2019, Gil, E. C., Kleimenova, A., Minucci, E., Padolski, S., Kudenko, Y., Куденко, Юрий Григорьевич

The NA62 experiment at CERN reports a search for the lepton number violating decays K+ -> pi(-)e(+)e(+) and K+ -> pi(-)mu(+)mu(+) using a data sample collected in 2017. No signals are observed, and upper limits on the branching fractions of these decays of 2.2 x 10(-10) and 4.2 x 10(-11) are obtained, respectively, at 90% confidence level. These upper limits improve on previously reported measurements by factors of 3 and 2, respectively. (C) 2019 The Author. Published by Elsevier B.V.

2020, Kudenko, Y., Куденко, Юрий Григорьевич

A next generation water Cherenkov detector Hyper-Kamiokande to be built in Japan is described. The main goals of this project include a sensitive measurement of CP violation in neutrino oscillations, a search for proton decay and study of solar, atmospherics and astrophysical neutrinos. Key features of the Hyper-Kamiokande detector are described. The main emphasis is put on large photosensors. The recent progress in development of near neutrino detectors is also presented.

2020, Abe, K., Akhlaq, N., Akutsu, R., Ali, A., Kudenko, Y., Куденко, Юрий Григорьевич

© 2020, The Author(s).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, dσ/dp and dσ/d cos(θ), and the total cross-sections in a limited phase-space in momentum and scattering angle (p > 300 MeV/c and θ ≤ 45°) are measured using a binned maximum likelihood fit and compared to the neutrino Monte Carlo generator predictions, resulting in good agreement.

2019, Kravtsov, V. I., Akimenko, S. A., Artamonov, A. V., Blik, A. M., Kudenko, Y. G., Куденко, Юрий Григорьевич

© 2019, The Author(s).A precise measurement of the vector and axial-vector form factors difference FV- FA in the K+→ μ+νμγ decay is presented. About 95K events of K+→ μ+νμγ are selected in the OKA experiment. The result is FV- FA= 0.134 ± 0.021 (stat) ± 0.027 (syst). Both errors are smaller than in the previous FV- FA measurements.

2020, Burtovoy, V. S., Akimenko, S. A., Artamonov, A. V., Blik, A. M., Kudenko, Y. G., Куденко, Юрий Григорьевич

© 2020, Pleiades Publishing, Inc.Abstract: On the statistics of ~1.7 × 108 interactions of positively charged kaons on copper nuclei, coherent events of the K+π0 system production are selected. The cross sections for the Coulomb and coherent strong components and their interference in the region of the K*(892) meson are measured. The partial width for the decay K*(892) → K+γ is determined. When studying the mass spectrum of the K+π0 system, an effect which can be interpreted as the interference of the chiral anomaly and the K*(892) s-channel amplitudes is found. This gives an estimate for the ratio of the observed amplitude of the chiral anomaly to the theoretical one: Aexp/Ath = 0.9 ± 0.24(stat.) ± 0.3(syst.).

2020, Blondel, A., Bogomilov, M., Bordoni, S., Cadoux, F., Kudenko, Y., Куденко, Юрий Григорьевич

© 2020 CERN.A novel scintillator detector, the SuperFGD, has been selected as the main neutrino target for an upgrade of the T2K experiment ND280 near detector. The detector design will allow nearly 4π coverage for neutrino interactions at the near detector and will provide lower energy thresholds, significantly reducing systematic errors for the experiment. The SuperFGD is made of optically-isolated scintillator cubes of size 10×10×10 mm3, providing the required spatial and energy resolution to reduce systematic uncertainties for future T2K runs. The SuperFGD for T2K will have close to two million cubes in a 1920 × 560 × 1840 mm3 volume. A prototype made of 24 × 8 × 48 cubes was tested at a charged particle beamline at the CERN PS facility. The SuperFGD Prototype was instrumented with readout electronics similar to the future implementation for T2K . Results on electronics and detector response are reported in this paper, along with a discussion of the 3D reconstruction capabilities of this type of detector. Several physics analyses with the prototype data are also discussed, including a study of stopping protons.

2020, Cortina, Gil, E., Kleimenova, A., Minucci, E., Padolski, S., Kudenko, Y., Куденко, Юрий Григорьевич

© 2020, The Author(s).The NA62 experiment reports an investigation of the K+→ π+νν¯ mode from a sample of K+ decays collected in 2017 at the CERN SPS. The experiment has achieved a single event sensitivity of (0.389 ± 0.024) × 10−10, corresponding to 2.2 events assuming the Standard Model branching ratio of (8.4 ± 1.0) × 10−11. Two signal candidates are observed with an expected background of 1.5 events. Combined with the result of a similar analysis conducted by NA62 on a smaller data set recorded in 2016, the collaboration now reports an upper limit of 1.78 × 10−10 for the K+→ π+νν¯ branching ratio at 90% CL. This, together with the corresponding 68% CL measurement of (0.48−0.48+0.72) × 10−10, are currently the most precise results worldwide, and are able to constrain some New Physics models that predict large enhancements still allowed by previous measurements.

2020, Gil, E. C., Kleimenova, A., Minucci, E., Padolski, S., Kudenko, Y., Куденко, Юрий Григорьевич

A search for heavy neutral lepton (N) production in K+ -> e(+)N decays using the data sample collected by the NA62 experiment at CERN in 2017-2018 is reported. Upper limits of the extended neutrino mixing matrix element vertical bar U-e4 vertical bar(2) are established at the level of 10(-9) over most of the accessible heavy neutral lepton mass range 144-462 MeV/c(2), with the assumption that the lifetime exceeds 50 ns. These limits improve significantly upon those of previous production and decay searches. The vertical bar U-e4 vertical bar(2) range favoured by Big Bang Nucleosynthesis is excluded up to a mass of about 340 MeV/c(2). (C) 2020 The Author(s). Published by Elsevier B.V.

2020, Acerbi, F., Bonesini, M., Bramati, F., Branca, A., Kudenko, Y., Куденко, Юрий Григорьевич

A prototype for the instrumented decay tunnel of ENUBET was tested in 2018 at the CERN East Area facility with charged particles up to 5 GeV. This detector is a longitudinal sampling calorimeter with lateral scintillation light readout. The calorimeter was equipped by an additional "t(0)-layer" for timing and photon discrimination. The performance of this detector in terms of electron energy resolution, linearity, response to muons and hadron showers are presented in this paper and compared with simulation. The t(0)-layer was studied both in standalone mode using pion charge exchange and in combined mode with the calorimeter to assess the light yield and the 1 mip/2 mip separation capability. We demonstrate that this system fulfills the requirements for neutrino physics applications and discuss performance and additional improvements.

2019, Gil, E. Cortina., Kleimenova, A., Minucci, E., Padolski, S., Kudenko, Y., Куденко, Юрий Григорьевич

The results of a search for (0) decays to a photon and an invisible massive dark photon at the NA62 experiment at the CERN SPS are reported. From a total of 4.12 x 10(8) tagged (0) mesons, no signal is observed. Assuming a kinetic-mixing interaction, limits are set on the dark photon coupling to the ordinary photon as a function of the dark photon mass, improving on previous searches in the mass range 60-110 MeV/c(2). The present results are interpreted in terms of an upper limit of the branching ratio of the electro-weak decay 0improving the current limit by more than three orders of magnitude.