1,238 research outputs found

    Lee-Yang zero analysis for the study of QCD phase structure

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    We comment on the Lee-Yang zero analysis for the study of the phase structure of QCD at high temperature and baryon number density by Monte-Carlo simulations. We find that the sign problem for non-zero density QCD induces a serious problem in the finite volume scaling analysis of the Lee-Yang zeros for the investigation of the order of the phase transition. If the sign problem occurs at large volume, the Lee-Yang zeros will always approach the real axis of the complex parameter plane in the thermodynamic limit. This implies that a scaling behavior which would suggest a crossover transition will not be obtained. To clarify this problem, we discuss the Lee-Yang zero analysis for SU(3) pure gauge theory as a simple example without the sign problem, and then consider the case of non-zero density QCD. It is suggested that the distribution of the Lee-Yang zeros in the complex parameter space obtained by each simulation could be more important information for the investigation of the critical endpoint in the (T,μq)(T, \mu_q) plane than the finite volume scaling behavior.Comment: 16 pages, 3 figures, 2 tables, minor change

    Solar Neutrinos as Background to Neutrinoless Double-beta Decay Experiments

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    Solar neutrinos interact within double-beta decay (\BB) detectors and contribute to backgrounds for \BB\ experiments. Background contributions due to charge-current solar neutrino interactions with \BB\ nuclei of 76^{76}Ge, 82^{82}Se, 100^{100}Mo, 130^{130}Te, 136^{136}Xe, and 150^{150}Nd are evaluated. They are shown to be significant for future high-sensitivity \BB\ experiments that may search for Majorana neutrino masses in the inverted-hierarchy mass region. The impact of solar neutrino backgrounds and their reduction are discussed for future \BB\ experiments.Comment: proceedings submission for MEDEX 201

    Resonant photonuclear isotope detection using medium-energy photon beam

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    Resonant photonuclear isotope detection (RPID) is a nondestructive detection/assay of nuclear isotopes by measuring gamma rays following photonuclear reaction products. Medium-energy wideband photons of 12-16 MeV are used for the photonuclear reactions and gamma rays characteristic of the reaction products are measured by means of high-sensitivity Ge detectors. Impurities of stable and radioactive isotopes of the orders of micro-nano gr and ppm-ppb are investigated. RPID is used to study nuclear isotopes of astronuclear and particle physics interests and those of geological and historical interests. It is used to identify radioactive isotopes of fission products as well.Comment: 6 pages, 3 figure

    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

    Isentropic thermodynamics in the PNJL model

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    We discuss the isentropic trajectories on the QCD phase diagram in the temperature and the quark chemical potential plane using the Nambu--Jona-Lasinio model with the Polyakov loop coupling (PNJL model). We impose a constraint on the strange quark chemical potential so that the strange quark density is zero, which is the case in the ultra relativistic heavy-ion collisions. We compare our numerical results with the truncated estimates by the Taylor expansion in terms of the chemical potential to quantify the reliability of the expansion used in the lattice QCD simulation. We finally discuss the strange quark chemical potential induced by the strangeness neutrality condition and relate it to the ratio of the Polyakov loop and the anti-Polyakov loop.Comment: 9 pages, 9 figure

    Towards the QCD equation of state at the physical point using Wilson fermion

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    We study the (2+1)-flavor QCD at nonzero temperatures using nonperturbatively improved Wilson quarks of the physical masses by the fixed scale approach. We perform physical point simulations at finite temperatures with the coupling parameters which were adopted by the PACS-CS Collaboration in their studies using the reweighting technique. Zero temperature values are obtained on the PACS-CS configurations which are open to the public on the ILDG/JLDG. Finite temperature configurations are generated with the RHMC algorithm. The lattice sizes are 323×Nt32^3 \times N_t with Nt=14N_t=14, 13, \cdots, 4 which correspond to T160T \approx 160--550 MeV. We present results of some basic observables at these temperatures and the status of our calculation of the equation of state.Comment: 7 pages, 3 figures, proceedings of the 33rd International Symposium on Lattice Field Theory, July 14-18, 2015, Kobe, Japa

    The isentropic equation of state of 2-flavor QCD

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    Using Taylor expansions of the pressure obtained previously in studies of 2-flavor QCD at non-zero chemical potential we calculate expansion coefficients for the energy and entropy densities up to O(μq6){\cal O}(\mu_q^6) in the quark chemical potential. We use these series in μq/T\mu_q/T to determine lines of constant entropy per baryon number (S/NBS/N_B) that characterize the expansion of dense matter created in heavy ion collisions. In the high temperature regime these lines are found to be well approximated by lines of constant μq/T\mu_q/T. In the low temperature phase, however, the quark chemical potential is found to increase with decreasing temperature. This is in accordance with resonance gas model calculations. Along the lines of constant S/NBS/N_B we calculate the energy density and pressure. Within the accuracy of our present analysis we find that the ratio p/ϵp/\epsilon for T>T0T>T_0 as well as the softest point of the equation of state, (p/ϵ)min0.075(p/\epsilon)_{min}\simeq 0.075, show no significant dependence on S/NBS/N_B.Comment: 7 pages, 10 figure

    Heavy quark free energies and screening at finite temperature and density

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    We study the free energies of heavy quarks calculated from Polyakov loop correlation functions in full 2-flavour QCD using the p4-improved staggered fermion action. A small but finite Baryon number density is included via Taylor expansion of the fermion determinant in the Baryo-chemical potential mu. For temperatures above Tc we extract Debye screening masses from the large distance behaviour of the free energies and compare their mu-dependence to perturbative results.Comment: 6 pages, Presented at 23rd International Symposium on Lattice Field Theory (Lattice 2005), Trinity College, Dublin, Ireland, 25-30 Jul 200