Journal of Physics G: Nuclear and Particle Physics 46
, 08LT01 (2019)
ISSN: 0954-3899, SCI
Search for neutral-current induced single photon production at the ND280 near detector in T2K
N. T. Hong Van et al. (T2K Collaboration)
Neutrino neutral-current (NC) induced single photon production is a subleading order process for accelerator-based neutrino beam experiments including T2K. It is, however, an important process to understand because it is
a background for electron (anti)neutrino appearance oscillation experiments. Here, we performed the first search of this process below 1 GeV using the finegrained
detector at the T2K ND280 off-axis near detector. By reconstructing single photon kinematics from electron–positron pairs, we achieved 95% pure gamma ray sample from 5.738 X 10^20 protons-on-targets neutrino mode data.
We do not find positive evidence of NC induced single photon production in this sample. We set the model-dependent upper limit on the cross-section for
this process, at 0.114 X 10^-38 cm2 (90% C.L.) per nucleon, using the J-PARC off-axis neutrino beam with an average energy of ⟨En⟩ ~ 0.6 GeV. This is the first limit on this process below 1 GeV which is important for current and future oscillation experiments looking for electron neutrino appearance oscillation signals.
Keywords: T2K, neutrino, neutrino oscillation, neutrino interaction, Mini-BooNE, CP violation