arXiv subjects

B. G. Zakharov

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

At least 55 records · Page 3Linked to original sources

arXiv2014

Medium modification of photon-tagged and inclusive jets in high-multiplicity proton-proton collisions

We study modification of the photon-tagged and inclusive jets in $pp$ collisions at $\sqrt{s}=7$ TeV due to mini-quark-gluon plasma which can be produced in high multiplicity events. We show that for underlying events with $dN_{ch}/dη\sim 20-60$ the medium effects lead to a considerable modification of the photon-tagged and inclusive jet fragmentation functions. For inclusive jets the magnitude of the effect is surprisingly large. The effect is quite strong even for typical underlying events. We find that at $\sqrt{s}=7$ TeV the spectrum of charged hadrons is suppressed by $\sim 35-40$ % at $p_{T}\sim 5-10$ GeV.

hep-ph↗

arXiv2013

Jet tomography of AA-collisions at RHIC and LHC energies

We present our recent results on jet tomography of AA-collisions at RHIC and LHC. We focus on flavor dependence of the nuclear modification factor. The computations are performed accounting for radiative and collisional parton energy loss with running coupling constant.

hep-ph↗

arXiv2013

Nuclear suppression of light hadrons and single electrons at RHIC and LHC

We examine whether it is possible to simultaneously describe the experimental data from RHIC and LHC on nuclear suppression of light hadrons and non-photonic single electrons in the pQCD picture of parton energy loss. We perform calculations accounting for both radiative and collisional energy loss. We show that once the coupling constant is fixed from comparison with data on the nuclear modification factor for light hadrons it gives a satisfactory agreement with data on the electron R_{AA} and azimuthal anisotropy v_2. Our results show that the collisional mechanism is only of marginal significance in nuclear suppression of single electrons except for the bottom contribution at momenta < 6-8 GeV.

hep-ph↗

arXiv2012

Nuclear modification factor for light and heavy flavors within pQCD and recent data from the LHC

We examine the flavor dependence of the nuclear modification factor $R_{AA}$ in the pQCD calculations at LHC energies. The computations are performed accounting for radiative and collisional parton energy loss with running coupling constant. Our results show that the recent LHC data on the $R_{AA}$ for charged hadrons, D-mesons and non-photonic electrons agree reasonably with the pQCD picture of the parton energy loss with the dominating contribution from the radiative mechanism.

hep-ph↗

arXiv2012

Parton energy loss in glasma

We study the synchrotron-like gluon emission in $AA$-collisions from fast partons due to interaction with the coherent glasma color fields. Our results show that for RHIC and LHC conditions the contribution of this mechanism to parton energy loss is much smaller than the radiative energy loss in the plasma phase.

hep-ph↗

arXiv2011

Jet color chemistry and anomalous baryon production in $AA$-collisions

We study anomalous high-$p_T$ baryon production in $AA$-collisions due to formation of the two parton collinear $gq$ system in the anti-sextet color state for quark jets and $gg$ system in the decuplet/anti-decuplet color states for gluon jets. Fragmentation of these states, which are absent for $NN$-collisions, after escaping from the quark-gluon plasma leads to baryon production. Our qualitative estimates show that this mechanism can be potentially important at RHIC and LHC energies.

hep-ph↗

arXiv2011

Jet quenching from RHIC to LHC

We perform a joint analysis of the data from PHENIX at RHIC and ALICE at LHC on the nuclear modification factor $R_{AA}$. The computations are performed within the light-cone path integral approach to induced gluon emission. Our results show that slow variation of $R_{AA}$ from RHIC to LHC energies indicates that the QCD coupling constant is suppressed in the quark-gluon plasma produced at LHC.

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arXiv2011

Variation of jet quenching from RHIC to LHC and thermal suppression of QCD coupling constant

We perform a joint jet tomographic analysis of the data on the nuclear modification factor $R_{AA}$ from PHENIX at RHIC and ALICE at LHC. The computations are performed accounting for radiative and collisional parton energy loss with running coupling constant. Our results show that the observed slow variation of $R_{AA}$ from RHIC to LHC indicates that the QCD coupling constant is suppressed in the quark-gluon plasma produced at LHC.

hep-ph↗

arXiv2010

Photon emission from bare quark stars

We investigate the photon emission from the electrosphere of a quark star. It is shown that at temperatures T\sim 0.1-1 MeV the dominating mechanism is the bremsstrahlung due to bending of electron trajectories in the mean Coulomb field of the electrosphere. The radiated energy for this mechanism is much larger than that for the Bethe-Heitler bremsstrahlung. The energy flux from the mean field bremsstrahlung exceeds the one from the tunnel e^{+}e^{-} pair creation as well. We demonstrate that the LPM suppression of the photon emission is negligible.

hep-ph↗

arXiv2010

Effect of electric field of the electrosphere on photon emission from quark stars

We investigate the photon emission from the electrosphere of a quark star. It is shown that at temperatures $T\sim 0.1-1$ MeV the dominating mechanism is the bremsstrahlung due to bending of electron trajectories in the mean Coulomb field of the electrosphere. The radiated energy flux from this mechanism exceeds considerably both the contribution from the bremsstrahlung due to electron-electron interaction and the tunnel $e^{+}e^{-}$ pair creation.

hep-ph↗

arXiv2009

Synchrotron-like gluon emission in the quark-gluon plasma

A quasiclassical theory of the synchrotron-like gluon emission is discussed. We show that the synchrotron emission may be important in the jet quenching if the plasma instabilities generate a chromomagnetic field about $m^{2}_{D}/g$. Our gluon spectrum disagrees with that obtained by Shuryak and Zahed within Schwinger's proper time method.

hep-ph↗

arXiv2009

Anomalous mass dependence of radiative quark energy loss in a finite-size quark-gluon plasma

We demonstrate that for a finite-size quark-gluon plasma the induced gluon radiation from heavy quarks is stronger than that for light quarks when the gluon formation length becomes comparable with (or exceeds) the size of the plasma. The effect is due to oscillations of the light-cone wave function for the in-medium $q\to gq$ transition. The dead cone model by Dokshitzer and Kharzeev neglecting quantum finite-size effects is not valid in this regime. The finite-size effects also enhance the photon emission from heavy quarks.

hep-ph↗

arXiv2009

Nuclear higher-twist effects in eA DIS

We discuss the relation between the treatments of the higher twist nuclear effects in eA DIS based on the pQCD collinear approximation and the light-cone path integral formalism. We show that in the collinear approximation the N=1 rescattering contribution to the gluon emission vanishes. It is demonstrated that the nonzero gluon spectrum obtained by Guo, Wang and Zhang is a consequence of unjustified neglect of some terms in the collinear expansion.

hep-ph↗

arXiv2008

Jet quenching with running coupling including radiative and collisional energy losses

We calculate the nuclear modification factor for RHIC and LHC conditions accounting for the radiative and collisional parton energy loss with the running coupling constant.We find that the RHIC data can be explained both in the scenario with the chemically equilibrium quark-gluon plasma and purely gluonic plasma with slightly different thermal suppression of the coupling constant. The role of the parton energy gain due to gluon absorption is also investigated. Our results show that the energy gain gives negligible effect.

hep-ph↗

arXiv2008

Parton energy loss due to synchrotron-like gluon emission

We develop a quasiclassical theory of the synchrotron-like gluon radiation. Our calculations show that the parton energy loss due to the synchrotron gluon emission may be important in the jet quenching phenomenon if the plasma instabilities generate a sufficiently strong chromomagnetic field. Our gluon spectrum disagrees with that obtained by Shuryak and Zahed within the Schwinger's proper time method.

hep-ph↗

arXiv2008

Comment on ``Success of collinear expansion in the calculation of induced gluon emission''

We show that the arguments against our recent paper on the failure of the collinear expansion in the calculation of the induced gluon emission raised by X.N. Wang are either incorrect or irrelevant.

hep-ph↗

arXiv2008

Parton Energy Loss in Collinear Expansion

We demonstrate that the N=1 rescattering contribution to the gluon radiation from a fast massless quark in eA DIS vanishes in the collinear approximation. It is shown that the nonzero N=1 gluon spectrum obtained in the higher-twist approach by Guo, Wang and Zhang is a consequence of unjustified neglecting some important terms in the collinear expansion.

hep-ph↗

arXiv2008

Failure of the collinear expansion in calculation of the induced gluon emission

We demonstrate that the collinear expansion fails in the case of gluon emission from a fast quark produced in $eA$ DIS. In this approximation the N=1 rescattering contribution to the gluon spectrum vanishes. We show that the higher-twist approach by Guo, Wang and Zhang [4,5] based on the collinear expansion is wrong. The nonzero gluon spectrum obtained in [4,5] is a consequence of unjustified neglecting some important terms in the collinear expansion.

hep-ph↗