301 research outputs found
Electromagnetic Corrections in Partially Quenched Chiral Perturbation Theory
We introduce photons in Partially Quenched Chiral Perturbation Theory and
calculate the resulting electromagnetic loop-corrections at NLO for the charged
meson masses and decay constants. We also present a numerical analysis to
indicate the size of the different corrections. We show that several
phenomenologically relevant quantities can be calculated consistently with
photons which couple only to the valence quarks, allowing the use of gluon
configurations produced without dynamical photons.Comment: 11 page
Dynamical fermions on anisotropic lattices
We report on our study of two-flavor full QCD on anisotropic lattices using
-improved Wilson quarks coupled with an RG-improved glue. The bare gauge
and quark anisotropies corresponding to the renormalized anisotropy
are determined as functions of and , using
the Wilson loop and the meson dispersion relation at several lattice cutoffs
and quark masses.Comment: Lattice2002(improve), 3 pages, 3 figure
Exploring QCD at small sea quark masses with improved Wilson-type quarks
We explore the region of small sea quark masses below in
two-flavor QCD using a mean-field improved clover quark action and an
RG-improved gauge action at fm on and lattices. We find that instability of the standard BiCGStab
algorithm at small quark masses can be mostly removed by the BiCGStab(DS-)
algorithm, which employs -th minimal residual polynomials with a dynamical
selection of . We also find singular spikes of in the HMC
algorithm at moderate values of . Nature of the spike is studied.
We also study finite-size effects and chiral properties of meson masses.Comment: 3 pages, 4 figures, Lattice2002(spectrum
Full QCD Algorithms towards the Chiral Limit
I discuss the behaviour of algorithms for dynamical fermions as the sea-quark
mass decreases. I focus on the Hybrid-Monte-Carlo (HMC) algorithm applied to
two degenerate flavours of Wilson fermions. First, I briefly review the
performance obtained in large scale HMC simulations. Then I discuss a modified
pseudo-fermion action for the HMC simulation that has been introduced three
years ago. I summarize recent results obtained with this pseudo-fermion action
by the QCDSF and the ALPHA collaborations. I comment on alternatives to the
HMC, like the Multiboson algorithm and variants of it.Comment: 7 pages, Lattice 2003 plenary talk, typos corrected, references
updated, discussion of the MB algorithm corrected/extende
Charmed-Baryon Spectroscopy from Lattice QCD with N_f=2+1+1 Flavors
We present the results of a calculation of the positive-parity ground-state
charmed-baryon spectrum using 2+1+1 flavors of dynamical quarks. The
calculation uses a relativistic heavy-quark action for the valence charm quark,
clover-Wilson fermions for the valence light and strange quarks, and HISQ sea
quarks. The spectrum is calculated with a lightest pion mass around 220 MeV,
and three lattice spacings (a \approx 0.12 fm, 0.09 fm, and 0.06 fm) are used
to extrapolate to the continuum. The light-quark mass extrapolation is
performed using heavy-hadron chiral perturbation theory up to O(m_pi^3) and at
next-to-leading order in the heavy-quark mass. For the well-measured charmed
baryons, our results show consistency with the experimental values. For the
controversial J=1/2 Xi_{cc}, we obtain the isospin-averaged value
M_{Xi_{cc}}=3595(39)(20)(6) MeV (the three uncertainties are statistics,
fitting-window systematic, and systematics from other lattice artifacts, such
as lattice scale setting and pion-mass determination), which shows a 1.7 sigma
deviation from the experimental value. We predict the yet-to-be-discovered
doubly and triply charmed baryons Xi_{cc}^*, Omega_{cc}, Omega_{cc}^* and
Omega_{ccc} to have masses 3648(42)(18)(7) MeV, 3679(40)(17)(5) MeV,
3765(43)(17)(5) MeV and 4761(52)(21)(6) MeV, respectively.Comment: 23 pages, 14 figure
No severe and global X chromosome inactivation in meiotic male germline of Drosophila
This article is a response to Vibranovski et al
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