118 research outputs found
The H dibaryon on the lattice
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
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
Further Evidence for an unstable H-Dibaryon?
We present preliminary results for the mass of the 6q flavor-singlet state
(, ) called H-dibaryon, calculated in quenched QCD on x30
and x30 lattices with improved gauge and fermion actions (Symanzik
improvement, Clover action). For both lattice sizes we applied the fuzzing
technique to enhance the overlap with the ground state. We observe a H-mass
above the threshold for strong decay. The difference in mass,
, increases with increasing lattice size.Comment: Poster at LATTICE99 (QCD Spectrum and Quark Masses), 3 pages, 4
figures, LaTeX2e using espcrc2.st
Meson Spectral Functions at finite Temperature
The Maximum Entropy Method provides a Bayesian approach to reconstruct the
spectral functions from discrete points in Euclidean time. The applicability of
the approach at finite temperature is probed with the thermal meson correlation
function. Furthermore the influence of fuzzing/smearing techniques on the
spectral shape is investigated. We present first results for meson spectral
functions at several temperatures below and above . The correlation
functions were obtained from quenched calculations with Clover fermions on
large isotropic lattices of the size . We compare the
resulting pole masses with the ones obtained from standard 2-exponential fits
of spatial and temporal correlation functions at finite temperature and in the
vacuum. The deviation of the meson spectral functions from free spectral
functions is examined above the critical temperature.Comment: Lattice2001(hightemp), 3 pages, 6 figure
Meson correlators above deconfinement
We review recent progress in studying spectral functions for mesonic
observables at finite temperatures, by analysis of imaginary time correlators
directly calculated on isotropic lattices. Special attention is paid to the
lattice artifacts present in such calculations.Comment: Latex, 3 figures uses iopart.cls, talk presented at Hot Quarks 2004,
July 18-24, 2004, Taos Valley New Mexico, US
A Lattice Calculation of Thermal Dilepton Rates
Using clover improved Wilson fermions we calculate thermal vector meson
correlation functions above the deconfinement phase transition of quenched QCD.
At temperatures 1.5 Tc and 3Tc they are found to differ by less than 15% from
that of a freely propagating quark anti-quark pair. This puts severe
constraints on the dilepton production rate and in particular rules out a
strong divergence of the dilepton rate at low energies. The vector spectral
function, which has been reconstructed using the Maximum Entropy Method, yields
an enhancement of the dilepton rate over the Born rate of at most a factor two
in the energy interval 4 < E/T < 8 and suggests that the spectrum is cut-off at
low energies by a thermal mass threshold of about (2-3)T.Comment: 9 pages, LaTeX2e File, 5 EPS files; minor corrections, modified error
bins in Fig.2
H-Dibaryon from Lattice QCD with Improved Anisotropic Actions
The six quark state(uuddss) called H dibaryon(,) has been
calculated to study its existence and stability. The simulations are performed
in quenched QCD on and anisotropic lattices
with Symanzik improved gauge action and Clover fermion action. The gauge
coupling is and aspect ratio . Preliminary results
indicate that mass of H dibaryon is 2134(100)Mev on lattice and
2167(59)Mev on respectively. It seems that the radius of H
dibaryon is very large and the finite size effect is very obvious
Scaling test of quenched Wilson twisted mass QCD at maximal twist
We present the results of an extended scaling test of quenched Wilson twisted
mass QCD. We fix the twist angle by using two definitions of the critical mass,
the first obtained by requiring the vanishing of the pseudoscalar meson mass
m_PS for standard Wilson fermions and the second by requiring restoration of
parity at non-zero value of the twisted mass mu and subsequently extrapolating
to mu=0. Depending on the choice of the critical mass we simulate at values of
beta in [5.7,6.45], for a range of pseudoscalar meson masses 250 MeV < m_PS < 1
GeV and we perform the continuum limit for the pseudoscalar meson decay
constant f_PS and various hadron masses (vector meson m_V, baryon octet m_oct
and baryon decuplet m_dec) at fixed value of r_0 m_PS. For both definitions of
the critical mass, lattice artifacts are consistent with O(a) improvement.
However, with the second definition, large O(a^2) discretization errors present
at small quark mass with the first definition are strongly suppressed. The
results in the continuum limit are in very good agreement with those from the
Alpha and CP-PACS Collaborations.Comment: 6 pages, Talk presented at Lattice 2005, Dublin, 25-30 July 200
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