arXiv subjects

V. Matveev

Publications and source records attributed to V. Matveev.

At least 19 recordsLinked to original sources

arXiv2026

NOvA Dual-Baseline Search for Active-to-Sterile Neutrino Oscillations using Neutrino- and Antineutrino-Enriched Samples

We report a search for neutrino oscillations to sterile neutrinos in the NOvA detectors under a model with three active and one sterile neutrinos. This search simultaneously fits data in the two NOvA detectors and is the first from NOvA to use both neutrino- and antineutrino-mode beams, with exposures of $26.61\times10^{20}$ and $12.50\times10^{20}$ protons on target, respectively. There is no evidence for sterile neutrinos in the data and we are able to exclude regions of parameter space that were allowed by previous experiments, including most of the allowed region reported by IceCube.

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arXiv2026

Neutron detector response modeling in NOvA

Neutrons can present a significant challenge for neutrino experiments in which energy reconstruction is critical. With the ability to escape detection completely and with a weak correlation between their kinetic energy and any eventual energy deposition, it is difficult to fully account for neutrons produced in neutrino interactions. This in turn leads to significant model dependence when evaluating neutron-related systematic uncertainties. The NOvA experiment is a long-baseline neutrino oscillation experiment with a high-statistics sample of antineutrino data collected by its near detector. We report an excess relative to data of simulated neutron candidates with low energy depositions when using standard Geant4 physics lists. The simulation excess is traced to an overabundance of secondary photons produced from interactions of neutrons with kinetic energy greater than \SI{20}{\mega\eV}. Improved agreement with data is obtained by applying the data-driven neutron-on-carbon \menate model for neutrons between \SI{20}{\mega\eV} and ${\sim}$\SI{100}{\mega\eV}. With \menate, the residual oversimulation is more uniform across the calorimetric neutron energy spectrum, suggesting possible overproduction of primary neutrons by the GENIE neutrino interaction generator. These results motivate the adoption of \menate-supplemented Geant4 simulation as the nominal simulation in the production of future \nova simulation.

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arXiv2026

$K^{*}(892)^0$ production and the time between freeze-outs in $^{40}$Ar+$^{45}$Sc collisions by NA61/SHINE at the CERN SPS

The analysis of the production of strange $K^{*}(892)^0$ resonances allows us to better understand the temporal evolution of high-energy nucleus--nucleus collisions. In particular, the ratio of $K^{*}(892)^0$ to charged kaon yields is used to determine the time interval between chemical and kinetic freeze-outs. In this paper, the first measurements of $K^{*}(892)^0$ production in central $^{40}$Ar+$^{45}$Sc collisions at the CERN Super Proton Synchrotron are reported. They were performed by NA61/SHINE at collision center-of-mass energies per nucleon pair $\sqrt{s_\mathrm{NN}}$ = 8.8, 11.9, 16.8 GeV. The obtained $\langle K^{*}(892)^0 \rangle/\langle K^{+} \rangle $ and $\langle K^{*}(892)^0 \rangle/\langle K^{-} \rangle$ mean multiplicity ratios are compared with corresponding results in $p$+$p$ collisions, allowing for an estimate of the time interval between chemical and thermal freeze-outs in the $^{40}$Ar+$^{45}$Sc system. These are the first such results reported for $^{40}$Ar+$^{45}$Sc collisions.

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arXiv2026

Baryon-antibaryon photoproduction cross sections off the proton

The GlueX experiment at Jefferson Lab has observed $p\bar{p}$ and, for the first time, $Λ\barΛ$ and $p\barΛ$ photoproduction from a proton target at photon energies up to 11.6 GeV. The angular distributions are forward peaked for all produced pairs, consistent with Regge-like $t$-channel exchange. Asymmetric wide-angle anti-baryon distributions show the presence of additional processes. In a phenomenological model, we find consistency with a double $t$-channel exchange process where anti-baryons are created only at the middle vertex. The model matches all observed distributions with a small number of free parameters. In the hyperon channels, we observe a clear distinction between photoproduction of the $Λ\barΛ$ and $p\barΛ$ systems but general similarity to the $p\bar{p}$ system. We report both total cross sections and cross sections differential with respect to momentum transfer and the invariant masses of the created particle pairs. No narrow resonant structures were found in these reaction channels. The suppression of $s\bar{s}$ quark pairs relative to $d\bar{d}$ quark pairs is similar to what has been seen in other reactions.

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arXiv2025

Search for Accelerator-Produced Sub-GeV Dark Matter with the NOvA Near Detector

The NuMI facility at Fermilab produces a high-intensity beam of muon neutrinos and antineutrinos, designed to study neutrino oscillations. This beam may also be a source of dark matter particles produced through a light mediator. We search for dark matter particles with masses between 1 and 200 MeV that interact with Standard Model particles via a vector portal, producing forward-scattered single-electron events in the NOvA near detector. We set limits on the dark-visible coupling based on an exposure of 2.55x10^21 protons of 120 GeV energy on the NuMI target. For the dark matter mass range 10-20 MeV, this analysis sets the tightest constraints on the coupling to date.

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arXiv2025

Measurement of the Total Compton Scattering Cross Section between 6.5 and 11 GeV

The total cross section for Compton scattering off atomic electrons, $γ+e\rightarrowγ'+e'$, was measured using photons with energies between 6.5 and 11.1 GeV incident on a $^9$Be target as part of the PrimEx-eta experiment in Hall D at Jefferson Lab. This is the first measurement of this fundamental QED process within this energy range. The total uncertainties of the cross section, combining the statistical and systematic components in quadrature, averaged to 3.4% across all energy bins. This not only demonstrates the capability of this experimental setup to perform precision cross-section measurements at forward angles but also allows us to compare with state-of-the-art QED calculations.

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arXiv2025

Measurements of hadron production in 90 GeV/c proton-carbon interactions

This paper presents the multiplicity of neutral and charged hadrons produced in 90 GeV$/c$ proton-carbon interactions from a dataset taken by the NA61/SHINE experiment in 2017. Particle identification via dE/dx was performed for the charged hadrons $π^\pm$, $K^\pm$, and $p / \bar{p}$; the neutral hadrons $K^0_S$, $Λ$, and $\barΛ$ were identified via an invariant mass analysis of their decays to charged hadrons. Double-differential multiplicity results as a function of laboratory momentum and polar angle are presented for each particle species; these results provide vital constraints on the predicted neutrino beam flux for current and future long-baseline neutrino oscillation experiments.

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arXiv2025

Proposal from the NA61/SHINE Collaboration for update of European Strategy for Particle Physics

Building on the current program's success and driven by new physics challenges, the NA61/SHINE Collaboration proposes to continue measuring hadron production properties in reactions induced by hadron and ion beams after CERN Long Shutdown 3. These measurements are of significant interest to the heavy-ion, cosmic-ray, and neutrino physics communities and will focus on: - Investigating hadron production in the light-ion systems to explore the diagram of high-energy nuclear collisions, and to obtain new insight into the unexpected violation of isospin (flavor) symmetry recently observed by the experiment; - Measuring charm-anticharm correlations to gain unique insights into the production locality of charm and anticharm quark pairs; - Examining strangeness and multi-strangeness production to improve our understanding of the early Universe's evolution and neutron star formation; - Measuring cross sections relevant for cosmic-ray measurements, significantly boosting searches for new physics in our Galaxy; - Conducting hadron production measurements with proton, pion, and kaon beams for neutrino physics, enhancing the precision of hadron production data needed for initial neutrino flux predictions in neutrino oscillation experiments; - Measuring hadron production processes relevant for understanding the flux of atmospheric neutrinos, as well as neutrinos and muons from spallation sources. To achieve these objectives, a detector upgrade and a beam upgrade are required, with data-taking planned for the period 2029-2032 and beyond.

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arXiv2025

Evidence of isospin-symmetry violation in high-energy collisions of atomic nuclei

Strong interactions preserve an approximate isospin symmetry between up ($u$) and down ($d$) quarks, part of the more general flavor symmetry. In the case of $K$ meson production, if this isospin symmetry were exact, it would result in equal numbers of charged ($K^+$ and $K^-$) and neutral ($K^0$ and $\overline K^{\,0}$) mesons in the final state. Here, we report results on the relative abundance of charged over neutral $K$ meson production in argon and scandium nuclei collisions at a center-of-mass energy of 11.9 GeV per nucleon pair. We find that the production of $K^+$ and $K^-$ mesons at mid-rapidity is $(18.4\pm 6.1)\%$ higher than that of the neutral $K$ mesons. Although with large uncertainties, earlier data on nucleus-nucleus collisions in the collision center-of-mass energy range $2.6 < \sqrt{s_{NN}} < 200$~\GeV are consistent with the present result. Using well-established models for hadron production, we demonstrate that known isospin-symmetry breaking effects and the initial nuclei containing more neutrons than protons lead only to a small (few percent) deviation of the charged-to-neutral kaon ratio from unity at high energies. Thus, they cannot explain the measurements. The significance of the flavor-symmetry violation beyond the known effects is 4.7$σ$ when the compilation of world data with uncertainties quoted by the experiments is used. New systematic, high-precision measurements and theoretical efforts are needed to establish the origin of the observed large isospin-symmetry breaking.

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arXiv2025

Multiplicity and net-electric charge fluctuations in central Ar+Sc interactions at 13A, 19A, 30A, 40A, 75A, and 150A GeV/c beam momenta measured by NA61/SHINE at the CERN SPS

This paper presents results on multiplicity fluctuations of positively and negatively charged hadrons as well as net-electric charge fluctuations measured in central Ar+Sc interactions at beam momenta 13A, 19A, 30A, 40A, 75A, and 150A GeV/c. The fluctuation analysis is one of the tools to search for the predicted critical point of strongly interacting matter. Results are corrected for the experimental biases and quantified using cumulant ratios. In most instances, multiplicity and net-charge distributions appear narrower than the corresponding Poisson or Skellam distributions. Cumulant ratios are compared with the EPOS1.99 model predictions, which provide a qualitative description that aligns with observations for positively and negatively charged particles. The obtained results are also compared to earlier NA61/SHINE results from inelastic p+p interactions in the same analysis acceptance.

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arXiv2025

Measurements of higher-order cumulants of multiplicity and net-electric charge distributions in inelastic proton-proton interactions by NA61/SHINE

This paper presents the energy dependence of multiplicity and net-electric charge fluctuations in p+p interactions at beam momenta 20, 31, 40, 80, and 158 GeV/c. Results are corrected for the experimental biases and quantified with the use of cumulants and factorial cumulants. Cumulant ratios are an essential tool in the search for the critical point of strongly interacting matter in heavy ion collisions. Measurements performed in p+p interactions provide a vital baseline estimation in these studies. The measured signals are compared with the string hadronic models EPOS1.99 and FTFP-BERT.

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arXiv2025

Upper Limit on the Photoproduction Cross Section of the Spin-Exotic $π_1(1600)$

The spin-exotic hybrid meson $π_{1}(1600)$ is predicted to have a large decay rate to the $ωππ$ final state. Using 76.6~pb$^{-1}$ of data collected with the GlueX detector, we measure the cross sections for the reactions $γp \to ωπ^+ π^- p$, $γp \to ωπ^0 π^0 p$, and $γp\toωπ^-π^0Δ^{++}$ in the range $E_γ=$ 8-10 GeV. Using isospin conservation, we set the first upper limits on the photoproduction cross sections of the $π^{0}_{1}(1600)$ and $π^{-}_{1}(1600)$. We combine these limits with lattice calculations of decay widths and find that photoproduction of $η'π$ is the most sensitive two-body system to search for the $π_1(1600)$.

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arXiv2025

First Measurement of $a^0_2(1320)$ Polarized Photoproduction Cross Section

We measure for the first time the differential photoproduction cross section $dσ/dt$ of the $a_2(1320)$ meson at an average photon beam energy of 8.5~GeV, using data with an integrated luminosity of 104~pb$^{-1}$ collected by the GlueX experiment. We fully reconstruct the $γp \to ηπ^0 p$ reaction and perform a partial-wave analysis in the $a_2(1320)$ mass region with amplitudes that incorporate the linear polarization of the beam. This allows us to separate for the first time the contributions of natural- and unnatural-parity exchanges. These measurements provide novel information about the photoproduction mechanism, which is critical for the search for spin-exotic states.

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arXiv2024

Measurement of Spin-Density Matrix Elements in $Δ^{++}(1232)$ photoproduction

We measure the spin-density matrix elements (SDMEs) of the $Δ^{++}(1232)$ in the photoproduction reaction $γp \to π^-Δ^{++}(1232)$ with the GlueX experiment in Hall D at Jefferson Lab. The measurement uses a linearly--polarized photon beam with energies from $8.2$ to $8.8$~GeV and the statistical precision of the SDMEs exceeds the previous measurement by three orders of magnitude for the momentum transfer squared region below $1.4$ GeV$^2$. The data are sensitive to the previously undetermined relative sign between couplings in existing Regge-exchange models. Linear combinations of the extracted SDMEs allow for a decomposition into natural and unnatural--exchange amplitudes. We find that the unnatural exchange plays an important role in the low momentum transfer region.

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arXiv2024

Two-pion femtoscopic correlations in Be+Be collisions at $\sqrt{s_{\textrm{NN}}} = 16.84$ GeV measured by the NA61/SHINE at CERN

This paper reports measurements of two-pion Bose-Einstein (HBT) correlations in Be+Be collisions at a beam momentum of 150$A\,\mbox{GeV}/\textit{c}$ by the $\mbox{NA61/SHINE}$ experiment at the CERN SPS accelerator. The obtained momentum space correlation functions can be well described by a Lévy distributed source model. The transverse mass dependence of the Lévy source parameters is presented, and their possible theoretical interpretations are discussed. The results show that the Lévy exponent $α$ is approximately constant as a function of $m_{\rm{T}}$ , and far from both the Gaussian case of $α= 2$ or the conjectured value at the critical endpoint, $α= 0.5$. The radius scale parameter $R$ shows a slight decrease in $m_{\rm{T}}$, which can be explained as a signature of transverse flow. Finally, an approximately constant trend of the intercept parameter $λ$ as a function of $m_{\rm{T}}$ was observed, different from measurement results at RHIC.

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arXiv2024

Measurement of the J/$ψ$ photoproduction cross section over the full near-threshold kinematic region

We report the total and differential cross sections for $J/ψ$ photoproduction with the large acceptance GlueX spectrometer for photon beam energies from the threshold at 8.2~GeV up to 11.44~GeV and over the full kinematic range of momentum transfer squared, $t$. Such coverage facilitates the extrapolation of the differential cross sections to the forward ($t = 0$) point beyond the physical region. The forward cross section is used by many theoretical models and plays an important role in understanding $J/ψ$ photoproduction and its relation to the $J/ψ-$proton interaction. These measurements of $J/ψ$ photoproduction near threshold are also crucial inputs to theoretical models that are used to study important aspects of the gluon structure of the proton, such as the gluon Generalized Parton Distribution (GPD) of the proton, the mass radius of the proton, and the trace anomaly contribution to the proton mass. We observe possible structures in the total cross section energy dependence and find evidence for contributions beyond gluon exchange in the differential cross section close to threshold, both of which are consistent with contributions from open-charm intermediate states.

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arXiv2024

Measurement of Spin-Density Matrix Elements in $ρ(770)$ Production with a Linearly Polarized Photon Beam at $E_γ= 8.2\,-\,8.8\,\text{GeV}$

The GlueX experiment at Jefferson Lab studies photoproduction of mesons using linearly polarized $8.5\,\text{GeV}$ photons impinging on a hydrogen target which is contained within a detector with near-complete coverage for charged and neutral particles. We present measurements of spin-density matrix elements for the photoproduction of the vector meson $ρ$(770). The statistical precision achieved exceeds that of previous experiments for polarized photoproduction in this energy range by orders of magnitude. We confirm a high degree of $s$-channel helicity conservation at small squared four-momentum transfer $t$ and are able to extract the $t$-dependence of natural and unnatural-parity exchange contributions to the production process in detail. We confirm the dominance of natural-parity exchange over the full $t$ range. We also find that helicity amplitudes in which the helicity of the incident photon and the photoproduced $ρ(770)$ differ by two units are negligible for $-t<0.5\,\text{GeV}^{2}/c^{2}$.

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arXiv2024

Measurements of $π^\pm$, $K^\pm$, $p$ and $\bar{p}$ spectra in $^{40}$Ar+$^{45}$Sc collisions at 13$A$ to 150$A$ GeV/$c$

The NA61/SHINE experiment at the CERN Super Proton Synchrotron studies the onset of deconfinement in strongly interacting matter through a beam energy scan of particle production in collisions of nuclei of varied sizes. 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 $^{40}$Ar+$^{45}$Sc collisions at beam momenta of 13$A$, 19$A$, 30$A$, 40$A$, 75$A$ and 150$A$~\GeVc. The analysis uses the 10\% most central collisions, where the observed forward energy defines centrality. 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 placed in between those found in inelastic $p$+$p$ and central Pb+Pb collisions. The results obtained here establish a system-size dependence of hadron production properties that so far cannot be explained either within statistical or dynamical models.

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