Using the ARGUS detector at the
e
+
e
− storage ring DORIS II, we have searched for the real and imaginary part of the electric dipole formfactor
d
τ
of the
τ lepton in the production of
τ pairs at
q
...2=100
GeV
2
. This is the first direct measurement of this
CP
violating formfactor. We applied the method of optimised observables which takes into account all available information on the observed
τ decay products. No evidence for
CP
violation was found, and we derive the following results:
Re(d
τ)=(1.6±1.9)·10
−16
e
cm
and
Im(d
τ)=(−0.2±0.8)·10
−16
e
cm
, where statistical and systematic errors have been combined.
A maximum likelihood analysis of ARGUS data on two-photon production of
π
+
π
+
π
0
π
0
π
−
π
− is presented. A small fraction of events is due to the production of omega pairs. The
γγ →
ωω cross ...section has its maximum value close to threshold.
Using the ARGUS detector at the e
+e
− storage ring DORIS II at DESY, we have searched for decays
b →
s
gluon through full reconstruction of a whole event. Two B
B
decays were found with one of B ...meson decaying into a final state without charmed particles. We also obtained an upper limit of
Br(B
+ →
τ
+
ν
τ
) of 1.04% at 90%
CL.
Using the detector ARGUS at the
e
+
e
− storage ring DORIS II at DESY, we have observed the decays
Λ
c
+ →
Ξ
−
K
+
π
+ and
Λ
c
+ → Ξ
∗0K
+
and obtained evidence for the decay
Ξ
c
0 →
ΛK
s
0. All ...three of these decays are of interest as they provide information about
W-exchange processes. The products of cross sections and branching ratios for
Λ
c
+ →
Ξ
−
K
+
π
+ and
Λ
c
+ → Ξ
∗0K
+
are (1.7±0.3±0.3) pb and (0.6±0.2±0.1) pb, respectively, which implies that (35±17) % of the
Ξ
−
K
+
π
+ final state is generated through a two-body decay via intermediate
W-exchange. The product of production cross section and branching ratio for
Ξ
c
0 →
Λ
K
s
0 is (2.1 ± 1.0 ± 0.6) pb.
Using the ARGUS detector at the
e
+
e
− storage ring DORIS II, we have measured the semileptonic branching ratios of the
D
0 meson to be
Br(
D
0 →
e
+
ν
e
X) = (6.9 ± 0.3 ± 0.5) % and
Br(
D
0 →
μ
+
ν
...μ
X) = (6.0 ± 0.7 ± 1.2) %, and the semileptonic branching ratio of the charmed hadron mixture from
e
+
e
− annihilation around 10 GeV to be
Br(
c →
e
+
ν
e
X) = (9.6 ± 0.4 ± 1.1) %.
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