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M. Bogomilov

Publications and source records attributed to M. Bogomilov.

At least 19 recordsLinked to original sources
arXiv2026

Study of Supernova Neutrinos at ESSnuSB

In this paper, we have studied the sensitivity of the ESSnuSB far detector to supernova neutrinos. ESSnuSB is a proposed long-baseline neutrino experiment in Sweden, which will use a 538 kt water Cherenkov detector to probe the leptonic phase $δ_{\rm CP}$ by studying the second oscillation maximum. However, given the very large detector volume, it will have an excellent sensitivity to supernova neutrinos if a supernova explosion occurs during the run-time of ESSnuSB. Motivated by this, we first estimate the expected event rates at the ESSnuSB far detector for three different supernova flux models and then we probe its capability to distinguish these flux models. Additionally, we also investigate the impact of systematic errors and detector efficiency. Our results show that depending on the model of the supernova neutrinos, the expected number of events detected at Earth varies significantly. Our results also show that the ESSnuSB far detector may have excellent potential in distinguishing these flux models depending upon the distance of the supernova explosion, systematic errors and detector efficiency.

hep-ex↗
arXiv2026

Exploring ESS$ν$SB Near Water Cherenkov Detector Designs Through Graph Neural Network Flavour Identification

The ESS$ν$SB experiment aims to measure CP violation in the leptonic sector with high precision, necessitating robust reconstruction of neutrino events in the water Cherenkov (WC) detectors. In this work, we investigate the flavour identification potential of the proposed near WC detector using graph neural network (GNN)-based classification, with a focus on variations of key detector design parameters. In particular, we study whether a smaller and/or less instrumented detector can achieve the required classification performance. Using detailed Monte Carlo simulations of charged-current (CC) neutrino interactions, we train GNN classifiers to distinguish electron and muon neutrino CC events. We find that GNN-based classification remains accurate even for detector configurations with volumes up to a factor of eight smaller than the nominal design, with only moderate degradation in classification efficiency at fixed background rejection. The resulting loss in efficiency can largely be compensated by increased exposure time. Furthermore, we demonstrate that reduced photomultiplier tube (PMT) coverage in the nominal detector has a limited impact on classification performance, provided that coverage is maintained in regions of highest signal yield, in particular near the forward end-cap.

hep-ex↗
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.

nucl-ex↗
arXiv2026

Measurement of the muon neutrino charged-current cross section with SND@LHC

We report a measurement of the muon neutrino charged-current (CC) interaction cross section on tungsten using the electronic detectors of the SND@LHC experiment at the CERN Large Hadron Collider. The analysis uses proton--proton collision data at a centre-of-mass energy of $\sqrt{s} = 13.6$ TeV, corresponding to an integrated luminosity of $68.6 ~\text{fb}^{-1}$ collected during LHC Run 3 in 2022 and 2023. A total of 31 $ν_μ$ CC candidates are selected against an expected background of $5.0 \pm 1.1$ events, consistent with a signal expectation of $24^{+10}_{-9}$ events. The signal strength is measured to be $\hatμ = 1.09^{+0.72}_{-0.37}$, and the combined muon neutrino and anti-neutrino CC cross section on tungsten is determined to be $σ(ν_μ+ \barν_μ) = (37^{+24}_{-12})\times 10^{-35}~\text{cm}^2$ at a median energy of $228$ GeV. In addition, a calorimetric measurement of the hadronic energies of the neutrino candidate events is performed, making use of calibration data from dedicated test-beam campaigns.

hep-ex↗
arXiv2026

Searching non-standard interactions with atmospheric neutrinos at ESSnuSB

Atmospheric neutrinos provide a unique avenue to study neutrino interactions in matter. In this work, the prospects of constraining non-standard neutrino interactions with atmospheric neutrino oscillations are investigated for the proposed ESSnuSB far detector. By analyzing atmospheric neutrino samples equivalent to 5.4 Mt$\cdot$year exposure, it is found that ESSnuSB could be able to set the upper bounds $|ε_{eμ}^m| < 0.053, |ε_{eτ}^m| < 0.057, |ε_{μτ}^m| < 0.021, ε_{ee}^m - ε_{μμ}^m < 0.075$ and $|ε_{ττ}^m - ε_{μμ}^m| < 0.031$ at $90\%$ CL, when the results are minimized for $ϕ_{eμ}^m, ϕ_{eτ}^m$ and $ϕ_{μτ}^m$ and normal ordering is assumed for neutrino masses. It is also shown that the presence of non-standard interactions could affect the sensitivities to neutrino mass ordering and $θ_{23}^{}$ octant in comparison to the standard interaction scheme. The results of this work highlight the complementarity between atmospheric and accelerator neutrino programs in ESSnuSB.

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arXiv2026

Complementarity between atmospheric and super-beam neutrinos at ESSnuSB

The ESSnuSB experiment aims to measure the leptonic CP phase $δ_{CP}$ with an unprecedented resolution by probing neutrino oscillations at the second oscillation maximum. In the present work, the complementarity between the long-baseline neutrino program and atmospheric neutrinos is investigated for ESSnuSB. By simulating atmospheric neutrino events equivalent of 5.4 Mt$\cdot$year exposure, the resolution for $δ_{\rm CP}^{}$ is found to improve from $7.5^\circ$ ($6.7^\circ$) to $7.1^\circ$ ($6.5^\circ$) at $1σ$~CL for $δ_{\rm CP}^{} = -90^\circ$ ($+90^\circ$) with respect to super-beam neutrinos, resolving also the degeneracies arising from neutrino mass ordering. These findings highlight the synergies that exist between super-beam neutrinos and atmospheric neutrinos in ESSnuSB.

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arXiv2025

Bulgarian national input to the European Strategy for Particle Physics

The present document summarizes the view and the vision of the Bulgarian subatomic physics scientific community for the development of the field of subatomic physics from the Bulgarian national perspective. It outlines the present activities and the strengths and weaknesses of the research field, together with the interests of the community for the future development of the technological and scientific landscape.

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arXiv2025

Probing Long-Range Forces in Neutrino Oscillations at the ESSnuSB Experiment

Neutrino oscillations constitute an excellent tool to probe physics beyond the Standard Model. In this paper, we investigate the potential of the ESSnuSB experiment to constrain the effects of flavour-dependent long-range forces (LRFs) in neutrino oscillations, which may arise due to the extension of the Standard Model gauge group by introducing new $U(1)$ symmetries. Focusing on three specific $U(1)$ symmetries -- $L_e - L_μ$, $L_e - L_τ$, and $L_μ- L_τ$, we demonstrate that ESSnuSB offers a favourable environment to search for LRF effects. Our analyses reveal that ESSnuSB can set $90\%$ confidence level bounds of $V_{eμ} < 2.99 \times 10^{-14} \, \text{eV}$, $V_{eτ} < 2.05 \times 10^{-14} \, \text{eV}$, and $V_{μτ} < 1.81 \times 10^{-14} \, \text{eV}$, which are competitive to the upcoming Deep Underground Neutrino Experiment (DUNE). It is also observed that reducing the systematic uncertainties from $5\%$ to $2\%$ improves the ESSnuSB limits on $V_{αβ}$. Interestingly, we find limited correlations between LRF parameters and the less constrained lepton mixing parameters $θ_{23}$ and $δ_{\text{CP}}$, preserving the robustness of ESSnuSB's sensitivity to CP violation. Even under extreme LRF potentials ($V_{αβ} \gg 10^{-13} \, \text{eV}$), the CP-violation sensitivity and $δ_{\text{CP}}$ precision remain largely unaffected. These results establish ESSnuSB as a competitive experimental setup for probing LRF effects, complementing constraints from other neutrino sources and offering critical insights into the physics of long-range forces.

hep-ph↗
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.

hep-ex↗
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.

nucl-ex↗
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.

nucl-ex↗
arXiv2025

Classification of Electron and Muon Neutrino Events for the ESS$ν$SB Near Water Cherenkov Detector using Graph Neural Networks

In the effort to obtain a precise measurement of leptonic CP-violation with the ESS$ν$SB experiment, accurate and fast reconstruction of detector events plays a pivotal role. In this work, we examine the possibility of replacing the currently proposed likelihood-based reconstruction method with an approach based on Graph Neural Networks (GNNs). As the likelihood-based reconstruction method is reasonably accurate but computationally expensive, one of the benefits of a Machine Learning (ML) based method is enabling fast event reconstruction in the detector development phase, allowing for easier investigation of the effects of changes to the detector design. Focusing on classification of flavour and interaction type in muon and electron events and muon- and electron neutrino interaction events, we demonstrate that the GNN reconstructs events with greater accuracy than the likelihood method for events with greater complexity, and with increased speed for all events. Additionally, we investigate the key factors impacting reconstruction performance, and demonstrate how separation of events by pion production using another GNN classifier can benefit flavour classification.

hep-ex↗
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.

nucl-ex↗
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.

hep-ex↗
arXiv2024

Exploring atmospheric neutrino oscillations at ESSnuSB

This study provides an analysis of atmospheric neutrino oscillations at the ESSnuSB far detector facility. The prospects of the two cylindrical Water Cherenkov detectors with a total fiducial mass of 540 kt are investigated over 10 years of data taking in the standard three-flavor oscillation scenario. We present the confidence intervals for the determination of mass ordering, $θ_{23}$ octant as well as for the precisions on $\sin^2θ_{23}$ and $|Δm_{31}^2|$. It is shown that mass ordering can be resolved by $3σ$ CL ($5σ$ CL) after 4 years (10 years) regardless of the true neutrino mass ordering. Correspondingly, the wrong $θ_{23}$ octant could be excluded by $3σ$ CL after 4 years (8 years) in the case where the true neutrino mass ordering is normal ordering (inverted ordering). The results presented in this work are complementary to the accelerator neutrino program in the ESSnuSB project.

hep-ex↗
arXiv2024

Decoherence in Neutrino Oscillation at the ESSnuSB Experiment

Neutrino oscillation experiments provide a unique window in exploring several new physics scenarios beyond the standard three flavour. One such scenario is quantum decoherence in neutrino oscillation which tends to destroy the interference pattern of neutrinos reaching the far detector from the source. In this work, we study the decoherence in neutrino oscillation in the context of the ESSnuSB experiment. We consider the energy-independent decoherence parameter and derive the analytical expressions for P$_{μe}$ and P$_{μμ}$ probabilities in vacuum. We have computed the capability of ESSnuSB to put bounds on the decoherence parameters namely, $Γ_{21}$ and $Γ_{32}$ and found that the constraints on $Γ_{21}$ are competitive compared to the DUNE bounds and better than the most stringent LBL ones from MINOS/MINOS+. We have also investigated the impact of decoherence on the ESSnuSB measurement of the Dirac CP phase $δ_{\rm CP}$ and concluded that it remains robust in the presence of new physics.

hep-ex↗
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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