Topic
Charm quark
About: Charm quark is a research topic. Over the lifetime, 2495 publications have been published within this topic receiving 47725 citations. The topic is also known as: c quark & Charm quark.
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TL;DR: In this paper, the authors review the theory and present status of the proton spin problem with emphasis on the transition between current quarks and constituent quarks in QCD, and propose a solution to the problem.
Abstract: We review the theory and present status of the proton spin problem with emphasis on the transition between current quarks and constituent quarks in QCD.
1,207 citations
TL;DR: In this article, the authors investigated the QCD equation of state with 2+1 staggered flavors and one-link stout improvement, and compared their results to the results obtained by the hotQCD collaboration.
Abstract: The present paper concludes our investigation on the QCD equation of state with 2+1 staggered flavors and one-link stout improvement. We extend our previous study [JHEP 0601:089 (2006)] by choosing even finer lattices. Lattices with $N_t=6,8$ and 10 are used, and the continuum limit is approached by checking the results at $N_t=12$. A Symanzik improved gauge and a stout-link improved staggered fermion action is utilized. We use physical quark masses, that is, for the lightest staggered pions and kaons we fix the $m_\pi/f_K$ and $m_K/f_K$ ratios to their experimental values. The pressure, the interaction measure, the energy and entropy density and the speed of sound are presented as functions of the temperature in the range $100 ...1000 \textmd{MeV}$. We give estimates for the pion mass dependence and for the contribution of the charm quark. We compare our data to the equation of state obtained by the "hotQCD" collaboration.
746 citations
TL;DR: In this article, the authors investigated the QCD equation of state with 2+1 staggered flavors and one-link stout improvement and compared their results to the results obtained by the hotQCD collaboration.
Abstract: The present paper concludes our investigation on the QCD equation of state with 2+1 staggered flavors and one-link stout improvement. We extend our previous study (JHEP 0601:089 (2006)) by choosing even finer lattices. Lattices with Nt = 6,8 and 10 are used, and the continuum limit is approached by checking the results at Nt = 12. A Symanzik improved gauge and a stout-link improved staggered fermion action is utilized. We use physical quark masses, that is, for the lightest staggered pions and kaons we fix the m�/fK and mK/fK ratios to their experimental values. The pressure, the interaction measure, the energy and entropy density and the speed of sound are presented as functions of the temperature in the range 100...1000MeV. We give estimates for the pion mass dependence and for the contribution of the charm quark. We compare our data to the equation of state obtained by the "hotQCD" collaboration.
693 citations
TL;DR: The discovery of narrow resonances at 3.1 and 3.7 GeV and their interpretation as charmed quark-antiquark bound states suggest additional narrow states between 3.0 and 4.3 GeV as mentioned in this paper.
Abstract: The discovery of narrow resonances at 3.1 and 3.7 GeV and their interpretation as charmed quark-antiquark bound states suggest additional narrow states between 3.0 and 4.3 GeV. A model which incorporates quark confinement is used to determine the quantum numbers and estimate masses and decay widths of these states. Their existence should be revealed by $\ensuremath{\gamma}$-ray transitions among them.
679 citations
TL;DR: In this paper, the diffusion coefficient in the perturbative quark gluon plasma and its relationship to collisional energy loss and momentum broadening were investigated. But the model is strictly valid in the nonrelativistic limit and for all velocities.
Abstract: We investigate the thermalization of charm quarks in high-energy heavy-ion collisions. To this end, we calculate the diffusion coefficient in the perturbative quark gluon plasma and relate it to collisional energy loss and momentum broadening. We then use these transport properties to formulate a Langevin model for the evolution of the heavy quark spectrum in the hot medium. The model is strictly valid in the nonrelativistic limit and for all velocities $\ensuremath{\gamma}vl\ensuremath{\alpha}{s}^{\ensuremath{-}1/2}$ to leading logarithm in $T/{m}_{D}$. The corresponding Fokker-Planck equation can be solved analytically for a Bjorken expansion and the solution gives a simple estimate for the medium modifications of the heavy quark spectrum as a function of the diffusion coefficient. Finally we solve the Langevin equations numerically in a hydrodynamic simulation of the heavy-ion reaction. The results of this simulation are the medium modifications of the charm spectrum ${R}_{\mathit{AA}}$ and the expected elliptic flow ${v}_{2}({p}_{T})$ as a function of the diffusion coefficient.
615 citations