The new wave of the APE project: APEmille Bartoloni, A.; Battista, C.; Bellacci, M. ...
Nuclear physics. Section B, Proceedings supplement,
04/1995, Volume:
42, Issue:
1-3
Journal Article
Peer reviewed
We describe APEmille, the latest generation of the APE parallel processors. This machine, an evolution of the APE100 concept, is very efficient for LGT simulations as well as for a broader class of ...applications requiring massive floating point computations. Several new features characterise this evolution. In particular local addressing capabilities are added to all computing nodes. APEmille also exhibits a higher degree of integration with a network of workstations acting as a global host system. An APEmille system in the Teraflops range will be completed in three-four years. The architecture proposed in this paper is being currently simulated and evaluated.
We report on the measurement of the direct emission (DE) and interference (INT) terms of the
K
±
→
π
±
π
0
γ
decay by the NA48/2 experiment at the CERN SPS. From the data collected during 2003 and ...2004 about 600k such decay candidates have been selected. The relative amounts of DE and INT with respect to the internal bremsstrahlung (IB) contribution have been measured in the range
MeV:
where
is the kinetic energy of the charged pion in the kaon rest frame. This is the first observation of an interference term in
K
±
→
π
±
π
0
γ
decays, thus allowing the normalised electric and magnetic amplitudes to be measured, giving
X
E
=(−24±6) GeV
−4
, and
X
M
=(254±9) GeV
−4
.
In addition, a limit on the CP violating asymmetry in the
K
+
and
K
−
branching ratios for this channel has been determined to be less than 1.5×10
−3
at 90% confidence level.
We present numerical results obtained in full QCD with 2 flavors of Wilson fermions. We discuss the relation between the phase of Polyakov loops and the sea quarks boundary conditions. We report ...preliminary results about the HMC autocorrelation of the hadronic masses, on a 163 × 32 lattice volume, at β = 5.55 with ksea = 0.1570.
A
bstract
A sample of 65210
K
±
→
π
0
π
0
e
±
ν
(K
e4
00
) decay candidates with 1% background contamination has been collected in 2003-2004 by the NA48/2 collaboration at the CERN SPS. A study of ...the differential rate provides the first measurement of the hadronic form factor variation in the plane (
M
ππ
2
,
M
eν
2
) and brings evidence for a cusp-like structure in the distribution of the squared
π
0
π
0
invariant mass around
4
m
π
+
2
. Exploiting a model independent description of this form factor, the branching ratio, inclusive of radiative decays, is obtained using the
K
±
→
π
0
π
0
π
±
decay mode as normalization. It is measured to be BR(K
e4
00
) = (2.552 ± 0.010
stat
± 0.010
syst
± 0.032
ext
) × 10
−5
, which improves the current world average precision by an order of magnitude while the 1.4% relative precision is dominated by the external uncertainty from the normalization mode. A comparison with the properties of the corresponding mode involving a
π
+
π
−
pair (K
e4
+ −
) is also presented.
We report the results from a study of the full sample of ∼6.031×10
7
K
±
→
π
±
π
0
π
0
decays recorded by the NA48/2 experiment at the CERN SPS. As first observed in this experiment, the
π
0
π
0
...invariant mass (
M
00
) distribution shows a cusp-like anomaly in the region around
M
00
=2
m
+
, where
m
+
is the charged pion mass. This anomaly has been interpreted as an effect due mainly to the final state charge exchange scattering process
π
+
π
−
→
π
0
π
0
in
K
±
→
π
±
π
+
π
−
decay. Fits to the
M
00
distribution using two different theoretical formulations provide the presently most precise determination of
a
0
−
a
2
, the difference between the
π
π
S-wave scattering lengths in the isospin
I
=0 and
I
=2 states. Higher-order
π
π
rescattering terms, included in the two formulations, allow also an independent, though less precise, determination of
a
2
.
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