摘要：
We calculate the shear viscosity (η) and bulk viscosity (ζ) to entropy density (s) ratios η/s and ζ/s of a gluon plasma system in kinetic theory, including both the elastic gg↔gg forward scattering and the inelastic soft gluon bremsstrahlung gg ↔ ggg processes. Due to the suppressed contribution to η and ζ in the gg ↔ gg forward scattering and the effective g↔gg gluon splitting, Arnold, Moore and Yaffe (AMY) and Arnold, Dogan and Moore (ADM) have got the leading order computations for η and ζ in high-temperature QCD matter. In this paper, we calculate the correction to η and ζ in the soft gluon bremsstrahlung gg ↔ ggg process with an analytic method. We find that the contribution of the collision term from the gg ↔ ggg soft gluon bremsstrahlung process is just a small perturbation to the gg↔gg scattering process and that the correction is at ~5% level. Then, we obtain the bulk viscosity of the gluon plasma for the number-changing process. Furthermore, our leading-order result for bulk viscosity is the formula ζ∝α_s~2T~3/lnα_s~(-1) in high-temperature gluon plasma.
摘要：
Taking doubly charged particles, positive-negative charge pair production and the effects of volume fluctuations into account, the Poisson baseline of the fluctuations of net-charge is studied. Within the Poisson baseline, the cumulants of net-charge are derived. Comparing to the Skellam baseline of net-charge, we infer that doubly charged particles broaden the distributions of net-charge, while positive-negative charge pairs narrow the distributions. Using the ratios of doubly charged particles and positive-negative charge pairs from neutral resonance decays to the total positive charges from THERMINATOR 2, the first four orders of moments and the corresponding moment products are calculated in the Poisson baseline for Au + Au collisions at (S_(NN))~(1/2)= 200 GeV at RHIC/STAR. We find that the standard deviation is mainly influenced by the resonance decay, while the third and fourth order moments and corresponding moment products are mainly modified and fit the data of RHIC/STAR much better after including the effects of volume fluctuations.
通讯机构：
[Fan, Yan] C;Cent China Normal Univ, PLAC, Key Lab Quark & Lepton Phys, MOE,Dept Phys Sci & Technol, Wuhan 430079, Hubei, Peoples R China.
关键词：
Bragg peak;Carbon ion;Prompt c-ray;Geant4
摘要：
Real-time monitoring of the Bragg peak location of carbon ions is urgently required for the quality control of hadron therapy. In this study, we design an annular detector to monitor the Bragg peak location of carbon ions with Geant4 simulation. This 360° surrounding structure has a high detection efficiency for the small-dose situation. The detector consists of a multilayered collimator system and an NaI scintillator for prompt gamma counting. The multilayered collimator includes a lead layer to prevent unwanted gammas and the paraffin and boron carbide layers to moderate and capture fast neutrons. An inclination of the detector further diminishes the background signal caused by neutrons. The detector, with optimized parameters, is applicable to carbon ions of different energies. In addition, the scintillator is replaced by an improved EJ301 organic liquid scintillator to discriminate gammas and neutrons. Inserting thin Fe slices into the liquid scintillator improves the energy deposition efficiency. The Bragg peak location of 200 MeV/u carbon ions can be monitored by prompt gamma detection with the improved liquid scintillator.
作者机构：
[夏巧桥] College of Physical Science and Technology, Central China Normal University, Wuhan, 430079, China;[王泉德; 张迪科] School of Electronic Information, Wuhan University, Wuhan, 430072, China
作者机构：
[胡森; 刘丹] Department of Physics and Mechanical & Electrical Engineering, Hubei University of Education, Wuhan;430205, China;[杨河林] College of Physical Science and Technology, Central China Normal University, Wuhan;430079, China;[胡森; 刘丹] 430205, China
通讯机构：
[Liu, D.] D;Department of Physics and Mechanical & Electrical Engineering, Hubei University of Education, Wuhan, China
作者机构：
[贺文武; 邹炼] School of Electronic Information, Wuhan University, Wuhan;430072, China;[夏巧桥] College of Physical Science and Technology, Central China Normal University, Wuhan;430079, China;[贺文武; 邹炼] 430072, China
通讯机构：
[Xia, Q.] C;College of Physical Science and Technology, Central China Normal University, Wuhan, China
摘要：
We calculate the decay constants of light and heavy-light pseudoscalar and vector mesons with improved soft-wall holographic wavefuntions, which take into account the effects of both quark masses and dynamical spins. We find that the predicted decay constants, especially for the ratio f_V/f_P, based on light-front holographic QCD, can be significantly improved, once the dynamical spin effects are taken into account by introducing the helicity-dependent wavefunctions. We also perform detailed χ~2 analyses for the holographic parameters (i.e. the mass-scale parameter κ and the quark masses), by confronting our predictions with the data for the charged-meson decay constants and the meson spectra. The fitted values for these parameters are generally in agreement with those obtained by fitting to the Regge trajectories. At the same time, most of our results for the decay constants and their ratios agree with the data as well as the predictions based on lattice QCD and QCD sum rule approaches, with only a few exceptions observed.
作者机构：
[Hou, Defu; Chen, Jun; Hou, Wenjie; Qiu, Taotao] Cent China Normal Univ, Key Lab Quark & Lepton Phys MOE, Wuhan 430079, Hubei, Peoples R China.;[Chen, Jun; Hou, Wenjie; Qiu, Taotao] Cent China Normal Univ, Inst Particle Phys, Wuhan 430079, Hubei, Peoples R China.;[Hou, Defu; Chen, Jun; Hou, Wenjie] Cent China Normal Univ, Inst Astrophys, Wuhan 430079, Hubei, Peoples R China.
通讯机构：
[Chen, Jun] C;Cent China Normal Univ, Key Lab Quark & Lepton Phys MOE, Wuhan 430079, Hubei, Peoples R China.;Cent China Normal Univ, Inst Particle Phys, Wuhan 430079, Hubei, Peoples R China.;Cent China Normal Univ, Inst Astrophys, Wuhan 430079, Hubei, Peoples R China.
关键词：
inflation;power spectrum;gravitaional waves
摘要：
In our previous work [1], a new kind of inflation model was proposed, which has the interesting property that its perturbation equation of motion gets a correction of k, due to the non-linearity of the kinetic term. Nonetheless, the scale-invariance of the power spectrum remains valid, both in large-k and small-k limits. In this paper, we investigate in detail the spectral index, the index running and the tensor/scalar ratio in this model, especially in the potential-driven case, and compare the results with the current PLANCK/BICEP observational data. We also discuss the tensor spectrum in this case, which is expected to be tested by future observations of primordial gravitational waves.
摘要：
The state of supranuclear matter in compact stars remains puzzling,and it is argued that pulsars could be strangeon stars.What would happen if binary strangeon stars merge? This kind of merger could result in the formation of a hyper-massive strangeon star,accompanied by bursts of gravitational waves and electromagnetic radiation (and even a strangeon kilonova explained in the paper).The tidal polarizability of binary strangeon stars is different from that of binary neutron stars,because a strangeon star is self-bound on the surface by the fundamental strong force while a neutron star by the gravity,and their equations of state are different.Our calculation shows that the tidal polarizability of merging binary strangeon stars is favored by GW170817.Three kinds of kilonovae (i.e.,of neutron,quark and strangeon) are discussed,and the light curve of the kilonova AT 2017gfo following GW170817 could be explained by considering the decaying strangeon nuggets and remnant star spin-down.Additionally,the energy ejected to the fireball around the nascent remnant strangeon star,being manifested as a gamma-ray burst,is calculated.It is found that,after a prompt burst,an X-ray plateau could follow in a timescale of 10~2 – 10~3 s.Certainly,the results could be tested also by further observational synergies between gravitational wave detectors (e.g.,Advanced LIGO) and X-ray telescopes (e.g.,the Chinese HXMT satellite and eXTP mission),and especially if the detected gravitational wave form is checked by peculiar equations of state provided by the numerical relativistical simulation.
摘要：
Here, PbCrO4 nanorods, a commonly used and low-cost yellow pigment, was synthesized via a simple pre-cipitation reaction and can serve as a highly efficient oxygen production and photodegradation photocatalyst. The obtained PbCrO4 nanorods exhibit excellent stability and pho-tocatalytic performance for O2 evolution from water. The production rate is approximately 314.0μmol h^-1 g^-1 under visible light, and the quantum efficiency is approximately 2.16% at 420±10 nm and 0.05% at 600±10 nm. In addition, the PhCrO4 shows good degradation performance for methylene blue, methyl blue, methyl orange and phenol under visible-light irradiation. These results indicate that it is potential to fabricate an effective, robust PbCrO4 photocatalyst by trans-forming heavy-metal pollutants Pb（II） and Cr（VI） into a highly efficient O2 evolution and photodegradation material. This strategy which uses pollutant to produce clean energy and degrade contaminants is completely green and environmentally benign, and thus could be a promising way for practical environmental applications. Keywords： 02 evolution, pollutant, PbCrO4 nanorods, visible-light-active, photocatalyst
作者机构：
[Jiang, Yin] Beihang Univ, Sch Phys & Nucl Energy Engn, Beijing 100191, Peoples R China.;[Jiang, Yin] Indiana Univ, Phys Dept, 2401 N Milo B Sampson Lane, Bloomington, IN 47408 USA.;[Shi, Shuzhe; Liao, Jinfeng] Indiana Univ, Ctr Explorat Energy & Matter, 2401 N Milo B Sampson Lane, Bloomington, IN 47408 USA.;[Yin, Yi] MIT, Ctr Theoret Phys, Cambridge, MA 02139 USA.;[Liao, Jinfeng] Cent China Normal Univ, Inst Particle Phys, Wuhan 430079, Hubei, Peoples R China.
通讯机构：
[Liao, Jinfeng] I;[Liao, Jinfeng] C;Indiana Univ, Ctr Explorat Energy & Matter, 2401 N Milo B Sampson Lane, Bloomington, IN 47408 USA.;Cent China Normal Univ, Inst Particle Phys, Wuhan 430079, Hubei, Peoples R China.;Cent China Normal Univ, Key Lab Quark & Lepton Phys MOE, Wuhan 430079, Hubei, Peoples R China.
关键词：
heavy ion collision;quark gluon plasma;chiral magnetic effect;chiral symmetry
摘要：
The Chiral Magnetic Effect (CME) is a macroscopic manifestation of fundamental chiral anomaly in a many-body system of chiral fermions, and emerges as an anomalous transport current in the fluid dynamics framework. Experimental observation of the CME is of great interest and has been reported in Dirac and Weyl semimetals. Significant efforts have also been made to look for the CME in heavy ion collisions. Critically needed for such a search is the theoretical prediction for the CME signal. In this paper we report a first quantitative modeling framework, Anomalous Viscous Fluid Dynamics (AVFD), which computes the evolution of fermion currents on top of realistic bulk evolution in heavy ion collisions and simultaneously accounts for both anomalous and normal viscous transport effects. AVFD allows a quantitative understanding of the generation and evolution of CME-induced charge separation during the hydrodynamic stage, as well as its dependence on theoretical ingredients. With reasonable estimates of key parameters, the AVFD simulations provide the first phenomenologically successful explanation of the measured signal in 200 AGeV AuAu collisions.
