We determine the masses of the light and the strange quarks in the
MS
-scheme using our high-statistics lattice simulation of QCD with dynamical Wilson fermions. For the light quark mass we find
m
...light
MS
(2
GeV) = 2.7 (2)
MeV
, which is lower than in quenched simulations. For the strange quark, in a sea of two dynamical light quarks, we obtain
m
strange
MS
(2
GeV) = 140(20)
MeV
.
SESAM and T χL results for Wilson action—A status report Lippert, Th; Bali, G.; Eicker, N. ...
Nuclear physics. B, Proceedings supplement/Nuclear physics. B, Proceedings supplements,
1998, 1998-1-00, Letnik:
60, Številka:
1
Journal Article
Recenzirano
Odprti dostop
Results from two studies of full QCD with two flavours of dynamical Wilson fermions are presented. At
β = 5.6, the region
0.83
>
m
x
m
p
>
0.56
at
m
x
a
>
(
0.23
L
)
−
1
is explored. The SESAM ...collaboration has generated ensembles of about 200 statistically independent configurations on a 16
3 × 32-lattice at three different
k-values and is entering the final phase of data analysis. The T
χL simulation on a 24
3 × 40-lattice at two
k-values has reached half statistics and data analysis has started recently, hence most results presented here are preliminary. The focus of this report is threefold: (
i) we demonstrate that algorithmic improvements like fast Krylov solvers and parallel preconditioning recently introduced can be put into practise in full QCD simulations, (
ii) we present encouraging observations as to the critical dynamics of the Hybrid Monte Carlo algorithm in the approach to the chiral limit, (
iii) we mention signal improvements of noisy estimator techniques for disconnected diagrams to the
π-
N σ term, and (iv) we report on SESAM's results for light hadron spectrum, light quark masses, and heavy quarkonia.
In a full QCD lattice study with
N
f
= 2 Wilson fermions, we seek to optimize the signals for the disconnected contributions to the matrix element of flavour-singlet operators between nucleon states, ...which are indicative for sea quark effects. We demonstrate, in form of a fluctuation analysis to the noisy estimator technique, that — in order to achieve a tolerable signal to noise-ratio in full QCD — it is advantageous to work with a
Z
2-
noise source rather than to rely only on gauge invariance to cancel non-gauge-invariant background. In the case of the
πN
σ-
term, we find that 10
Z
2-
noise sources suffice on our sample (about 150 independent QCD configurations at
β = 5.6
on 16
3 × 32
with
κ
sea
= 0.157, equivalent to
M
π
/
M
ϱ
= 0.76 (1), to achieve decent signals and adequate fluctuations, rather than 300 such sources as recently used in quenched simulations.
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