arXiv subjects

N. Rakhimov

Publications and source records attributed to N. Rakhimov.

5 recordsLinked to original sources

arXiv2025

Heavy-light quark systems from the QCD instanton vacuum: $N_f=1$ light flavor case

We investigate heavy-light quark systems within the framework of the QCD instanton vacuum, focusing on the $N_f = 1$ light flavor case. We derive an effective heavy-light quark interaction from the low-energy QCD partition function and construct a heavy-meson effective Lagrangian. The physical residual mass of heavy mesons, $Λ$, is determined by employing compositeness and normalization conditions. We calculate the masses of $D$ and $B$ mesons and their weak decay constants to the leading order and next-to-leading order in the $1/m_Q$ expansion. The current results for $f_D$ and $f_B$ are in good agreement with recent lattice QCD data and PDG average values.

hep-ph↗

arXiv2021

ILM gluons in perturbative QCD

In this paper we extend our previous work on gluon propagator in the Instanton Liquid Model (ILM) of the QCD vacuum. This objects presents a lot of interest for studies of the heavy quarkonium $Q\bar Q$ observables in the framework of potential Nonrelativistic QCD (pNRQCD). Our goal is to evaluate the gluon polarization operator in ILM, and understand if it gets contributions from infrared (IR) renormalons. We perform a systematic analyis, taking into account both perturbative and nonperturbative effects, and making a double series expansion in terms of the strong coupling $α_s(ρ)\sim 0.5$ (the scale is given by average instanton size $ρ\approx1/3$ fm) and the instanton gas packing fraction $λ=ρ^4/R^4\sim 0.01$ ($R\approx 1$ fm is average inter-instanton distance). We demonstrate that there are no IR renormalon related to ILM gluon propagator, since instantons generate a ILM gluon dynamical mass.

hep-ph↗

arXiv2020

Heavy quark correlators in Instanton Liquid Model with perturbative corrections

In the present work we consider the influence on the heavy quark correlators due to the instanton background in the framework of instanton liquid model (ILM) of QCD vacuum by taking into account also the perturbative gluon effects. For a single heavy quark this leads to the mass shift due to the direct-instanton nonperturbative and ILM modified perturbative contributions, respectively. In the heavy quark-antiquark ($Q\bar{Q}$) sector we obtain the potential consisting the direct instanton induced part and the one-gluon exchange (OGE) perturbative part which is screened at large distances due to the nonperturbative dynamics. At the region of interest corresponding to the heavy quark physics the screening effect in OGE can be well approximated by a Yukawa-type potential in terms of the dynamically generated gluon mass. A possible implication of the present studies to the phenomenology of heavy quarkonium is also discussed.

hep-ph↗

arXiv2019

Dynamical gluon mass at non-zero temperature in instanton vacuum model

In the framework of the instanton liquid model (ILM), we consider thermal modifications of the gluon properties in different scenarios of temperature $T$ dependence of the average instanton size $\barρ(T)$ and the instanton density $n(T)$ known from the literature. Due to interactions with instantons, the gluons acquire the dynamical temperature dependent "electric" gluon mass $M_{el}(q,T).$ We found that at small momenta and zero temperature $M_{el}(0,0)\approx362\,{\rm MeV}$ at the phenomenological values of $\barρ(0)=1/3\,{\rm fm}$ and $n(0)=1\,{\rm fm}^{-4}$, however the $T$-dependence of the mass is very sensitive to the temperature dependence of the instanton vacuum parameters $\barρ(T),\,n(T)$: it is very mild in case of the lattice-motivated dependence and decreases steeply in the whole range with theoretical parametrization. We see that in region $0<T<T_{c}$ ILM is able to reproduce lattice results for the dynamical "electric" gluon mass.

hep-ph↗

arXiv2018

Heavy quarkonium and dynamical gluon mass at non-zero temperature in instanton vacuum model

In the framework of the Instanton Liquid Model we evaluate the heavy quark $\bar{Q}Q$ potential at nonzero temperature $T$. The potential has two components: contribution due to direct interaction with instantons, and the modification of the one-gluon exchange contribution via instanton-generated dynamical \char`\"{}electric\char`\"{} gluon mass $M_{el}(q,T)$. We conclude that the nonperturbative ILM contributions to the $Q\bar{Q}$ potential have pronounced temperature dependence, which might be tested in phenomenological analyses of charmonia production data.

hep-ph↗