A Search for Neutrino Induced Coherent NC(π0) Production in the MINOS Near Detector.
Abstract: The production of single, highly forward
π0 mesons by NC coherent neutrino-nucleus interactions
(νμ + N →
νμ + N + π0) is a
process which probes fundamental aspects of the weak interaction. This reaction may also
pose as a limiting background for long baseline searches for
ν&mu → νe
oscillations if the neutrino mixing angle θ13 is very
small. The high-statistics sample of neutrin... read moreo interactions recorded by the MINOS Near
Detector provides an opportunity to measure the cross section of this coherent reaction on
a relatively large-A nucleus at an average Enu; = 4.9 GeV. A major
challenge for this measurement is the isolation of forward-going electromagnetic (EM)
showers produced by the relatively rare coherent NC(π0)
process amidst an abundant rate of incoherently produced EM showers. The backgrounds arise
from single π0 dominated NC events and also from
quasi-elastic-like CC scattering of electron neutrinos. In this Thesis the theory of
coherent interactions is summarized, and previous measurements of the coherent
NC(π0 ) cross section are reviewed. Then, methods for
selecting a sample of coherent NC(π0) like events,
extracting the coherent NC(π0) event rate from that
sample, estimating the analysis uncertainties, and calculating a cross section, are
presented. A signal for neutrino-induced NC(π0)
production is observed in the relevant kinematic regime as an excess of events of three
standard deviations above background. The reaction cross section, averaged over an energy
window of 2.4 ≤ Eν ≤ 9.0 GeV is determined to
cm2 /nucleus. The result is the ﬁrst evidence
obtained for neutrino-nucleus coherent NC(π0) scattering
on iron, and is the ﬁrst measurement on an average nuclear target above A = 30.
The cross section measurement is in agreement with NEUGEN3 implementation of the model by
Rein and Sehgal which is motivated by the PCAC hypothesis.
Thesis (Ph.D.)--Tufts University, 2011.
Submitted to the Dept. of Physics.
Advisor: W Mann.
Committee: Hugh Gallagher, Gary Goldstein, Jack Schneps, and Jorge Morfin.
Keywords: Physics, and Particle Physics.read less