arXiv subjects

A. Izmaylov

Publications and source records attributed to A. Izmaylov.

At least 19 recordsLinked to original sources

arXiv2026

The Super Fine-Grained Detector for the T2K neutrino oscillation experiment

The magnetised near detector ND280 of the long-baseline neutrino experiment T2K has been upgraded to improve its detection performance and, consequently, enhance our understanding of neutrino-nucleus interactions, reducing the systematic uncertainties in measurements of the neutrino oscillation parameters. A key component of the upgrade is a novel segmented plastic scintillator detector, called the Super Fine-Grained Detector (SuperFGD), made of approximately 2 million optically isolated 1 cm$^3$ cubes read out by three orthogonal wavelength-shifting (WLS) fibres. Scintillation photons are detected by 55,888 Hamamatsu Multi-Pixel Photon Counters (MPPCs). The SuperFGD provides 3D images of neutrino interactions by tracking the final-state charged particles produced isotropically, including protons down to a threshold of around 330 MeV/$c$. The high light yield of SuperFGD greatly improves particle identification and the sub-nanosecond time resolution provides an excellent identification of Michel electrons. The SuperFGD is also able to detect neutrons from neutrino interactions and, for the first time in a neutrino experiment, to reconstruct their kinetic energy using a fine detector segmentation and by measuring the time-of-flight with sub-nanosecond precision. In this article the details of the detector design, construction and performance are described. The detector was installed in ND280 and successfully commissioned with cosmic data in 2023 and, later, with the T2K neutrino beam. The detector response has been characterised with the 2023 and 2024 data and the results are reported in this article.

physics.ins-det↗

arXiv2025

Introducing a Markov Chain-Based Time Calibration Procedure for Multi-Channel Particle Detectors: Application to the SuperFGD and ToF Detectors of the T2K Experiment

Inter-channel mis-synchronisation can be a limiting factor to the time resolution of high performance timing detectors with multiple readout channels and independent electronics units. In these systems, time calibration methods employed must be able to efficiently correct for minimal mis-synchronisation between channels and achieve the best detector performance. We present an iterative time calibration method based on Markov Chains, suitable for detector systems with multiple readout channels. Starting from correlated hit pairs alone, and without requiring an external reference time measurement, the method solves for fixed per-channel offsets, with precision limited only by the intrinsic single-channel resolution. A mathematical proof that the method is able to find the correct time offsets to be assigned to each detector channel in order to achieve inter-channel synchronisation is given, and it is shown that the number of iterations to reach convergence within the desired precision is controllable with a single parameter. Numerical studies are used to confirm unbiased recovery of true offsets. Finally, the application of the calibration method to the Super Fine-Grained Detector (SuperFGD) and the Time of Flight (TOF) detector at the upgraded T2K near detector (ND280) shows good improvement in overall timing resolution, demonstrating the effectiveness in a real-world scenario and scalability.

physics.ins-det↗

arXiv2024

White Paper on Light Sterile Neutrino Searches and Related Phenomenology

This white paper provides a comprehensive review of our present understanding of experimental neutrino anomalies that remain unresolved, charting the progress achieved over the last decade at the experimental and phenomenological level, and sets the stage for future programmatic prospects in addressing those anomalies. It is purposed to serve as a guiding and motivational "encyclopedic" reference, with emphasis on needs and options for future exploration that may lead to the ultimate resolution of the anomalies. We see the main experimental, analysis, and theory-driven thrusts that will be essential to achieving this goal being: 1) Cover all anomaly sectors -- given the unresolved nature of all four canonical anomalies, it is imperative to support all pillars of a diverse experimental portfolio, source, reactor, decay-at-rest, decay-in-flight, and other methods/sources, to provide complementary probes of and increased precision for new physics explanations; 2) Pursue diverse signatures -- it is imperative that experiments make design and analysis choices that maximize sensitivity to as broad an array of these potential new physics signatures as possible; 3) Deepen theoretical engagement -- priority in the theory community should be placed on development of standard and beyond standard models relevant to all four short-baseline anomalies and the development of tools for efficient tests of these models with existing and future experimental datasets; 4) Openly share data -- Fluid communication between the experimental and theory communities will be required, which implies that both experimental data releases and theoretical calculations should be publicly available; and 5) Apply robust analysis techniques -- Appropriate statistical treatment is crucial to assess the compatibility of data sets within the context of any given model.

hep-ex↗

arXiv2021

Improved constraints on neutrino mixing from the T2K experiment with $\mathbf{3.13\times10^{21}}$ protons on target

The T2K experiment reports updated measurements of neutrino and antineutrino oscillations using both appearance and disappearance channels. This result comes from an exposure of $14.9~(16.4) \times 10^{20}$ protons on target in neutrino (antineutrino) mode. Significant improvements have been made to the neutrino interaction model and far detector reconstruction. An extensive set of simulated data studies have also been performed to quantify the effect interaction model uncertainties have on the T2K oscillation parameter sensitivity. T2K performs multiple oscillation analyses that present both frequentist and Bayesian intervals for the PMNS parameters. For fits including a constraint on \ssqthonethree from reactor data and assuming normal mass ordering T2K measures $\sin^2θ_{23} = 0.53^{+0.03}_{-0.04}$ and $Δm^2_{32} = (2.45 \pm 0.07) \times 10^{-3}$ eV$^{2}$c$^{-4}$. The Bayesian analyses show a weak preference for normal mass ordering (89% posterior probability) and the upper $\sin^2θ_{23}$ octant (80% posterior probability), with a uniform prior probability assumed in both cases. The T2K data exclude CP conservation in neutrino oscillations at the $2σ$ level.

hep-ex↗

arXiv2021

First T2K measurement of transverse kinematic imbalance in the muon-neutrino charged-current single-$π^+$ production channel containing at least one proton

This paper reports the first T2K measurement of the transverse kinematic imbalance in the single-$π^+$ production channel of neutrino interactions. We measure the differential cross sections in the muon-neutrino charged-current interaction on hydrocarbon with a single $π^+$ and at least one proton in the final state, at the ND280 off-axis near detector of the T2K experiment. The extracted cross sections are compared to the predictions from different neutrino-nucleus interaction event generators. Overall, the results show a preference for models which have a more realistic treatment of nuclear medium effects including the initial nuclear state and final-state interactions.

hep-ex↗

arXiv2020

T2K measurements of muon neutrino and antineutrino disappearance using $3.13\times 10^{21}$ protons on target

We report measurements by the T2K experiment of the parameters $θ_{23}$ and $Δm^2_{32}$ which govern the disappearance of muon neutrinos and antineutrinos in the three-flavor PMNS neutrino oscillation model at T2K's neutrino energy and propagation distance. Utilizing the ability of the experiment to run with either a mainly neutrino or a mainly antineutrino beam, muon-like events from each beam mode are used to measure these parameters separately for neutrino and antineutrino oscillations. Data taken from $1.49 \times 10^{21}$ protons on target (POT) in neutrino mode and $1.64 \times 10^{21}$ POT in antineutrino mode are used. The best-fit values obtained by T2K were $\sin^2\left(θ_{23}\right)=0.51^{+0.06}_{-0.07} \left(0.43^{+0.21}_{-0.05}\right)$ and $Δm^2_{32}=2.47^{+0.08}_{-0.09} \left(2.50^{+0.18}_{-0.13}\right)$\evmass for neutrinos (antineutrinos). No significant differences between the values of the parameters describing the disappearance of muon neutrinos and antineutrinos were observed. An analysis using an effective two-flavor neutrino oscillation model where the sine of the mixing angle is allowed to take non-physical values larger than 1 is also performed to check the consistency of our data with the three-flavor model. Our data were found to be consistent with a physical value for the mixing angle.

hep-ex↗

arXiv2019

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

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 $σ^{\rm{H_{2}O}}_{\rm{CC}}$ = (0.840$\pm 0.010$(stat.)$^{+0.10}_{-0.08}$(syst.))$\times$10$^{-38}$cm$^2$/nucleon, $σ^{\rm{CH}}_{\rm{CC}}$ = (0.817$\pm 0.007$(stat.)$^{+0.11}_{-0.08}$(syst.))$\times$10$^{-38}$cm$^2$/nucleon, and $σ^{\rm{Fe}}_{\rm{CC}}$ = (0.859$\pm 0.003$(stat.) $^{+0.12}_{-0.10}$(syst.))$\times$10$^{-38}$cm$^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 ${σ^{\rm{H_{2}O}}_{\rm{CC}}}/{σ^{\rm{CH}}_{\rm{CC}}}$ = 1.028$\pm 0.016$(stat.)$\pm 0.053$(syst.), ${σ^{\rm{Fe}}_{\rm{CC}}}/{σ^{\rm{H_{2}O}}_{\rm{CC}}}$ = 1.023$\pm 0.012$(stat.)$\pm 0.058$(syst.), and ${σ^{\rm{Fe}}_{\rm{CC}}}/{σ^{\rm{CH}}_{\rm{CC}}}$ = 1.049$\pm 0.010$(stat.)$\pm 0.043$(syst.). 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.

hep-ex↗

arXiv2019

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

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$\times 10^{20}$ 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$\times 10^{-38}$ cm$^2$ (90\% C.L.) per nucleon, using the J-PARC off-axis neutrino beam with an average energy of $\left \sim 0.6$ 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.

hep-ex↗

arXiv2018

Hyper-Kamiokande Design Report

On the strength of a double Nobel prize winning experiment (Super)Kamiokande and an extremely successful long baseline neutrino programme, the third generation Water Cherenkov detector, Hyper-Kamiokande, is being developed by an international collaboration as a leading worldwide experiment based in Japan. The Hyper-Kamiokande detector will be hosted in the Tochibora mine, about 295 km away from the J-PARC proton accelerator research complex in Tokai, Japan. The currently existing accelerator will be steadily upgraded to reach a MW beam by the start of the experiment. A suite of near detectors will be vital to constrain the beam for neutrino oscillation measurements. A new cavern will be excavated at the Tochibora mine to host the detector. The experiment will be the largest underground water Cherenkov detector in the world and will be instrumented with new technology photosensors, faster and with higher quantum efficiency than the ones in Super-Kamiokande. The science that will be developed will be able to shape the future theoretical framework and generations of experiments. Hyper-Kamiokande will be able to measure with the highest precision the leptonic CP violation that could explain the baryon asymmetry in the Universe. The experiment also has a demonstrated excellent capability to search for proton decay, providing a significant improvement in discovery sensitivity over current searches for the proton lifetime. The atmospheric neutrinos will allow to determine the neutrino mass ordering and, together with the beam, able to precisely test the three-flavour neutrino oscillation paradigm and search for new phenomena. A strong astrophysical programme will be carried out at the experiment that will detect supernova neutrinos and will measure precisely solar neutrino oscillation.

physics.ins-det↗

arXiv2018

Characterisation of nuclear effects in muon-neutrino scattering on hydrocarbon with a measurement of final-state kinematics and correlations in charged-current pionless interactions at T2K

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$_8$H$_8$) target. The data were taken between years 2010 and 2013, corresponding to approximately 6$\times10^{20}$ 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.

hep-ex↗

arXiv2018

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

This paper reports 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 (\mbox{stat}) \pm 0.06 (\mbox{det. syst.}) \pm 0.04(\mbox{model syst.}) \pm{} 0.08(\mbox{flux}) ) \times 10^{-38} \mbox{cm}^2$ per n.

hep-ex↗

arXiv2018

Measurement of inclusive double-differential $ν_μ$ charged-current cross section with improved acceptance in the T2K off-axis near detector

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 corresponds to $5.7 \times 10^{20}$ protons-on-target. The total flux-integrated cross section is measured to be $(6.950 \pm 0.662) \times 10^{-39}$ cm$^2$nucleon$^{-1}$ and is consistent with our simulation.

hep-ex↗

arXiv2017

Baby MIND: A magnetized segmented neutrino detector for the WAGASCI experiment

T2K (Tokai-to-Kamioka) is a long-baseline neutrino experiment in Japan designed to study various parameters of neutrino oscillations. A near detector complex (ND280) is located 280~m downstream of the production target and measures neutrino beam parameters before any oscillations occur. ND280's measurements are used to predict the number and spectra of neutrinos in the Super-Kamiokande detector at the distance of 295~km. The difference in the target material between the far (water) and near (scintillator, hydrocarbon) detectors leads to the main non-cancelling systematic uncertainty for the oscillation analysis. In order to reduce this uncertainty a new WAter-Grid-And-SCintillator detector (WAGASCI) has been developed. A magnetized iron neutrino detector (Baby MIND) will be used to measure momentum and charge identification of the outgoing muons from charged current interactions. The Baby MIND modules are composed of magnetized iron plates and long plastic scintillator bars read out at the both ends with wavelength shifting fibers and silicon photomultipliers. The front-end electronics board has been developed to perform the readout and digitization of the signals from the scintillator bars. Detector elements were tested with cosmic rays and in the PS beam at CERN. The obtained results are presented in this paper.

physics.ins-det↗

arXiv2017

Measurement of neutrino and antineutrino oscillations by the T2K experiment including a new additional sample of $ν_e$ interactions at the far detector

The T2K experiment reports an updated analysis of neutrino and antineutrino oscillations in appearance and disappearance channels. A sample of electron neutrino candidates at Super-Kamiokande in which a pion decay has been tagged is added to the four single-ring samples used in previous T2K oscillation analyses. Through combined analyses of these five samples, simultaneous measurements of four oscillation parameters, $|Δm^2_{32}|$, $\sin^2(θ_{23})$, $\sin^2(θ_{13})$, and $δ_{CP}$ and of the mass ordering are made. A set of studies of simulated data indicates that the sensitivity to the oscillation parameters is not limited by neutrino interaction model uncertainty. Multiple oscillation analyses are performed, and frequentist and Bayesian intervals are presented for combinations of the oscillation parameters with and without the inclusion of reactor constraints on $\sin^2(θ_{13})$. When combined with reactor measurements, the hypothesis of CP conservation ($δ_{CP}$$=0$ or $π$) is excluded at 90% confidence level. The 90% confidence region for $δ_{CP}$ is [-2.95,-0.44] ([-1.47, -1.27]) for normal (inverted) ordering. The central values and 68\% confidence intervals for the other oscillation parameters for normal (inverted) ordering are $Δm^{2}_{32}=2.54\pm0.08$ ($2.51\pm0.08$) $\times 10^{-3}$ eV$^2 / c^4$ and $\sin^2(θ_{23}) = 0.55^{+0.05}_{-0.09}$ ($0.55^{+0.05}_{-0.08}$), compatible with maximal mixing. In the Bayesian analysis, the data weakly prefer normal ordering (Bayes factor 3.7) and the upper octant for $\sin^2(θ_{23})$ (Bayes factor 2.4).

hep-ex↗

arXiv2017

Measurement of $\barν_μ$ and $ν_μ$ charged current inclusive cross sections and their ratio with the T2K off-axis near detector

We report a measurement of cross section $σ(ν_μ+{\rm nucleus}\rightarrowμ^{-}+X)$ and the first measurements of the cross section $σ(\barν_μ+{\rm nucleus}\rightarrowμ^{+}+X)$ and their ratio $R(\frac{σ(\bar ν)}{σ(ν)})$ at (anti-)neutrino energies below 1.5 GeV. We determine the single momentum bin cross section measurements, averaged over the T2K $\barν/ν$-flux, for the detector target material (mainly Carbon, Oxygen, Hydrogen and Copper) with phase space restricted laboratory frame kinematics of $θ_μ<32^\circ$ and $p_μ>$500 MeV/c. The results are $σ(\barν)=\left( 0.900\pm0.029{\rm (stat.)}\pm0.088{\rm (syst.)}\right)\times10^{-39}$ and $σ(ν)=\left( 2.41\ \pm0.022{\rm{(stat.)}}\pm0.231{\rm (syst.)}\ \right)\times10^{-39}$ in units of cm$^{2}$/nucleon and $R\left(\frac{σ(\barν)}{σ(ν)}\right)= 0.373\pm0.012{\rm (stat.)}\pm0.015{\rm (syst.)}$.

hep-ex↗

arXiv2017

Baby MIND Experiment Construction Status

Baby MIND is a magnetized iron neutrino detector, with novel design features, and is planned to serve as a downstream magnetized muon spectrometer for the WAGASCI experiment on the T2K neutrino beam line in Japan. One of the main goals of this experiment is to reduce systematic uncertainties relevant to CP-violation searches, by measuring the neutrino contamination in the anti-neutrino beam mode of T2K. Baby MIND is currently being constructed at CERN, and is planned to be operational in Japan in October 2017.

physics.ins-det↗

arXiv2017

Baby MIND: A magnetised spectrometer for the WAGASCI experiment

The WAGASCI experiment being built at the J-PARC neutrino beam line will measure the difference in cross sections from neutrinos interacting with a water and scintillator targets, in order to constrain neutrino cross sections, essential for the T2K neutrino oscillation measurements. A prototype Magnetised Iron Neutrino Detector (MIND), called Baby MIND, is being constructed at CERN to act as a magnetic spectrometer behind the main WAGASCI target to be able to measure the charge and momentum of the outgoing muon from neutrino charged current interactions.

physics.ins-det↗

arXiv2017

First combined analysis of neutrino and antineutrino oscillations at T2K

T2K reports its first results in the search for CP violation in neutrino oscillations using appearance and disappearance channels for neutrino- and antineutrino-mode beam. The data include all runs from Jan 2010 to May 2016 and comprise $7.482\times10^{20}$,protons on target in neutrino mode, which yielded in the far detector 32 e-like and 135 $μ$-like events, and $7.471\times10^{20}$,protons on target in antineutrino mode which yielded 4 e-like and 66 $μ$-like events. Reactor measurements of $\sin^{2}2θ_{13}$ have been used as an additional constraint. The one-dimensional confidence interval at 90% for $δ_{CP}$ spans the range ($-3.13$, $-0.39$) for normal mass ordering. The CP conservation hypothesis ($δ_{CP}=0,π$) is excluded at 90% C.L.

hep-ex↗