1,238 research outputs found

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

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 $(T, \mu_q)$ 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

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 $^{76}$Ge,
$^{82}$Se, $^{100}$Mo, $^{130}$Te, $^{136}$Xe, and $^{150}$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

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

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

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

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 $32^3 \times N_t$ with $N_t=14$, 13, $\cdots$, 4 which correspond to
$T \approx 160$--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

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 ${\cal O}(\mu_q^6)$ in the quark
chemical potential. We use these series in $\mu_q/T$ to determine lines of
constant entropy per baryon number ($S/N_B$) 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 $\mu_q/T$.
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 $S/N_B$ we calculate the energy
density and pressure. Within the accuracy of our present analysis we find that
the ratio $p/\epsilon$ for $T>T_0$ as well as the softest point of the equation
of state, $(p/\epsilon)_{min}\simeq 0.075$, show no significant dependence on
$S/N_B$.Comment: 7 pages, 10 figure

### Heavy quark free energies and screening at finite temperature and density

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

- â€¦