Tue·Sep 24, 2002Tuesday·September 24, 2002

1. 01*

   Finite density QCD via imaginary chemical potential

   M. D'Elia🇮🇹 · M.-P. Lombardo🇮🇹

   We study QCD at nonzero temperature and baryon density in the framework of the analytic continuation from imaginary chemical potential. We carry out simulations of QCD with four flavor of staggered fermions, and reconstruct the phase diagram in the temperature-imaginary \mu plane. We consider ansätze for the analytic continuation of the critical line and other observables motivated both by theoretical considerations and mean field calculations in four fermion models and random matrix theory. We determine the critical line, and the analytic continuation of the chiral condensate, up to \mu_B approx. 500 MeV. The results are in qualitative agreement with the predictions of model field theories, and consistent with a first order chiral transition. The correlation between the chiral transition and the deconfinement transition observed at \mu=0 persists at nonzero density.

   hep-lathep-phPRD(2003)·739 citations
2. 02*

   Nucleon Magnetic Moments, their Quark Mass Dependence and Lattice QCD Extrapolations

   Thomas R. Hemmert (1)🇩🇪 · Wolfram Weise (1,2) ((1) TU Muenchen, (2) ECT Trento)🇩🇪

   We calculate the quark mass dependence of both isovector and isoscalar anomalous magnetic moments of the nucleon in a chiral effective field theory with explicit pion, nucleon and Delta(1232) degrees of freedom to leading-one-loop order. In the isovector sector we fit 3 unknown couplings of the effective Lagrangian to available lattice data and obtain a surprisingly well-behaved extrapolation function connecting the chiral limit, experimental data and the lattice simulations. We also discuss the polynomial quark mass dependence in the isoscalar sector and finally compare with the Pade formula of the Adelaide group.

   hep-lat0 citations
3. 03*

   A non-perturbative determination of Z_V and b_V for O(a) improved quenched and unquenched Wilson fermions

   T. Bakeyev🇷🇺 · M. Gockeler🇩🇪 · R. Horsley🇬🇧 · D. Pleiter🇩🇪 · P.E.L. Rakow🇩🇪 · A. Schafer🇩🇪 · G. Schierholz🇩🇪 · H. Stuben🇩🇪

   By considering the local vector current between nucleon states and imposing charge conservation we determine, for $O(a)$ improved Wilson fermions, its renormalisation constant and quark mass improvement coefficient. The computation is performed for both quenched and two flavour unquenched fermions.

   hep-latNucl.Phys.B Proc.Suppl.(2003)·3 citations
4. 04*

   Electric and Magnetic Fluxes in SU(2) Yang-Mills Theory

   Lorenz von Smekal (1)🇩🇪 · with Philippe de Forcrand (2) ((1) University Erlangen-Nuremberg, (2) ETH Zurich and CERN)🇨🇭

   We measure the free energies in SU(2) of static fundamental charges and center monopoles. Dual to temporal center fluxes, the former provide a well-defined (dis)order parameter for deconfinement. In contrast, the monopole free energies vanish in the thermodynamic limit at all temperatures and are thus irrelevant for the transition.

   hep-lathep-phNucl.Phys.B Proc.Suppl.(2003)·18 citations
5. 05*

   A precise determination of the charm quark's mass in quenched QCD

   Juri Rolf🇩🇪 · Stefan Sint🇨🇭

   We present a lattice determination of the charm quark's mass, using the mass of the D_s meson as experimental input. All errors are under control with the exception of the quenched approximation. Setting the scale with F_K=160 MeV, our final result for the renormalization group invariant (RGI) quark mass is M_c = 1.654(45) GeV, which translates to m_c(m_c) =1.301(34) GeV for the running mass in the MSbar scheme. A 6 percent increase of the RGI quark mass is observed when the scale is set by the nucleon mass. This is a typical quenched scale ambiguity, which is reduced to about 3 percent for m_c(m_c), and to 4 percent for the mass ratio M_c/M_s. In contrast, the mass splitting m(Dstar_s)-m(D_s) changes from 117(11) MeV to 94(11) MeV, which is significantly smaller than the experimental value of 144 MeV.

   ↳ hep-phhep-latJHEP(2002)·79 citations
6. 06*

   Calculation of Hadronic Excitations of the Quark-Gluon Plasma

   Hu Li🇺🇸 · C. M. Shakin🇺🇸

   We present calculations of the spectral functions of various hadronic current correlators at finite temperature, making use of the Nambu--Jona-Lasinio (NJL) model and the real-time finite-temperature formalism. We study the scalar-isoscalar correlation function in a SU(3)-flavor model, as well as the pseudoscalar and vector correlation functions. We relate our analysis to our recent calculations of the properties of mesons for $T<T_c$, which made use of a generalized NJL model that includes a covariant model of confinement. Here, we exhibit values of the spectral functions for a range of values of $T>T_c$, where it is possible to neglect the effects of confinement. We find important excitations in the scalar sector corresponding to what are predominately singlet and octet states. The singlet state, which is at 247 MeV at $T=1.2T_c$, evolves from the $f_0(980)$ which has an energy of about 400 MeV before it disappears from the spectrum of bound states for $T>0.95T_c$. The octet state seen at $T=1.2T_c$, which has a mass of about 860 MeV, evolves from a nodeless state that has an energy of about 1470 MeV at T=0 in our model. As noted in the literature, these modes may play an important role in the cooling and hadronization of quark-gluon droplets excited in heavy-ion collisions. We note that the real-time formalism has some advantages over the imaginary-time formalism, since the real-time formalism provides information concerning the widths of the excitations calculated using our model.

   ↳ hep-phhep-lat4 citations

* Reconstructed cohort: no mailing for this day survives in the archive. Papers are grouped by their submission times and arXiv's announcement cut-off, assuming announcement without delay; positions follow identifier order. Validated at ~91% exact-day agreement against the archived era.