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V. Kuznetsov

Publications and source records attributed to V. Kuznetsov.

At least 19 recordsLinked to original sources
arXiv2022

Observation of night-time emissions of the Earth in the near UV range from the International Space Station with the Mini-EUSO detector

Mini-EUSO (Multiwavelength Imaging New Instrument for the Extreme Universe Space Observatory) is a telescope observing the Earth from the International Space Station since 2019. The instrument employs a Fresnel-lens optical system and a focal surface composed of 36 multi-anode photomultiplier tubes, 64 channels each, for a total of 2304 channels with single photon counting sensitivity. Mini-EUSO also contains two ancillary cameras to complement measurements in the near infrared and visible ranges. The scientific objectives of the mission range from the search for extensive air showers generated by Ultra-High Energy Cosmic Rays (UHECRs) with energies above 10$^{21}$ eV, the search for nuclearites and Strange Quark Matter (SQM), up to the study of atmospheric phenomena such as Transient Luminous Events (TLEs), meteors and meteoroids. Mini-EUSO can map the night-time Earth in the near UV range (between 290-430 nm) with a spatial resolution of about 6.3 km (full field of view of 44{\deg}) and a maximum temporal resolution of 2.5 $\mu$s, observing our planet through a nadir-facing UV-transparent window in the Russian Zvezda module. The detector saves triggered transient phenomena with a sampling rate of 2.5 $\mu$s and 320 $\mu$s, as well as continuous acquisition at 40.96 ms scale. In this paper we discuss the detector response and the flat-fielding and calibration procedures. Using the 40.96 ms data, we present $\simeq$6.3 km resolution night-time Earth maps in the UV band, and report on various emissions of anthropogenic and natural origin. We measure ionospheric airglow emissions of dark moonless nights over the sea and ground, studying the effect of clouds, moonlight, and artificial (towns, boats) lights. In addition to paving the way forward for the study of long-term variations of natural and artificial light, we also estimate the observation live-time of future UHECR detectors.

astro-ph.IM↗
arXiv2020

Mini-EUSO mission to study Earth UV emissions on board the ISS

Mini-EUSO is a telescope observing the Earth in the ultraviolet band from the International Space Station. It is a part of the JEM-EUSO program, paving the way to future larger missions, such as KEUSO and POEMMA, devoted primarily to the observation of Ultra High Energy Cosmic Rays from space. Mini-EUSO is capable of observing Extensive Air Showers generated by Ultra-High Energy Cosmic Rays with an energy above 10^21 eV and detect artificial showers generated with lasers from the ground. Other main scientific objectives of the mission are the search for nuclearites and Strange Quark Matter, the study of atmospheric phenomena such as Transient Luminous Events, meteors and meteoroids, the observation of sea bioluminescence and of artificial satellites and man-made space debris. Mini-EUSO will map the night-time Earth in the UV range (290 - 430 nm), with a spatial resolution of about 6.3 km and a temporal resolution of 2.5 microseconds, through a nadir-facing UV-transparent window in the Russian Zvezda module. The instrument, launched on August 22, 2019 from the Baikonur cosmodrome, is based on an optical system employing two Fresnel lenses and a focal surface composed of 36 Multi-Anode Photomultiplier tubes, 64 channels each, for a total of 2304 channels with single photon counting sensitivity and an overall field of view of 44 degrees. Mini-EUSO also contains two ancillary cameras to complement measurements in the near infrared and visible ranges. In this paper we describe the detector and present the various phenomena observed in the first months of operations.

astro-ph.IM↗
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 $K\Sigma$ and $\omega p$ production (cusps).

nucl-ex↗
arXiv2015

Evidence for narrow resonant structures at $W \approx 1.68$ and $W \approx 1.72$ GeV in real Compton scattering off the proton

First measurement of the beam asymmetry $\Sigma$ for Compton scattering off the proton in the energy range $E_{\gamma}=0.85 - 1.25$ GeV is presented. The data reveals two narrow structures at $E_{\gamma}= 1.036$ and $E_{\gamma}=1.119$ GeV. They may signal narrow resonances with masses near $1.68$ and $1.72$ GeV, or they may be generated by the sub-threshold $K\Lambda$ and $\omega p$ production. Their decisive identification requires additional theoretical and experimental efforts.

nucl-ex↗
arXiv2014

The neutron anomaly in the gamma N --> eta N cross section through the looking glass of the flavour SU(3) symmetry

We study the implications of the flavour SU(3) symmetry for various interpretations of the neutron anomaly in the $\gamma N\to\eta N$ cross section. We show that the explanation of the neutron anomaly due to interference of known N(1535) and N(1650) resonances implies that N(1650) resonance should have a huge coupling to $\phi$-meson -- at least 5 times larger than the corresponding $\rho^0$ coupling. In terms of quark degrees of freedom this means that the well-known N(1650) resonance must be a "cryptoexotic pentaquark"-- its wave function should contain predominantly an $s\bar s$ component. It turns out that the "conventional" interpretation of the neutron anomaly by the interference of known resonances metamorphoses into unconventional physics picture of N(1650).

nucl-th↗
arXiv2012

Observation of a narrow structure in p(gamma,K_s)X via interference with phi-meson production

We report observation of a narrow peak structure at ~1.54 GeV with a Gaussian width sigma=6 MeV in the missing of K_s in the reaction gamma+p = pK_sK_L. The observed structure may be due to the interference between a strange (or anti-strange) baryon resonance in the pK_L system and the phi(K_sK_L) photoproduction leading to the same final state. The statistical significance of the observed excess of events estimated as the log likelihood ratio of the resonant signal+background hypothesis and the phi-production based background only hypothesis corresponds to 5.3 sigma.

hep-ex↗
arXiv2012

Evidence for the Onset of Color Transparency in $\rho^0$ Electroproduction off Nuclei

We have measured the nuclear transparency of the incoherent diffractive $A(e,e'\rho^0)$ process in $^{12}$C and $^{56}$Fe targets relative to $^2$H using a 5 GeV electron beam. The nuclear transparency, the ratio of the produced $\rho^0$'s on a nucleus relative to deuterium, which is sensitive to $\rho A$ interaction, was studied as function of the coherence length ($l_c$), a lifetime of the hadronic fluctuation of the virtual photon, and the four-momentum transfer squared ($Q^2$). While the transparency for both $^{12}$C and $^{56}$Fe showed no $l_c$ dependence, a significant $Q^2$ dependence was measured, which is consistent with calculations that included the color transparency effects.

nucl-ex↗
arXiv2011

Precise Measurements of Beam Spin Asymmetries in Semi-Inclusive $π^0$ production

We present studies of single-spin asymmetries for neutral pion electroproduction in semi-inclusive deep-inelastic scattering of 5.776 GeV polarized electrons from an unpolarized hydrogen target, using the CEBAF Large Acceptance Spectrometer (CLAS) at the Thomas Jefferson National Accelerator Facility. A substantial $\sin ϕ_h$ amplitude has been measured in the distribution of the cross section asymmetry as a function of the azimuthal angle $ϕ_h$ of the produced neutral pion. The dependence of this amplitude on Bjorken $x$ and on the pion transverse momentum is extracted with significantly higher precision than previous data and is compared to model calculations.

hep-ex↗
arXiv2011

Search for Narrow Nucleon Resonance in $γp\to ηp$

Results of a partial wave analysis of new high-statistics data on $γp\to pη$ from MAMI are presented. A fit using known broad resonances and only standard background amplitudes can not describe the relatively narrow peaking structure in the cross section in the mass region of 1660-1750 MeV which follows a minimum. An improved description of the data can be reached by either assuming the existence of a narrow resonance at a mass of about 1700 MeV with small photo-coupling or by a threshold effect. In the latter case the observed structure is explained by a strong (resonant or non-resonant) $γp\toωp$ coupling in the $S_{11}$ partial wave. When the beam asymmetry data, published by part of the GRAAL collaboration, are included in the fit, the solution with a narrow $P_{11}$ state is slightly preferred. In that fit, mass and width of the hypothetical resonance are determined to $M\sim$1694 MeV and $Γ\sim 40$ MeV, respectively, and the photo-coupling to $\sqrt{{\rm Br}_{ηN}} A_{1/2}^p \sim 2.6\cdot 10^{-3}$ GeV$^{-1/2}$. High precision measurements of the target asymmetry and $F$-observable are mandatory to establish the possible existence of such a narrow state and to provide the necessary information to define which partial wave is responsible for the structure observed in the data.

hep-ph↗
arXiv2011

On Narrow Nucleon Excitation N*(1685)

We collected notes and simple estimates about putative narrow nucleon N*(1685) - the candidate for the non-strange member of the exotic anti-decuplet of baryons. In particular, we consider the recent high precision data on eta photoproduction off free proton obtained by the Crystal Ball Collaboration at MAMI. We show that it is difficult to describe peculiarities of these new data in the invariant energy interval of W ~ 1650-1750 MeV in terms of known wide resonances. Using very simple estimates, we show that the data may indicate an existence of a narrow N*(1685) with small photocoupling to the proton.

hep-ph↗
arXiv2011

Evidence for Narrow N*(1685) Resonance in Quasifree Compton Scattering on the Neutron

The first study of quasi-free Compton scattering on the neutron in the energy range of $E_γ=0.75 - 1.5$ GeV is presented. The data reveals a narrow peak at $W\sim 1.685$ GeV. This result, being considered in conjunction with the recent evidence for a narrow structure at $W\sim 1.68$GeV in the $η$ photoproduction on the neutron, suggests the existence of a new nucleon resonance with unusual properties: the mass $M\sim 1.685$GeV, the narrow width $Γ\leq 30$MeV, and the much stronger photoexcitation on the neutron than on the proton.

hep-ex↗
arXiv2010

Near-threshold Photoproduction of Phi Mesons from Deuterium

We report the first measurement of the differential cross section on $ϕ$-meson photoproduction from deuterium near the production threshold for a proton using the CLAS detector and a tagged-photon beam in Hall B at Jefferson Lab. The measurement was carried out by a triple coincidence detection of a proton, $K^+$ and $K^-$ near the theoretical production threshold of 1.57 GeV. The extracted differential cross sections $\frac{dσ}{dt}$ for the initial photon energy from 1.65-1.75 GeV are consistent with predictions based on a quasifree mechanism. This experiment establishes a baseline for a future experimental search for an exotic $ϕ$-N bound state from heavier nuclear targets utilizing subthreshold/near-threshold production of $ϕ$ mesons.

nucl-ex↗
arXiv2010

Tensor Correlations Measured in 3He(e,e'pp)n

We have measured the 3He(e,e'pp)n reaction at an incident energy of 4.7 GeV over a wide kinematic range. We identified spectator correlated pp and pn nucleon pairs using kinematic cuts and measured their relative and total momentum distributions. This is the first measurement of the ratio of pp to pn pairs as a function of pair total momentum, $p_{tot}$. For pair relative momenta between 0.3 and 0.5 GeV/c, the ratio is very small at low $p_{tot}$ and rises to approximately 0.5 at large $p_{tot}$. This shows the dominance of tensor over central correlations at this relative momentum.

nucl-ex↗
arXiv2010

Measurement of Single and Double Spin Asymmetries in Deep Inelastic Pion Electroproduction with a Longitudinally Polarized Target

We report the first measurement of the transverse momentum dependence of double spin asymmetries in semi-inclusive production of pions in deep inelastic scattering off the longitudinally polarized proton. Data have been obtained using a polarized electron beam of 5.7 GeV with the CLAS detector at the Thomas Jefferson National Accelerator Facility (JLab). A significant non-zero $\sin2ϕ$ single spin asymmetry was also observed for the first time indicating strong spin-orbit correlations for transversely polarized quarks in the longitudinally polarized proton. The azimuthal modulations of single spin asymmetries have been measured over a wide kinematic range.

hep-ex↗
arXiv2009

Test Measurements of Prototype Counters for CLAS12 Central Time-of-Flight System using 45 MeV protons

A comparative measurement of timing properties of magnetic-resistant fine mesh R7761-70 and ordinary fast R2083 photomultipliers is presented together with preliminary results on the operation of R7761-70 PMs in magnetic field up to 1100 Gauss. The results were obtained using the proton beam of the MC50 Cyclotron of Korea Institute of Radilogical and Medical Sciences. The ratio of the effective R7761-70 and R2083 TOF (or timing) resolutions was extracted by using two different methods. The results are $1.05\pm 0.066$ and $1.07\pm 0.062$. The gain of R7761-70 PMs is not affected by magnetic field. The R7761-70 TOF/timing resolution becomes $\sim 8%$ better at 1100 Gauss if the external field is oriented parallel to the PM axis. The results prove the advantages of the design of the CLAS12 Central Time-of-flight system with fine-mesh photomultipliers in comparison with the "conservative" design based on ordinary R2083 PMs and long bent light guides.

physics.ins-det↗
arXiv2008

Total and nuclear photoabsorption cross section of 52Cr in the energy range of 8 - 70 MeV

Total (atomic+nuclear) photoabsorption cross section of $^{52}Cr$ was for the first time measured in the energy range of 8-70 MeV. Experimental data was produced with small statistic and systematic errors. The results deviate from calculations of atomic cross section at photon energies above 40 MeV. Photonuclear cross section in the region of the E1 giant dipole resonance (GDR) clearly exhibits three peaks at 18.9, 20.9 and 23.1 MeV. At higher energies, the measured cross section hints a dip-peak structure at 40-48 MeV.

nucl-ex↗
arXiv2008

New Narrow Nucleon N*(1685)

We argue that the existence of a new narrow (Gamma < 25 MeV) nucleon resonance N*(1685) is strongly supported by recent data on eta photoproduction off the nucleon. The resonance has much stronger photo-coupling to the neutron than to the proton. This nucleon resonance is a good candidate for the non-strange member of the exotic anti-decouplet of baryons -- the partner of the pentaquark Theta+. All up to date known properties of new N*(1685) are summarized.

hep-ph↗