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تسجيل مستخدم جديدOpen Quantum Systems for Quarkonia
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تأليف
Xiaojun Yao
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I review recent applications of the open quantum system framework in the understanding of quarkonium suppression in heavy-ion collisions, which has been used as a probe of the quark-gluon plasma for decades. The derivation of the Lindblad equations for quarkonium in both the quantum Brownian motion and the quantum optical limits and their semiclassical counterparts is explained. The hierarchy of time scales assumed in the derivation is justified from the separation of energy scales in nonrelativistic effective field theories of QCD. Physical implications of the open quantum system approach are also discussed. Finally, I list some open questions for future studies.
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After an introduction motivating the study of quarkonium production, we review the recent developments in the phenomenology of quarkonium production in inclusive scatterings of hadrons and leptons. We naturally address data and predictions relevant f
or the LHC, the Tevatron, RHIC, HERA, LEP, B factories and EIC. An up-to-date discussion of the contributions from feed downs within the charmonium and bottomonium families as well as from b hadrons to charmonia is also provided. This contextualises an exhaustive overview of new observables such as the associated production along with a Standard Model boson (photon, W and Z), with another quarkonium, with another heavy quark as well as with light hadrons or jets. We address the relevance of these reactions in order to improve our understanding of the mechanisms underlying quarkonium production as well as the physics of multi-parton interactions, in particular the double parton scatterings. An outlook towards future studies and facilities concludes this review.
We present the probability preserving description of the decaying particle within the framework of quantum mechanics of open systems taking into account the superselection rule prohibiting the superposition of the particle and vacuum. In our approach
the evolution of the system is given by a family of completely positive trace preserving maps forming one-parameter dynamical semigroup. We give the Kraus representation for the general evolution of such systems which allows one to write the evolution for systems with two or more particles. Moreover, we show that the decay of the particle can be regarded as a Markov process by finding explicitly the master equation in the Lindblad form. We also show that there are remarkable restrictions on the possible strength of decoherence.
We solve the Lindblad equation describing the Brownian motion of a Coulombic heavy quark-antiquark pair in a strongly coupled quark-gluon plasma using the highly efficient Monte Carlo wave-function method. The Lindblad equation has been derived in th
e framework of pNRQCD and fully accounts for the quantum and non-Abelian nature of the system. The hydrodynamics of the plasma is realistically implemented through a 3+1D dissipative hydrodynamics code. We compute the bottomonium nuclear modification factor and compare with the most recent LHC data. The computation does not rely on any free parameter, as it depends on two transport coefficients that have been evaluated independently in lattice QCD. Our final results, which include late-time feed down of excited states, agree well with the available data from LHC 5.02 TeV PbPb collisions.
Valuable data on quarkonia (the bound states of a heavy quark Q=c,b and the corresponding antiquark) have recently been provided by a variety of sources, mainly e+ e- collisions, but also hadronic interactions. This permits a thorough updating of the
experimental and theoretical status of electromagnetic and strong transitions in quarkonia. We discuss QQbar transitions to other QQbar states, with some reference to processes involving QQbar annihilation.
We have investigated the effects of strong magnetic field on the properties of quarkonia immersed in a thermal medium of quarks and gluons and studied its quasi-free dissociation due to the Landau-damping. Thermalizing the Schwinger propagator in the
lowest Landau levels for quarks and the Feynman propagator for gluons in real-time formalism, we have calculated the resummed retarded and symmetric propagators, which in turn give the real and imaginary components of dielectric permittivity, respectively. The magnetic field affects the large-distance interaction more than the short-distance interaction, as a result, the real part of potential becomes more attractive and the magnitude of imaginary part too becomes larger, compared to the thermal medium in absence of strong magnetic field. As a consequence the average size of $J/psi$s and $psi^prime$s are increased but $chi_c$s get shrunk. Similarly the magnetic field affects the binding of $J/psi$s and $chi_c$s discriminately, i.e. it decreases the binding of $J/psi$ and increases for $chi_c$. However, the further increase in magnetic field results in the decrease of binding energies. On contrary the magnetic field increases the width of the resonances, unless the temperature is sufficiently high. We have finally studied how the presence of magnetic field affects the dissolution of quarkonia in a thermal medium due to the Landau damping, where the dissociation temperatures are found to increase compared to the thermal medium in absence of magnetic field. However, further increase of magnetic field decreases the dissociation temperatures. For example, $J/psi$s and $chi_c$s are dissociated at higher temperatures at 2 $T_c$ and 1.1 $T_c$ at a magnetic field $eB approx 6~{rm{and}}~4~m_pi^2$, respectively, compared to the values 1.60 $T_c$ and 0.8 $T_c$ in the absence of magnetic field, respectively.
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