arXiv subjects

A. Korzenev

Publications and source records attributed to A. Korzenev.

At least 19 recordsLinked to original sources

arXiv2026

Commissioning and Performance of the Time-of-Flight Detector for the T2K Neutrino Oscillation Experiment

The T2K ND280 Upgrade aims to reduce systematic uncertainties in measurements of neutrino oscillation parameters and improve sensitivity to the charge-parity (CP)-violating phase, $δ_{\mathrm{CP}}$. A key component is the Time-of-Flight (ToF) detector, comprising six panels with 118 EJ-200 plastic-scintillator bars surrounding the Super Fine-Grained Detector (SuperFGD) and two High-Angle Time Projection Chambers (HA-TPCs). Each bar is read out at both ends by silicon photomultiplier arrays and digitised using SAMPIC waveform electronics. The ToF provides precise timing and particle-direction information for particle identification and rejection of backgrounds entering the tracker from outside. This article presents the detector design, construction, signal reconstruction, integration, commissioning, and performance. Dedicated single-bar measurements achieve a time resolution of approximately 130 ps and a longitudinal position resolution of 2.6 cm. After installation in ND280, cosmic-ray calibration yields an in situ single-bar time resolution of $169 \pm 1$ ps for Top-Bottom crossing events. Beam data clearly resolve the eight-bunch T2K spill structure, confirming synchronisation with the ND280 trigger and data-acquisition systems. The ToF has been successfully commissioned and operates stably within the upgraded ND280 detector.

physics.ins-det↗

arXiv2025

Modeling Scintillation Photon Transport and Reconstruction Algorithms for the Time-of-Flight Detector in the T2K Neutrino Experiment

The T2K ND280 upgrade aims to reduce the systematic uncertainty of the CP-violating phase, $δ_{CP}$, to reject non-CP violation hypothesis at $3σ$ confidence level. A crucial component of the ND280 upgrade, alongside the Super Fine Grained Detector (SuperFGD) and two High-Angle Time Projection Chambers (TPCs), is the Time-of-Flight (ToF) detector, which significantly enhances background rejection and particle identification capabilities. The ToF detector features six modules in a cube configuration, each with 20 plastic scintillator bars measuring $\text{220}\times\text{12}\times\text{1}\,\text{cm}^3$ and is equipped with Silicon Photomultiplier (SiPM) arrays at both ends to capture scintillation light. This letter outlines the modelling of the detector response and the signal reconstruction process.

hep-ex↗

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

Characterization of the optical model of the T2K 3D segmented plastic scintillator detector

The magnetised near detector (ND280) of the T2K long-baseline neutrino oscillation experiment has been recently upgraded aiming to satisfy the requirement of reducing the systematic uncertainty from measuring the neutrinonucleus interaction cross section, which is the largest systematic uncertainty in the search for leptonic charge-parity symmetry violation. A key component of the upgrade is SuperFGD, a 3D segmented plastic scintillator detector made of approximately 2,000,000 optically-isolated 1 cm3 cubes. It will provide a 3D image of GeV neutrino interactions by combining tracking and stopping power measurements of final state particles with sub-nanosecond time resolution. The performance of SuperFGD is characterized by the precision of its response to charged particles as well as the systematic effects that might affect the physics measurements. Hence, a detailed Geant4 based optical simulation of the SuperFGD building block, i.e. a plastic scintillating cube read out by three wavelength shifting fibers, has been developed and validated with the different datasets collected in various beam tests. In this manuscript the description of the optical model as well as the comparison with data are reported.

hep-ex↗

arXiv2024

$K_S^0$ meson production in inelastic p+p interactions at 31, 40 and 80 GeV/c beam momentum measured by NA61/SHINE at the CERN SPS

Measurements of $K_S^0$ meson production via its $π^{+} π^{-}$ decay mode in inelastic $\textit{p+p}$ interactions at incident projectile momenta of 31, 40 and 80 GeV/$c$ ($\sqrt{s_{NN}}=7.7, 8.8$ and $12.3$ GeV, respectively) are presented. The data were recorded by the NA61/SHINE spectrometer at the CERN Super Proton Synchrotron. Double-differential distributions were obtained in transverse momentum and rapidity. The mean multiplicities of $K_S^0$ mesons were determined to be $(5.95 \pm 0.19 (stat) \pm 0.22 (sys)) \times 10^{-2}$ at 31 GeV/$c$, $(7.61 \pm 0.13 (stat) \pm 0.31 (sys)) \times 10^{-2}$ at 40 GeV/$c$ and $(11.58 \pm 0.12 (stat) \pm 0.37 (sys)) \times 10^{-2}$ at 80 GeV/$c$. The results on $K^{0}_{S}$ production are compared with model calculations (Epos1.99, SMASH 2.0 and PHSD) as well as with published data from other experiments.

hep-ex↗

arXiv2023

Measurements of $K^0_{\textrm{S}}$, $Λ$ and $\barΛ$ production in 120 GeV/$c$ p + C interactions

This paper presents multiplicity measurements of $K^0_{\textrm{S}}$, $Λ$, and $\barΛ$ produced in 120 GeV/$c$ proton-carbon interactions. The measurements were made using data collected at the NA61/SHINE experiment during two different periods. Decays of these neutral hadrons impact the measured $π^+$, $π^-$, $p$ and $\bar{p}$ multiplicities in the 120 GeV/$c$ proton-carbon reaction, which are crucial inputs for long-baseline neutrino experiment predictions of neutrino beam flux. The double-differential multiplicities presented here will be used to more precisely measure charged-hadron multiplicities in this reaction, and to re-weight neutral hadron production in neutrino beam Monte Carlo simulations.

hep-ex↗

arXiv2023

SuperFGD prototype time resolution studies

The SuperFGD will be a part of the ND280 near detector of the T2K and Hyper Kamiokande projects, that will help to reduce systematic uncertainties related with neutrino flux and cross-section modeling. The upgraded ND280 will be able to perform a full exclusive reconstruction of the final state from neutrino-nucleus interactions, including measurements of low momentum protons, pions and, for the first time, event-by event measurements of neutron kinematics. The time resolution defines the neutron energy resolution. We present the results of time resolution measurements made with the SuperFGD prototype that consists of 9216 plastic scintillator cubes (cube size is 1 cm$^3$) readout with 1728 wavelength-shifting fibers going along three orthogonal directions. We use data from the muon beam exposure at CERN. The time resolution of 0.97 ns was obtained for one readout channel after implementing the time calibration with a correction for the time-walk effect. The time resolution improves with energy deposited in a scintillator cube. Averaging two readout channels for one scintillator cube improves the time resolution to 0.68 ns which means that signals in different channels are not synchronous. Therefore the contribution from the time recording step of 2.5 ns is averaged as well. Averaging time values from N channels improves the time resolution by $\sim 1/\sqrt{N}$. Therefore a very good time resolution should be achievable for neutrons since neutron recoils hit typically several scintillator cubes and in addition produce larger amplitudes than muons. Measurements performed with a laser and a wide-bandwidth oscilloscope demonstrated that the time resolution obtained with the muon beam is not far from its expected limit. The intrinsic time resolution of one channel is 0.67 ns for signals of 56 photo-electron typical for minimum ionizing particles.

physics.ins-det↗

arXiv2023

Measurements of $π^\pm$, $K^\pm$, $p$ and $\bar{p}$ spectra in $^7$Be+$^9$Be collisions at beam momenta from 19$A$ to 150$A$ GeV/$c$ with the NA61/SHINE spectrometer at the CERN SPS

The NA61/SHINE experiment at the CERN Super Proton Synchrotron (SPS) studies the onset of deconfinement in hadron matter by a scan of particle production in collisions of nuclei with various sizes at a set of energies covering the SPS energy range. This paper presents results on inclusive double-differential spectra, transverse momentum and rapidity distributions and mean multiplicities of $π^\pm$, $K^\pm$, $p$ and $\bar{p}$ produced in the 20$\%$ most $central$ $^7$Be+$^9$Be collisions at beam momenta of 19$A$, 30$A$, 40$A$, 75$A$ and 150$A$ GeV/$c$. The energy dependence of the $K^\pm$/$π^\pm$ ratios as well as of inverse slope parameters of the $K^\pm$ transverse mass distributions are close to those found in inelastic $p$+$p$ reactions. The new results are compared to the world data on $p$+$p$ and Pb+Pb collisions as well as to predictions of the EPOS, UrQMD, AMPT, PHSD and SMASH models.

hep-ex↗

arXiv2022

Measurement of Hadron Production in $π^-$-C Interactions at 158 and 350 GeV/c with NA61/SHINE at the CERN SPS

We present a measurement of the momentum spectra of $π^\pm$, K$^\pm$, p$^\pm$, $Λ$, $\barΛ$ and K$^{0}_{S}$ produced in interactions of negatively charged pions with carbon nuclei at beam momenta of 158 and 350 GeV/c. The total production cross sections are measured as well. The data were collected with the large-acceptance spectrometer of the fixed target experiment NA61/SHINE at the CERN SPS. The obtained double-differential $p$-$p_T$ spectra provide a unique reference data set with unprecedented precision and large phase-space coverage to tune models used for the simulation of particle production in extensive air showers in which pions are the most numerous projectiles.

nucl-ex↗

arXiv2022

Search for Highly-Ionizing Particles in pp Collisions at the LHC's Run-1 Using the Prototype MoEDAL Detector

A search for highly electrically charged objects (HECOs) and magnetic monopoles is presented using 2.2 fb-1 of p - p collision data taken at a centre of mass energy (ECM) of 8 TeV by the MoEDAL detector during LHC's Run-1. The data were collected using MoEDAL's prototype Nuclear Track Detector array and the Trapping Detector array. The results are interpreted in terms of Drell-Yan pair production of stable HECO and monopole pairs with three spin hypotheses (0, 1/2 and 1). The search provides constraints on the direct production of magnetic monopoles carrying one to four Dirac magnetic charges (4gD) and with mass limits ranging from 590 GeV/c^2 to 1 TeV/c^2. Additionally, mass limits are placed on HECOs with charge in the range 10e to 180e, where e is the charge of an electron, for masses between 30 GeV/c^2 and 1 TeV/c^2.

hep-ex↗

arXiv2022

$K^{*}(892)^0$ meson production in inelastic $p+p$ interactions at 40 and 80 GeV/$c$ beam momenta measured by NA61/SHINE at the CERN SPS

Measurements of $K^{*}(892)^0$ resonance production via its $K^{+}π^{-}$ decay mode in inelastic $p+p$ collisions at beam momenta 40 and 80 GeV/$c$ ($\sqrt{s_{NN}}=8.8$ and 12.3 GeV) are presented. The data were recorded by the NA61/SHINE hadron spectrometer at the CERN Super Proton Synchrotron. The \textit{template} method was used to extract the $K^{*}(892)^0$ signal. Transverse momentum and rapidity spectra were obtained. The mean multiplicities of $K^{*}(892)^0$ mesons were found to be $(35.1 \pm 1.3 \mathrm{(stat)} \pm 3.6 \mathrm{(sys)) \cdot 10^{-3}}$ at 40 GeV/$c$ and $(58.3 \pm 1.9 \mathrm{(stat)} \pm 4.9 \mathrm{(sys)) \cdot 10^{-3}}$ at 80 GeV/$c$. The NA61/SHINE results are compared with the EPOS1.99 and Hadron Resonance Gas models as well as with world data. The transverse mass spectra of $K^{*}(892)^0$ mesons and other particles previously reported by NA61/SHINE were fitted within the Blast-Wave model. The transverse flow velocities are close to 0.1--0.2 of the speed of light and are significantly smaller than the ones determined in heavy nucleus-nucleus interactions at the same beam momenta.

nucl-ex↗

arXiv2022

Double $J/ψ$ production in pion-nucleon scattering at COMPASS

We present the study of the production of double $J/ψ$ mesons using COMPASS data collected with a 190 GeV/$c$ $π^-$ beam scattering off NH$_{3}$, Al and W targets. Kinematic distributions of the collected double $J/ψ$ events are analysed, and the double $J/ψ$ production cross section is estimated for each of the COMPASS targets. The results are compared to predictions from single- and double-parton scattering models as well as the pion intrinsic charm and the tetraquark exotic resonance hypotheses. It is demonstrated that the single parton scattering production mechanism gives the dominant contribution that is sufficient to describe the data. An upper limit on the double intrinsic charm content of pion is evaluated. No significant signatures that could be associated with exotic tetraquarks are found in the double $J/ψ$ mass spectrum.

hep-ex↗

arXiv2022

$K^{0}_{S}$ meson production in inelastic $\textit{p+p}$ interactions at 158 GeV/c beam momentum measured by NA61/SHINE at the CERN SPS

The production of $K^{0}_{S}$ mesons in inelastic $\textit{p+p}$ collisions at beam momentum 158 GeV/c ($\sqrt{s_{NN}}=17.3$ GeV) was measured with the NA61/SHINE spectrometer at the CERN Super Proton Synchrotron. Double-differential distributions were obtained in transverse momentum and rapidity. The mean multiplicity of $K^{0}_{S}$ was determined to be $0.162 \pm 0.001 (stat.) \pm 0.011 (sys.)$. The results on $K^{0}_{S}$ production are compared with model predictions (EPOS 1.99, SMASH 2.0, PHSD and UrQMD 3.4 models) as well as with published world data.

hep-ex↗

arXiv2022

First experimental search for production of magnetic monopoles via the Schwinger mechanism

Schwinger showed that electrically-charged particles can be produced in a strong electric field by quantum tunnelling through the Coulomb barrier. By electromagnetic duality, if magnetic monopoles (MMs) exist, they would be produced by the same mechanism in a sufficiently strong magnetic field. Unique advantages of the Schwinger mechanism are that its rate can be calculated using semiclassical techniques without relying on perturbation theory, and the finite MM size and strong MM-photon coupling are expected to enhance their production. Pb-Pb heavy-ion collisions at the LHC produce the strongest known magnetic fields in the current Universe, and this article presents the first search for MM production by the Schwinger mechanism. It was conducted by the MoEDAL experiment during the 5.02 TeV/nucleon heavy-ion run at the LHC in November 2018, during which the MoEDAL trapping detectors (MMTs) were exposed to 0.235 nb$^{-1}$ of Pb-Pb collisions. The MMTs were scanned for the presence of magnetic charge using a SQUID magnetometer. MMs with Dirac charges 1$g_D$ $\leq$ $g$ $\leq$ 3$g_D$ and masses up to 75 GeV/c$^2$ were excluded by the analysis. This provides the first lower mass limit for finite-size MMs from a collider search and significantly extends previous mass bounds.

hep-ex↗

arXiv2022

Measurements of $Ξ^{-}$ and $\overlineΞ^{+}$ production in proton-proton interactions at $\sqrt{s_{NN}}$ = 17.3 GeV in the NA61/SHINE experiment

The production of $Ξ(1321)^{-}$ and $\overlineΞ(1321)^{+}$ hyperons in inelastic p+p interactions is studied in a fixed target experiment at a beam momentum of 158 GeV/textit{c}. Double differential distributions in rapidity y and transverse momentum $p_{T}$ are obtained from a sample of 33M inelastic events. They allow to extrapolate the spectra to full phase space and to determine the mean multiplicity of both $Ξ^{-}$ and $\overlineΞ^{+}$. The rapidity and transverse momentum spectra are compared to transport model predictions. The $Ξ^{-}$ mean multiplicity in inelastic p+p interactions at 158~\GeVc is used to quantify the strangeness enhancement in A+A collisions at the same centre-of-mass energy per nucleon pair.

nucl-ex↗

arXiv2021

A 4pi time-of-flight detector for the ND280/T2K upgrade

ND280 is a near detector of the T2K experiment which is located in the J-PARC accelerator complex in Japan. After a decade of fruitful data-taking, ND280 is scheduled for upgrade. The time-of-flight (ToF) detector, which is described in this article, is one of three new detectors that will be installed in the basket of ND280. The ToF detector has a modular structure. Each module represents an array of 20 plastic scintillator bars which are stacked in a plane of 2.4 x 2.2 m2 area. Six modules of similar construction will be assembled in a cube, thus providing an almost 4pi enclosure for an active neutrino target and two TPCs. The light emitted by scintillator is absorbed by arrays of large-area silicon photo-multipliers (SiPMs) which are attached to both ends of every bar. The readout of SiPMs, shaping and analog sum of individual SiPM signals within the array are performed by a discrete circuit amplifier. An average time resolution of about 0.14 ns is achieved for a single bar when measured with cosmic muons. The detector will be installed in the basket of ND280, where it will be used to veto particle originating outside the neutrino target, improve the particle identification and provide a cosmic trigger for calibration of detectors which are enclosed inside it.

physics.ins-det↗

arXiv2021

Measurements of $Ξ\left(1530\right)^{0}$ and $\overlineΞ\left(1530\right)^{0}$ production in proton-proton interactions at $\sqrt{s_{NN}}$ = 17.3 GeV in the NA61/SHINE experiment

Double-differential yields of $Ξ\left(1530\right)^{0}$ and $\overlineΞ\left(1530\right)^{0}$ resonances produced in \pp interactions were measured at a laboratory beam momentum of 158~\GeVc. This measurement is the first of its kind in \pp interactions below LHC energies. It was performed at the CERN SPS by the \NASixtyOne collaboration. Double-differential distributions in rapidity and transverse momentum were obtained from a sample of 26$\cdot$10$^6$ inelastic events. The spectra are extrapolated to full phase space resulting in mean multiplicity of $Ξ\left(1530\right)^{0}$ (6.73 $\pm$ 0.25 $\pm$ 0.67)$\times10^{-4}$ and $\overlineΞ\left(1530\right)^{0}$ (2.71 $\pm$ 0.18 $\pm$ 0.18)$\times10^{-4}$. The rapidity and transverse momentum spectra and mean multiplicities were compared to predictions of string-hadronic and statistical model calculations.

nucl-ex↗

arXiv2021

First search for dyons with the full MoEDAL trapping detector in 13 TeV pp collisions

The MoEDAL trapping detector, consists of approximately 800 kg of aluminium volumes. It was exposed during Run-2 of the LHC program to 6.46 fb^-1 of 13 TeV proton-proton collisions at the LHCb interaction point. Evidence for dyons (particles with electric and magnetic charge) captured in the trapping detector was sought by passing the aluminium volumes comprising the detector through a SQUID magnetometer. The presence of a trapped dyon would be signalled by a persistent current induced in the SQUID magnetometer. On the basis of a Drell-Yan production model, we exclude dyons with a magnetic charge ranging up to 5 Dirac charges, and an electric charge up to 200 times the fundamental electric charge for mass limits in the range 790 - 3130 GeV.

hep-ex↗