It is shown that an increase in the area of photodetectors allows the PHOS electromagnetic calorimeter of the ALICE experiment to operate at room temperature with better spectrometric ...characteristics. The linearity of the calorimeter response has been investigated in the 1–110 GeV energy range using both Hamamatsu S8664-1010 avalanche photodiodes with a large area (10 × 10 mm
2
) and arrays of MPPC Hamamatsu S12572-015C silicon photomultipliers with a sensitive area of 6 × 6 mm
2
. The calorimeter based on avalanche photodiodes is linear in the energy range under investigation compared to a calorimeter composed of silicon-photomultiplier arrays.
—
The time and energy resolutions were measured for four prototypes of the PHOS electromagnetic calorimeter for the ALICE experiment at the Large Hadron Collider at CERN. Each prototype was made up ...of nine identical detection elements assembled as a 3 × 3 array. The detection element was based on a lead tungstate (PbWO
4
) scintillating crystal with a length of 180 mm and a cross section of 22 × 22 mm
2
, which was viewed from its end face by a photodetector. Avalanche photodiodes and silicon photomultipliers with different active areas (Hamamatsu, Japan) were used as photodetectors. The measurements were made with the electron component of secondary particle beams of the PS proton synchrotron at CERN in the momentum range of 1−10 GeV/
c
at a temperature of 17.5°C.
A prototype detector based on thin-walled segmented tubes has been developed and its parameters have been studied. The detector contains 360 registration channels with a straw diameter of 4
mm. The ...prototype’ granularity is 4
сm
2 and the length of insensitive region due to straw internal elements is less than 5% of its full sensitive area. Deterioration of the spatial resolution near these elements is observed for 1.0% of the detector sensitive area. The time and spatial parameters of the detector do not differ from those of conventional tracking detectors based on drift tubes.
New diphenylsulfimide derivatives containing substituents with the 2,6-di-
tert
-butylphenol moiety at the nitrogen atom were synthesized. Their molecular structures were established by X-ray ...diffraction. Antioxidant activity was experimentally evaluated by spectrophotometry based on hydrogen transfer to the stable radicals, namely, 2,2-diphenyl-1-picrylhydrazyl and the 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) radical cation (ABTS
·+
), and using
in vitro
lipid peroxidation in rat brain and liver homogenates. The presence of phenol and diphenylsulfimide moieties in one molecule leads to a significant enhancement of antioxidant activity. The new compounds exhibit moderate inhibitory activity against enzymes involved in carbohydrate and lipid metabolism. The evaluation of antiglycation activity showed that the new sulfimides taken at a concentration of 100 μmol L
–1
have activity comparable with that of aminoguanidine.
Spatial resolution of thin-walled high-pressure drift tubes Davkov, V.I.; Gregor, I.; Haas, D. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
04/2011, Letnik:
634, Številka:
1
Journal Article
Recenzirano
A small prototype detector based on high pressure thin-walled tubes (straws) has been developed and its parameters have been studied on a bench at JINR, Dubna, and SPS at CERN. The inner diameter of ...the straws is 9.53
mm. The pressure of the active gas mixture Ar/CO
2 (80/20) was varied from 1 to 5
bar. The best spatial resolution achieved in this pressure range is ∼40
μm. Both the high efficiency and high rate capability are retained.
Experimental and theoretical studies of direct photon production in hadronic collisions essentially expand our insights in multiparticle production mechanisms. These photons are useful probes to ...investigate nuclear matter at all stages of the interaction. Soft photons play a particular role in these studies. Until now we have no explanation for the experimentally observed excess of soft photons. These photons have low transverse momenta GeV/c, . In this domain their yield exceeds the theoretical estimates by 5-8 times. The registration of soft photons at Nuclotron (LHEP, JINR) has been carried out by the electromagnetic calorimeter built by the SVD-2 Collaboration. Soft photon electromagnetic calorimeter was tested at U-70, IHEP (Protvino). For the first time the soft photon yield at interactions of 3.5A GeV/c per nucleon deuterium and lithium beams has been measured. The obtained energy spectra confirm the increased yield of soft photons with their energy less than 50MeV (in the laboratory system) in comparison with theoretical predictions and agree with previous experiments at high-energy interactions. It is planned to continue soft photon study at the future accelerator complex NICA with heavy-ion beams.
The use of S12572 MPPC silicon photomultipliers (Hamamatsu) for improving the timing characteristics of the PHOS electromagnetic calorimeter in the ALICE experiment at CERN is described. It is shown ...that by introducing an additional photodetector, that is, a silicon photomultiplier, it is possible, without worsening the energy resolution, to significantly improve the time resolution of the PHOS spectrometer from the current values of 3–4 ns to 150–200 ps.
.
Experimental and theoretical studies of direct photon production in hadronic collisions essentially expand our insights in multiparticle production mechanisms. These photons are useful probes to ...investigate nuclear matter at all stages of the interaction. Soft photons play a particular role in these studies. Until now we have no explanation for the experimentally observed excess of soft photons. These photons have low transverse momenta
GeV/
c
,
. In this domain their yield exceeds the theoretical estimates by 5-8 times. The registration of soft photons at Nuclotron (LHEP, JINR) has been carried out by the electromagnetic calorimeter built by the SVD-2 Collaboration. Soft photon electromagnetic calorimeter was tested at U-70, IHEP (Protvino). For the first time the soft photon yield at interactions of 3.5
A
GeV/
c
per nucleon deuterium and lithium beams has been measured. The obtained energy spectra confirm the increased yield of soft photons with their energy less than 50MeV (in the laboratory system) in comparison with theoretical predictions and agree with previous experiments at high-energy interactions. It is planned to continue soft photon study at the future accelerator complex NICA with heavy-ion beams.
A soft photon calorimeter for the SVD-2 experiment Ardashev, E. N.; Britvich, G. I.; Vorobiev, A. P. ...
Instruments and experimental techniques (New York),
03/2015, Letnik:
58, Številka:
2
Journal Article
Recenzirano
The design of the soft photon calorimeter for the SVD-2 experiment is described. The aperture of the calorimeter is 210 × 210 mm. The first results of its testing in the course of data acquisition in ...the E-190 experiment at the U-70 accelerator of the Institute for High Energy Physics are presented.
Data from the SVD-2 experiment that were obtained at the IHEP accelerator in 70-GeV/c proton-nucleus interactions are analyzed with the aim of searches for an exotic {theta}{sup +} baryon that decays ...through the pK{sup 0}{sub S} channel. The reaction pN {yields} pK{sup 0}{sub S} + X characterized by a bounded multiplicity of charged secondaries is used for this analysis. A resonance of mass M = 1526 {+-} 3(stat.) {+-} 3(syst.) MeV/c{sup 2} and width {gamma} < 24 MeV/c{sup 2} is observed in the invariant-mass spectrum of the pK{sup 0}{sub S} system at a statistical significance of 5.6{sigma}. The mass and the width of this resonance correspond to the recently found positive-strangeness {theta}{sup +} baryon, which was predicted to be an exotic baryon consisting of five quarks (pentaquark), uudds-bar. The total cross section for the production of a {theta}{sup +} baryon in pA interactions is estimated at a value within the range 30-120 {mu}b for x{sub F} {>=} 0. An analysis of the A dependence of the cross section for {theta}{sup +}-baryon production does not reveal a significant deviation from the A dependence for inelastic events ({approx}A{sup 0.7})
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