arXiv subjects

A. V. Belyaev

Publications and source records attributed to A. V. Belyaev.

At least 19 recordsLinked to original sources

arXiv2022

Status and initial physics performance studies of the MPD experiment at NICA

The Nuclotron-base Ion Collider fAcility (NICA) is under construction at the Joint Institute for Nuclear Research (JINR), with commissioning of the facility expected in late 2022. The Multi-Purpose Detector (MPD) has been designed to operate at NICA and its components are currently in production. The detector is expected to be ready for data taking with the first beams from NICA. This document provides an overview of the landscape of the investigation of the QCD phase diagram in the region of maximum baryonic density, where NICA and MPD will be able to provide significant and unique input. It also provides a detailed description of the MPD set-up, including its various subsystems as well as its support and computing infrastructures. Selected performance studies for particular physics measurements at MPD are presented and discussed in the context of existing data and theoretical expectations.

physics.ins-det↗

arXiv2022

Conceptual design of the Spin Physics Detector

The Spin Physics Detector, a universal facility for studying the nucleon spin structure and other spin-related phenomena with polarized proton and deuteron beams, is proposed to be placed in one of the two interaction points of the NICA collider that is under construction at the Joint Institute for Nuclear Research (Dubna, Russia). At the heart of the project there is huge experience with polarized beams at JINR. The main objective of the proposed experiment is the comprehensive study of the unpolarized and polarized gluon content of the nucleon. Spin measurements at the Spin Physics Detector at the NICA collider have bright perspectives to make a unique contribution and challenge our understanding of the spin structure of the nucleon. In this document the Conceptual Design of the Spin Physics Detector is presented.

hep-ex↗

arXiv2016

Charmed meson and charmonium production in PbPb collisions at the LHC

The phenomenological analysis of various characteristics of $J/ψ$ and $D$ meson production in PbPb collisions at the center-of-mass energy 2.76 TeV per nucleon pair is presented. The data on momentum spectra and elliptic flow are reproduced by two-component model HYDJET++ including thermal and non-thermal charm production mechanisms. The significant part of $D$-mesons is found to be in a kinetic equilibrium with the created medium, while $J/ψ$-mesons are characterized by earlier (as compared to light hadrons) freeze-out.

hep-ph↗

arXiv2015

Spectra and elliptic flow of charmed hadrons in HYDJET++ model

Heavy-flavour quarks are predominantly produced in hard scatterings on a short time-scale and traverse the medium interacting with its constituents, thus they are one of the effective probes of the transport properties of the medium formed in relativistic heavy ion collisions. On the other hand, the thermal production of heavy-flavour quarks in quark-gluon plasma (QGP) is itself of interest. In this report, the production and elliptic flow of the prompt charmed mesons $D^0$, $D^+$, $D^{*+}$ and $J/ψ$ in PbPb collisions at the center-of-mass energy 2.76 TeV per nucleon pair are described in the framework of two-component HYDJET++ model. The model combines thermal and pQCD production mechanisms. The spectra and elliptic flow of charmed mesons are presented, the results are compared with LHC data.

hep-ph↗

arXiv2015

Study of the quasi-free $np \to np π^+π^-$ reaction with a deuterium beam at 1.25 GeV/nucleon

The tagged quasi-free $np \to npπ^+π^-$ reaction has been studied experimentally with the High Acceptance Di-Electron Spectrometer (HADES) at GSI at a deuteron incident beam energy of 1.25 GeV/nucleon ($\sqrt s \sim$ 2.42 GeV/c for the quasi-free collision). For the first time, differential distributions for $π^{+}π^{-}$ production in $np$ collisions have been collected in the region corresponding to the large transverse momenta of the secondary particles. The invariant mass and angular distributions for the $np\rightarrow npπ^{+}π^{-}$ reaction are compared with different models. This comparison confirms the dominance of the $t$-channel with $ΔΔ$ contribution. It also validates the changes previously introduced in the Valencia model to describe two-pion production data in other isospin channels, although some deviations are observed, especially for the $π^{+}π^{-}$ invariant mass spectrum. The extracted total cross section is also in much better agreement with this model. Our new measurement puts useful constraints for the existence of the conjectured dibaryon resonance at mass M$\sim$ 2.38 GeV and with width $Γ\sim$ 70 MeV.

nucl-ex↗

arXiv2015

Thermal and non-thermal charmed meson production in heavy ions collisions at the LHC

The phenomenological analysis of the LHC data on transverse momentum spectrum and elliptic flow of $J/ψ$ and D mesons in PbPb collisions at center-of-mass energy 2.76 TeV per nucleon pair is presented. The charmed meson production pattern in PbPb collisions may be reproduced by two-component model HYDJET++ including thermal and non-thermal components. The significant part of D-mesons is found to be in a kinetic equilibrium with the created medium, while $J/ψ$-mesons are not.

hep-ph↗

arXiv2015

Electro-hydrodynamics near Hydrophobic Surfaces

We show that an electro-osmotic flow near the slippery hydrophobic surface depends strongly on the mobility of surface charges, which are balanced by counter-ions of the electrostatic diffuse layer. For a hydrophobic surface with immobile charges the fluid transport is considerably amplified by the existence of a hydrodynamic slippage. In contrast, near the hydrophobic surface with mobile adsorbed charges it is also controlled by an additional electric force, which increases the shear stress at the slipping interface. To account for this, we formulate electro-hydrodynamic boundary conditions at the slipping interface, which should be applied to quantify electro-osmotic flows instead of hydrodynamic boundary conditions. Our theoretical predictions are fully supported by dissipative particle dynamics simulations with explicit charges. These results lead to a new interpretation of zeta-potential of hydrophobic surfaces.

physics.flu-dyn↗

arXiv2015

Subthreshold Xi- Production in Collisions of p(3.5 GeV)+Nb

Results on the production of the double-strange cascade hyperon $\mathrm{Ξ^-}$ are reported for collisions of p\,(3.5~GeV)\,+\,Nb, studied with the High Acceptance Di-Electron Spectrometer (HADES) at SIS18 at GSI Helmholtzzentrum for Heavy-Ion Research, Darmstadt. For the first time, subthreshold $\mathrm{Ξ^-}$ production is observed in proton-nucleus interactions. Assuming a $\mathrm{Ξ^-}$ phase-space distribution similar to that of $\mathrmΛ$ hyperons, the production probability amounts to $P_{\mathrm{Ξ^-}}=(2.0\,\pm0.4\,\mathrm{(stat)}\,\pm 0.3\,\mathrm{(norm)}\,\pm 0.6\,\mathrm{(syst)})\times10^{-4}$ resulting in a $\mathrm{Ξ^-/(Λ+Σ^0)}$ ratio of $P_{\mathrm{Ξ^-}}/\ P_{\mathrm{Λ+Σ^0}}=(1.2\pm 0.3\,\mathrm{(stat)}\pm0.4\,\mathrm{(syst)})\times10^{-2}$. Available model predictions are significantly lower than the estimated $\mathrm{Ξ^-}$ yield.

nucl-ex↗

arXiv2014

Lambda hyperon production and polarization in collisions of p(3.5 GeV) + Nb

Results on $Λ$ hyperon production are reported for collisions of p(3.5 GeV) + Nb, studied with the High Acceptance Di-Electron Spectrometer (HADES) at SIS18 at GSI Helmholtzzentrum for Heavy-Ion Research, Darmstadt. The transverse mass distributions in rapidity bins are well described by Boltzmann shapes with a maximum inverse slope parameter of about $90\,$MeV at a rapidity of $y=1.0$, i.e. slightly below the center-of-mass rapidity for nucleon-nucleon collisions, $y_{cm}=1.12$. The rapidity density decreases monotonically with increasing rapidity within a rapidity window ranging from 0.3 to 1.3. The $Λ$ phase-space distribution is compared with results of other experiments and with predictions of two transport approaches which are available publicly. None of the present versions of the employed models is able to fully reproduce the experimental distributions, i.e. in absolute yield and in shape. Presumably, this finding results from an insufficient modelling in the transport models of the elementary processes being relevant for $Λ$ production, rescattering and absorption. The present high-statistics data allow for a genuine two-dimensional investigation as a function of phase space of the self-analyzing $Λ$ polarization in the weak decay $Λ\rightarrow p π^-$. Finite negative values of the polarization in the order of $5-20\,\%$ are observed over the entire phase space studied. The absolute value of the polarization increases almost linearly with increasing transverse momentum for $p_t>300\,$MeV/c and increases with decreasing rapidity for $y < 0.8$.

nucl-ex↗

arXiv2013

pK+Λfinal state: towards the extraction of the ppK- contribution

The reaction p(@3.5\,GeV)+p -> p+Λ+ K^+ can be studied to search for the existence of kaonic bound states like ppK^- leading to this final state. This effort has been motivated by the assumption that in p+p collisions the Λ(1405) resonance can act as a doorway to the formation of the kaonic bound states. The status of this analysis within the HADES collaboration, with particular emphasis on the comparison to simulations, is shown in this work and the deviation method utilized by the DISTO collaboration in a similar analysis is discussed. The outcome suggests the employment of a partial wave analysis to disentangle the different contributions to the measured pK^+Λfinal state.

nucl-ex↗

arXiv2013

Baryonic resonances close to the Kbar-N threshold: the case of Lambda(1405) in pp collisions

We present an analysis of the Lambda(1405) resonance produced in the reaction p+p->Sigma^{pm}+pi^{mp}+K+p at 3.5 GeV kinetic beam energy measured with HADES at GSI. The two charged decay channels Lambda(1405) -> Sigma^{\pm}+pi^{\mp} have been reconstructed for the first time in p+p collisions. The efficiency and acceptance-corrected spectral shapes show a peak position clearly below 1400 MeV/c^2. We find a total production cross section of sigma_{Lambda(1405)}=9.2 +- 0.9 +- 0.7 +3.3-1.0 mub. The analysis of its polar angle distribution suggests that the Lambda(1405) is produced isotropically in the p-p center of mass system.

nucl-ex↗

arXiv2012

Hadron spectra, flow and correlations in PbPb collisions at the LHC: interplay between soft and hard physics

The started LHC heavy ion program makes it possible to probe new frontiers of the high temperature Quantum Chromodynamics. It is expected that the role of hard and semi-hard particle production processes may be significant at ultra-high energies even for bulk properties of the created matter. In this paper, the LHC data on multiplicity, hadron spectra, elliptic flow and femtoscopic correlations from PbPb collisions at center-of-mass energy 2.76 TeV per nucleon pair are analyzed in the framework of the HYDJET++ model. The influence of the jet production mechanism on these observables is discussed.

hep-ph↗

arXiv2012

Determination of the $\mathbf{Σ(1385)^{0}/Λ(1405)}$ ratio in p+p collisions at 3.5 GeV

The aim of the present analysis is to determine the relative production cross sections of the $Λ$(1405) and $Σ(1385)^{0}$ resonances in p+p collisions at E$_{kin}$=3.5 GeV measured with HADES. Upper and lower limits have been determined for the ratio $σ_{(Σ(1385)^{0}+p+K^{+})}/σ_{(Λ(1405)+p+K^{+})}=0.76_{-0.26}^{+0.54}$. The knowledge of this ratio is an essential input for the analysis of the decay $Λ(1405)\rightarrowΣ^{\pm}π^{\mp}$, where an unambiguous separation of the $Λ$(1405) and $Σ(1385)^{0}$ signals is not possible.

nucl-ex↗

arXiv2011

Baryonic resonances close to the Kbar-N threshold: the case of Sigma(1385)^+ in pp collisions

We present results of an exclusive measurement of the first excited state of the Sigma hyperon, Sigma(1385)^+, produced in p+p -> Sigma^+ + K^+ + n at 3.5 GeV beam energy. The extracted data allow to study in detail the invariant mass distribution of the Sigma(1385)^+. The mass distribution is well described by a relativistic Breit-Wigner function with a maximum at m_0 = 1383.2 +- 0.9 MeV/c^2 and a width of 40.2 +- 2.1 MeV/c^2. The exclusive production cross-section comes out to be 22.27 +- 0.89 +- 1.56 +3.07 -2.10 mu b. Angular distributions of the Sigma(1385)^+ in different reference frames are found to be compatible with the hypothesis that 33 % of Sigma(1385)^+ result from the decay of an intermediate Delta^{++} resonance.

nucl-ex↗

arXiv2011

Jet quenching pattern at LHC in PYQUEN model

The first LHC data on high transverse momentum hadron and dijet spectra in PbPb collisions at center-of-mass energy 2.76 TeV per nucleon pair are analyzed in the frameworks of PYQUEN jet quenching model. The presented studies for the nuclear modification factor of high-pT hadrons and the imbalance in dijet transverse energy support the supposition that the intensive wide-angular ("out-of-cone") medium-induced partonic energy loss is seen in central PbPb collisions at the LHC.

hep-ph↗

arXiv2011

Study of the Reaction $np \rightarrow np π^+ π^-$ at Intermediate Energies

The reaction $np \rightarrow np π^+ π^-$ was studied at the various momenta of incident neutrons. It was shown that the characteristics of the reaction at the momenta above 3 GeV/c could be described by the model of reggeized $π$ exchange (OPER). At the momenta below 3 GeV/c, it was necessary to use additionally the mechanism of one baryon exchange (OBE).

hep-ex↗

arXiv2010

In-Medium Effects on K0 Mesons in Relativistic Heavy-Ion Collisions

We present the transverse momentum spectra and rapidity distributions of $π^{-}$ and K$^0_S$ in Ar+KCl reactions at a beam kinetic energy of 1.756 A GeV measured with the spectrometer HADES. The reconstructed K$^0_S$ sample is characterized by good event statistics for a wide range in momentum and rapidity. We compare the experimental $π^{-}$ and K$^0_S$ distributions to predictions by the IQMD model. The model calculations show that K$^0_S$ at low tranverse momenta constitute a particularly well suited tool to investigate the kaon in-medium potential. Our K$^0_S$ data suggest a strong repulsive in-medium K$^0$ potential of about 40 MeV strength.

nucl-ex↗

arXiv2010

Modeling the jet quenching, thermal resonance production and hydrodynamical flow in relativistic heavy ion collisions

The event topology in relativistic heavy ion collisions is determined by various multi-particle production mechanisms. The simultaneous model treatment of different collective nuclear effects at high energies (such as a hard multi-parton fragmentation in hot QCD-matter, thermal resonance production, hydrodynamical flows, etc.) is actual but rather complicated task. We discuss the simulation of the above effects by means of Monte-Carlo model HYDJET++.

hep-ph↗