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D. A. Morozov

Publications and source records attributed to D. A. Morozov.

16 recordsLinked to original sources
arXiv2021

Short-Timescale Variability of the Blazar Mrk 421 from AstroSat and Simultaneous Multi-Wavelength Observations

We study the multi-wavelength variability of the blazar Mrk 421 at minutes to days timescales using simultaneous data at $γ$-rays from Fermi, 0.7-20 keV energies from AstroSat, and optical and near-infrared (NIR) wavelengths from ground-based observatories. We compute the shortest variability timescales at all of the above wavebands and find its value to be ~1.1 ks at the hard X-ray energies and increasingly longer at soft X-rays, optical and NIR wavelengths as well as at the GeV energies. We estimate the value of the magnetic field to be 0.5 Gauss and the maximum Lorentz factor of the emitting electrons ~1.6 x $10^5$ assuming that synchrotron radiation cooling drives the shortest variability timescale. Blazars vary at a large range of timescales often from minutes to years. These results, as obtained here from the very short end of the range of variability timescales of blazars, are a confirmation of the leptonic scenario and in particular the synchrotron origin of the X-ray emission from Mrk 421 by relativistic electrons of Lorentz factor as high as $10^5$. This particular mode of confirmation has been possible using minutes to days timescale variability data obtained from AstroSat and simultaneous multi-wavelength observations.

astro-ph.HE↗
arXiv2009

The Completion of Single-Spin Asymmetry Measurements at the Proza Setup

Single spin asymmetry in inclusive $π^0$-production was measured in the polarized target fragmentation region using 50 GeV proton beam. The asymmetry is in agreement with asymmetry measurements in the polarized beam fragmentation region carried out at higher energies. The measurement completed 30-years history of polarized measurements at the PROZA setup.

hep-ex↗
arXiv2009

The First Stage of Polarization Program Spascharm at the Accelerator U-70 of Ihep

The first stage of the proposed polarization program SPASCHARM includes the measurements of the single-spin asymmetry (SSA) in exclusive and inclusive reactions with production of stable hadrons and the light meson and baryon resonances.In this study we foresee of using the variety of the unpolarized beams (pions, kaons, protons and antiprotons) in the energy range of 30-60 GeV. The polarized proton and deuteron targets will be used for revealing the flavor and isotopic spin dependencies of the polarization phenomena. The neutral and charged particles in the final state will be detected.

hep-ex↗
arXiv2008

Performance of a fine-sampling electromagnetic calorimeter prototype in the energy range from 1 to 19 GeV

The fine-sampling electromagnetic calorimeter prototype has been experimentally tested using the 1-19 GeV/c tagged beams of negatively charged particles at the U70 accelerator at IHEP, Protvino. The energy resolution measured by electrons is Delta{E}/E=2.8%/\sqrt{E} + 1.3%. The position resolution for electrons is Delta{x}=3.1 + 15.4/sqrt{E} mm in the center of the cell. The lateral non-uniformity of the prototype energy response to electrons and MIPs has turned out to be negligible. Obtained experimental results are in a good agreement with Monte-Carlo simulations.

physics.ins-det↗
arXiv2007

The Comparative Study of the Inclusive $π^0$ Analyzing Power in Reactions p+p(pol)->π^0 + X and π^-+p(pol)->π^0 + X at 50 and 40 Gev/C Respectively

Single-spin asymmetries $A_N$ in reactions p+p(pol)->π^0 + X and π^-+p(pol)->π^0 + X at 50 and 40 GeV/c respectively behave in drastically different ways in function of transverse momentum in the central region. At the same time $A_N$ in the polarized proton fragmentation region of these reactions are practically coinciding. Our new data on the analyzing power at 50 GeV/c in the polarized proton fragmentation region in reaction p+p(pol)->π^0 + X confirm this conclusion with better statistics and coincide with our previous data at 70 GeV/c for the same reaction.

hep-ex↗
arXiv2007

New Polarization Program at U70 (SPASCHARM Project)

The new polarization program SPASCHARM is being prepared in Protvino. The program has two stages. The first stage is dedicated to single-spin asymmetries in the production of miscellaneous light resonances with the use of 34 GeV $π^-$-beam. Inclusive and exclusive reactions will be studied simultaneously. The second stage is dedicated to single-spin and double-spin asymmetries in charmonium production with the use of 70 GeV polarized proton beam which will allow us to understand charmonium hadronic production mechanism and make gluon polarization $Δg(x)$ extraction at large $x$.

hep-ex↗
arXiv2005

Spin effects in large rapidity pi0 production at STAR

Measurements by the STAR collaboration of neutral pion production at large Feynman $x$ ($x_F$) in the first polarized proton collisions at $\sqrt{s}=200$ GeV were reported previously. During the following two runs additional statistics were acquired with an improved forward calorimeter for the $π^0$ cross-section and analyzing power measurements. First data from $pp$ collisions at $\sqrt{s}=410$ GeV were taken during the RHIC run that ended in June, 2005. The cross section was measured at $η=$3.3, 3.8 and 4.0 and was found to be consistent with next-to-leading order perturbative QCD calculations. The analyzing power was found to be zero at negative $x_F$ and at positive $x_F$ up to ~0.3, then increased with increasing $x_F$. This behavior can be described by phenomenological models including the Sivers effect, the Collins effect or higher twist contributions in initial and final states. Results for the analyzing power at $η=$3.7 and 4.0 from all data acquired at $\sqrt{s}=200$ GeV and the status of the analysis of the $\sqrt{s}=410$ GeV data will be presented. Future upgrade plans and status will also be discussed.

hep-ex↗
arXiv2005

Expected Accuracy in a Measurement of the CKM Angle $α$ Using a Dalitz Plot Analysis of $\boldmath B^0 \to ρπ$ Decays in the BTeV Project

A precise measurement of the angle $α$ in the CKM triangle is very important for a complete test of Standard Model. A theoretically clean method to extract $α$ is provided by B$^0 \to ρπ$ decays. Monte Carlo simulations to obtain the BTeV reconstruction efficiency and to estimate the signal to background ratio for these decays were performed. Finally the time-dependent Dalitz plot analysis, using the isospin amplitude formalism for tree and penguin contributions, was carried out. It was shown that in one year of data taking BTeV could achieve an accuracy on $α$ better than 5$^{\circ}$.

hep-ex↗
arXiv2005

Spin physics program in the U70 polarized proton beam

A possibility to accelerate a high intensity polarized proton beam up to 70 GeV at the IHEP accelerator, extract it from the main ring and deliver to several experimental setups is being studied now. We propose to study a wealth of single- and double-spin observables in various reactions using longitudinally and transverserly polarized proton beams at U70. The proposed measurements can be done at the existing detectors as well as require to create a few new experimental setups at U70.

hep-ex↗
arXiv2005

Design and performance of LED calibration system prototype for the lead tungstate crystal calorimeter

A highly stable monitoring system based on blue and red light emitting diodes coupled to a distribution network comprised of optical fibers has been developed for an electromagnetic calorimeter that uses lead tungstate crystals readout with photomultiplier tubes. We report of the system prototype design and on the results of laboratory tests. Stability better than 0.1% (r.m.s.) has been achieved during one week of prototype operation.

physics.ins-det↗
arXiv2005

Spin Effects in Forward pi^0-production in Polarized Proton-Proton Collisions at STAR

We report some results in large pseudo rapidity pi^0-production in polarized proton collisions at 200 GeV center of mass energy. The single spin asymmetry for positive Feynman x (x_F) is consistent with zero up to ~0.35, then increases with increasing x_F. This behavior can be described by phenomenological models including the Sivers effect, Collins effect or twist-3 contributions in initial and final states. The asymmetry is found to be zero for negative x_F (-0.6 pi^0+X cross sections at η=3.3, 3.8 and 4.0 are consistent with next-to-leading order perturbative QCD calculations.

hep-ex↗
arXiv2005

Correlation of Beam Electron and LED Signal Losses under Irradiation and Long-term Recovery of Lead Tungstate Crystals

Radiation damage in lead tungstate crystals reduces their transparency. The calibration that relates the amount of light detected in such crystals to incident energy of photons or electrons is of paramount importance to maintaining the energy resolution the detection system. We report on tests of lead tungstate crystals, read out by photomultiplier tubes, exposed to irradiation by monoenergetic electron or pion beams. The beam electrons themselves were used to measure the scintillation light output, and a blue light emitting diode (LED) was used to track variations of crystals transparency. We report on the correlation of the LED measurement with radiation damage by the beams and also show that it can accurately monitor the crystals recovery from such damage.

physics.ins-det↗
arXiv2005

Future of low-x forward physics at RHIC

The rapidity dependence of inclusive and coincident particle production in d(p)+Au collisions at RHIC can be used to probe nuclear parton distribution functions down to small momentum fractions where theory anticipates that parton saturation could be present. This paper describes how such experiments could be completed.

hep-ex↗
arXiv2004

Study of Possible Scintillation Mechanism Damage in PbWO4 Crystals After Pion Irradiation

We employed two independent methods to study possible damage to the scintillation mechanism in lead tungstate crystals due to irradiation by a 34 GeV pion beam. First, 10 crystals were irradiated simultaneously over 30 hours by a narrow beam, so that only a small region of each crystal was affected. We studied the effect of the irradiation on the light output non-uniformity. If a localized degradation was observed, it would indicate damage to the scintillation mechanism. Secondly, we detected light output using two phototubes attached to sides of a crystal. Since these phototubes detect scintillation light only from a small localized region, the effect of transmission loss should be minimal. We did not see any statistically significant evidence for scintillation mechanism damage with either method. The effect is consistent with zero, and the upper limit is 0.5% at 95% C.L.

physics.ins-det↗
arXiv2002

Development of a Momentum Determined Electron Beam in the 1 -45 GeV Range

A beam line for electrons with energies in the range of 1 to 45 GeV, low contamination of hadrons and muons and high intensity up to 10^6 per accelerator spill at 27 GeV was setup at U70 accelerator in Protvino, Russia. A beam tagging system based on drift chambers with 160 micron resolution was able to measure relative electron beam momentum precisely. The resolution sigma_p p was 0.13% at 45 GeV where multiple scattering is negligible. This test beam setup provided the possibility to study properties of lead tungstate crystals (PbWO_4) for the BTeV experiment at Fermilab.

hep-ex↗