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Alexey Guskov

Publications and source records attributed to Alexey Guskov.

13 recordsLinked to original sources
arXiv2022

50 Years of Quantum Chromodynamics

This paper presents a comprehensive review of both the theory and experimental successes of Quantum Chromodynamics, starting with its emergence as a well defined theory in 1972-73 and following developments and results up to the present day. Topics include a review of the earliest theoretical and experimental foundations; the fundamental constants of QCD; an introductory discussion of lattice QCD, the only known method for obtaining exact predictions from QCD; methods for approximating QCD, with special focus on effective field theories; QCD under extreme conditions; measurements and predictions of meson and baryon states; a special discussion of the structure of the nucleon; techniques for study of QCD at high energy, including treatment of jets and showers; measurements at colliders; weak decays and quark mixing; and a section on the future, which discusses new experimental facilities or upgrades currently funded. The paper is intended to provide a broad background for Ph.D. students and postdocs starting their career. Some contributions include personal accounts of how the ideas or experiments were developed.

hep-ph↗
arXiv2021

Spin Physics Detector project at JINR

The Spin Physics Detector at the constructing NICA collider (JINR, Dubna) is a universal facility to investigate the spin structure of the proton and deuteron and the other spin-related phenomena with polarized proton and deuteron beams at a collision energy up to 27 GeV. A comprehensive study of the unpolarized and polarized gluon content of the nucleon at large Bjorken-x using different complementary probes such as charmonia, open charm, and prompt photon production processes is the central point of the SPD physics program. In the polarized proton-proton collisions, the SPD experiment at NICA will cover the kinematic gap between the low-energy measurements at ANKE-COSY and SATURNE and the high-energy measurements at the Relativistic Heavy Ion Collider, as well as the planned fixed-target experiments at the LHC. The possibility for NICA to operate with polarized deuteron beams at such energies is unique. The SPD experimental setup is planned as a multipurpose universal 4$π$ detector with advanced tracking and particle identification capabilities, electromagnetic calorimeter, and muon (range) system. To minimize possible systematic effects, SPD will be equipped with a free-running data acquisition system. The spin physics program at the SPD is expected to start after 2025 and to extend for about 10 years.

hep-ex↗
arXiv2021

Production of the bottomonium-like states $Z_b$ states at $e$-$h$ and ultraperipheral $h$-$h$ collisions

The photoproduction of bottomonium-like states $Z_{b}(10610)$ and $Z_{b}(10650)$ via $γp$ scattering is studied within an effectiv Lagrangian approach and the vector-meson-dominance model. The Regge model is employed to calculate the photoproduction of $Z_{b}$ states via $t$-channel with $π$ exchange.The numerical results show that the values of the total cross-sections of $Z_{b}(10610)$ and $Z_{b}(10650)$ can reach 0.09 nb and 0.02 nb, respectively, near the center of mass energy of 22 GeV. The experimental measurements and studies on the photoproduction of $Z_{b}$ states near energy region around $W\simeq 22$ GeV is suggested. Moreover, with the help of eSTARlight and STARlight programs, one obtains the cross-sections and event numbers of $Z_{b}(10610)$ production in electron-ion collision (EIC) and Ultraperipheral collisions (UPCs). The results show that a considerable number of events from $Z_{b}(10610)$ can be produced on the relevant experiments of EICs and UPCs. Also, one calculates the rates and kinematic distributions for $γp\rightarrow Z_{b}n$ in $ep$ and $pA$ collisions via EICs and UPCs, and the relevant results will provide an important reference for the RHIC, LHC, EIC-US, LHeC, and FCC experiments to search for the bottomonium-like $Z_{b}$ states.

hep-ph↗
arXiv2019

Physics with prompt photons at SPD

Prompt photons is a proven instrument for exploration of the gluonic structure of hadrons. The SPD experiment at the NICA collider plans to use prompt photons for study of the gluon contribution to the spin structure of the nucleon in the polarised proton-proton and deutron-deutron collisions.

hep-ex↗
arXiv2018

PHOTON-2017 conference proceedings

This document collects the proceedings of the PHOTON 2017 conference ("International Conference on the Structure and the Interactions of the Photon", including the 22th "International Workshop on Photon-Photon Collisions", and the "International Workshop on High Energy Photon Colliders") held at CERN (Geneva) in May 2017. The latest experimental and theoretical developments on the topics of the PHOTON conference series are covered: (i) $γ\,γ$ processes in e$^+$e$^-$, proton-proton (pp) and nucleus-nucleus (AA) collisions at current and future colliders, (ii) $γ$-hadron interactions in e$^\pm$p, pp, and AA collisions, (iii) final-state photon production (including Standard Model studies and searches beyond it) in pp and AA collisions, and (iv) high-energy $γ$-ray astrophysics. These proceedings are dedicated to the memory of Maria Krawczyk.

hep-ph↗
arXiv2018

Search for muoproduction of the X(3872) at COMPASS

Exotic charmonium-like states have been observed by various experiments over the last 15 years, but their nature is still under discussion. Photo-(muo)production is a new promising instrument to study them. COMPASS, a fixed target experiment at CERN, analyzed the full set of the data collected with a muon beam between 2002 and 2011, covering the range from 7 GeV to 19 GeV in the centre-of-mass energy of the virtual photon-nucleon system. A signal in the mass spectrum of $J/ψπ^+π^-$ with the statistical significance of 4.1 $σ$ was observed in the reaction $μ^+~N \rightarrow μ^+(J/ψπ^+π^- )π^{\pm} N'$. Its mass and width are consistent with those of the $X(3872)$. The shape of the $π^+π^-$ mass distribution from the observed decay into $J/ψπ^+π^-$ is different from previous observations for $X(3872)$. The observed signal may be interpreted as possible evidence of a new charmonium state $\widetilde{X}(3872)$. It could be associated with a neutral partner of $X(3872)$ with $C = -1$ predicted by a tetraquark model.

hep-ex↗
arXiv2016

Photoproduction of $a_{2}(1320)$ in a Regge model

In this work, the photoproduction of $a_{2}(1320)$ off a proton target is investigated within an effective Lagrangian approach and the Regge model. The theoretical result indicates that the shapes of {the} total and differential cross sections of the $γp\rightarrow a_{2}^{+}n$ reaction within the Feynman (isobar) model are much different from that of the Reggeized treatment. The obtained cross section is compared with the existing experimental results at low energies. The $a_{2}(1320)$ production cross section at high energies can be tested by the COMPASS experiment, which can provide important information for clarifying the role of the Reggeized treatment at that energy range.

hep-ph↗
arXiv2015

Charmed hadron photoproduction at COMPASS

Photoproduction of the charmonium-like state $Z_{c}(4200)$ and the charmed baryon $Λ_{c}^{\ast }(2940)$ is investigated with an effective Lagrangian approach and the Regge trajectories applying to the COMPASS experiment. Combining the experimental data from COMPASS and our theoretical model we estimate the upper limit of $Γ_{Z_{c}(4200)\rightarrow J/ψπ}$ to be of about 37 MeV. Moreover, the possibility to produce $Λ_{c}^{\ast }(2940)$ at COMPASS is discussed. It seems one can try to search for this hadron in the missing mass spectrum since the $t$-channel is dominating for the $Λ_{c}^{\ast }(2940)$ photoproduction.

hep-ph↗
arXiv2015

Measurement of the charged-pion polarisability at COMPASS

The electric ($α_π$) and the magnetic ($β_π$) polarisabilities are fundamental properties of the pion characterising the rigidity of its internal structure. They have been precisely measured at the COMPASS experiment at CERN with a $π^{-}$ beam of 190~GeV/c assuming $α_π+β_π=0$. Muons of the same momentum were used for controlling of systematic effects. The obtained result $α_π=-β_π=(2.0\pm 0.6_{stat.}\pm 0.7_{syst.})\times 10^{-4} fm^3$ is in agreement with the prediction of the Chiral Perturbation Theory.

hep-ex↗
arXiv2015

Search for exclusive photoproduction of $Z_c(3900)$ at COMPASS

The $Z_{c}(3900)$ hadron state has been found by the BES-III and Belle experiments in the decay of the hadron state with higher mass. The first attempt to search for the direct exclusive production of the $Z_c^{\pm}(3900)$ hadron by virtual photons has been performed in the reaction $μ^+ N \rightarrow μ^+ N' Z_c(3900)^{\pm} \rightarrow μ^+ N' J/ψπ^{\pm}$ at COMPASS \cite{Adolph:2014hba}. The data cover the range from 7~GeV to 19~GeV in the centre-of-mass energy of the photon-nucleon system. The full COMPASS data set collected with a muon beam between 2002 and 2011 has been used. An upper limit for the ratio $BR(Z_c^{\pm}(3900)\rightarrow J/ψπ^{\pm} )\times (σ_{ γ~N \rightarrow Z_c^{\pm}(3900)~ N} /σ_{ γ~N \rightarrow J/ψ~ N})$ of $3.7\times10^{-3}$ has been established at the confidence level of 90\%.

hep-ex↗
arXiv2015

$Λ_{c}^{+}(2940)$ photoproduction off the neutron

By assuming that the $Λ_{c}^{\ast }(2940)$ is a $pD^{\ast 0}$ molecular state with spin-parity $J^{P}=\frac{1}{2}^{+}$ and $J^{P}=\frac{1}{2}^{-}$, the photoproduction of charmed $Λ_{c}^{\ast }(2940)$ baryon in the $γn\rightarrow D^{-}Λ_{c}^{\ast }(2940)^{+}$ process is investigated with an effective Lagrangian approach. It is found that the contributions from $t$-channel with $D^{\ast }$ exchange are dominant, while the $s$-channel with nucleon pole exchange give a sizeable contribution around the threshold. The contributions from the $u$-channel and contact term are very small. The total cross section of the $γn\rightarrow D^{-}Λ_{c}^{\ast }(2940)^{+}$ reaction is estimated, which indicate it is feasible to searching for the charmed $Λ_{c}^{\ast }(2940)$ baryon at the COMPASS experiment.

hep-ph↗
arXiv2015

Photoproduction of the charged charmoniumlike $Z_{c}^{+}(4200)$

In this work, inspired by the observation of charmoniumlike $Z_{c}^{+}(4200)$% , we study the photoproduction of charged charmoniumlike $Z_{c}^{+}(4200)$ with an effective Lagrangian approach and the Regge trajectories model. The numerical results indicate that the Reggeized treatment can lead to a lower total cross section of the $Z_{c}^{+}(4200)$ photoproduction and the peak position of cross section was moved to the higher energy point when the Reggeized treatment was added. {Moreover, using the data from the COMPASS experiment and presented theoretical predictions, an upper limit of the decay width of $Z_{c}(4200)\rightarrow J/ψπ$ is estimated.} The relevant results not only shed light on the further experiment of searching for the charmoniumlike $Z_{c}(4200)$ state via meson photoproduction, but also provide valuable informations for having a better comprehension of the nature of charmoniumlike $Z_{c}(4200)$ state.

hep-ph↗