Searcharxiv⌕ Search

arXiv subjects

A. Antonov

Publications and source records attributed to A. Antonov.

At least 19 recordsLinked to original sources
arXiv2026

Development and integration of the NA64-DTC automation controller for the CERN "DESY Table" motorized platform

We report on the development, construction, and integration of a remote automation controller \texttt{NA64-DTC} for the so-called ``DESY Table'' motorised platform widely used at CERN East-Area and North-Area experimental installations. The device is based on an ESP32-C3 System-on-Module that interfaces with the table manual control panel via a signal duplication connector. Button presses are emulated through opto-isolated switches, to allow for simultaneous operation with the manual system without modifying the original hardware. A \texttt{HTTP} server running on the controller allows interfacing with the device, enabling experiment-specific integration solutions. \\ The device was successfully commissioned at CERN, exploiting the experimental installations at PS-T9 and SPS-H4 beamlines. This work describes in detail the device technical design and operation, as well as the performance obtained during the commissioning operations. Although initially conceived for the NA64 experiment, the proposed solution can be of interest to all CERN experiments making use of the DESY Table platform, enabling remote and automated operation while reducing manual intervention during beam activities.

physics.ins-det↗
arXiv2026

Improved limits on a new $Z'$ in $B-L$ scenarios with the NA64 experiment at CERN

Extensions of the Standard Model featuring an additional $U(1)_{B-L}$ gauge symmetry provide a compelling framework linking the origin of neutrino masses to possible dark matter candidates. The associated gauge boson, $Z'$, couples directly to Standard Model fermions and can be produced in fixed-target experiments through electron-nucleus interactions. In this work, we present new constraints on the coupling constant $g_{B-L}$ obtained with the NA64 experiment using the full electron-beam dataset collected between 2016 and 2022, corresponding to $(9.4\pm0.5)\times10^{11}$ electrons on target. The analysis includes the resonant $e^{+}e^{-}$ annihilation production channel, which enhances sensitivity in the mass range $m_{Z'}\in[200,300]$ MeV. The larger dataset provides approximately three times the statistics of previous analyses, thereby improving sensitivity. For the unbroken $U(1)_{B-L}$ case, the new limits exceed those from dedicated neutrino-scattering experiments, providing the most stringent laboratory bounds on $g_{B-L}$ for sub-GeV masses of the new boson. In scenarios where the $Z'$ couples to dark matter, the decay width is dominated by invisible channels, and the corresponding exclusion limits can be directly derived from the NA64 invisible-mode analysis.

hep-ex↗
arXiv2025

Proof of principle for a light dark matter search with low-energy positron beams at NA64

Thermal light dark matter (LDM) with particle masses in the 1 MeV - 1 GeV range could successfully explain the observed dark matter abundance as a relic from the primordial Universe. In this picture, a new feeble interaction acts as a "portal" between the Standard Model and LDM particles, allowing for the exploration of this paradigm at accelerator experiments. In the last years, the "missing energy" experiment NA64e at CERN SPS (Super Proton Synchrotron) has set world-leading constraints in the vector-mediated LDM parameter space, by exploiting a 100 GeV electron beam impinging on an electromagnetic calorimeter, acting as an active target. In this paper, we report a detailed description of the analysis of a preliminary measurement with a 70 GeV positron beam at NA64e, performed during summer 2023 with an accumulated statistic of 1.6 x 10^10 positrons on target. This data set was analyzed with the primary aim of evaluating the performance of the NA64e detector with a lower energy positron beam, towards the realization of the post-LS3 program. The analysis results, other than additionally probing unexplored regions in the LDM parameter space, provide valuable information towards the future NA64e positron campaign.

hep-ex↗
arXiv2025

Searching for Light Dark Matter and Dark Sectors with the NA64 experiment at the CERN SPS

Since its approval in 2016, NA64 has pioneered light dark matter (LDM) searches with electron, positron, muon, and hadron beams. The experiment has successfully met its primary objectives, as outlined in the EPPS input (2018), and even exceeded them, producing results that demonstrate its ability to operate in a near-background-free environment. The Physics Beyond Collider (PBC) initiative at CERN recognizes NA64's contributions as complementary and worthy of continued exploration. Its key advantage over beam-dump approaches is that the signal rate scales as the square of the coupling rather than the fourth power, reducing the required number of beam particles for the same sensitivity. To fully exploit the NA64 physics potential, an upgrade during LS3 will enable the experiment to run in background-free mode at higher SPS beam rates. Planned upgrades include: (a) improved detector hermeticity with a new veto hadron calorimeter, (b) enhanced particle identification with a synchrotron radiation detector, and (c) increased beam rates via upgraded electronics. With the recently strengthened NA64 collaboration, stable operations and timely data analysis are planned for LHC Run 4. The expected beam exposures are approximately 1e13 electrons, 1e11 positrons (at 40 and 60 GeV), and 2e13 muons on target. This will allow NA64 to explore new LDM parameter space, with the potential for discovery or conclusive exclusion of many well-motivated models.

hep-ex↗
arXiv2025

High efficiency veto hadron calorimeter in the NA64 experiment at CERN

NA64 is a fixed-target experiment at the CERN SPS designed to search for Light particle Dark Matter (LDM) candidates with masses in the sub-GeV range. During the 2016-2022 runs, the experiment obtained the world-leading constraints, leaving however part of the well-motivated region of parameter space suggested by benchmark LDM models still unexplored. To further improve sensitivity, as part of the upgrades to the setup of NA64 at the CERN SPS H4 beamline, a prototype veto hadron calorimeter (VHCAL) was installed in the downstream region of the experiment during the 2023 run. The VHCAL, made of Cu-Sc layers, was expected to be an efficient veto against upstream electroproduction of large-angle hadrons or photon-nuclear interactions, reducing the background from secondary particles escaping the detector acceptance. With the collected statistics of $4.4\times10^{11}$ electrons on target (EOT), we demonstrate the effectiveness of this approach by rejecting this background by more than an order of magnitude. This result provides an essential input for designing a full-scale optimized VHCAL to continue running background-free during LHC Run 4, when we expect to collect $10^{13}$ EOT. Furthermore, this technique combined with improvements in the analysis enables us to decrease our missing energy threshold from 50 GeV to 40 GeV thereby enhancing the signal sensitivity of NA64.

hep-ex↗
arXiv2024

First constraints on the $L_μ-L_τ$ explanation of the muon $g-2$ anomaly from NA64-$e$ at CERN

The inclusion of an additional $U(1)$ gauge $L_μ-L_τ$ symmetry would release the tension between the measured and the predicted value of the anomalous muon magnetic moment: this paradigm assumes the existence of a new, light $Z^\prime$ vector boson, with dominant coupling to $μ$ and $τ$ leptons and interacting with electrons via a loop mechanism. The $L_μ-L_τ$ model can also explain the Dark Matter relic abundance, by assuming that the $Z'$ boson acts as a "portal" to a new Dark Sector of particles in Nature, not charged under known interactions. In this work we present the results of the $Z'$ search performed by the NA64-$e$ experiment at CERN SPS, that collected $\sim 9\times10^{11}$ 100 GeV electrons impinging on an active thick target. Despite the suppressed $Z'$ production yield with an electron beam, NA64-$e$ provides the first accelerator-based results excluding the $g-2$ preferred band of the $Z'$ parameter space in the 1 keV $ < m_{Z'} \lesssim 2$ MeV range, in complementarity with the limits recently obtained by the NA64-$μ$ experiment with a muon beam.

hep-ex↗
arXiv2024

50 GeV $π^-$ in, nothing out: a sensitive probe of invisible $η$ and $η'$ decays with NA64h

We present the first results from a proof-of-concept search for dark sectors via invisible decays of pseudoscalar $η$ and $η'$ mesons in the NA64h experiment at the CERN SPS. Our novel technique uses the charge-exchange reaction of 50 GeV $π^-$ on nuclei of an active target as the source of neutral mesons. The $η, η' \to invisible$ events would exhibit themselves via a striking signature - the complete disappearance of the incoming beam energy in the detector. No evidence for such events has been found with $2.9\times10^{9}$ pions on target accumulated during one day of data taking. This allows us to set a stringent limit on the branching ratio ${\rm Br}(η' \to invisible) < 2.1 \times 10^{-4}$ improving the current bound by a factor of $\simeq3$. We also set a limit on ${\rm Br}(η\to invisible) < 1.1 \times 10^{-4}$ comparable with the existing one. These results demonstrate the great potential of our approach and provide clear guidance on how to enhance and extend the sensitivity for dark sector physics from future searches for invisible neutral meson decays.

hep-ex↗
arXiv2024

Technical Design Report of the Spin Physics Detector at NICA

The Spin Physics Detector collaboration proposes to install a universal detector in the second interaction point of the NICA collider under construction (JINR, Dubna) to study the spin structure of the proton and deuteron and other spin-related phenomena using a unique possibility to operate with polarized proton and deuteron beams at a collision energy up to 27 GeV and a luminosity up to $10^{32}$ cm$^{-2}$ s$^{-1}$. As the main goal, the experiment aims to provide access to the gluon TMD PDFs in the proton and deuteron, as well as the gluon transversity distribution and tensor PDFs in the deuteron, via the measurement of specific single and double spin asymmetries using different complementary probes such as charmonia, open charm, and prompt photon production processes. Other polarized and unpolarized physics is possible, especially at the first stage of NICA operation with reduced luminosity and collision energy of the proton and ion beams. This document is dedicated exclusively to technical issues of the SPD setup construction.

hep-ex↗
arXiv2023

Probing Light Dark Matter with positron beams at NA64

We present the results of a missing-energy search for Light Dark Matter which has a new interaction with ordinary matter transmitted by a vector boson, called dark photon $A^\prime$. For the first time, this search is performed with a positron beam by using the significantly enhanced production of $A^\prime$ in the resonant annihilation of positrons with atomic electrons of the target nuclei, followed by the invisible decay of $A^\prime$ into dark matter. No events were found in the signal region with $(10.1 \pm 0.1)~\times~10^{9}$ positrons on target with 100 GeV energy. This allowed us to set new exclusion limits that, relative to the collected statistics, prove the power of this experimental technique. This measurement is a crucial first step toward a future exploration program with positron beams, whose estimated sensitivity is here presented.

hep-ex↗
arXiv2023

Transition between metastable equilibria: applications to binary-choice games

Transitions between metastable equilibria in the low-temperature phase of dynamical Ising game with activity spillover are studied in the infinite time limit. It is shown that exponential enhancement due to activity spillover, which takes place in finite-time transitions, is absent in the infinite time limit. In order to demonstrate that, the analytical description for infinite time trajectory is developed. An analytical approach to estimate the probability of transition between metastable equilibria in the infinite time limit is introduced and its results are compared with those of kinetic Monte Carlo simulation. Our study sheds light on the dynamics of the Ising game and has implications for the understanding of transitions between metastable states in complex systems.

cond-mat.stat-mech↗
arXiv2020

Self-Excited Ising Game

Effects of dynamical activity spillover in a noisy binary choice game (Ising game) on a complete graph are studied. Binary choice games are very important for both economics and statistical physics playing a role of the bridge between these two fields. In this paper we investigate the effects of self-excited activity induced by activity spillover on relaxation to equilibria and transitions between metastable equilibria at finite times. Using the formalism of master equations we show that both relaxation and interequilibria transitions at finite time are accelerated by the effects of activity spillover.

cond-mat.stat-mech↗
arXiv2014

Measurement of high-Q2 neutral current deep inelastic e+p scattering cross sections with a longitudinally polarised positron beam at HERA

Measurements of neutral current cross sections for deep inelastic scattering in e+p collisions at HERA with a longitudinally polarised positron beam are presented. The single-differential cross-sections d(sigma)/dQ2, d(sigma)/dx and d(sigma)/dy and the reduced cross-section were measured in the kinematic region Q2 > 185 GeV2 and y < 0.9, where Q2 is the four-momentum transfer squared, x the Bjorken scaling variable, and y the inelasticity of the interaction. The measurements were performed separately for positively and negatively polarised positron beams. The measurements are based on an integrated luminosity of 135.5 pb-1 collected with the ZEUS detector in 2006 and 2007 at a centre-of-mass energy of 318 GeV. The structure functions F3 and F3(gamma)Z were determined by combining the e+p results presented in this paper with previously published e-p neutral current results. The asymmetry parameter A+ is used to demonstrate the parity violation predicted in electroweak interactions. The measurements are well described by the predictions of the Standard Model.

hep-ex↗
arXiv2012

Production of Z0 bosons in elastic and quasi-elastic ep collisions at HERA

The production of Z0 bosons in the reaction ep -> eZ0p*, where p* stands for a proton or a low-mass nucleon resonance, has been studied in ep collisions at HERA using the ZEUS detector. The analysis is based on a data sample collected between 1996 and 2007, amounting to 496 pb-1 of integrated luminosity. The Z0 was measured in the hadronic decay mode. The elasticity of the events was ensured by a cut on eta_max < 3.0, where eta_max is the maximum pseudorapidity of energy deposits in the calorimeter defined with respect to the proton beam direction. A signal was observed at the Z0 mass. The cross section of the reaction ep -> eZ0p* was measured to be sigma(ep -> eZ0p*) = 0.13 +/- 0.06 (stat.) +/- 0.01 (syst.) pb, in agreement with the Standard Model prediction of 0.16 pb. This is the first measurement of Z0 production in ep collisions.

hep-ex↗
arXiv2012

Inclusive-jet photoproduction at HERA and determination of alphas

Inclusive-jet cross sections have been measured in the reaction ep->e+jet+X for photon virtuality Q2 < 1 GeV2 and gamma-p centre-of-mass energies in the region 142 < W(gamma-p) < 293 GeV with the ZEUS detector at HERA using an integrated luminosity of 300 pb-1. Jets were identified using the kT, anti-kT or SIScone jet algorithms in the laboratory frame. Single-differential cross sections are presented as functions of the jet transverse energy, ETjet, and pseudorapidity, etajet, for jets with ETjet > 17 GeV and -1 < etajet < 2.5. In addition, measurements of double-differential inclusive-jet cross sections are presented as functions of ETjet in different regions of etajet. Next-to-leading-order QCD calculations give a good description of the measurements, except for jets with low ETjet and high etajet. The influence of non-perturbative effects not related to hadronisation was studied. Measurements of the ratios of cross sections using different jet algorithms are also presented; the measured ratios are well described by calculations including up to O(alphas2) terms. Values of alphas(Mz) were extracted from the measurements and the energy-scale dependence of the coupling was determined. The value of alphas(Mz) extracted from the measurements based on the kT jet algorithm is alphas(Mz) = 0.1206 +0.0023 -0.0022 (exp.) +0.0042 -0.0035 (th.); the results from the anti-kT and SIScone algorithms are compatible with this value and have a similar precision.

hep-ex↗
arXiv2012

Scaled momentum distributions for K0s and Lambda/bar Lambda in DIS at HERA

Scaled momentum distributions for the strange hadrons K0s and Lambda/bar Lambda were measured in deep inelastic ep scattering with the ZEUS detector at HERA using an integrated luminosity of 330 pb-1. The evolution of these distributions with the photon virtuality, Q2, was studied in the kinematic region 10<Q2<40000 GeV2 and 0.001<x<0.75, where x is the Bjorken scaling variable. Clear scaling violations are observed. Predictions based on different approaches to fragmentation were compared to the measurements. Leading-logarithm parton-shower Monte Carlo calculations interfaced to the Lund string fragmentation model describe the data reasonably well in the whole range measured. Next-to-leading-order QCD calculations based on fragmentation functions, FFs, extracted from e+e- data alone, fail to describe the measurements. The calculations based on FFs extracted from a global analysis including e+e-, ep and pp data give an improved description. The measurements presented in this paper have the potential to further constrain the FFs of quarks, anti-quarks and gluons yielding K0s and Lambda/bar Lambda strange hadrons.

hep-ex↗
arXiv2012

Search for single-top production in ep collisions at HERA

A search for single-top production, $ep \rightarrow etX$, has been performed with the ZEUS detector at HERA using data corresponding to an integrated luminosity of $0.37\fbi$. No evidence for top production was found, consistent with the expectation from the Standard Model. Limits were computed for single-top production via flavour changing neutral current transitions. The result was combined with a previous ZEUS result yielding a total luminosity of 0.50fb-1. A 95% credibility level upper limit of 0.13 pb was obtained for the cross section at the centre-of-mass energy of $\sqrt{s}=315\gev$.

hep-ex↗
arXiv2011

Exclusive electroproduction of two pions at HERA

The exclusive electroproduction of two pions in the mass range 0.4 < Mππ < 2.5 GeV has been studied with the ZEUS detector at HERA using an integrated luminosity of 82 pb-1. The analysis was carried out in the kinematic range of 2 < Q2 < 80 GeV2, 32 < W < 180 GeV and |t| < 0.6 GeV2, where Q2 is the photon virtuality, W is the photon-proton centre-of-mass energy and t is the squared four-momentum transfer at the proton vertex. The two-pion invariant-mass distribution is interpreted in terms of the pion electromagnetic form factor, |F(Mππ)|, assuming that the studied mass range includes the contributions of the ρ, ρ' and ρ" vector-meson states. The masses and widths of the resonances were obtained and the Q2 dependence of the cross-section ratios σ(ρ' \rightarrow ππ)/σ(ρ) and σ(ρ" \rightarrow ππ)/σ(ρ) was extracted. The pion form factor obtained in the present analysis is compared to that obtained in e+e- \rightarrow π+π-.

hep-ex↗