The T2K fine-grained detectors

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376

We report on measurements of neutrino oscillation using data from the T2K long-baseline neutrino experiment collected between 2010 and 2013. In an analysis of muon neutrino disappearance alone, we find the following estimates and 68% confidence intervals for the two possible mass hierarchies: normal hierarchy∶ sin 2 θ 23 ¼ 0.514 þ0.055 −0.056 and Δm 2 32 ¼ ð2.51 AE 0.10Þ × 10 −3 eV 2 =c 4 and inverted hierarchy∶ sin 2 θ 23 ¼ 0.511 AE 0.055 and Δm 2 13 ¼ ð2.48 AE 0.10Þ × 10 −3 eV 2 =c 4 . The analysis accounts for multinucleon mechanisms in neutrino interactions which were found to introduce negligible bias. We describe our first analyses that combine measurements of muon neutrino disappearance and electron neutrino appearance to estimate four oscillation parameters, jΔm 2 j, sin 2 θ 23 , sin 2 θ 13 , δ CP , and the mass hierarchy. Frequentist and Bayesian intervals are presented for combinations of these parameters, with and without including recent reactor measurements. At 90% confidence level and including reactor measurements, we exclude the region δ CP ¼ ½0.15; 0.83 π for normal hierarchy and δ CP ¼ ½−0.08; 1.09 π for inverted hierarchy. The T2K and reactor data weakly favor the normal hierarchy with a Bayes factor of 2.2. The most probable values and 68% one-dimensional credible intervals for the other oscillation parameters, when reactor data are included, are sin 2 θ 23 ¼ 0.528 þ0.055 −0.038 and jΔm 2 32 j ¼ ð2.51 AE 0.11Þ × 10 −3 eV 2 =c 4 .

Section: Nd280 Detectormentioning

confidence: 99%

Section: Nd280 ν μ Tracker Analysismentioning

confidence: 99%

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Measurements of neutrino oscillation in appearance and disappearance channels by the T2K experiment with6.6×1020protons on target

Abe¹,

Adam²,

Aihara³

et al. 2015

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280

376

“…The ND280 Tracker region contains two fine-grained detectors (FGDs [32]) which are used as the neutrino interaction target, sandwiched between three gaseous time projection chambers (TPCs [33]) which are used to track charged particles. The most upstream FGD (FGD1) primarily consists of polystyrene scintillator bars with layers oriented alternately in the x and y directions allowing 3D tracking of charged particles.…”

Section: Near Detectormentioning

confidence: 99%

First measurement of the muon neutrino charged current single pion production cross section on water with the T2K near detector

Abe¹,

Drapier²,

Huang³

et al. 2017

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The T2K off-axis near detector, ND280, is used to make the first differential cross section measurements of muon neutrino charged current single positive pion production on a water target at energies ∼0.8 GeV.The differential measurements are presented as a function of the muon and pion kinematics, in the restricted phase space defined by p π þ > 200 MeV=c, p μ > 200 MeV=c, cosðθ π þ Þ > 0.3 and cosðθ μ Þ > 0.3. The total flux integrated ν μ charged current single positive pion production cross section on water in the restricted phase space is measured to be hσi ϕ ¼ 4.25 AE 0.48ðstatÞ AE 1.56ðsystÞ × 10 −40 cm 2 =nucleon. The total cross section is consistent with the NEUT prediction (5.03 × 10 −40 cm 2 =nucleon) and 2σ lower than the GENIE prediction (7.68 × 10 −40 cm 2 =nucleon). The differential cross sections are in good agreement with the NEUT generator. The GENIE simulation reproduces well the shapes of the distributions, but overestimates the overall cross section normalization.

“…For this analysis neutrino charged current (CC) interactions in the fine grained detectors (FGDs) [8] are selected. The combination of the particle identification (PID) capabilities of three time projection chambers (TPC) [9] and a set of electromagnetic calorimeters (ECals) [10] is used to distinguish electrons from muons, allowing the selection of a clean sample of ν e CC interactions with a purity of about 65%.…”

Section: Introductionmentioning

confidence: 99%

Measurement of the intrinsic electron neutrino component in the T2K neutrino beam with the ND280 detector

Abe¹,

Adam²,

Aihara³

et al. 2014

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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 AE 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 AE 0.30 and 1.10 AE 0.14, respectively.