No Arabic abstract
The T2K experiment has reported the first observation of the appearance of electron neutrinos in a muon neutrino beam. The main and irreducible background to the appearance signal comes from the presence in the neutrino beam of a small intrinsic component of electron neutrinos originating from muon and kaon decays. In T2K, this component is expected to represent 1.2% of the total neutrino flux. A measurement of this component using the near detector (ND280), located 280 m from the target, is presented. The charged current interactions of electron neutrinos are selected by combining the particle identification capabilities of both the time projection chambers and electromagnetic calorimeters of ND280. The measured ratio between the observed electron neutrino beam component and the prediction is 1.01+-0.10 providing a direct confirmation of the neutrino fluxes and neutrino cross section modeling used for T2K neutrino oscillation analyses. Electron neutrinos coming from muons and kaons decay are also separately measured, resulting in a ratio with respect to the prediction of 0.68+-0.30 and 1.10+-0.14, respectively.
This paper presents a measurement of the charged current interaction rate of the electron neutrino beam component of the beam above $1.5$~GeV using the large fiducial mass of the T2K $pi^0$ detector. The predominant poriton of the $ u_e$ flux ($sim$85 %) at these energies comes from kaon decays. The measured ratio of the observed beam interaction rate to the predicted rate in the detector with water targets filled is 0.89 $pm$ 0.08 (stat.) $pm$ 0.11 (sys.), and with the water targets emptied is 0.90 $pm$ 0.09 (stat.) $pm$ 0.13 (sys.). The ratio obtained for the interactions on water only from an event subtraction method is 0.87 $pm$ 0.33 (stat.) $pm$ 0.21 (sys.). This is the first measurement of the interaction rate of electron neutrinos on water, which is particularly of interest to experiments with water Cherenkov detectors.
The electron (anti-)neutrino component of the T2K neutrino beam constitutes the largest background in the measurement of electron (anti-)neutrino appearance at the far detector. The electron neutrino scattering is measured directly with the T2K off-axis near detector, ND280. The selection of the electron (anti-)neutrino events in the plastic scintillator target from both neutrino and anti-neutrino mode beams is discussed in this paper. The flux integrated single differential charged-current inclusive electron (anti-)neutrino cross-sections, $dsigma/dp$ and $dsigma/dcos(theta)$, and the total cross-sections in a limited phase-space in momentum and scattering angle ($p > 300$ MeV/c and $theta leq 45^{circ}$) are measured using a binned maximum likelihood fit and compared to the neutrino Monte Carlo generator predictions, resulting in good agreement.
Two independent methods are employed to measure the neutrino flux of the anti-neutrino-mode beam observed by the MiniBooNE detector. The first method compares data to simulated event rates in a high purity $ umu$ induced charged-current single $pip$ (CC1$pip$) sample while the second exploits the difference between the angular distributions of muons created in $ umu$ and $ umub$ charged-current quasi-elastic (CCQE) interactions. The results from both analyses indicate the prediction of the neutrino flux component of the pre-dominately anti-neutrino beam is over-estimated - the CC1$pip$ analysis indicates the predicted $ umu$ flux should be scaled by $0.76 pm 0.11$, while the CCQE angular fit yields $0.65 pm 0.23$. The energy spectrum of the flux prediction is checked by repeating the analyses in bins of reconstructed neutrino energy, and the results show that the spectral shape is well modeled. These analyses are a demonstration of techniques for measuring the neutrino contamination of anti-neutrino beams observed by future non-magnetized detectors.
We report the measurements of single and double differential cross section of muon neutrino charged-current interactions on carbon with a single positively charged pion in the final state at the T2K off-axis near detector using $5.56times10^{20}$ protons on target. The analysis uses data control samples for the background subtraction and the cross section signal, defined as a single negatively charged muon and a single positively charged pion exiting from the target nucleus, is extracted using an unfolding method. The model dependent cross section, integrated over the T2K off-axis neutrino beam spectrum peaking at $0.6$~GeV, is measured to be $sigma = (11.76 pm 0.44 text{(stat)} pm 2.39 text{(syst)}) times 10^{-40} text{cm}^2$~$text{nucleon}^{-1}$. Various differential cross sections are measured, including the first measurement of the Adler angles for single charged pion production in neutrino interactions with heavy nuclei target.
The T2K off-axis near detector, ND280, is used to make the first differential cross-section measurements of electron neutrino charged current interactions at energies ~1 GeV as a function of electron momentum, electron scattering angle and four-momentum transfer of the interaction. The total flux-averaged $ u_e$ charged current cross-section on carbon is measured to be $1.11pm0.09~(stat)pm0.18~(syst)times10^{-38} cm^2/nucleon$. The differential and total cross-section measurements agree with the predictions of two leading neutrino interaction generators, NEUT and GENIE. The NEUT prediction is $1.23times10^{-38} cm^2/nucleon$ and the GENIE prediction is $1.08times10^{-38} cm^2/nucleon$. The total $ u_e$ charged current cross-section result is also in agreement with data from the Gargamelle experiment.