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N. Kozlenko

Publications and source records attributed to N. Kozlenko.

16 recordsLinked to original sources
arXiv2026

Observation of light production by charged particles in WLS fibers

Wavelength shifting (WLS) fibers are widely used in particle physics for light collection from scintillators. Light production by charged particles directly in WLS fibers is traditionally ignored. In this study, light produced by charged particles in WLS fibers is clearly observed. The light yield of different batches of Y11(200) 1 mm diameter WLS fibers expressed in the number of detected photo electrons is as large as $23\pm2~\%$ with respect to the light yield of the Bicron BCF-12 1 mm diameter scintillating fiber. This corresponds to about 1200 photons per MeV light production after taking into account different fiber light trapping efficiencies and emission spectra. In clear fibers of the same diameter, no scintillation light is produced, while Cherenkov light is clearly seen at the 45-degree crossing angle. The observed amount of light produced by charged particles in the WLS fibers is not small and should be taken into account in advanced detector simulations.

physics.ins-det↗
arXiv2026

Precision Light Yield and Crosstalk Characterization for the SuperFGD scintillator cubes

A detailed study of a $5\times5\times5$ cube prototype of the SuperFGD detector was performed using a 730 MeV/$c$ pion beam at the SC-1000 synchrocyclotron (PNPI, Gatchina, Russia). The detector, based on plastic scintillation cubes with orthogonal wavelength-shifting (WLS) fiber readout and silicon photomultipliers (SiPMs), was tested to evaluate its performance in terms of light yield, spatial uniformity, and optical crosstalk. Using high-resolution tracking, the spatial distribution of light yield was mapped with a granularity of 0.5 mm. An average light response map was obtained by combining data from 27 cubes. Optical crosstalk between adjacent cubes was also measured and characterized in four directions (left, right, up, down). Position-dependent crosstalk values ranged from 2% to 6%, with the highest levels observed near cube interfaces. These results confirm the excellent performance and scalability of the SuperFGD design, and provide valuable input for simulation tuning and reconstruction algorithms in the ND280 upgrade of the T2K experiment. The obtained result on the response uniformity and crosstalk are reasonably well described by simple MC model of the setup.

physics.ins-det↗
arXiv2023

Measurement of the $γn\rightarrow K^0Σ^0$ differential cross section over the $K^*$ threshold

The differential cross section for the quasi-free photoproduction reaction $γn\rightarrow K^0Σ^0$ was measured at BGOOD at ELSA from threshold to a centre-of-mass energy of 2400 MeV. Close to threshold the results are consistent with existing data and are in agreement with partial wave analysis solutions over the full measured energy range, with a large coupling to the $Δ$(1900)1/2- evident. This is the first dataset covering the K* threshold region, where there are model predictions of dynamically generated vector meson-baryon resonance contributions.

nucl-ex↗
arXiv2022

Optimized scintillation strip design for the DANSS upgrade

DANSS is a one cubic meter plastic scintillator detector with a primary goal of the sterile neutrino searches at a commercial nuclear reactor. Due to its highly advantageous location, fine segmentation and ability to change the distance to the neutrino production origin DANSS is ahead of many similar experiments around the world in terms of the counting rate, signal to background ratio and sterile neutrino exclusion regions. Yet a moderate energy resolution of the detector prevents the further progress in the physics program. The main challenge of the planned upgrade is to achieve the energy resolution of 12% at 1 MeV. The new design of the main sensitive element - the plastic scintillation strip - is the most important step forward. The strip prototypes were manufactured and tested at the pion beam of the PNPI synchrocyclotron. More than twice higher light output together with fairly flat detector response uniformity, longitudinal timing information and other optimizations will surely help to reach the upgrade goal. The paper discusses the drawbacks of the current strip version, outlines the new features of the proposed upgrade, describes the beam test procedure and presents the test results reflecting the advantages of the new strip design in comparison with the currently used version.

physics.ins-det↗
arXiv2022

Photoproduction of $K^+Λ(1405) \rightarrow K^+π^0Σ^0$ extending to forward angles and low momentum transfer

$K^+Λ(1405)$ photoproduction has been studied at the BGOOD experiment via the all neutral decay, $Λ(1405)\rightarrowΣ^0π^0$. The unique BGOOD experimental setup allows both the cross section and $Λ(1405)$ invariant mass distribution (line shape) to be measured over a broad $K^+$ polar angle range, extending to extreme forward $K^+$ angles unattainable at previous experiments. Evidence is provided for the role of a triangle singularity driven by the $N^*(2030)$ resonance, which appears to contribute significantly to $K^+Λ(1405)$ photoproduction. This is observed in both the angular distributions and the integrated cross section which was determined with unprecedented energy resolution. The measured line shape is also in agreement with the previous results of CLAS and ANKE, and is consistent with two poles derived in $χ$PT based models.

nucl-ex↗
arXiv2022

Evidence of a dibaryon spectrum in coherent $\pi^0\pi^0 d$ photoproduction at forward deuteron angles

The coherent reaction, $\gamma d \rightarrow \pi^0\pi^0 d$ was studied with the BGOOD experiment at ELSA from threshold to a centre-of-mass energy of 2850\,MeV. A full kinematic reconstruction was made, with final state deuterons identified in the forward spectrometer and $\pi^0$ decays in the central BGO Rugby Ball. The strength of the differential cross section exceeds what can be described by models of coherent photoproduction and instead supports the three isoscalar dibaryon candidates reported by the ELPH collaboration at 2.38, 2.47 and 2.63\,GeV/c$^2$. A low mass enhancement in the $\pi^0\pi^0$ invariant mass is also observed at the $d^*(2380)$ centre-of-mass energy which is consistent with the ABC effect. At higher centre-of-mass energies, a narrow peak in the $\pi^0 d$ invariant mass at 2114\,MeV/c$^2$ with a width of 20\,MeV/c$^2$ supports a sequential two-dibaryon decay mechanism.

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arXiv2021

Observation of a cusp-like structure in the $γp \rightarrow K^+Σ^0$ cross section at forward angles and low momentum transfer

The $γp \rightarrow K^+Σ^0$ differential cross section at extremely forward angles was measured at the BGOOD experiment. A three-quarter drop in strength over a narrow range in energy and a strong dependence on the polar angle of the $K^+$ in the centre-of-mass of the reaction is observed at a centre-of-mass energy of 1900\,MeV. Residing close to multiple open and hidden strangeness thresholds, the structure appears consistent with meson-baryon threshold effects which may contribute to the reaction mechanism.

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arXiv2021

$K^+Λ$ photoproduction at forward angles and low momentum transfer

$γp \rightarrow K^+ Λ$ differential cross sections and recoil polarisation data from threshold for extremely forward angles are presented. The measurements were performed at the BGOOD experiment at ELSA, utilising the high angular and momentum resolution forward spectrometer for charged particle identification. The data discriminates between conflicting results in the world data set and enable extraction of the cross section as the minimum momentum transfer to the recoiling hyperon is approached.

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arXiv2020

Strangeness Photoproduction at the BGO-OD experiment

The BGO-OD experiment at the ELSA accelerator facility uses an energy tagged bremsstrahlung photon beam to investigate the excitation structure of the nucleon. The setup consists of a highly segmented BGO calorimeter surrounding the target, with a particle tracking magnetic spectrometer at forward angles. BGO-OD is ideal for investigating low momentum transfer processes due to the acceptance and high momentum resolution at forward angles. In particular, this enables the investigation of strangeness photoproduction where t-channel exchange mechanisms play an important role. This also allows access to low momentum exchange kinematics where extended, molecular structure may manifest in reaction mechanisms. First key results at low $t$ indicate a cusp-like structure in $K^+Σ^0$ photoproduction at $W = 1900$\,MeV, line shapes and differential cross sections for $K^+Λ$(1405)$\rightarrow K^+Σ^0π^0$, and a peak structure in $K^0_SΣ^0$ photoproduction. The peak in the $K^0_SΣ^0$ channel appears consistent with meson-baryon generated states, where equivalent models have been used to describe the $P_C$ pentaquark candidates in the heavy charmed quark sector.

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arXiv2020

The BGOOD experimental setup at ELSA

The BGOOD experiment at the ELSA facility in Bonn has been commissioned within the framework of an international collaboration. The experiment pursues a systematic investigation of non-strange and strange meson photoproduction, in particular $t$-channel processes at low momentum transfer. The setup uniquely combines a central almost $4π$ acceptance BGO crystal calorimeter with a large aperture forward magnetic spectrometer providing excellent detection of both neutral and charged particles, complementary to other setups such as Crystal Barrel, Crystal Ball, LEPS and CLAS.

physics.ins-det↗
arXiv2017

New Narrow $N(1685)$ and $N(1726)$? Remarks on the Interpretation of the Neutron Anomaly as an Interference Phenomenon

Different interpretations of narrow structures at $W\sim 1.68$ and $W\sim 1.72$ GeV observed in several reactions are discussed. It is questionable whether interference phenomena could explain the whole complex of experimental findings. More probable hypotheses would be the existence of one or two narrow resonances $N(1685)$ and $N(1726)$ and/or the sub-threshold virtual $KΣ$ and $ωp$ production (cusps).

nucl-ex↗
arXiv2010

Measurement of $K^- p$ radiative capture to $γΛ$ and $γΣ^0$ for $p_{K^-}$ between 514 and 750 MeV/$c$

Differential cross sections for $K^-$ radiative capture in flight on the proton, leading to the $γΛ$ and $γΣ^0$ final states, have been measured at eight $K^-$ momenta between 514 and 750 MeV/$c$. The data were obtained with the Crystal Ball multiphoton spectrometer installed at the separated $K/π$ beam line C6 of the BNL Alternating Gradient Synchrotron. The results substantially improve the existing experimental data available for studying radiative decays of excited hyperon states. An exploratory theoretical analysis is performed within the Regge-plus-resonance approach. According to this analysis, the $γΣ^0$ final state is dominated by hyperonresonance exchange and hints at an important role for a resonance in the mass region of 1700 MeV. In the $γΛ$ final state, on the other hand, the resonant contributions account for only half the strength, and the data suggest the importance of a resonance in the mass region of 1550 MeV.

hep-ex↗
arXiv2009

Differential cross sections of the charge-exchange reaction pi- p --> pi0 n in the momentum range from 103 to 178 MeV/c

Measured values of the differential cross sections for pion-nucleon charge exchange, pi- p --> pi0 n, are presented for pi- momenta of 103, 112, 120, 130, 139, 152, and 178 MeV/c. Complete angular distributions were obtained by using the Crystal Ball detector at the Alternating Gradient Synchrotron at Brookhaven National Laboratory. Statistical uncertainties of the differential cross sections vary from 3% to 6% in the backward angle region, and from 6% to about 20% in the forward region with the exception of the two most forward angles. The systematic uncertainties are estimated to be about 3% for all momenta.

hep-ex↗
arXiv2009

Measurement of $π^0 Λ$, $\bar{K}^0 n$, and $π^0 Σ^0$ production in $K^- p$ interactions for $p_{K^-}$ between 514 and 750 MeV/$c$

Differential cross sections and hyperon polarizations have been measured for $\bar{K}^0 n$, $π^0 Λ$, and $π^0 Σ^0$ production in $K^- p$ interactions at eight $K^-$ momenta between 514 and 750 MeV/$c$. The experiment detected the multiphoton final states with the Crystal Ball spectrometer using a $K^-$ beam from the Alternating Gradient Synchrotron of BNL. The results provide significantly greater precision than the existing data, allowing a detailed reexamination of the excited hyperon states in our energy range.

hep-ex↗
arXiv2004

Measurement of Inverse Pion Photoproduction at Energies Spanning the N(1440) Resonance

Differential cross sections for the process pi^- p -> gamma n have been measured at Brookhaven National Laboratory's Alternating Gradient Synchrotron with the Crystal Ball multiphoton spectrometer. Measurements were made at 18 pion momenta from 238 to 748 MeV/c, corresponding to E_gamma for the inverse reaction from 285 to 769 MeV. The data have been used to evaluate the gamma n multipoles in the vicinity of the N(1440) resonance. We compare our data and multipoles to previous determinations. A new three-parameter SAID fit yields 36 +/- 7 (GeV)^-1/2 X 10^-3 for the A^n_1/2 amplitude of the P_11.

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