The Wake of a Heavy Quark in Non-Abelian Plasmas : Comparing Kinetic Theory and the AdS/CFT Correspondence

We compute the non-equilibrium stress tensor induced by a heavy quark moving through weakly coupled QCD plasma at the speed of light and compare the result to N = 4 Super Yang Mills theory at strong coupling. The QCD Boltzmann equation is reformulated as a Fokker-Planck equation in a leading log approximation which is used to compute the induced stress. The transition from nonequilibrium at short distances to equilibrium at large distances is analyzed with first and second order hydrodynamics. Even after accounting for the obvious differences in shear lengths, the strongly coupled theory is significantly better described by hydrodynamics at sub-asymptotic distances. We argue that this difference between the kinetic and AdS/CFT theories is related to the second order hydrodynamic coefficient $\tau_\pi$. $\tau_\pi$ is numerically large in units of the shear length for theories based on the Boltzmann equation.Comment: 31 pages, 8 figure

Spectral densities for hot QCD plasmas in a leading log approximation

We compute the spectral densities of $T^{\mu\nu}$ and $J^{\mu}$ in high temperature QCD plasmas at small frequency and momentum,\, $\omega,k \sim g^4 T$. The leading log Boltzmann equation is reformulated as a Fokker Planck equation with non-trivial boundary conditions, and the resulting partial differential equation is solved numerically in momentum space. The spectral densities of the current, shear, sound, and bulk channels exhibit a smooth transition from free streaming quasi-particles to ideal hydrodynamics. This transition is analyzed with conformal and non-conformal second order hydrodynamics, and a second order diffusion equation. We determine all of the second order transport coefficients which characterize the linear response in the hydrodynamic regime.Comment: 39 pages, 6 figures. v3 contains an analysis of the bulk channel with non-conformal hydrodynamics. Otherwise no significant change

Parameter Assessment of Beam Transport Line for Nuclear Physics Research

The IBA CP30 cyclotron was installed at the 108 Central Hospital in Hanoi, Vietnam. A proton beam with energy range from 15 to 30 MeV can be delivered by this facility. Currently, facility is mainly used for medical radioactive isotope production. There is an idea to use this accelerator for scientific research as well. For this purpose, a new beam line should be designed. A high energy resolution with minimum momentum spread is a key point for designing. A preliminary design of the beam line using matrix codes, modeling 3D optical elements, magnetic field calculations, and beam dynamics analysis is presented in this paper

Aquarius Final Release Product and Full Range Calibration of L-band Radiometers

Aquarius final product V5.0 has been released. The dataset includes close to four years of global radiometric measurements at L-band. The mission's objective was to monitor sea surface salinity, but other applications of its data over land and the cryosphere have been developed. For this reason, it is important to have accurate calibration over the full range of antenna temperatures from natural targets. It is also needed in order to combine Aquarius measurements with other L-band sensors. Aquarius calibration is strongly focused on the ocean. We present a research product which is part of the final release and aims at producing an accurate calibration from the low end (celestial sky) to the high end (land and ice) of the brightness temperature scale. We calibrate the Aquarius radiometers using measurements over the Sky and oceans and assess the new calibration using measurements over land

Emissivity of Frozen Regions Retrieved from Aquarius Measurements

The land emissivity model used in the Aquarius data processing has been updated for the latest data release (V5.0). In order to improve the estimates of the brightness temperatures of frozen regions, the new model uses values of surface emissivity that have been estimated from the Aquarius measurements averaged over the entire duration of the mission. The retrieved emissivities depend on the geographic location, but they depend only marginally on time, temperature and snow cover

The calculation of the equation of state of QCD at finite chemical potential and zero temperature

In this paper, we give a direct method for calculating the partition function, and hence the equation of state (EOS) of Quantum Chromodynamics (QCD) at finite chemical potential and zero temperature. In the EOS derived in this paper the pressure density is the sum of two terms: the first term ${\cal P}(\mu)|_{\mu=0}$ (the pressure density at $\mu=0$) is a $\mu$-independent constant; the second term, which is totally determined by $G_R[\mu](p)$ (the renormalized dressed quark propagator at finite $\mu$), contains all the nontrivial $\mu$-dependence. By applying a general result in the rainbow-ladder approximation of the Dyson-Schwinger approach obtained in our previous study [Phys. Rev. {\bf C 71}, 015205 (2005)], $G_R[\mu](p)$ is calculated from the meromorphic quark propagator proposed in [Phys. Rev. {\bf D 70}, 014014 (2004)]. From this the full analytic expression of the EOS of QCD at finite $\mu$ and zero $T$ is obtained (apart from the constant term ${\cal P}(\mu)|_{\mu=0}$ which can in principle be calculated from the CJT effective action). A comparison between our EOS and the cold, perturbative EOS of QCD of Fraga, Pisarski and Schaffner-Bielich is made. It is expected that our EOS can provide a possible new approach for the study of neutron stars.Comment: 15 pages, 4 figures, revtex

The decay rate of ψ(2S)\psi(2S) to Λc+Σ+ˉ\Lambda_c+\bar{\Sigma^+} in SM and beyond

With rapid growth of the database of the BES III and the proposed super flavor factory, measurement on the rare $\psi(2S)$ decays may be feasible, especially the weak decays into baryon final states. In this work we study the decay rate of $\psi(2S)$ to $\Lambda_c+\overline{\Sigma^+}$ in the SM and physics beyond the SM (here we use the unparticle model as an example). The QPC model is employed to describe the creation of a pair of $q\bar q$ from vacuum. We find that the rate of $\psi(2S)\rightarrow \Lambda_c+\overline{\Sigma^+}$ is at order of $10^{-10}$ in the SM, whereas the contribution of the unparticle is too small to be substantial. Therefore if a large branching ratio is observed, it must be due to new physics beyond SM, but by no means the unparticle.Comment: 9 pages, 1 figure

Lifetime Effects in Color Superconductivity at Weak Coupling

Present computations of the gap of color superconductivity in weak coupling assume that the quarks which participate in the condensation process are infinitely long-lived. However, the quasiparticles in a plasma are characterized by having a finite lifetime. In this article we take into account this fact to evaluate its effect in the computation of the color gap. By first considering the Schwinger-Dyson equations in weak coupling, when one-loop self-energy corrections are included, a general gap equation is written in terms of the spectral densities of the quasiparticles. To evaluate lifetime effects, we then model the spectral density by a Lorentzian function. We argue that the decay of the quasiparticles limits their efficiency to condense. The value of the gap at the Fermi surface is then reduced. To leading order, these lifetime effects can be taken into account by replacing the coupling constant of the gap equation by a reduced effective one.Comment: 16 pages, 2 figures; explanations on the role of the Meissner effect added; 2 references added; accepted for publication in PR