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B. G. Zakharov

Publications and source records attributed to B. G. Zakharov.

At least 19 recordsLinked to original sources
arXiv2026

Odderon exchange in high-energy $K^0_S$ regeneration at the LHC

We revisit the possibility of detecting the Odderon exchange through high-energy neutral-kaon regeneration, focusing on the in-matter $K^0_L\to K^0_S$ conversion of $(\sim\!0.2-2)$~TeV $K^0_L$ mesons originating from $pp$ collisions at $\sqrt{s}=13.6$~TeV, and on the practical constraints of realizing such a measurement in the very-forward region of an LHC interaction point. The analysis has two complementary parts. First, we reproduce the original coherent-forward-regeneration estimates for a liquid-hydrogen regenerator and extend them to realistic C, Cu and Pb regenerators of an LHC-compatible geometry, including neutral-kaon attenuation. We show that an Odderon-induced regeneration phase produces a measurable distortion of the $K^0\toπ^0π^0$ decay-vertex distribution at TeV kaon energies, but that the survival of primary $K^0_S$ mesons from the interaction point imposes severe baseline requirements, while a competing electromagnetic $C=-1$ (photon-exchange) amplitude limits the interpretation of the coherent mode as a clean Odderon measurement. Second, we examine non-forward (diffractive) regeneration at lower kaon energies of $0.2-0.8$~TeV, where the primary-$K^0_S$ contamination is naturally suppressed, and estimate the competing Odderon, Pomeron--Odderon-cut, $ω$-Reggeon and photon-exchange contributions to the regeneration amplitude. We identify neutron-induced neutral-only strangeness production and inelastic Regge backgrounds as the dominant limitations, quantify the background suppression required for an observable Odderon signal, and formulate the ingredients of an active double-regenerator subtraction strategy.

hep-ph↗
arXiv2025

Predictions for $R_{AA}$ in 5.36 TeV C+C, O+O, and Ne+Ne collisions at the LHC

Experiments on collisions of light nuclei at $\sqrt{s}=5.36$ TeV have recently begun at the LHC. In this regard we make predictions for nuclear modification factor $R_{AA}$ in 5.36 TeV C+C, O+O, and Ne+Ne collisions for scenarios with and without quark-gluon plasma formation in $pp$ collisions. We find a sizeable difference in $R_{AA}$ for these two scenarios, which grows with decreasing atomic number. This says that data on $R_{AA}$ for light nuclei could potentially give information on the presence of jet quenching in $pp$ collisions.

hep-ph↗
arXiv2025

Nuclear modification factor $I_{AA}$ in $AA$ collisions at RHIC and LHC energies in scenarios with and without quark-gluon plasma formation in $pp$ collisions

We calculate the away-side hadron-triggered modification factor $I_{AA}$ in $AA$ collisions at RHIC and LHC energies for scenarios with and without quark-gluon plasma formation in $pp$ collision. We find that for both scenarios theoretical results for $I_{AA}$ agree well with the available data for 2.76 TeV Pb+Pb and 0.2 TeV Au+Au collisions. We make predictions for $I_{AA}$ in 7 TeV O+O collisions that are planned at the LHC. Our results show that measuring $I_{OO}$ in the whole centrality interval and at small centrality ($\lesssim 5$%) may give information on the presence of jet quenching in $pp$ collisions.

hep-ph↗
arXiv2024

Jet quenching for hadron-tagged jets in $pA$ collisions

We calculate the medium modification factor $I_{pA}$ for 5.02 TeV $p$+Pb collisions. We use the Monte-Carlo Glauber model to determine the parameters of the quark-gluon plasma fireball in $pA$ jet events. Our calculations show that the jet quenching effect for $I_{pA}$ turns out to be rather small. We have found that the theoretical $I_{pA}$ as a function of the underlying event charged multiplicity density, within errors, agrees with data from ALICE for 5.02 TeV $p$+Pb collisions. However, the experimental errors are too large to draw a firm conclusion on the possible presence of jet quenching.

hep-ph↗
arXiv2023

Effect of color randomization on $p_T$ broadening of fast partons in turbulent quark-gluon plasma

We analyze the effect of the parton color randomization on $p_T$ broadening in the quark-gluon plasma with turbulent color fields. We calculate the transport coefficient for a simplified model of fluctuating color fields in the form of alternating sequential transverse layers with homogenous transverse chromomagnetic fields with random orientation in the SU(3) group and gaussian distribution in the magnitude. Our numerical results show that the color randomization can lead to a sizable reduction of the turbulent contribution to $\hat{q}$. The magnitude of the effect grows with increasing ratio of the electric and magnetic screening masses.

hep-ph↗
arXiv2023

Jet quenching in mini-quark-gluon plasma: Medium modification factor $I_{pA}$ for photon-tagged jets

We calculate the medium modification factor $I_{pA}$ for the photon-tagged jet fragmentation functions for scenario with the quark-gluon plasma formation in $pA$ and $pp$ collisions. We perform calculations of radiative and collisional parton energy loss in the quark-gluon plasma with running $α_s$ which has a plateau around $Q\sim κT$ with $κ$ fitted to the LHC data on the heavy ion $R_{AA}$. We find that the theoretical prediction for $I_{pA}$ in $5.02$ TeV $p$+Pb collisions are within errors consistent with the data from ALICE [1]. However, a definite conclusion about the presence or absence of jet quenching in $pA$ collisions cannot be drawn due to large experimental errors of the ALICE data [1]. Our calculations show that this requires a significantly more accurate measurement of $I_{pA}$.

hep-ph↗
arXiv2022

Jet quenching for heavy flavors in $AA$ and $pp$ collisions

We perform a global analysis of experimental data on jet quenching for heavy flavors for scenarios with and without quark-gluon plasma formation in $pp$ collisions. We find that the theoretical predictions for the nuclear modification factor $R_{AA}$ for heavy flavors at the LHC energies are very similar for these scenarios, and the results for $R_{AA}$ and $v_2$ agree reasonably with the LHC data. The agreement with data at the RHIC top energy becomes somewhat better for the intermediate scenario, in which the quark-gluon plasma formation in $pp$ collisions occurs only at the LHC energies. Our fits to heavy flavor $R_{AA}$ show that description of jet quenching for heavy flavors requires somewhat bigger $α_s$ than data on jet quenching for light hadrons.

hep-ph↗
arXiv2022

Medium effects for hadron-tagged jets in proton-proton collisions

We study the medium modification factor $I_{pp}$ within the light-cone path integral approach to induced gluon emission. We use parametrization of the running coupling $α_s(Q,T)$ which has a plateau around $Q\sim κT$. We calculate $I_{pp}$ with no free parameters using $κ$ fitted to the LHC data on the nuclear modification factor $R_{AA}$. We find that the theoretical multiplicity dependence of the ratio $I_{pp}/\langle I_{pp}\rangle$ for $5.02$ TeV $pp$ collisions agrees reasonably with the recent preliminary data from ALICE [1].

hep-ph↗
arXiv2021

Influence of collective nuclear vibrations on initial state eccentricities in Pb+Pb collisions

We study within the Monte Carlo Glauber model the influence of collective quantum effects in the Pb nucleus on the azimuthal anisotropy coefficients $ε_{2,3}$ in Pb+Pb collisions at the LHC energies. To account for the quantum effects, we modify the sampling of the nucleon positions by applying suitable filters that guarantee that the colliding nuclei have the mean squared quadrupole and octupole moments consistent with the ones extracted from the experimental quadrupole and octupole strength functions for the Pb nucleus with the help of the energy weighted sum rule. Our Monte Carlo Glauber model with the modified sampling of the nucleon positions leads to $ε_2\{2\}/ε_3\{2\}\approx 0.8$ at centrality $\lesssim 1$\%, which allows to resolve the $v_2$-to-$v_3$ puzzle.

nucl-th↗
arXiv2021

Jet quenching from heavy to light ion collisions

We perform an analysis of jet quenching in heavy and light ion collisions for scenarios without and with quark-gluon plasma formation in $pp$ collisions. We find that the results for these scenarios are very similar, and both of them are in reasonable agreement with data for heavy ion collisions. However, their results become differ significantly for light nuclei. Using the parameters fitted to heavy ion data on the nuclear modification factor $R_{AA}$, we make predictions for 0.2 and 7 TeV O+O collisions that can be verified by future experiments at RHIC and the LHC.

hep-ph↗
arXiv2021

Radiative $p_{\perp}$-broadening of fast partons in an expanding quark-gluon plasma

We study contribution of radiative processes to $p_{\perp}$-broadening of fast partons in an expanding quark-gluon plasma. It is shown that the radiative correction to $\langle p_{\perp}^2\rangle$ for the QGP produced in $AA$-collisions at RHIC and LHC may be negative, and comparable in absolute value with the non-radiative contribution. We have found that the QGP expansion enhances the radiative suppression of $p_\perp$-broadening as compared to the static medium.

hep-ph↗
arXiv2020

Updated analysis of jet quenching at RHIC and LHC within the light cone path integral approach

We present results of a detailed analysis of experimental data on the nuclear modification factor $R_{AA}$ and the flow coefficient $v_2$ for light hadrons from RHIC for $0.2$ TeV Au+Au collisions and from LHC for $2.76$ and $5.02$ TeV Pb+Pb, and $5.44$ TeV Xe+Xe collisions. We perform calculations within the light-cone path integral approach to induced gluon emission. We use running $α_s$ which is frozen at low momenta at some value $α_{s}^{fr}$. We find that the RHIC data support somewhat larger value of $α_{s}^{fr}$. For the $χ^2$ optimized values of $α_{s}^{fr}$, the theoretical predictions are in reasonable agreement with data on $R_{AA}$ and $v_2$. Calculations made for different formation times and life-times of the QGP show that jet quenching at the RHIC and LHC energies is only weakly sensitive to the initial and final stages of the QCD matter evolution.

hep-ph↗
arXiv2020

Jet quenching with $T$-dependent running coupling

We perform an analysis of jet quenching in heavy ion collisions at RHIC and LHC energies with the temperature dependent running QCD coupling. Our results show that the $T$-dependent QCD coupling largely eliminates the difference between the optimal values of $α_s$ for the RHIC and LHC energies. It may be viewed as direct evidence of the increase of the thermal suppression of $α_s$ with rising temperature.

hep-ph↗
arXiv2020

Collective nuclear vibrations and initial state shape fluctuations in central Pb+Pb collisions: resolving the $v_2$ to $v_3$ puzzle

We have studied, for the first time, the influence of the collective quantum effects in the nuclear wave functions on the azimuthal anisotropy coefficients $ε_{2,3}$ in the central Pb+Pb collisions at the LHC energies. With the help of the energy weighted sum rule we demonstrate that the classical treatment with the Woods-Saxon nuclear density overestimates the mean square quadrupole moment of the $^{208}$Pb nucleus by a factor of $\sim 2.2$. The Monte-Carlo Glauber simulation of the central Pb+Pb collisions accounting for the restriction on the quadrupole moment leads to $ε_2/ε_3\approx 0.8$ which allows to resolve the $v_2$-to-$v_3$ puzzle.

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arXiv2019

Radiative contribution to $p_{\perp}$-broadening of fast partons in a quark-gluon plasma

The contribution of radiative processes to $p_\perp$-broadening of fast partons in a quark-gluon plasma is investigated. Calculations are performed beyond the soft gluon approximation. It is shown that the radiative correction to $\langle p_{\perp}^2\rangle$ for conditions of heavy ion collisions at RHIC and LHC is negative and can be comparable in absolute value with the nonradiative contribution. This prediction differs radically from the essentially positive contribution of radiative processes to $p_{\perp}$-broadening, which was predicted earlier in the literature.

hep-ph↗
arXiv2019

Radiative parton energy loss and baryon stopping in $AA$ collisions

We study the radiative energy loss contribution to proton stopping in $AA$ collisions. The analyses is performed within the light-cone path integral approach to induced gluon emission. We have found that the radiative correction can fill in partly the midrapidity dip in the net proton rapidity distribution in $AA$ collisions at $\sqrt{s}\sim 10$ GeV. We argue that at $\sqrt{s}\sim 10$ GeV the net proton fluctuations at midrapidity may be dominated by the initial fluctuations of the proton flow, which, to a good accuracy, should be binomial.

nucl-th↗
arXiv2018

Effect of giant resonances on fluctuations of electromagnetic fields in heavy ion collisions

We perform quantum calculations of fluctuations of the electromagnetic fields in $AA$ collisions at RHIC and LHC energies. Calculations are performed with the help of the fluctuation-dissipation theorem accounting for the giant dipole and quadrupole resonances. We find that in the quantum picture the field fluctuations are much smaller than that predicted by the classical Monte-Carlo simulation with the Woods-Saxon nuclear density used in previous analyses.

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