771 research outputs found
Static quark free energies at finite temperature with two flavors of improved Wilson quarks
Polyakov loop correlations at finite temperature in two-flavor QCD are
studied in lattice simulations with the RG-improved gluon action and the
clover-improved Wilson quark action. From the simulations on a
lattice, we extract the free energies, the effective running coupling and the Debye screening mass for various color channels of
heavy quark--quark and quark--anti-quark pairs above the critical temperature.
The free energies are well approximated by the screened Coulomb form with the
appropriate Casimir factors. The magnitude and the temperature dependence of
the Debye mass are compared to those of the next-to-leading order thermal
perturbation theory and to a phenomenological formula given in terms of . Also we made a comparison between our results with the Wilson quark
and those with the staggered quark previously reported.Comment: 7 pages, 9 figures, talk given at Lattice 2006 (high temperature and
density
Nuclear matrix element for two neutrino double beta decay from 136Xe
The nuclear matrix element for the two neutrino double beta decay (DBD) of
136Xe was evaluated by FSQP (Fermi Surface Quasi Particle model), where
experimental GT strengths measured by the charge exchange reaction and those by
the beta decay rates were used. The 2 neutrino DBD matrix element is given by
the sum of products of the single beta matrix elements via low-lying (Fermi
Surface) quasi-particle states in the intermediate nucleus. 136Xe is the
semi-magic nucleus with the closed neutron-shell, and the beta + transitions
are almost blocked. Thus the 2 neutrino DBD is much suppressed. The evaluated 2
neutrino DBD matrix element is consistent with the observed value.Comment: 7 pages 6 figure
Finite temperature phase transition of two-flavor QCD with an improved Wilson quark action
We study the phase structure of QCD at finite temperatures with two flavors
of dynamical quarks on a lattice with the size , using a renormalization group improved gauge action and a clover improved
Wilson quark action. The simulations are made along the lines of constant
physics determined in terms of at zero-temperature. We
show preliminary results for the spatial string tension in the high temperature
phase.Comment: 7 pages, 7 figures, talk presented at Lattice 2006 (high temperature
and density
Thermodynamics and heavy-quark free energies at finite temperature and density with two flavors of improved Wilson quarks
Thermodynamics of two-flavor QCD at finite temperature and density is studied
on a lattice, using a renormalization group improved gauge
action and the clover improved Wilson quark action. In the simulations along
lines of constant , we calculate the Taylor expansion
coefficients of the heavy-quark free energy with respect to the quark chemical
potential () up to the second order. By comparing the expansion
coefficients of the free energies between quark()and antiquark(),
and between and , we find a characteristic difference at finite
due to the first order coefficient of the Taylor expansion. We also calculate
the quark number and isospin susceptibilities, and find that the second order
coefficient of the quark number susceptibility shows enhancement around the
pseudo-critical temperature.Comment: Talk given at the XXV International Symposium on Lattice Field Theory
(Lattice 2007), July 30 - August 4, 2007, Regensburg, German
Heavy-Quark Free Energy, Debye Mass, and Spatial String Tension at Finite Temperature in Two Flavor Lattice QCD with Wilson Quark Action
We study Polyakov loop correlations and spatial Wilson loop at finite
Temperature in two-flavor QCD simulations with the RG-improved gluon action and
the clover-improved Wilson quark action on a lattice. From the
line of constant physics at and 0.80, we extract
the heavy-quark free energies, the effective running coupling
and the Debye screening mass for various color channels of heavy
quark--quark and quark--anti-quark pairs above the critical temperature. The
free energies are well approximated by the screened Coulomb form with the
appropriate Casimir factors at high temperature. The magnitude and the
temperature dependence of the Debye mass are compared to those of the
next-to-leading order thermal perturbation theory and to a phenomenological
formula in terms of . We make a comparison between our results
with the Wilson quark action and the previous results with the staggered quark
action. The spatial string tension is also studied in the high temperature
phase and is compared to the next-to-next-leading order prediction in an
effective theory with dimensional reduction.Comment: 25 pages, 37 EPS figure
Equation of state at finite density in two-flavor QCD with improved Wilson quarks
We study the equation of state in two-flavor QCD at finite temperature and
density. Simulations are made with the RG-improved gluon action and the
clover-improved Wilson quark action. Along the lines of constant physics for
and 0.80, we compute the derivatives of the quark
determinant with respect to the quark chemical potential up to the
fourth order at . We adopt several improvement techniques in the
evaluation. We study thermodynamic quantities and quark number susceptibilities
at finite using these derivatives. We find enhancement of the quark
number susceptibility at finite , in accordance with previous
observations using staggered-type quarks. This suggests the existence of a
nearby critical point.Comment: 7 pages, 16 figures, presented at the XXVI International Symposium on
Lattice Field Theory (LATTICE 2008), July 14-19, 2008, Williamsburg,
Virginia, US
Equation of State and Heavy-Quark Free Energy at Finite Temperature and Density in Two Flavor Lattice QCD with Wilson Quark Action
We study the equation of state at finite temperature and density in
two-flavor QCD with the RG-improved gluon action and the clover-improved Wilson
quark action on a lattice. Along the lines of constant physics
at and 0.80, we compute the second and forth
derivatives of the grand canonical partition function with respect to the quark
chemical potential and the isospin chemical potential
at vanishing chemical potentials, and study the
behaviors of thermodynamic quantities at finite using these derivatives
for the case . In particular, we study density fluctuations at
none-zero temperature and density by calculating the quark number and isospin
susceptibilities and their derivatives with respect to . To suppress
statistical fluctuations, we also examine new techniques applicable at low
densities. We find a large enhancement in the fluctuation of quark number when
the density increased near the pseudo-critical temperature, suggesting a
critical point at finite terminating the first order transition line
between hadronic and quark gluon plasma phases. This result agrees with the
previous results using staggered-type quark actions qualitatively. Furthermore,
we study heavy-quark free energies and Debye screening masses at finite density
by measuring the first and second derivatives of these quantities for various
color channels of heavy quark-quark and quark-anti-quark pairs. The results
suggest that, to the leading order of , the interaction between two
quarks becomes stronger at finite densities, while that between quark and
anti-quark becomes weaker.Comment: 38 pages, 63 figure
Supernova-Neutrino Studies with Mo
We show that supernova neutrinos can be studied by observing their
charged-current interactions with Mo, which has strong spin-isospin
giant resonances. Information about both the effective temperature of the
electron neutrino sphere and the oscillation into electron neutrinos of other
flavors can be extracted from the electron (inverse ) spectrum. We use
measured hadronic charge-exchange spectra and the Quasiparticle Random Phase
Approximation to calculate the charged-current response of Mo to
electron neutrinos from supernovae, with and without the assumption of
oscillations. A scaled up version of the MOON detector for and
solar-neutrino studies could potentially be useful for spectroscopic studies of
supernova neutrinos as well.Comment: 7 pages, 1 figur
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