arXiv subjects

A. Yu. Semenov

Publications and source records attributed to A. Yu. Semenov.

9 recordsLinked to original sources

arXiv2020

Electromagnetic Calorimeter for MPD Spectrometer at NICA Collider

The Multi-Purpose Detector (MPD) is designed to study a hot and dense baryonic matter formed in heavy-ion collisions at SQRT(sNN)=4-11 GeV at the NICA accelerator complex (Dubna, Russia). Large-sized electromagnetic calorimeter (ECal) of the MPD spectrometer will provide precise spatial and energy measurements for photons and electrons in the central pseudorapidity region of |eta|<1.2. The Shashlyk-type sampling structure of the ECal is optimized for the photons energy range from about 40 MeV to 2-3 GeV. Fine segmentation and projective geometry of the calorimeter allow to deal with high multiplicity of secondary particles from Au-Au reactions. In this talk, we report on a design, a construction status and expected parameters of the ECal.

physics.ins-det↗

arXiv2020

Calibration of MPD Electromagnetic Calorimeter with Muons

Shashlyk-type electromagnetic calorimeter (ECal) of the Multi-Purpose Detector at heavy-ion NICA collider is optimized to provide precise spatial and energy measurements for photons and electrons in the energy range from about 40 MeV to 2-3 GeV. To deal with high multiplicity of secondary particles from Au-Au reactions, ECal has a fine segmentation and consists of 38,400 cells ("towers"). Given the big number of "towers" and the time constraint, it is not possible to calibrate every ECal "tower" with beam. In this paper, we describe the strategy of the first-order calibration of ECal with cosmic muons.

physics.ins-det↗

arXiv2017

Measurement of the beam asymmetry $Σ$ for $π^0$ and $η$ photoproduction on the proton at $E_γ= 9$ GeV

We report measurements of the photon beam asymmetry $Σ$ for the reactions $\vecγp\to pπ^0$ and $\vecγp\to pη$ from the GlueX experiment using a 9 GeV linearly-polarized, tagged photon beam incident on a liquid hydrogen target in Jefferson Lab's Hall D. The asymmetries, measured as a function of the proton momentum transfer, possess greater precision than previous $π^0$ measurements and are the first $η$ measurements in this energy regime. The results are compared with theoretical predictions based on $t$-channel, quasi-particle exchange and constrain the axial-vector component of the neutral meson production mechanism in these models.

nucl-ex↗

arXiv2016

First Results from The GlueX Experiment

The GlueX experiment at Jefferson Lab ran with its first commissioning beam in late 2014 and the spring of 2015. Data were collected on both plastic and liquid hydrogen targets, and much of the detector has been commissioned. All of the detector systems are now performing at or near design specifications and events are being fully reconstructed, including exclusive production of $π^{0}$, $η$ and $ω$ mesons. Linearly-polarized photons were successfully produced through coherent bremsstrahlung and polarization transfer to the $ρ$ has been observed.

nucl-ex↗

arXiv2005

Measurements of the neutron electric to magnetic form factor ratio GEn/GMn via the ^2H(\vec{e},e'\vec{n})^1H reaction to Q^2 = 1.45 (GeV/c)^2

We report values for the neutron electric to magnetic form factor ratio, GEn/GMn, deduced from measurements of the neutron's recoil polarization in the quasielastic 2H(\vec{e},e'\vec{n})1H reaction, at three Q^2 values of 0.45, 1.13, and 1.45 (GeV/c)^2. The data at Q^2 = 1.13 and 1.45 (GeV/c)^2 are the first direct experimental measurements of GEn employing polarization degrees of freedom in the Q^2 > 1 (GeV/c)^2 region and stand as the most precise determinations of GEn for all values of Q^2.

nucl-ex↗

arXiv2005

Tensor Ayy and vector Ay analyzing powers in the H(d,d')X and ^{12}C(d,d')X reactons at initial deuteron momenta of 9 GeV/c in the region of baryonic resonances excitation

The angular dependence of the tensor Ayy and vector Ay analyzing powers in the inelastic scattering of deuterons with a momentum of 9.0 GeV/c on hydrogen and carbon have been measured. The range of measurements corresponds to the baryonic resonance excitation with masses 2.2--2.6 GeV/c^2. The Ayy data being in good agreement with the previous results demonstrate an approximate $t$ scaling up to -1.5 (GeV/c)^2. The large values of A_y show a significant role of the spin-dependent part of the elementary amplitude of the NN->NN* reaction. The results of the experiment are compared with model predictions of the plane-wave impulse approximation.

nucl-ex↗

arXiv2004

Investigation of the Angular Dependence of the Tensor Analyzing Power of 9 Gev/C Deuteron Breakup

An angular dependence of the tensor analyzing power of the breakup of polarized deuterons at 9 GeV/$c$ has been investigated. The measurements have been made on hydrogen and carbon targets at angles in the range from 85 to 160 mr. The data obtained are analyzed within the framework of the light-front dynamics using the deuteron wave functions for Paris and Bonn CD potentials, and the relativistic deuteron wave function by Karmanov et al. The experimental data are in rough agreement with calculations with the use of Karmanov's deuteron wave function.

nucl-ex↗

arXiv2004

Tensor analyzing power Ayy in deuteron inclusive breakup at large Pt and spin structure of deuteron at short internucleonic distances

The Ayy data for deuteron inclusive breakup off hydrogen and carbon at a deuteron momentum of 9.0 GeV/c and large Pt of emitted protons are presented. The large values of Ayy independent of the target mass reflect the sensitivity of the data to the deuteron spin structure. The data obtained at fixed $x$ and plotted versus Pt clearly demonstrate the dependence of the deuteron spin structure at short internucleonic distances on two variables. The data are compared with the calculations using Paris, CD-Bonn and Karmanov's deuteron wave functions.

nucl-ex↗

arXiv2003

Measurements of GEn/GMn from the ^2H(vec{e},e'vec{n})^1H Reaction to Q^2=1.45 (GeV/c)^2

We report new measurements of the ratio of the electric form factor to the magnetic form factor of the neutron, GEn/GMn, obtained via recoil polarimetry from the quasielastic ^2H(vec{e},e'vec{n})^1H reaction at Q^2 values of 0.45, 1.13, and 1.45 (GeV/c)^2 with relative statistical uncertainties of 7.6 and 8.4% at the two higher Q^2 points, which were not reached previously via polarization measurements. Scale and systematic uncertainties are small.

nucl-ex↗