arXiv subjects

V. Kushpil

Publications and source records attributed to V. Kushpil.

6 recordsLinked to original sources

arXiv2024

The $v^{1/3}_{3}/v^{1/2}_{2}$ ratio in PbAu collisions at $\sqrt{s_{\mathrm{NN}}} = $ 17.3 GeV: a hint of a hydrodynamic behavior

The Fourier harmonics, $v_2$ and $v_3$ of negative pions are measured at center-of-mass energy per nucleon pair of $\sqrt{s_{\mathrm{NN}}}$= 17.3 GeV around midrapidity by the CERES/NA45 experiment at the CERN SPS in 0--30\% central PbAu collisions with a mean centrality of 5.5\%. The analysis is performed in two centrality bins as a function of the transverse momentum $\mathrm{p_{\mathrm{T}}}$ from 0.05 GeV/$c$ to more than 2 GeV/$c$. This is the first measurement of the $v^{1/3}_{3}/v^{1/2}_{2}$ ratio as a function of transverse momentum at SPS energies, that reveals, independently of the hydrodynamic models, hydrodynamic behavior of the formed system. For $\mathrm{p_{\mathrm{T}}}$ above 0.5 GeV/$c$, the ratio is nearly flat in accordance with the hydrodynamic prediction and as previously observed by the ATLAS and ALICE experiments at the much higher LHC energies. The results are also compared with the SMASH-vHLLE hybrid model predictions, as well as with the SMASH model applied alone.

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arXiv2020

Characterisation of SiPM radiation hardness for application in hadron calorimeters at FAIR, CERN and NICA

Silicon PhotoMultipliers (SiPM) are an excellent choice for the scintillator light readout at hadron calorimeters due to their insensitivity to magnetic fields, low operating voltages, low cost, compactness and mechanical endurance. They are already successfully utilized in Projectile Spectator Detector (PSD) of NA61 at CERN, and will be utilized soon in PSD of CBM at FAIR and Forward Hadron CALorimeters (FHCAL) of BM@N at NICA heavy-ion collision experiments. The main issue of SiPM application is their degradation due to high neutron fluence that can reach up to 2E11 neq/cm2 per year of the experiment operation. Multiple irradiation tests of SiPMs produced by Ketek, Zecotek, Hamamatsu and Sensl manufacturers were conducted at the cyclotron of NPI Rez with a broad neutron spectrum and total fluences in the wide range of 5E10 - 6E12 neq/cm2. Detailed characterisation of all SiPMs was performed based on dependencies of dark current on voltage, capacitance on voltage and frequency, and response to LED light on voltage. SiPM's breakdown voltage, quenching resistance, pixel capacitance, gain and signal to noise ratio were extracted from these measurements. Those parameters' dependence on neutron fluence and their variability are discussed. Performance of the PSD calorimeter module equipped with irradiated SiPMs in CERN during the beam scan with 2 - 80 GeV/c protons is briefly overviewed.

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arXiv2015

Investigation of avalanche photodiodes radiation hardness for baryonic matter studies

Modern avalanche photodiodes (APDs) with high gain are good device candidates for light readout from detectors applied in relativistic heavy ion collisions experiments. The results of the investigations of the APDs properties from Zecotek, Ketek and Hamamatsu manufacturers after irradiation using secondary neutrons from cyclotron facility U120M at NPI of ASCR in Řež are presented. The results of the investigations can be used for the design of the detectors for the experiments at NICA and FAIR.

physics.ins-det↗

arXiv2012

Elliptic flow of charged pions, protons and strange particles emitted in Pb+Au collisions at top SPS energy

Differential elliptic flow spectra v2(pT) of π-, K0short, p, Λhave been measured at \sqrt(s NN)= 17.3 GeV around midrapidity by the CERN-CERES/NA45 experiment in mid-central Pb+Au collisions (10% of σ(geo)). The pT range extends from about 0.1 GeV/c (0.55 GeV/c for Λ) to more than 2 GeV/c. Protons below 0.4 GeV/c are directly identified by dE/dx. At higher pT, proton elliptic flow v2(pT) is derived as a constituent, besides π+ and K+, of the elliptic flow of positive pion candidates. The retrieval requires additional inputs: (i) of the particle composition, and (ii) of v2(pT) of positive pions. For (i), particle ratios obtained by NA49 were adapted to CERES conditions; for (ii), the measured v2(pT) of negative pions is substituted, assuming π+ and π- elliptic flow magnitudes to be sufficiently close. The v2(pT) spectra are compared to ideal-hydrodynamics calculations. In synopsis of the series π- - K0short - p - Λ, flow magnitudes are seen to fall with decreasing pT progressively even below hydro calculations with early kinetic freeze-out (Tf= 160 MeV) leaving not much time for hadronic evolution. The proton v2(pT) data show a downward swing towards low pT with excursions into negative v2 values. The pion-flow isospin asymmetry observed recently by STAR at RHIC, invalidating in principle our working assumption, is found in its impact on proton flow bracketed from above by the direct proton flow data, and not to alter any of our conclusions. Results are discussed in perspective of recent viscous dynamics studies which focus on late hadronic stages.

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arXiv2008

Azimuthal dependence of pion source radii in Pb+Au collisions at 158 A GeV

We present results of a two-pion correlation analysis performed with the Au+Pb collision data collected by the upgraded CERES experiment in the fall of 2000. The analysis was done in bins of the reaction centrality and the pion azimuthal emission angle with respect to the reaction plane. The pion source, deduced from the data, is slightly elongated in the direction perpendicular to the reaction plane, similarly as was observed at the AGS and at RHIC.

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arXiv2005

Beam test results of the irradiated Silicon Drift Detector for ALICE

The Silicon Drift Detectors will equip two of the six cylindrical layers of high precision position sensitive detectors in the ITS of the ALICE experiment at LHC. In this paper we report the beam test results of a SDD irradiated with 1 GeV electrons. The aim of this test was to verify the radiation tolerance of the device under an electron fluence equivalent to twice particle fluence expected during 10 years of ALICE operation.

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