arXiv subjects

Venelin Kozhuharov

Publications and source records attributed to Venelin Kozhuharov.

18 recordsLinked to original sources

arXiv2026

The COSMIC WISPers White Paper: The physics case for Weakly Interacting Slim Particles

Axions and other very weakly interacting slim particles (WISPs), with masses below 1 GeV, arise naturally in many extensions of the Standard Model of particle physics. In particular, they could offer a new framework to explain the nature of dark matter and may help address a range of puzzling observations in astrophysics and particle physics. This review provides an overview of ongoing WISP searches and outlines the prospects for the next decade, spanning their theoretical motivation, indirect signatures in astrophysical observations, and dedicated laboratory experiments. It is based on the work carried on by the EU-funded COST Action ``Cosmic WISPers in the Dark Universe: Theory, astrophysics, and experiments'' (CA21106, https://www.cost.eu/actions/CA21106). This network plays a key role in coordinating and supporting WISP searches across Europe, while also contributing to the development of a roadmap aimed at securing European leadership in this research area. It is emphasized that Europe is currently pursuing a rich, diverse, and cost-effective experimental program, with the potential to deliver one or more transformative discoveries.

hep-ph↗

arXiv2025

Multichannel SiPM test readout system for gamma-ray measurements with monolithic inorganic CeBr_{3}

Energy resolution and the detection efficiency for gamma quanta are fundamental properties in the construction of detectors for ionizing radiation. In this study, a SiPM-based photodetector coupled to a monolithic inorganic CeBr_{3} crystal is exposed to gamma rays in order to study the performance of the CeBr_{3} crystal. Measurements are made using three different radioactive sources - ^{137}Cs, ^{22}Na, and ^{60}Co. For each source, the measurements are conducted at several SiPM bias voltages. Furthermore, two CeBr_{3} crystals with different thicknesses are used in order to study how detector efficiency is affected by crystal dimensions. A preliminary analysis of the data is presented.

physics.ins-det↗

arXiv2025

Cluster Reconstruction in Electromagnetic Calorimeters Using Machine Learning Methods

Machine-learning-based methods can be developed for the reconstruction of clusters in segmented detectors for high energy physics experiments. Convolutional neural networks with autoencoder architecture trained on labeled data from a simulated dataset reconstruct events by providing information about the hit point and energy of each particle that has entered the detector. The correct reconstruction of the positionand the energy of the incident particles is crucial for the accurate events reconstruction. The presented method shows the ability to reconstruct the impact point within the same segment as the true position and determines the particle energy with good precision. It can be applied in a wide range of cases of event reconstruction where the good separation of overlapping signals plays a key role in the data analysis.

physics.ins-det↗

arXiv2025

Development and Explainability of Models for Machine-Learning-Based Reconstruction of Signals in Particle Detectors

Machine learning methods are being introduced at all stages of data reconstruction and analysis in various high-energy physics experiments. We present the development and application of convolutional neural networks with modified autoencoder architecture for the reconstruction of the pulse arrival time and amplitude in individual scintillating crystals in electromagnetic calorimeters and other detectors. The network performance is discussed as well as the application of xAI methods for further investigation of the algorithm and improvement of the output accuracy.

physics.ins-det↗

arXiv2025

Applicability Evaluation of Selected xAI Methods for Machine Learning Algorithms for Signal Parameters Extraction

Machine learning methods find growing application in the reconstruction and analysis of data in high energy physics experiments. A modified convolutional autoencoder model was employed to identify and reconstruct the pulses from scintillating crystals. The model was further investigated using four xAI methods for deeper understanding of the underlying reconstruction mechanism. The results are discussed in detail, underlining the importance of xAI for knowledge gain and further improvement of the algorithms.

physics.comp-ph↗

arXiv2025

Blind unblinding procedure for the PADME X17 data sample

The PADME experiment at the Frascati DA$Φ$NE LINAC has performed a search for the hypothetical X17 particle, with a mass of around 17 MeV, by scanning the energy of a positron beam striking a fixed target. The X17 should be produced from the resulting $e^+e^-$ annihilation. Since the expected mass of this particle is only roughly known, data sidebands cannot be clearly defined. Furthermore, the need to keep the analysis blind to potentially sizable signal contributions prevents a clear assessment even of the quality of the data sample in this search. In light of these challenges, this paper presents an innovative strategy adopted by the PADME Collaboration to perform data quality checks without disclosing the X17 sample. Moreover, the procedure designed to eventually unblind the data is described, together with the statistical approach adopted to extract the limits on the coupling between the X17 and the Standard Model.

hep-ex↗

arXiv2023

Status and Prospects of PADME

The Positron Annihilation to Dark Matter Experiment (PADME) was designed and constructed to search for dark photons ($A'$) in the process $e^+e^-\rightarrowγA'$, using the positron beam at the Beam Test Facility (BTF) at the National Laboratories of Frascati (LNF). Since the observation of an anomalous spectra in internal pair creation decays of nuclei seen by the collaboration at the ATOMKI institute, the PADME detector has been modified and a new data-taking run has been undertaken to probe the existance of the so-called ``X17" particle

hep-ex↗

arXiv2023

Dark sector studies with the PADME experiment

The Positron Annihilation to Dark Matter Experiment (PADME) uses the positron beam of the DA$Φ$NE Beam-Test Facility, at the Laboratori Nazionali di Frascati (LNF) to search for a Dark Photon $A'$. The search technique studies the missing mass spectrum of single-photon final states in $e^+e^-\rightarrow A'γ$ annihilation in a positron-on-thin-target experiment. This approach facilitates searches for new particles such as long lived Axion-Like-Particles, protophobic X bosons and Dark Higgs. This talk illustrated the scientific program of the experiment and its first physics results. In particular, the measurement of the cross-section of the SM process $e^+e^-\rightarrow γγ$ at $\sqrt{s}$=21 MeV was shown.

hep-ex↗

arXiv2019

Search for heavy neutrinos at CERN SPS

The phenomenology in the neutrino sector requires physics beyond the Standard Model. One possibility is the existence of new massive leptonic states which could be probed at the high intensity machines. The present results on heavy neutral leptons from the study of kaon decays in flight with the NA48/2 and NA62 experiments are presented and the future prospects for such searches at CERN SPS are discussed.

hep-ex↗

arXiv2015

The PADME experiment at LNF

Massive photon-like particles are predicted in many extensions of the Standard Model. They have interactions similar to the photon, are vector bosons, and can be produced together with photons. The PADME experiment proposes a search for the dark photon ($A'$) in the $e^+e^- \to γA'$ process in a positron-on-target experiment, exploiting the positron beam of the DA$Φ$NE linac at the Laboratori Nazionali di Frascati, INFN. In one year of running a sensitivity in the relative interaction strength down to $10^{-6}$ is achievable, in the mass region from 2.5 MeV $<M_{A'}<$ 22.5 MeV. The proposed experimental setup and the analysis technique is discussed.

hep-ex↗

arXiv2014

NA62 experiment at CERN SPS

The NA62 experiment at SPS is a continuation of the long standing CERN kaon physics program. The high statistics and the unprecedent precision allow to probe the Standard Model and test the description of the strong interactions at low energy. The final results on the the lepton universality test by measuring the ratio $R_K = Γ(K^{+}\to e^{+}ν) / Γ(K^{+}\to μ^{+}ν)$ and the study of the $K^\pm\toπ^{\pm}γγ$ decay are presented. The major goal of the NA62 experiment is to perform a measurement of the $Br(K^{+} \to π^{+} ν\barν)$ with a precision of 10% in two years of data taking. The detector setup together with the analysis technique is described.

hep-ex↗

arXiv2014

Measurement of the ratio of the charged kaon leptonic decays at NA62

The ratio of the leptonic charged kaon decays $R_K= Γ(K^{\pm} \to e^{\pm}ν) / Γ(K^{\pm} \to μ^{\pm}ν)$ is sensitive to the structure of the week interactions and can be precisely calculated within the Standard Model. Presence of New Physics can introduce a shift on its value of the order of a percent. The NA62 experiment at CERN SPS used data from a dedicated run in 2007 to perform a measurement of this ratio and probe the lepton universality. The data analysis technique and the final results are presented.

hep-ex↗

arXiv2014

Proposal to search for a dark photon in $e^+$ on target collisions at DA$Φ$NE linac

Photon-like particles are predicted in many extensions of the Standard Model. They have interactions similar to the photon, are vector bosons, and can be produced together with photons. The present paper proposes a search for such particles in the $ e^+e^- \to Uγ$ process in a positron-on-target experiment, exploiting the positron beam of the DA$Φ$NE linac at the Laboratori Nazionali di Frascati, INFN. In one year of running a sensitivity in the relative interaction strength down to $\sim10^{-6}$ is achievable, in the mass region from 2.5 MeV$<M_U<$ 20 MeV. The proposed experimental setup and the analysis technique is discussed.

physics.ins-det↗

arXiv2013

Rare K Decays: Present and perspectives with NA62

Rare kaon decays provide unique opportunity to test the Standard Model and probe its possible extensions. The final result on the lepton universality test by measuring the ratio R_K = G(K+- to e+- nu)/G(K+- to mu+- nu) is presented as well as the status of the study of the rare decays K+- to pi+- gamma gamma and K+ to e+ nu gamma. The primary goal of the NA62 experiment is the measurement of the Br(K+ to pi+ nu anti-nu) decay with a precision of 10% in two years of data taking. The detector setup together with the analysis technique is described.

hep-ex↗

arXiv2012

Multigap RPC for PET: development and optimisation of the detector design

Transforming the resistive plate chambers from charged-particle into gamma-quanta detectors opens the way towards their application as a basic element of a hybrid imaging system, which combines positron emission tomography (PET) with magnetic resonance imaging (MRI) in a single device and provides non- and minimally- invasive quantitative methods for diagnostics. To this end, we performed detailed investigations encompassing the whole chain from the annihilation of the positron in the body, through the conversion of the created photons into electrons and to the optimization of the electron yield in the gas. GEANT4 based simulations of the efficiency of the RPC photon detectors with different converter materials and geometry were conducted for optimization of the detector design. The results justify the selection of a sandwich-type gas-insulator-converter design, with Bi or Pb as converter materials.

physics.ins-det↗

arXiv2007

Testing mu-e universality with Kl2 decays

The ratio R_K=Gamma(Ke2)/Gamma(Kmu2) provides a very powerful probe for the weak interactions structure. This ratio of decay rates is calculated with very high precision within the Standard Model but the corrections due to the presence of New Physics could be as high as 3%. The data obtained by the NA48 experiment at the CERN SPS accelerator during a 56 hours special run in 2004 has been analyzed.The precision of the preliminary result for R_K is two times better than the world average but is still insufficient to probe the existence of physics Beyond the Standard Model. Currently the experiment is taking data dedicated to the sub-percent precision measurement of R_K.

hep-ex↗

arXiv2007

Recent results on Vus from KLOE, KTeV and NA48

In the last few years a significant progress in the kaon physics has been made by three experiments - KLOE, KTeV and NA48. The reflection of their results to the extraction of the parameter Vus of the CKM matrix is presented. The obtained combined result for Vus = 0.2241(15) together with the latest value for Vud = 0.97377(27) are consistent with the Standard Model and the unitarity of the CKM matrix.

hep-ph↗

arXiv2005

Precise measurement of Br($K^+ \to π^+ ν\barν$) at CERN SPS

An experimental proposal to measure Br($K^+ \to π^+ ν\barν$) has been submitted at the CERN SPSC. The goal is to collect ~80 $K^+\to π^+ ν\barν$ events with signal to background ratio of 10:1 in two years of data taking. This will allow determination of the CKM parameter $V_{td}$ with ~10% accuracy.

hep-ex↗