This paper reports on the search for heavy neutrinos with masses in the range 140<MN<493 MeV/c2 using the off-axis near detector ND280 of the T2K experiment. These particles can be produced from kaon ...decays in the standard neutrino beam and then subsequently decay in ND280. The decay modes under consideration are N→ℓα±π∓ and N→ℓα+ℓβ−ν(−)(α,β=e,μ). A search for such events has been made using the Time Projection Chambers of ND280, where the background has been reduced to less than two events in the current dataset in all channels. No excess has been observed in the signal region. A combined Bayesian statistical approach has been applied to extract upper limits on the mixing elements of heavy neutrinos to electron-, muon- and tau- flavored currents (Ue2, Uμ2, Uτ2) as a function of the heavy neutrino mass, e.g., Ue2<10−9 at 90% C.L. for a mass of 390 MeV/c2. These constraints are competitive with previous experiments.
We perform a search for light sterile neutrinos using the data from the T2K far detector at a baseline of 295 km, with an exposure of 14.7(7.6)×1020 protons on target in neutrino (antineutrino) mode. ...A selection of neutral-current interaction samples is also used to enhance the sensitivity to sterile mixing. No evidence of sterile neutrino mixing in the 3+1 model was found from a simultaneous fit to the charged-current muon, electron and neutral-current neutrino samples. We set the most stringent limit on the sterile oscillation amplitude sin2θ24 for the sterile neutrino mass splitting Δm412<3×10−3 eV2/c4.
Neutrino- and antineutrino-oxygen neutral-current quasielasticlike interactions are measured at Super-Kamiokande using nuclear deexcitation γ rays to identify signal-like interactions in data from a ...14.94(16.35)×1020 protons-on-target exposure of the T2K neutrino (antineutrino) beam. The measured flux-averaged cross sections on oxygen nuclei are ⟨σν−NCQE⟩=1.70±0.17(stat.)−0.38+0.51(syst.)×10−38 cm2/oxygen with a flux-averaged energy of 0.82 GeV and ⟨σν¯−NCQE⟩=0.98±0.16(stat.)−0.19+0.26(syst.)×10−38 cm2/oxygen with a flux-averaged energy of 0.68 GeV, for neutrinos and antineutrinos, respectively. These results are the most precise to date, and the antineutrino result is the first cross section measurement of this channel. They are compared with various theoretical predictions. The impact on evaluation of backgrounds to searches for supernova relic neutrinos at present and future water Cherenkov detectors is also discussed.
The second phase of the T2K experiment is expected to start data taking in autumn 2022. An upgrade of the Near Detector (ND280) is under development and includes the construction of two new Time ...Projection Chambers called High-Angle TPC (HA-TPC). The two endplates of these TPCs will be paved with eight Micromegas type charge readout modules. The Micromegas detector charge amplification structure uses a resistive anode to spread the charges over several pads to improve the space point resolution. This innovative technique is combined with the bulk-Micromegas technology to compose the “Encapsulated Resistive Anode Micromegas” detector. A prototype has been designed, built and exposed to an electron beam at the DESY II test beam facility.
The data have been used to characterize the charge spreading and to produce its map. Spatial resolution better than 600 μm and energy resolution better than 9% are obtained for all incident angles. These performances fulfil the requirements for the upgrade of the ND280 TPC.
We present studies of proton fluxes in the T10 beamline at CERN. A prototype high pressure gas time projection chamber (TPC) was exposed to the beam of protons and other particles, using the 0.8 ...GeV/c momentum setting in T10, in order to make cross section measurements of low energy protons in argon. To explore the energy region comparable to hadrons produced by GeV-scale neutrino interactions at oscillation experiments, i.e., near 0.1 GeV of kinetic energy, methods of moderating the T10 beam were employed: the dual technique of moderating the beam with acrylic blocks and measuring scattered protons off the beam axis was used to decrease the kinetic energy of incident protons, as well as change the proton/minimum ionising particle (MIP) composition of the incident flux. Measurements of the beam properties were made using time of flight systems upstream and downstream of the TPC. The kinetic energy of protons reaching the TPC was successfully changed from ∼0.3 GeV without moderator blocks to less than 0.1 GeV with four moderator blocks (40 cm path length). The flux of both protons and MIPs off the beam axis was increased. The ratio of protons to MIPs vary as a function of the off-axis angle allowing for possible optimisation of the detector to select the type of required particles. Simulation informed by the time of flight measurements show that with four moderator blocks placed in the beamline, (5.6 ± 0.1) protons with energies below 0.1 GeV per spill traversed the active TPC region. Measurements of the beam composition and energy are presented.
We report an updated measurement of the νμ-induced, and the first measurement of the $\overline{v}$μ-induced coherent charged pion production cross section on 12C nuclei in the Tokai-to-Kamioka ...experiment. This is measured in a restricted region of the final-state phase space for which pμ,π > 0.2 GeV, cos(θμ) > 0.8 and cos(θπ) > 0.6, and at a mean (anti)neutrino energy of 0.85 GeV using the T2K near detector. The measured νμ charged current coherent pion production flux-averaged cross section on 12C is (2.98 ± 0.37(stat)±0.31(syst)$^{+0.49}_{–0.00}$(Q2 model))×10–40 cm2. The new measurement of the $\overline{v}$μ-induced cross section on 12C is (3.05 ± 0.71(stat) ± 0.39(syst)$^{+0.74}_{–0.00}$(Q2 model)) × 10–40 cm2. The results are compatible with both the NEUT 5.4.0 Berger-Sehgal (2009) and GENIE 2.8.0 Rein-Sehgal (2007) model predictions.
An upgrade of the near detector of the T2K long baseline neutrino oscillation experiment is currently being conducted. This upgrade will include two new Time Projection Chambers, each equipped with ...16 charge readout resistive Micromegas modules.
A procedure to validate the performance of the detectors at different stages of production has been developed and implemented to ensure a proper and reliable operation of the detectors once installed. A dedicated X-ray test bench is used to characterize the detectors by scanning each pad individually and to precisely measure the uniformity of the gain and the deposited energy resolution over the pad plane. An energy resolution of about 10% is obtained.
A detailed physical model has been developed to describe the charge dispersion phenomena in the resistive Micromegas anode. The detailed physical description includes initial ionization, electron drift, diffusion effects and the readout electronics effects. The model provides an excellent characterization of the charge spreading of the experimental measurements and allowed the simultaneous extraction of gain and charge spreading information of the modules.
Abstract
The T2K experiment presents new measurements of neutrino oscillation parameters using
$$19.7(16.3)\times 10^{20}$$
19.7
(
16.3
)
×
10
20
protons on target (POT) in (anti-)neutrino mode at ...the far detector (FD). Compared to the previous analysis, an additional
$$4.7\times 10^{20}$$
4.7
×
10
20
POT neutrino data was collected at the FD. Significant improvements were made to the analysis methodology, with the near-detector analysis introducing new selections and using more than double the data. Additionally, this is the first T2K oscillation analysis to use NA61/SHINE data on a replica of the T2K target to tune the neutrino flux model, and the neutrino interaction model was improved to include new nuclear effects and calculations. Frequentist and Bayesian analyses are presented, including results on
$$\sin ^2\theta _{13}$$
sin
2
θ
13
and the impact of priors on the
$$\delta _{\textrm{CP}}$$
δ
CP
measurement. Both analyses prefer the normal mass ordering and upper octant of
$$\sin ^2\theta _{23}$$
sin
2
θ
23
with a nearly maximally CP-violating phase. Assuming the normal ordering and using the constraint on
$$\sin ^2\theta _{13}$$
sin
2
θ
13
from reactors,
$$\sin ^2\theta _{23}=0.561^{+0.021}_{-0.032}$$
sin
2
θ
23
=
0
.
561
-
0.032
+
0.021
using Feldman–Cousins corrected intervals, and
$$\varDelta {}m^2_{32}=2.494_{-0.058}^{+0.041}\times 10^{-3}~\text {eV}^2$$
Δ
m
32
2
=
2
.
494
-
0.058
+
0.041
×
10
-
3
eV
2
using constant
$$\varDelta \chi ^{2}$$
Δ
χ
2
intervals. The CP-violating phase is constrained to
$$\delta _{\textrm{CP}}=-1.97_{-0.70}^{+0.97}$$
δ
CP
=
-
1
.
97
-
0.70
+
0.97
using Feldman–Cousins corrected intervals, and
$$\delta _{\textrm{CP}}=0,\pi $$
δ
CP
=
0
,
π
is excluded at more than 90% confidence level. A Jarlskog invariant of zero is excluded at more than
$$2\sigma $$
2
σ
credible level using a flat prior in
$$\delta _{\textrm{CP}},$$
δ
CP
,
and just below
$$2\sigma $$
2
σ
using a flat prior in
$$\sin \delta _{\textrm{CP}}.$$
sin
δ
CP
.
When the external constraint on
$$\sin ^2\theta _{13}$$
sin
2
θ
13
is removed,
$$\sin ^2\theta _{13}=28.0^{+2.8}_{-6.5}\times 10^{-3},$$
sin
2
θ
13
=
28
.
0
-
6.5
+
2.8
×
10
-
3
,
in agreement with measurements from reactor experiments. These results are consistent with previous T2K analyses.
The T2K experiment presents new measurements of neutrino oscillation parameters using
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\usepackage{wasysym}
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...\usepackage{amsbsy}
\usepackage{mathrsfs}
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\setlength{\oddsidemargin}{-69pt}
\begin{document}$$19.7(16.3)\times 10^{20}$$\end{document}
19.7
(
16.3
)
×
10
20
protons on target (POT) in (anti-)neutrino mode at the far detector (FD). Compared to the previous analysis, an additional
\documentclass12pt{minimal}
\usepackage{amsmath}
\usepackage{wasysym}
\usepackage{amsfonts}
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\setlength{\oddsidemargin}{-69pt}
\begin{document}$$4.7\times 10^{20}$$\end{document}
4.7
×
10
20
POT neutrino data was collected at the FD. Significant improvements were made to the analysis methodology, with the near-detector analysis introducing new selections and using more than double the data. Additionally, this is the first T2K oscillation analysis to use NA61/SHINE data on a replica of the T2K target to tune the neutrino flux model, and the neutrino interaction model was improved to include new nuclear effects and calculations. Frequentist and Bayesian analyses are presented, including results on
\documentclass12pt{minimal}
\usepackage{amsmath}
\usepackage{wasysym}
\usepackage{amsfonts}
\usepackage{amssymb}
\usepackage{amsbsy}
\usepackage{mathrsfs}
\usepackage{upgreek}
\setlength{\oddsidemargin}{-69pt}
\begin{document}$$\sin ^2\theta _{13}$$\end{document}
sin
2
θ
13
and the impact of priors on the
\documentclass12pt{minimal}
\usepackage{amsmath}
\usepackage{wasysym}
\usepackage{amsfonts}
\usepackage{amssymb}
\usepackage{amsbsy}
\usepackage{mathrsfs}
\usepackage{upgreek}
\setlength{\oddsidemargin}{-69pt}
\begin{document}$$\delta _{\textrm{CP}}$$\end{document}
δ
CP
measurement. Both analyses prefer the normal mass ordering and upper octant of
\documentclass12pt{minimal}
\usepackage{amsmath}
\usepackage{wasysym}
\usepackage{amsfonts}
\usepackage{amssymb}
\usepackage{amsbsy}
\usepackage{mathrsfs}
\usepackage{upgreek}
\setlength{\oddsidemargin}{-69pt}
\begin{document}$$\sin ^2\theta _{23}$$\end{document}
sin
2
θ
23
with a nearly maximally CP-violating phase. Assuming the normal ordering and using the constraint on
\documentclass12pt{minimal}
\usepackage{amsmath}
\usepackage{wasysym}
\usepackage{amsfonts}
\usepackage{amssymb}
\usepackage{amsbsy}
\usepackage{mathrsfs}
\usepackage{upgreek}
\setlength{\oddsidemargin}{-69pt}
\begin{document}$$\sin ^2\theta _{13}$$\end{document}
sin
2
θ
13
from reactors,
\documentclass12pt{minimal}
\usepackage{amsmath}
\usepackage{wasysym}
\usepackage{amsfonts}
\usepackage{amssymb}
\usepackage{amsbsy}
\usepackage{mathrsfs}
\usepackage{upgreek}
\setlength{\oddsidemargin}{-69pt}
\begin{document}$$\sin ^2\theta _{23}=0.561^{+0.021}_{-0.032}$$\end{document}
sin
2
θ
23
=
0
.
561
-
0.032
+
0.021
using Feldman–Cousins corrected intervals, and
\documentclass12pt{minimal}
\usepackage{amsmath}
\usepackage{wasysym}
\usepackage{amsfonts}
\usepackage{amssymb}
\usepackage{amsbsy}
\usepackage{mathrsfs}
\usepackage{upgreek}
\setlength{\oddsidemargin}{-69pt}
\begin{document}$$\varDelta {}m^2_{32}=2.494_{-0.058}^{+0.041}\times 10^{-3}~\text {eV}^2$$\end{document}
Δ
m
32
2
=
2
.
494
-
0.058
+
0.041
×
10
-
3
eV
2
using constant
\documentclass12pt{minimal}
\usepackage{amsmath}
\usepackage{wasysym}
\usepackage{amsfonts}
\usepackage{amssymb}
\usepackage{amsbsy}
\usepackage{mathrsfs}
\usepackage{upgreek}
\setlength{\oddsidemargin}{-69pt}
\begin{document}$$\varDelta \chi ^{2}$$\end{document}
Δ
χ
2
intervals. The CP-violating phase is constrained to
\documentclass12pt{minimal}
\usepackage{amsmath}
\usepackage{wasysym}
\usepackage{amsfonts}
\usepackage{amssymb}
\usepackage{amsbsy}
\usepackage{mathrsfs}
\usepackage{upgreek}
\setlength{\oddsidemargin}{-69pt}
\begin{document}$$\delta _{\textrm{CP}}=-1.97_{-0.70}^{+0.97}$$\end{document}
δ
CP
=
-
1
.
97
-
0.70
+
0.97
using Feldman–Cousins corrected intervals, and
\documentclass12pt{minimal}
\usepackage{amsmath}
\usepackage{wasysym}
\usepackage{amsfonts}
\usepackage{amssymb}
\usepackage{amsbsy}
\usepackage{mathrsfs}
\usepackage{upgreek}
\setlength{\oddsidemargin}{-69pt}
\begin{document}$$\delta _{\textrm{CP}}=0,\pi $$\end{document}
δ
CP
=
0
,
π
is excluded at more than 90% confidence level. A Jarlskog invariant of zero is excluded at more than
\documentclass12pt{minimal}
\usepackage{amsmath}
\usepackage{wasysym}
\usepackage{amsfonts}
\usepackage{amssymb}
\usepackage{amsbsy}
\usepackage{mathrsfs}
\usepackage{upgreek}
\setlength{\oddsidemargin}{-69pt}
\begin{document}$$2\sigma $$\end{document}
2
σ
credible level using a flat prior in
\documentclass12pt{minimal}
\usepackage{amsmath}
\usepackage{wasysym}
\usepackage{amsfonts}
\usepackage{amssymb}
\usepackage{amsbsy}
\usepackage{mathrsfs}
\usepackage{upgreek}
\setlength{\oddsidemargin}{-69pt}
\begin{document}$$\delta _{\textrm{CP}},$$\end{document}
δ
CP
,
and just below
\documentclass12pt{minimal}
\usepackage{amsmath}
\usepackage{wasysym}
\usepackage{amsfonts}
\usepackage{amssymb}
\usepackage{amsbsy}
\usepackage{mathrsfs}
\usepackage{upgreek}
\setlength{\oddsidemargin}{-69pt}
\begin{document}$$2\sigma $$\end{document}
2
σ
using a flat prior in
\documentclass12pt{minimal}
\usepackage{amsmath}
\usepackage{wasysym}
\usepackage{amsfonts}
\usepackage{amssymb}
\usepackage{amsbsy}
\usepackage{mathrsfs}
\usepackage{upgreek}
\setlength{\oddsidemargin}{-69pt}
\begin{document}$$\sin \delta _{\textrm{CP}}.$$\end{document}
sin
δ
CP
.
When the external constraint on
\documentclass12pt{minimal}
\usepackage{amsmath}
\usepackage{wasysym}
\usepackage{amsfonts}
\usepackage{amssymb}
\usepackage{amsbsy}
\usepackage{mathrsfs}
\usepackage{upgreek}
\setlength{\oddsidemargin}{-69pt}
\begin{document}$$\sin ^2\theta _{13}$$\end{document}
sin
2
θ
13
is removed,
\documentclass12pt{minimal}
\usepackage{amsmath}
\usepackage{wasysym}
\usepackage{amsfonts}
\usepackage{amssymb}
\usepackage{amsbsy}
\usepackage{mathrsfs}
\usepackage{upgreek}
\setlength{\oddsidemargin}{-69pt}
\begin{document}$$\sin ^2\theta _{13}=28.0^{+2.8}_{-6.5}\times 10^{-3},$$\end{document}
sin
2
θ
13
=
28
.
0
-
6.5
+
2.8
×
10
-
3
,
in agreement with measurements from reactor experiments. These results are consistent with previous T2K analyses.
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