Magnetic component of Yang-Mills plasma

Confinement in non-Abelian gauge theories is commonly ascribed to percolation of magnetic monopoles, or strings in the vacuum. At the deconfinement phase transition the condensed magnetic degrees of freedom are released into gluon plasma as thermal magnetic monopoles. We point out that within the percolation picture lattice simulations can be used to estimate the monopole content of the gluon plasma. We show that right above the critical temperature the monopole density remains a constant function of temperature, as for a liquid, and then grows, like for a gas.Comment: 4 pages, no figures; replaced to match published versio

Validation of the Voluntary Participation in Online Surveys Scale

A comprehensive understanding of participants' motives to complete web-based surveys has the potential to improve dataquality. In this study we tested the construct validity of a scale developed to measure motivation to participate in webbasedsurveys. We expected that 7 different motivations observed in our previous study will form a 3-factor structure, aspredicted by Self-Determination Theory. This web-based questionnaire study comprised 257 participants completing theVoluntary Participation in Online Studies Scale. Their responses to 21 items underwent a principal component analysisand confi rmatory factor analysis. As we expected, three factors were identifi ed: intrinsic motivation, extrinsic motivationand amotivation. In line with Self-Determination Theory there are three distinct groups of motives among web-surveysparticipants with amotivation as an understudied motivational state. We discuss the results suggesting which types ofmotivation might lead to higher quality of data with an emphasis on possible negative effects of amotivation

Heavy-Quark Diffusion and Hadronization in Quark-Gluon Plasma

We calculate diffusion and hadronization of heavy quarks in high-energy heavy-ion collisions implementing the notion of a strongly coupled quark-gluon plasma in both micro- and macroscopic components. The diffusion process is simulated using relativistic Fokker-Planck dynamics for elastic scattering in a hydrodynamic background. The heavy-quark transport coefficients in the medium are obtained from non-perturbative $T$-matrix interactions which build up resonant correlations close to the transition temperature. The latter also form the basis for hadronization of heavy quarks into heavy-flavor mesons via recombination with light quarks from the medium. The pertinent resonance recombination satisfies energy conservation and provides an equilibrium mapping between quark and meson distributions. The recombination probability is derived from the resonant heavy-quark scattering rate. Consequently, recombination dominates at low transverse momentum ($p_T$) and yields to fragmentation at high $p_T$. Our approach thus emphasizes the role of resonance correlations in the diffusion and hadronization processes. We calculate the nuclear modification factor and elliptic flow of $D$- and $B$-mesons for Au-Au collisions at the Relativistic Heavy Ion Collider, and compare their decay-electron spectra to available data. We also find that a realistic description of the medium flow is essential for a quantitative interpretation of the data.Comment: 16 pages, 14 figure

Would You Be Happier If You Looked Better? A Focusing Illusion

Some people might believe that individuals who are more satisfied with their body are also happier. However, people tend to overrate the influence of some factors (e.g. money or health) on their happiness; a phenomenon termed the focusing illusion. Our aim was to examine the focusing illusion in relation to body satisfaction. We experimentally manipulated body satisfaction and life satisfaction focus by varying the order of relevant measurement scales. Volunteers (N = 97) completed two questionnaires placed in separate envelopes to control the order of scales administration. Participants either completed the Body Satisfaction Scale followed by the Satisfaction with Life Scale or vice versa. In line with the focusing illusion the association between body satisfaction and life satisfaction was significantly stronger when participants were asked about their body satisfaction first. Body satisfaction as a focusing illusion may need to be considered by scientist as well as lay people who try to look better and be happier

String Breaking in Lattice Quantum Chromodynamics

The separation of a heavy quark and antiquark pair leads to the formation of a tube of flux, or string, which should break in the presence of light quark-antiquark pairs. This expected zero temperature phenomenon has proven elusive in simulations of lattice QCD. We present simulation results that show that the string does break in the confining phase at nonzero temperature.Comment: 11 pages RevTeX, including 4 encapsulated Postscript figures. version2: minor corrections to reference

An experimental and modeling study on the reactivity of extremely fuel-rich methane/dimethyl ether mixtures

Chemical reactions in stoichiometric to fuel-rich methane/dimethyl ether/air mixtures (fuel air equiva- lence ratio φ=1–20) were investigated by experiment and simulation with the focus on the conversion of methane to chemically more valuable species through partial oxidation. Experimental data from dif- ferent facilities were measured and collected to provide a large database for developing and validating a reaction mechanism for extended equivalence ratio ranges. Rapid Compression Machine ignition delay times and species profiles were collected in the temperature range between 660 and 1052 K at 10 bar and equivalence ratios of φ= 1–15. Ignition delay times and product compositions were measured in a shock tube at temperatures of 630–1500 K, pressures of 20–30 bar and equivalence ratios of φ= 2 and 10. Ad- ditionally, species concentration profiles were measured in a flow reactor at temperatures between 473 and 973 K, a pressure of 6 bar and equivalence ratios of φ= 2, 10, and 20. The extended equivalence ratio range towards extremely fuel-rich mixtures as well as the reaction-enhancing effect of dimethyl ether were studied because of their usefulness for the conversion of methane into chemically valuable species through partial oxidation at these conditions. Since existing reaction models focus only on equivalence ratios in the range of φ= 0.3–2.5, an extended chemical kinetics mechanism was developed that also covers extremely fuel-rich conditions of methane/dimethyl ether mixtures. The measured ignition delay times and species concentration profiles were compared with the predictions of the new mechanism, which is shown to predict well the ignition delay time and species concentration evolution measure- ments presented in this work. Sensitivity and reaction pathway analyses were used to identify the key reactions governing the ignition and oxidation kinetics at extremely fuel-rich conditions

Quarkonium Suppression

I discuss quarkonium suppression in equilibriated strongly interacting matter. After a brief review of basic features of quarkonium production I discuss the application of recent lattice data on the heavy quark potential to the problem of quarkonium dissociation as well as the problem of direct lattice determination of quarkonium properties in finite temperature lattice QCD.Comment: Invited plenary talk presented on 4th International Conference on Physics and Astrophysics of Quark Gluon Plasma (ICPAQGP-2001), November 26-30, 2001, Jaipur; 12 pp, LaTeX, uses pramana.st

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.Comment: 9 pages, 2 figure

On the Quasiparticle Description of Lattice QCD Thermodynamics

We propose a novel quasiparticle interpretation of the equation of state of deconfined QCD at finite temperature. Using appropriate thermal masses, we introduce a phenomenological parametrization of the onset of confinement in the vicinity of the predicted phase transition. Lattice results of the energy density, the pressure and the interaction measure of pure SU(3) gauge theory are excellently reproduced. We find a relationship between the thermal energy density of the Yang-Mills vacuum and the chromomagnetic condensate _T. Finally, an extension to QCD with dynamical quarks is discussed. Good agreement with lattice data for 2, 2+1 and 3 flavour QCD is obtained. We also present the QCD equation of state for realistic quark masses.Comment: 20 pages, 10 eps figure

Fluctuations as probe of the QCD phase transition and freeze-out in heavy ion collisions at LHC and RHIC

We discuss the relevance of higher order moments of net baryon number fluctuations for the analysis of freeze-out and critical conditions in heavy ion collisions at LHC and RHIC. Using properties of O(4) scaling functions, we discuss the generic structure of these higher moments at vanishing baryon chemical potential and apply chiral model calculations to explore their properties at non-zero baryon chemical potential. We show that the ratios of the sixth to second and eighth to second order moments of the net baryon number fluctuations change rapidly in the transition region of the QCD phase diagram. Already at vanishing baryon chemical potential they deviate considerably from the predictions of the hadron resonance gas model which reproduce the second to fourth order moments of the net proton number fluctuations at RHIC. We point out that the sixth order moments of baryon number and electric charge fluctuations remain negative at the chiral transition temperature. Thus, they offer the possibility to probe the proximity of the thermal freeze-out to the crossover line.Comment: 24 pages, 12 EPS files, revised version, to appear in EPJ