The T2K Experiment

Measurement of the muon neutrino charged-current cross sections on water, hydrocarbon and iron, and their ratios, with the T2K on-axis detectors

September 26, 2019

We report a measurement of the flux-integrated

ν_{μ}

charged-current cross sections on water, hydrocarbon, and iron in the T2K on-axis neutrino beam with a mean neutrino energy of 1.5 GeV. The measured cross sections on water, hydrocarbon, and iron are

$σ_{C C}^{H_{2} O} = (0.840 \pm 0.010 (s t a t .)_{- 0.08}^{+ 0.10} (s y s t .)) \times 10^{- 38} {c m}^{2}$ /nucleon, $σ_{C C}^{C H} = (0.817 \pm 0.007 (s t a t .)_{- 0.08}^{+ 0.11} (s y s t .)) \times 10^{- 38} {c m}^{2}$ /nucleon, and $σ_{C C}^{F e} = (0.859 \pm 0.003 (s t a t .)_{- 0.10}^{+ 0.12} (s y s t .)) \times 10^{- 38} {c m}^{2}$ /nucleon,

respectively, for a restricted phase space of induced muons: $θ_{μ} < 45^{\circ}$ and $p_{μ} >$ 0.4 GeV/ $c$ in the laboratory frame. The measured cross section ratios are $σ_{C C}^{H_{2} O} / σ_{C C}^{C H} = 1.028 \pm 0.016 (s t a t .) \pm 0.053 (s y s t .)$ ⁠, $σ_{C C}^{F e} / σ_{C C}^{H_{2} O} = 1.023 \pm 0.012 (s t a t .) \pm 0.058 (s y s t .)$ ⁠, and $σ_{C C}^{F e} / σ_{C C}^{C H} = 1.049 \pm 0.010 (s t a t .) \pm 0.043 (s y s t .)$ ⁠. These results, with an unprecedented precision for the measurements of neutrino cross sections on water in the studied energy region, show good agreement with the current neutrino interaction models used in the T2K oscillation analyses.

arXiv preprint: https://arxiv.org/abs/1904.09611
DOI: https://doi.org/10.1093/ptep/ptz070
Reference: PTEP 2019 (2019) 9, 093C02

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

June 20, 2019

Neutrino neutral-current 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 5.738×10^{20} protons-on-targets neutrino mode data. We do not find positive evidence of neutral current induced single photon production in this sample. We set the model-dependent upper limit on the cross-section for this process, at 0.114×10^{−38} cm^2 (90\% C.L.) per nucleon, using the J-PARC off-axis neutrino beam with an average energy of ⟨Eν⟩∼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.

DOI: https://dx.doi.org/10.1088/1361-6471/ab227d
ArXiv: https://arxiv.org/abs/1902.03848
Physics World: https://physicsworld.com/a/t2k-searches-for-single-gamma-rays-from-neutrino-interactions

arXiv preprint: https://arxiv.org/abs/1902.03848
DOI: https://doi.org/10.1088/1361-6471/ab227d
Reference: J.Phys.G 46 (2019) 8, 08LT01

Measurement of muon- antineutrino and neutrino charged-current inclusive cross sections and their ratio with the T2K off-axis near detector

July 19, 2018

We report a measurement of cross section σ(νμ+nucleus→μ-+X) and the first measurements of the cross section σ(ν¯μ+nucleus→μ++X) and their ratio R(σ(ν¯)σ(ν)) at (anti) neutrino energies below 1.5 GeV. We determine the single momentum bin cross section measurements, averaged over the T2K ν¯/ν-flux, for the detector target material (mainly carbon, oxygen, hydrogen and copper) with phase space restricted laboratory frame kinematics of θμ<32° and pμ>500 MeV/c. The results are σ(ν¯)=(0.900±0.029(stat)±0.088(syst))×10-39 and σ(ν)=(2.41±0.022(stat)±0.231(syst))×10-39 in units of cm2/nucleon and R(σ(ν¯)σ(ν))=0.373±0.012(stat)±0.015(syst).

arXiv preprint: https://arxiv.org/abs/1706.04257
Reference: Phys.Rev. D96 (2017) no.5, 052001
DOI: https://doi.org/10.1103/PhysRevD.96.052001

Measurement of inclusive double-differential νμ charged-current cross section with improved acceptance

July 13, 2018

We report a measurement of the flux-integrated cross section for inclusive muon neutrino charged-current interactions on carbon. The double differential measurements are given as function of the muon momentum and angle. Relative to our previous publication on this topic, these results have an increased angular acceptance and higher statistics. The data sample presented here is 5.7 × 10^20 protons-on-target. The total flux-integrated cross section is measured to be (6.950 ± 0.662) × 10^−39 cm^2/nucleon and is consistent with our simulation.

t2k-ccinc-4pi-2018

arXiv preprint: https://arxiv.org/abs/1801.05148
Data release: https://t2k-experiment.org/results/2018-ccinc-4pi/
DOI: https://doi.org/10.1103/PhysRevD.98.012004
Reference: Phys.Rev.D 98 (2018) 012004

Characterisation of nuclear effects in neutrino scattering with a measurement of final-state kinematics (2018)

July 11, 2018

This paper reports measurements of final-state proton multiplicity, muon and proton kinematics, and their correlations in charged-current pionless neutrino interactions, measured by the T2K ND280 near detector in its plastic scintillator (C

_{8}

_{8}

) target. The data were taken between years 2010 and 2013, corresponding to approximately 6

\times 10^{20}

protons on target. Thanks to their exploration of the proton kinematics and of kinematic imbalances between the proton and muon kinematics, the results offer a novel probe of the nuclear-medium effects most pertinent to the (sub-)GeV neutrino-nucleus interactions that are used in accelerator-based long-baseline neutrino oscillation measurements. These results are compared to many neutrino-nucleus interaction models which all fail to describe at least part of the observed phase space. In case of events without a proton above a detection threshold in the final state, a fully consistent implementation of the local Fermi gas model with multinucleon interactions gives the best description of the data. In the case of at least one proton in the final state the spectral function model agrees well with the data, most notably when measuring the kinematic imbalance between the muon and the proton in the plane transverse to the incoming neutrino. A clear indication of existence of multinucleon interactions is observed. The effect of final-state interactions is also discussed.

The data release for this paper is here.

arXiv preprint: https://arxiv.org/abs/1802.05078
DOI: https://doi.org/10.1103/PhysRevD.98.032003
Reference: Phys.Rev.D 98 (2018) 3, 032003
Data release: https://t2k-experiment.org/results/2018-transverse-cc0pi/

First measurement of the νμ charged-current cross section without pions in the final state on a water target

December 5, 2017

We report the first differential measurement of the charged-current interaction cross section of

ν_{μ}

on water with no pions in the final state. This flux-averaged measurement has been made using the T2K experiment’s off-axis near detector, and is reported in doubly-differential bins of muon momentum and angle. The flux-averaged total cross section in a restricted region of phase space was found to be

σ = (0.95 \pm 0.08 (stat) \pm 0.06 (det. syst.) \pm 0.04 (model syst.) \pm 0.08 (flux)) \times 10^{- 38} {cm}^{2}

per n.

arXiv:1708.06771 [hep-ex], Phys.Rev. D97 (2018) no.1, 012001. The data release for this paper is here.

PastedGraphic-1

arXiv preprint: https://arxiv.org/abs/1708.06771
DOI: https://doi.org/10.1103/PhysRevD.97.012001
Reference: Phys.Rev.D 97 (2018) 1, 012001
Data release: https://t2k-experiment.org/results/2017-cc0pi-water-xsec/

Measurement of Coherent π+ Production in Low Energy Neutrino-Carbon Scattering

February 17, 2017

We report the first measurement of the flux-averaged cross section for charged current coherent π+ production on carbon for neutrino energies less than 1.5 GeV, and with a restriction on the final state phase space volume in the T2K near detector, ND280. Comparisons are made with predictions from the Rein-Sehgal coherent production model and the model by Alvarez-Ruso et al., the latter representing the first implementation of an instance of the new class of microscopic coherent models in a neutrino interaction Monte Carlo event generator. We observe a clear event excess above background, disagreeing with the null results reported by K2K and SciBooNE in a similar neutrino energy region. The measured flux-averaged cross sections are below those predicted by both the Rein-Sehgal and Alvarez-Ruso et al. models.

arXiv preprint: https://arxiv.org/abs/1604.04406
DOI: https://doi.org/10.1103/PhysRevLett.117.192501
Reference: Phys.Rev.Lett. 117 (2016) 19, 192501

First Measurement of the Muon Neutrino Charged Current Single Pion Production Cross Section on Water with the T2K Near Detector

May 26, 2016

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 muon and pion kinematics, in the restricted phase-space defined by p_π+>200MeV/c, p_μ− >200MeV/c, cosθ_π+ >0.3 and cosθ_μ− >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 ⟨σ⟩_ϕ=4.25±0.48 (stat)±1.56 (syst)×10⁻⁴⁰ cm²/nucleon. The total cross section is consistent with the NEUT prediction (5.03×10⁻⁴⁰ cm²/nucleon) and 2σ lower than the GENIE prediction (7.68×10⁻⁴⁰ cm²/nucleon). The differential cross sections are in good agreement with the NEUT generator. The GENIE simulation reproduces well the shapes of the distributions, but over-estimates the overall cross section normalization.

arXiv preprint: https://arxiv.org/abs/1605.07964
DOI: https://doi.org/10.1103/PhysRevD.95.012010
Reference: Phys.Rev.D 95 (2017) 1, 012010

Measurement of double-differential muon neutrino charged-current interactions on C₈H₈ without pions in the final state using the T2K off-axis beam

February 16, 2016

We report the measurement of muon neutrino charged-current interactions on carbon without pions in the final state at the T2K beam energy using 5.734×10²⁰ protons on target. For the first time the measurement is reported as a flux-integrated, double-differential cross-section in muon kinematic variables (cosθμ, pμ), without correcting for events where a pion is produced and then absorbed by final state interactions. Two analyses are performed with different selections, background evaluations and cross-section extraction methods to demonstrate the robustness of the results against biases due to model-dependent assumptions. The measurements compare favorably with recent models which include nucleon-nucleon correlations but, given the present precision, the measurement does not solve the degeneracy between different models. The data also agree with Monte Carlo simulations which use effective parameters that are tuned to external data to describe the nuclear effects. The total cross-section in the full phase space is σ=(0.417±0.047(syst)±0.005(stat))×10⁻³⁸cm² nucleon⁻¹ and the cross-section integrated in the region of phase space with largest efficiency and best signal-over-background ratio (cosθ_μ>0.6 and p_μ>200 MeV) is σ=(0.202±0.0359(syst)±0.0026(stat))×10⁻³⁸cm² nucleon⁻¹.

arXiv preprint: https://arxiv.org/abs/1602.03652
DOI: https://doi.org/10.1103/PhysRevD.93.112012
Reference: Phys.Rev.D 93 (2016) 11, 112012

Measurement of the muon neutrino inclusive charged-current cross section in the energy range of 1-3 GeV with the T2K INGRID detector

September 24, 2015

We report a measurement of the νμ-nucleus inclusive charged current cross section (=σ^cc) on iron using data from exposed to the J-PARC neutrino beam. The detector consists of 14 modules in total, which are spread over a range of off-axis angles from 0° to 1.1°. The variation in the neutrino energy spectrum as a function of the off-axis angle, combined with event topology information, is used to calculate this cross section as a function of neutrino energy. The cross section is measured to be σ^cc(1.1 GeV)=1.10±0.15 (10⁻³⁸cm²/nucleon), σ^cc(2.0 GeV)=2.07±0.27 (10⁻³⁸cm²/nucleon), and σ^cc(3.3 GeV)=2.29±0.45 (10⁻³⁸cm²/nucleon), at energies of 1.1, 2.0, and 3.3 GeV, respectively. These results are consistent with the cross section calculated by the neutrino interaction generators currently used by T2K. More importantly, the method described here opens up a new way to determine the energy dependence of neutrino-nucleus cross sections.

arXiv preprint: https://arxiv.org/abs/1509.06940
DOI: https://doi.org/10.1103/PhysRevD.93.072002
Reference: Phys.Rev.D 93 (2016) 7, 072002

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