15858058
Non-zero density QCD by the Taylor expansion method: The isentropic equation of state, hadronic fluctuations and more
We discuss the Taylor expansion approach to non-zero baryon chemical potential ($\mu_B$) and present results on expanion coefficients of the pressure and energy density up to the 6-th order in $\mu_B$. Calculations have been performed with (2+1)-flavor of improved staggerd fermions (p4fat3) and almost physical masses on lattices with temporal extent of four and six time slices. We use the expansion coefficients to construct the isentropic equation of state on lines of constant entropy per baryon number and various different hadronic fluctuations. Furthermore, we estimate the radius of convegence of our expansion, which can be seen as a method to analyze the structure of the QCD phase diagram.
16115905
Flavor and quark mass dependence of QCD thermodynamics
We calculate the transition temperature in 2 and 3-flavor QCD using improved gauge and staggered fermion actions on lattices with temporal extent Nτ = 4. We find Tc = 173 (8) MeV and 154 (8) MeV for nf = 2 and 3, respectively. In the case of 3-flavor QCD we present evidence that the chiral critical point, i.e. the second order endpoint of the line of first order chiral phase transitions, belongs to the universality class of the 3d Ising model.
17537588
Lattice simulations with chemical potential
After giving an overview of recently invented methods for simulating lattice QCD at small mu/T, we discuss some results for bulk thermodynamic quantities of QCD matter coming from those methods. We focus on the transition line and the critical endpoint in the QCD phase diagram.
14794189
The density of states method at non-zero chemical potential
We study the QCD phase diagram by first principle lattice calculations at so far unreached high densities. For this purpose we employ the density of states method. Unimproved staggered fermions, which describe four quark flavors in the continuum are used in this analysis. Though the method is quite expensive, small lattices show an indication for a triple-point connecting three different phases on the phase diagram.
16120128
Bulk thermodynamics and charge fluctuations at non-vanishing baryon density
We present results on bulk thermodynamic quantities as well as net baryon number, strangeness and electric charge fluctuations in QCD at non-zero density and temperature obtained from lattice calculations with almost physical quark masses for two values of the lattice cut-off aT = 1/4 and 1/6. We show that with our improved p4fa3-action the cut-off effects are under control when using lattices with a temporal extent of 6 or larger and that the contribution to the equation of state, which is due to a finite chemical potential is small for {mu}{sub q}/T < 1. Moreover, at vanishing chemical potential, i.e. under conditions almost realized at RHIC and the LHC, quartic fluctuations of net baryon number and strangeness are large in a narrow temperature interval characterizing the transition region from the low to high temperature phase. At non-zero baryon number density, strangeness fluctuations are enhanced and correlated to fluctuations of the net baryon number. If strangeness is furthermore forced to vanish, as it may be the case in systems created in heavy ion collisions, strangeness fluctuations are significantly smaller than baryon number fluctuations.
119274896
Quark number susceptibilities at high temperatures
We calculate second and fourth order quark number susceptibilities for 2+1 flavor QCD in the high temperature region. In our study we use two improved staggered fermion formulations, namely the highly improved staggered quark formulation, and the so-called p4 formulation, as well as several lattice spacings. Second order quark number susceptibilities are calculated using both improved staggered fermion formulations, and we show that in the continuum limit the two formulations give consistent results. The fourth order quark number susceptibilities are studied only using the p4 formulation and at non-zero lattice spacings. We compare our results on quark number susceptibilities with recent weak coupling calculations, and find that these agree reasonably well with the lattice calculations within the estimated uncertainties.
138225269
DC surface-plasma source with high emission current density.
119495100
QCD phenomenology of charm production at HERA
We compare different schemes for the treatment of heavy quark production in Deep-Inelastic Scattering (DIS). For fully-integrated quantities such as F{sub 2}(x,Q{sup 2}), we advocate the use of the General-Massive Variable-Flavor-Number (GM-VFN) scheme; we present some results showing the progress of a Next-to-Leading Order calculation in this scheme. For differential quantities, the Fixed-Flavor-Number (FFN) scheme provides a more appropriate starting point. We present a new calculation of the azimuthal distribution of charm quark production in DIS. All results have been obtained using a Monte Carlo program under development.
8018207
Top Quark Physics at the NLC
A high energy $e^+e^-$ linear collider (NLC) is an excellent tool for studying the properties of the top quark. In this talk I review some of the theory of top quark production and decay in $e^+e^-$ collisions both at threshold and in the continuum. I also report on the results of phenomenological analyses of $t\bar t$ production at the NLC.
119331939
Chiral perturbation theory for lattice QCD with a twisted mass term
Quantum chromodynamics on a lattice with Wilson fermions and a chirally twisted mass term for two degenerate quark flavours is considered in the framework of chiral perturbation theory. The pion mass and decay constant are calculated in next-to-leading order including terms linear in the lattice spacing a.
59063827
Emittance Measurement Techniques used in the 1 MeV RFQ for the PET Isotope Linac at Fermilab
Beam emittance measurements have been performed on the {sup 3}He{sup +} beam at the PET isotope production accelerator, being commissioned at Fermilab for the Biomedical Research Foundation in Shreveport, Louisiana, USA. Emittances have been measured at injection to and extraction from the first RFQ, at 20 keV and 1 MeV, respectively. A single slit followed by a 48 electrode collector is used in the standard way to measure the divergence of the {sup 3}He{sup +} beam as a function of position. Noise reduction operations have been developed, both in hardware and software. These techniques and the emittance measurement results are presented.