A search for neutrino-induced single photons and measurement of oscillation analysis systematic errors with electron and anti-electron neutrino selections, using the o -axis near detector of the Tokai to Kamioka experiment
Abstract
This thesis describes the search for neutrino-production of single photons using the o -
axis near detector at 280 metres (ND280) of the T2K experiment. A photon selection is
used to perform the searches using the rst Fine Grained Detector (FGD1) of the ND280.
The thesis also highlights the importance of systematic uncertainties in the analysis, since
the selection is background dominated. After careful characterisation of the systematic
uncertainties and estimation of the e ciency, it is concluded that, with the selected 39
data events and the expected background of 45 events, the limit for neutrino-induced
single photons, at T2K energies, is 0:0903 x 10-38cm2=nucleon. This result can be com-
pared with the expected limit of 0:1068 x 10-38cm2=nucleon. Using ND280's neutrino
energy distribution (peaked at 600 MeV), NEUT predicts a
ux-averaged cross section of
0:000239 x 10-38cm2=nucleon.
A t to the muon and electron (anti-) neutrinos selections in the ND280 was per-
formed. The aim of this analysis is to use a data-driven method to constrain the electron
(anti-) neutrinos background events at SK, the far detector and electron neutrino cross
section parameters for oscillation analyses. These are fundamental inputs in the context
of the searches for Charge-Parity (CP) violation in the neutrino sector. After a t to
the nominal Monte Carlo was realised, the electron neutrino and anti-neutrino cross sec-
tion normalisation uncertainties are found to be 7:6% and 19:3%, repectively. Although
these numbers are much higher than the assumed 3% uncertainty of all the CP violation
searches performed at T2K up to now, the difference in the CP log-likelihood is found to
be acceptable as the one sigma contours are not very di erent and the exclusion of the
CP = 0 is roughly the same.
Authors
Lasorak, PierreCollections
- Theses [4137]