arXiv subjects

Edward V. Shuryak

Publications and source records attributed to Edward V. Shuryak.

15 recordsLinked to original sources

arXiv2014

The Magneto-Sono-Luminescence and its signatures in photon and dilepton production in heavy ion collisions

The matter produced in the early stages of heavy ion collisions consists mostly of gluons, and is penetrated by coherent magnetic field produced by spectator nucleons. The fluctuations of gluonic matter in an external magnetic field couple to real and virtual photons through virtual quark loops. We study the resulting contributions to photon and dilepton production that stem from the fluctuations of the stress tensor $T_{μν}$ in the background of a coherent magnetic field $\vec{B}$. Our study extends significantly the earlier work by two of us and Skokov, in which only the fluctuations of the trace of the stress tensor $T_{μμ}$ were considered (the coupling of $T_{μμ}$ to electromagnetic fields is governed by the scale anomaly). In the present paper we derive more general relations using the Operator Product Expansion (OPE). We also extend the previous study to the case of dileptons which offers the possibility to discriminate between various production mechanisms. Among the phenomena that we study are Magneto-Sono-Luminescence (MSL, the interaction of magnetic field $\vec{B}(x,t)$ with the sound perturbations of the stress tensor $δT_{μν}(x,t)$) and Magneto-Thermo-Luminescence (MTL, the interaction of $\vec{B}(x,t)$ with smooth average $ $). We calculate the rates of these process and find that they can dominate the photon and dilepton production at early stage of heavy ion collisions. We also point out the characteristic signatures of MSL and MTL that can be used to establish their presence and to diagnose the produced matter.

hep-ph↗

arXiv2006

Classical Strongly Coupled QGP II: Screening and Equation of State

We analyze the screening and bulk energy of a classical and strongly interacting plasma of color charges, a model we recently introduced for the description of a quark-gluon plasma at T=(1-3)Tc. The partition function is organized around the Debye-Huckel limit. The linear Debye-Huckel limit is corrected by a virial expansion. For the pressure, the expansion is badly convergent even in the dilute limit. The non-linear Debye-Huckel theory is studied numerically as an alternative for moderately strong plasmas. We use Debye theory of solid to extend the analysis to the crystal phase at very strong coupling. The analytical results for the bulk energy per particle compare well with the numerical results from molecular dynamics simulation for all couplings.

nucl-th↗

arXiv2006

Classical Strongly Coupled QGP I: The Model and Molecular Dynamics Simulations

We propose a model for the description of strongly interacting quarks and gluon quasiparticles at $T=(1-3)T_c$, as a classical and nonrelativistic colored Coulomb gas. The sign and strength of the inter-particle interactions are fixed by the scalar product of their classical {\it color vectors} subject to Wong's equations. The model displays a number of phases as the Coulomb coupling is increased ranging from a gas, to a liquid, to a crystal with antiferromagnetic-like color ordering. We analyze the model using Molecular Dynamics (MD) simulations and discuss the density-density correlator in real time. We extract pertinent decorrelation times, diffusion and viscosity constants for all phases. The classical results when extrapolated to the sQGP suggest that the phase is liquid-like, with a diffusion constant $D\approx 0.1/T$ and a bulk viscosity to entropy density ratio $η/s\approx 1/3$.

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arXiv2005

Polymer Chains and Baryons in a Strongly Coupled Quark-Gluon Plasma

Recently there was a significant change of views on physical properties and underlying dynamics of Quark-Gluon Plasma at $T=170-350 MeV$, produced in heavy ion collisions at RHIC. Instead of being a gas of $q,g$ quasiparticles, a near-perfect liquid is observed. Also, precisely in this temperature interval, the interaction deduced from lattice studies is strong enough to support multiple binary bound states. This work is the first variational study of {\em multibody} bound states. We will consider: (i) ``polymer chains'' of the type $\bar q g g ..g q$; (ii) baryons $(qqq)$; (iii) closed (3-)chains of gluons $(ggg)$. We found that chains (i) form in exactly the same $T$ range as binary states, with the same binding {\em per bond}. The binding and $T$-range for diquarks, baryons and closed 3-chains are also established. We point out that the presence of chains, or possibly even a chain network, may drastically change the transport properties of matter, such as charm diffusion or jet energy loss. We further suggest that it seems to exist only for $T=(1-1.5)T_c$ and thus there may be a ``latent period'' for charm/jet quenching in RHIC collisions, while matter cools down to such $T$.

hep-ph↗

arXiv2005

What do lattice baryonic susceptibilities tell us about quarks, diquarks and baryons at $T>Tc$?

Lattice data on QCD thermodynamics, especially recent study of high order susceptibilities by UK-Bielefeld collaboration, have provided valuable information about matter properties around and above the critical temperature $T_c$. In this work we tried to understand what physical picture would explain these numerical data. We found two scenarios which will do it: (i) a quark quasiparticle gas, with the effective mass which is strongly $decreasing$ near the phase boundary into the QGP phase; or (ii) a picture including baryons at $T>T_c$, with the mass rapidly $increasing$ across the phase boundary toward QGP. We further provide several arguments in favor of the latter scenario, one of which is a natural continuity with the baryon gas picture at $T<T_c$.

hep-ph↗

arXiv2005

Cold Strongly Coupled Atoms Make a Near-perfect Liquid

Feshbach resonances of trapped ultracold alkali atoms allow to vary the atomic scattering length a. At very large values of a the system enters an universal strongly coupled regime in which its properties--the ground state energy, pressure {\it etc.}--become independent of a. We discuss transport properties of such systems. In particular, the universality arguments imply that the shear viscosity of ultracold Fermi atoms at the Feschbach resonance is proportional to the particle number density n, and the Plank constant \hbar η=\hbar n α_η, where α_ηis a universal constant. Using Heisenberg uncertainty principle and Einstein's relation between diffusion and viscosity we argue that the viscosity has the lower bound given by α_η \leq (6π)^{-1}. We relate the damping of low-frequency density oscillations of ultracold optically trapped ^{6}Li atoms to viscosity and find that the value of the coefficient α_ηis about 0.3. We also show that such a small viscosity can not be explained by kinetic theory based on binary scattering. We conclude that the system of ultracold atoms near the Feshbach resonance is a near-ideal liquid.

nucl-th↗

arXiv2004

Can Binary Bound States in a Strongly Coupled Quark-Gluon Plasma be observed via dileptons and photons?

Recently there was a significant change of views on physical properties and underlying dynamics of Quark-Gluon Plasma at $T=170-350 MeV$, produced in heavy ion collisions at RHIC. Instead of weakly coupled gas of quasiparticles, it is rather a liquid-like matter with multiple bound states. In this paper we discuss how one can test these ideas experimentally, using the ``penetrating probes'' and looking for certain peaks at some invariant masses. In dileptons the most promising are modified $ρ,ω$, with $M(T\approx T_c)\sim .5 GeV$ and also near zero binding at $M(T\approx (1.5-2)T_c)=1.5-2 GeV$. We also discuss the observability of peaks corresponding to scalar/pseudoscalar mesons in the two-photon channel.

hep-ph↗

arXiv2004

Ionization of Binary Bound States in a Strongly Coupled Quark-Gluon Plasma

Although at temperatures $T\gg Λ_{QCD}$ the quark-gluon plasma (QGP) is a gas of weakly interacting quasiparticles (modulo long-range magnetism), it is strongly interacting (sQGP) in the temperature range $(1-3) T_c$. One aspect of these interactions is the existence of many binary bound states of quasiparticles. Only $\bar q q$ ones have been so far directly seen on the lattice, for charmed and light quarks, but other attractive channels in $ qg, gg$ are likely to have them as well. It was argued in our previous paper that such bound states account for a significant part of the bulk properties such as density and pressure. Using the same model, we evaluate the energy loss $dE/dx$ due to the ionization of these states. We found that it is substantial, but only in the narrow interval of temperatures $T=(1.4-1.7)T_c$. In contrast to that, we show that radiative and elastic losses are not likely to be modified much by binding, as the total density of color charges is close to what it is for weakly coupled quasiparticles. These distinctions would be important for understanding the energy dependence of jet quenching.

hep-ph↗

arXiv2004

Towards a Theory of Binary Bound States in the Quark-Gluon Plasma

Although at temperatures $T\gg Λ_{QCD}$ the quark-gluon plasma (QGP) is a gas of weakly interacting quasiparticles (modulo long-range magnetism), it is strongly interacting in the regime $T=(1-3) T_c$. As both heavy ion experiments and lattice simulations are now showing, in this region the QGP displays rather strong interactions between the constituents. In this paper we investigate the relationship between four (previously disconnected) lattice results: {\bf i.} spectral densities from MEM analysis of correlators; {\bf ii.} static quark free energies $F(R)$; {\bf iii.} quasiparticle masses; {\bf iv.} bulk thermodynamics $p(T)$. We show a high degree of consistency among them not known before. The potentials $V(R)$ derived from $F(R)$ lead to large number of binary bound states, mostly colored, in $gq, qq, gg$, on top of the usual $\bar q q$ mesons. Using the Klein-Gordon equation and ({\bf ii-iii}) we evaluate their binding energies and locate the zero binding endpoints on the phase diagram, which happen to agree with ({\bf i}). We then estimate the contribution of all states to the bulk thermodynamics in agreement with ({\bf iv}). We also address a number of theoreticall issues related with to the role of the quark/gluon spin in binding at large $α_s$, although we do not yet include those in our estimates. Also the issue of the transport properties (viscosity, color conductivity) in this novel description of the QGP will be addressed elsewhere.

hep-ph↗

arXiv2003

Spin-Spin and Spin-Orbit Interactions in Strongly Coupled Gauge Theories

We evaluate the spin-orbit and spin-spin interaction between two fermions in strongly coupled gauge theories in their Coulomb phase. We use the quasi-instantaneous character of Coulomb's law at strong coupling to resum a class of ladder diagrams. For ${\cal N}=4$ SYM we derive both weak and strong coupling limits of the the spin-orbit and spin-spin interactions, and find that in the latter case these interactions are subleading corrections and do not seriously affect the deeply bound Coulomb states with large angular momentum, pointed out in our previous paper. The results are important for understanding of the regime of intermediate coupling, which is the case for QCD somewhat above the chiral transition temperature.

hep-th↗

arXiv2003

Understanding the Non-Perturbative Deep-Inelastic Scattering: Instanton-induced Inelastic Dipole-Dipole Cross Section

We derive the semiclassical (instanton-induced) contribution to the inelastic cross section of two color dipoles at large $\sqrt{s}$. We study its dependence on the dipole sizes, orientations and, most importantly, the impact parameter. The inelastic cross section is approximately quadratic in the dipole sizes, and Gaussian-like in the impact parameter with a width of the order of the instanton size. These results are directly relevant to double DIS $γ^*γ^*$, as well as $γ^*γ$ and standard DIS $γ^* h$ at small x when a real photon and a hadron can be approximated by a dipole. For such cases, with one small dipole scattering on a large dipole, the impact parameter profile exhibits a width of about 1/2 fm, which is in good agreement with the impact parameter profile recently extracted from DIS HERA data, including diffractive $γ^*\to J/ψ$.

hep-ph↗

arXiv2003

Rethinking the Properties of the Quark-Gluon Plasma at $T\sim T_c$

We argue that although at asymptotically high temperatures the QGP in bulk behaves as a gas of weakly interacting quasiparticles (modulo long-range magnetism), at temperatures up to few times the critical temperature $T_c$ it displays different properties. If the running of the QCD coupling constant continues in the Coulomb phase till the screening length scale, it reaches the strong coupling treshold $α_s(m_D)\sim 1$. As a result, the Coulomb phase supports weakly bound Coulombic s-wave $\bar c c$, light quark and even $gg$ states. The existence of shallow bound states dramatically increases the quasiparticle rescattering at low energies, reducing the viscosity and thereby explaining why heavy ion collisions at RHIC exhibit robust collective phenomena. In conformal gauge theories at finite temperature the Coulomb binding persists further in the strong coupling regime, as found for ${\cal N}=4$ SUSY YM in the Maldacena regime.

hep-ph↗

arXiv2001

The Instanton/Sphaleron Mechanism of Prompt Gluon Production in High Energy Heavy Ion Collisions at RHIC

We argue that if the growing part of hadron-hadron cross section (described phenomenologically by the supercritical soft Pomeron) is due to instanton/sphaleron mechanism, one should find certain qualitative features of the produced cluster which differ from the usual string fragmentation. Furthermore, we suggest that this mechanism should be even more important for heavy ion collisions in the RHIC energy domain. Large number of parton-parton collisions should result in hundreds of produced sphaleron-like gluomagnetic clusters per unit rapidity. Unlike perturbative gluons (or mini-jets), these {\em classically unstable} objects promptly decay into several gluons and quarks in mini-explosions, leading to very rapid entropy generation. This may help to explain why the QGP seem to be produced at RHIC so early. We further argue that this mechanism cannot be important at higher energies (LHC), where perturbative description should apply.

hep-ph↗

arXiv2001

Nonperturbative Phenomena and Phases of QCD

Lectures discuss applications of semiclassical methods based on instantons to vacuum structure (chiral symmetry breaking), hadronic structure (various correlation functions), and high energy collisions of hadrons and heavy ions. We discuss phase diagram of hot/dense hadronic matter, and in the last lecture review current puzzles/lesons from the first RHIC run in summer of 2000.

hep-ph↗

arXiv2000

Instanton-induced Inelastic Collisions in QCD

We show that the instanton-induced inelastic processes, leading to multi-gluon production in in high-energy parton-parton scattering, are considerably enhanced over the quasi-elastic ones, by a factor of 100. The basic instanton-induced inelastic contribution cause the parton-parton cross section to increase as ${\rm ln} {s}$, and their Poisson resummation in hadron-hadron scattering yield a regge-type cross section. The pomeron slope and intercept due to instanton-induced contributions are evaluated. We show that the small intercept is due to the diluteness of the instantons in the QCD vacuum, while the small slope is related to the smallness of the instanton sizes.

hep-ph↗