445 research outputs found
Hard and thermal probes of QGP from the perspective of Lattice QCD
In this talk I review the current status of lattice QCD results on the hard
and thermal probes of QGP, including jet quenching parameters, the melting of
quarkonia and open heavy flavours, thermal photon/dilepton rates, electrical
conductivity as well as heavy quark diffusion coefficients.Comment: 6 pages, plenary talk given at the 6th International Conference on
Hard and Electromagnetic Probes of High-energy Nuclear Collisions (Hard
Probes 2013), accepted version to appear in NP
Exploring QCD phase diagram at vanishing baryon density on the lattice
I report on the current status of QCD phase diagram at vanishing baryon
density. I focus on the QCD phase diagram with three degenerate quark flavor
using Highly Improved Staggered Quarks on lattices. No evidence of
a first order phase transition in the pion mass window of MeV is found. The pion mass at the critical point where the
chiral first order phase transition ends is estimated to be MeV.Comment: proceedings for Extreme QCD (XQCD 2012), August 21-23, 2012, The
George Washington University, Washington DC, US
Momentum dependences of charmonium properties from lattice QCD
Charmonia produced in initial hard parton scatterings during heavy ion
collisions move with respect to the medium rather than flow with the medium.
Lattice studies suggest that charmonium bound states at the rest are
dissociated at . We present results on momentum dependences
of charmonium properties in a hot medium from lattice QCD Monte Carlo
simulations. The dispersion relation of the screening mass and the change of
correlation and spectral functions at various temperatures and momenta are
discussed.Comment: parallel talk given at the Quark Matter 2012 International
Conference, August 13-18, Washington D.C., US
Recent lattice QCD results and phase diagram of strongly interacting matter
I review recent lattice QCD results on a few selected topics which are
relevant to the heavy ion physics community. Special emphasis is put on the QCD
equation of state at vanishing and nonzero baryon chemical potential, the onset
of deconfinement of open strange and charmed hadrons, the contribution from
experimentally not yet observed hadrons to the thermodynamics of the hadronic
gas and their influence on freeze-out conditions of strange and light-quark
hadrons.Comment: plenary talk given at Quark Matter 2014, Darmstadt, May 2014, 8 page
Chiral phase transition of =2+1 and 3 QCD at vanishing baryon chemical potential
We present updated results on chiral phase structure in (2+1)-flavor
(=2+1) and 3-flavor () QCD based on the simulations using Highly
Improved Staggered Quarks on lattices with temporal extent =6 at
vanishing baryon chemical potential. In =2+1 QCD we have performed
simulations with a strange quark fixed to its physical value and two degenerate
light quarks whose values are adjusted to have 5 values of Goldstone pion
masses in the region of 160 - 80 MeV in the continuum limit. The universal
scaling behavior of chiral condensates as well as chiral susceptibilities is
discussed and the tri-critical point is suggested to be located below the
physical point, i.e. at smaller than physical strange quark mass. In =3
QCD simulations with 6 different masses of 3 degenerate quarks corresponding to
the Goldstone pion masses in the region of 230 - 80 MeV have also been
performed. Our results suggest that the QCD transition with these values of
quark masses is of crossover type and an upper bound of the critical pion mass
where the first order phase transition starts is estimated to be about 50 MeV.Comment: Proceedings of the 33rd International Symposium on Lattice Field
Theory, July 14-18, 2015, Kobe, Japa
The curvature of the chiral phase transition line for small values of
We present preliminary results from an ongoing calculation to determine the
curvature of the chiral phase transition line in the chiral limit along the
light-light, light-strange and strange-strange chemical potential directions.
We do this by studying the appropriate -derivatives of the chiral
condensate as a function of the quark mass and comparing them to the scaling
predictions of - theory. We work at a fixed lattice spacing,
and at four different quark masses 140, 110, 90 and
80 MeV. For the light quark curvature, we obtain a value
0.030.11. We also find that both strange and
light-strange curvatures are around an order of magnitude smaller. Currently,
the light-strange curvature is the least constrained curvature and could have
either sign, though our results seem to prefer a slightly negative value.Comment: Contribution to the proceedings of the 33rd International Symposium
on Lattice Field Theory, July 14-18, Kobe Japa
New developments in lattice QCD on equilibrium physics and phase diagram
I review recent new lattice QCD results on a few selected topics which are
relevant to the heavy ion physics community. Special emphasis is put on the QCD
phase diagram towards the chiral limit and at nonzero baryon density as well as
the fate of quarkonia and heavy quark drag coefficients.Comment: 8 pages, 5 figures, plenary talk given at the XXVIIIth International
Conference on Ultrarelativistic Nucleus-Nucleus Collisions (Quark Matter
2019), November 4th-9th 2019, Wuhan, Chin
Vector spectral functions and transport properties in quenched QCD
We present new results on the reconstruction of mesonic spectral functions
for three temperatures , and in quenched QCD. Making
use of non-perturbatively improved clover Wilson valence quarks allows for a
clean extrapolation of correlator data to the continuum limit. For the case of
vanishing momentum the spectral function is obtained by fitting the data to a
well motivated ansatz, using the full covariance matrix of the continuum
extrapolated data in the fit. We found that vector correlation function is
almost temperature independent in the current temperature window. The
electrical conductivity of the hot medium, related to the origin of the vector
spectral function at zero momentum, is computed from the resulting parameters
at all three temperatures, leading to an estimate of . The dilepton rates resulting from the obtained
spectral functions show no significant temperature dependence.Comment: 7 pages, 5 figures, PoS LATTICE 201
Imprints of relic gravitational waves on pulsar timing
Relic gravitational waves (RGWs) , a background originated during inflation,
would give imprints on the pulsar timing residuals. This makes RGWs be one of
important sources for detection using the method of pulsar timing. In this
paper, we discuss the effects of RGWs on the single pulsar timing, and give
quantitively the timing residuals caused by RGWs with different model
parameters. In principle, if the RGWs are strong enough today, they can be
detected by timing a single millisecond pulsar with high precision after the
intrinsic red noise in pulsar timing residuals were understood, even though
observing simultaneously multiple millisecond pulsars is a more powerful
technique in extracting gravitational wave signals. We corrected the
normalization of RGWs using observations of the cosmic microwave background
(CMB), which leads to the amplitudes of RGWs being reduced by two orders of
magnitude or so compared to our previous works. We made new constraints on RGWs
using the recent observations from the Parkes Pulsar Timing Array, employing
the tensor-to-scalar ratio due to the tensor-type polarization
observations of CMB by BICEP2 as a referenced value even though it has been
denied. Moreover, the constraints on RGWs from CMB and BBN (Big Bang
nucleosynthesis) will also be discussed for comparison.Comment: 17 pages, 6 figures, accepted by RA
Meson masses in external magnetic fields with HISQ fermions
We studied the temporal correlation function of mesons in the pseudo-scalar
channel in (2+1)-flavor QCD in the presence of external magnetic fields at zero
temperature. The simulations were performed on lattices using
the Highly Improved Staggered Quarks (HISQ) action with 230
MeV. The strength of magnetic fields ranges from 0 to around 3.3 GeV
(). We found that the masses of neutral pseudo-scalar
particles, e.g. neutral pion and kaon, monotonouslly decrease as the magnetic
field grows and then saturate at a nonzero value. It is observed that heavier
neutral pseudo-scalars are less affected by magnetic fields. Moreover, we found
a non-monotonous behavior of charged pion and kaon mass in magnetic field for
the first time. In the case of small magnetic field (0 0.3
GeV ) the mass of charged pseudo-scalar grows with magnetic
field and can be well described by the Lowest Landau Level approximation, while
for larger than 0.3 GeV the mass starts to decrease. The possible
connection between dependences of neutral pion mass and the decreasing
behavior of pseudo-critical temperature in magnetic field is discussed. Due to
the nonzero value of neutral pion mass our simulation indicates that the
superconducting phase of QCD does not exist in the current window of magnetic
field.Comment: 7 pages, 7 figures; Proceedings of the 37th International Symposium
on Lattice Field Theory - Lattice 2019, Wuhan (China
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