require running times (or detector masses or proton
beam exposures) that are an order of magnitude larger than the stage II
program. The ultimate goal of this stage is to shed light on the
possibility that the source of matter-antimatter asymmetry in today's
Universe can be found in the neutrino sector. **Enabling this goal
through a precise and thorough understanding of how neutrinos interact
in matter is the mission of MINERvA.**

Figure 3 shows the effective running time that would be saved by the
inclusion of MINERvA measurements as a function of runing time for the
MINOS and NOvA experiments.