1,431 research outputs found

    Hadronic fluctuations in the QGP

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    We analyze fluctuations of quark number and electric charge, in 2-flavour QCD at finite temperature and vanishing net baryon number density. In the hadronic phase we find that an enhancement of charge fluctuations arises from contributions of doubly charged hadrons to the thermodynamics. The rapid suppression of fluctuations seen in the high temperature phase suggests that in the QGP quark number and electric charge are predominantly carried by quasi-particles with the quantum numbers of quarks.Comment: 4 pages, 6 EPS-files, talk presented at Quark Matter 2005, Budapes

    Flavor and Quark Mass Dependence of QCD Thermodynamics

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    We calculate the transition temperature in 2 and 3-flavor QCD using improved gauge and staggered fermion actions on lattices with temporal extent Nt=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.Comment: Talk given at Lattice 2000 (Finite Temperature), 4 pages, 6 EPS-figure

    The H dibaryon on the lattice

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    We present our final results for the mass of the six quark flavor singlet state (J^P=0^+, S=-2) called H dibaryon, which would be the lightest possible strangelet in the context of strange quark matter. The calculations are performed in quenched QCD on (8-24)^3 x 30 lattices with the (1,2) Symanzik improved gauge action and the clover fermion action. Furthermore the fuzzing technique for the fermion fields and smearing of the gauge fields is applied in order to enhance the overlap with the ground state. Depending on the lattice size we observe an H mass slightly above or comparable with the \Lambda\Lambda threshold for strong decay. Therefore a bound H dibaryon state seemed to be ruled out by our simulation.Comment: Lattice2002(spectrum), 3 pages, 2 figures, Proceedings of the XX International Symposium on Lattice Field Theory, June 24-29, 2002 (MIT, Cambridge, USA

    Testing MEM with Diquark and thermal Meson Correlation Functions

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    When applying the maximum entropy method (MEM) to the analysis of hadron correlation functions in QCD a central issue is to understand to what extent this method can distinguish bound states, resonances and continuum contributions to spectral functions. We discuss these issues by analyzing meson and diquark correlation functions at zero temperature as well as free quark anti-quark correlators. The latter test the applicability of MEM to high temperature QCD.Comment: 6 pages, 6 figures. Contribution to the proceedings of the Conference on Strong and Electroweak Matter (SEWM 2000), Marseille, France, 14-17 June 2000; Figure 3(b) change

    Thermodynamics and in-medium hadron properties from lattice QCD

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    Non-perturbative studies of the thermodynamics of strongly interacting elementary particles within the context of lattice regularized QCD are being reviewed. After a short introduction into thermal QCD on the lattice we report on the present status of investigations of bulk properties. In particular, we discuss the present knowledge of the phase diagram including recent developments of QCD at non-zero baryon number density. We continue with the results obtained so far for the transition temperature as well as the temperature dependence of energy and pressure and comment on screening and the heavy quark free energies. A major section is devoted to the discussion of thermal modifications of hadron properties, taking special account of recent progress through the use of the maximum entropy method.Comment: prepared for "Quark-Gluon Plasma III", R.Hwa (ed.

    Free Meson Spectral Functions on the Lattice

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    We present results from an analytic calculation of thermal meson spectral functions in the infinite temperature (free field) limit. We compare spectral functions for various lattice fermion formulations used at present in studies of in-medium properties of hadrons based on the maximum entropy method (MEM). In particular, we will present a new calculation of spectral functions performed with extended quark sources.Comment: 3 pages, Lattice2003(nonzero

    Charmonium at finite temperature

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    We study charmoinum correlators and spectral functions at finite temperature within the quenched approximation using isotropic lattices with lattice spacing a^-1=4.86 GeV and 9.72 GeV. Although we observe some medium modifications of the ground state charmonium spectral function above deconfinement, we find that ground state charmonia (J/psi and eta_c) exist in the deconfined phase at least up to temperatures as high as 1.5Tc. P-wave charmonia (chi_c) on the other hand are dissociated already at 1.12Tc.Comment: Contribution to Lattice 2003 (non-zero) LaTeX, 3 pages, 3 figures, uses espcrc2 styl

    Thermodynamics of two-colour QCD

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    We discuss the thermodynamics of two-colour QCD with four flavours of staggered quarks on 8^3x4 and 16^3x4 lattices. In our simulations we use the Naik action for the fermions and a (1,2) tree-level improved gauge action. We analyze the deconfinement and chiral phase transitions for four different quark masses (m=0.1,0.05,0.025,0.015). Contrary to three-colour QCD the peak in the Polyakov loop susceptibility decreases with decreasing quark mass. This reflects an early breaking of the string in the heavy quark potential, which we verify explicitly by calculating the heavy quark potential at finite temperature using Polyakov loop correlations.Comment: LATTICE98(hightemp), 3 pages, LaTeX2e File, 5 EPS-figures, espcrc2.st

    Infrared features of unquenched finite temperature lattice Landau gauge QCD

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    The color diagonal and color antisymmetric ghost propagators slightly above TcT_c of Nf=2N_f=2 MILC 243√ó1224^3\times 12 lattices are measured and compared with zero temperature unquenched Nf=2+1N_f=2+1 MILCc_c 203√ó6420^3\times 64 and MILCf_f 283√ó9628^3\times 96 lattices and zero temperature quenched 56456^4 ő≤=6.4\beta=6.4 and 6.45 lattices. The expectation value of the color antisymmetric ghost propagator Ōēc(q)\phi^c(q) is zero but its Binder cumulant, which is consistent with that of Nc2‚ąí1N_c^2-1 dimensional Gaussian distribution below TcT_c, decreases above TcT_c. Although the color diagonal ghost propagator is temperature independent, the l1l^1 norm of the color antisymmetric ghost propagator is temperature dependent. The expectation value of the ghost condensate observed at zero temperature unquenched configuration is consistent with 0 in T>TcT>T_c. We also measure transverse, magnetic and electric gluon propagator and extract gluon screening masses. The running coupling measured from the product of the gluon dressing function and the ghost dressing function are almost temperature independent but the effect of A2A^2 condensate observed at zero temperature is consistent with 0 in T>TcT>T_c. The transverse gluon dressing function at low temperature has a peak in the infrared but it becomes flatter at high temperature. Its absolute value in the high momentum is larger for high temperature and similar to the magnetic gluon dressing function. The electric gluon propagator at high momentum is temperature independent. These data imply that the magnetic gluon propagator and the color antisymmetric ghost propagator are affected by the presence of dynamical quarks and there are strong non-perturbative effects through the temperature dependent color anti-symmetric ghost propagator.Comment: 11 pages 16 figures, version accepted for publication in Phys. Rev.
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