Appearance Oscillation Experiments Research Articles

Search for neutral-current induced single photon production at the ND280 near detector in T2K

Neutrino neutral-current (NC) induced single photon production is a sub-leading 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 fine-grained 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 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 cm2 (90% C.L.) per nucleon, using the J-PARC off-axis neutrino beam with an average energy of 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.

Single neutral pion production by charged-current [formula omitted] interactions on hydrocarbon at [formula omitted

Single neutral pion production via muon antineutrino charged-current interactions in plastic scintillator (CH) is studied using the MINERvA detector exposed to the NuMI low-energy, wideband antineutrino beam at Fermilab. Measurement of this process constrains models of neutral pion production in nuclei, which is important because the neutral-current analog is a background for ν¯e appearance oscillation experiments. The differential cross sections for π0 momentum and production angle, for events with a single observed π0 and no charged pions, are presented and compared to model predictions. These results comprise the first measurement of the π0 kinematics for this process.

Review of electron neutrino appearance oscillation experiments

A review of νe appearance oscillation experiments is presented. The measurement of the appearance signal is of particular interest because this mode is sensitive to both θ13, δ CP and other mixing parameters. Using the value of θ13 measured by reactor neutrino experiments (disappearance studies) present and next generation appearance experiments can explore CP violation.

Photon emission in neutral-current interactions at intermediate energies

Neutral current photon emission reactions with nucleons and nuclei are studied. These processes are important backgrounds for nu_mu to nu_e (bar(nu)_mu to bar(nu)_e) appearance oscillation experiments where electromagnetic showers instigated by electrons (positrons) and photons are not distinguishable. At intermediate energies, these reactions are dominated by the weak excitation of the Delta(1232) resonance and its subsequent decay into Ngamma There are also non-resonant contributions that, close to threshold, are fully determined by the effective chiral Lagrangian of strong interactions. In addition, we have also included mechanisms mediated by nucleon excitations (N*) from the second resonance region above the Delta(1232). From these states, the contribution of the D13 N*(1520) turns out to be sizable for (anti)neutrino energies above 1.5 GeV. We have extended the model to nuclear targets taking, into account Pauli blocking, Fermi motion and the in-medium Delta resonance broadening. We present our predictions for both the incoherent and coherent channels, showing the relevance of the nuclear corrections. We also discuss the target mass dependence of the cross sections. This study is important in order to reduce systematic effects in neutrino oscillation experiments.

Review of electron neutrino appearance oscillation experiments

A review of νe appearance oscillation experiments is presented. The measurement of the appearance signal is of particular interest because this mode is sensitive to both θ13, δCP and other mixing parameters. Using the value of θ13 measured by reactor neutrino experiments (disappearance studies) present and next generation appearance experiments can explore CP violation.