C. Frankl

Measurement of the polarization in the decay B → J/ψK∗

Abstract Polarization in the exclusive decay B → J/ψK ∗ was measured using the ARGUS detector at the e+e− storage ring DORIS II. The ratio of the transverse to the total decay width was found to be ΓT/Γ = 0.03±0.16±0.15. This measurement demonstrates that the B 0 → J/ψK ∗0 decay channel can be effectively used for CP violation studies.

Measurement of the polarization in the decay B ---> J / psi K*

Abstract Polarization in the exclusive decay B → J/ψK ∗ was measured using the ARGUS detector at the e+e− storage ring DORIS II. The ratio of the transverse to the total decay width was found to be ΓT/Γ = 0.03±0.16±0.15. This measurement demonstrates that the B 0 → J/ψK ∗0 decay channel can be effectively used for CP violation studies.

Determination of the structure of τ decays in the reaction e+e− → τ+τ− → ϱ+vτϱ−vτ and a precision measurement of the τ-neutrino helicity

Abstract Using the ARGUS detector at the DORIS II storage ring we have investigated the Lorentz structure of the electroweak interaction in semi-hadronic τ decays. Spin correlations in the process e + e − → τ + τ − → v τ π + π 0 v τ π − π 0 are exploited for a measurement of the normalized product of the vector ( g V ) and axial vector ( g A ) couplings of the τ lepton, γin AV = 2 Re {g A g V ∗ } (|g V | 2 ) . The correlations are sensitive to the product of the couplings in both τ decays: γ AV 2 = γ AV (τ − → ν τ W − ) AV = −h(v τ )h( v τ ) . The measured value, γ AV 2 = 1.044±0.057±0.060, determines the relative sign of the neutrino helicities. Assuming CP invariance, the absolute value | γ AV | = 1.022±0.028±0.030 was found to be incellent agreement with the Standard Model. The contribution of scalar ( g s ) or pseudoscalar ( g P ) couplings was also investigated. No evidence for a scalar-like coupling was found.

Determination of the radiative decay width of the ηc meson

Abstract An analysis of the reaction γ → η c was performed in five different decay channels of the η c : K S 0 K ± π ∓ , K + K − π + π − , 2 π + 2 π − , φφ and 2 K + 2 k − . A value Γ γγ ( η c ) = (11.3±4.2) keV was obtained for the radiative decay width by combining the results from the first four channels. Using our result on the two-photon width we also determined the branching ratio for the decay η c → 2 K + 2 K − .

Measurement of the absolute branching fractions for D0 decays into K− π+, K− π+ π+ π−, K0 π+ π−

Abstract Using the ARGUS detector at the e+ e− storage ring DORIS II we have measured the absolute branching ratios of the D0 meson, Br(D0→K− π+)=(3.41±0.12±0.28)%, Br(D0→K− π+ π+ π−)=(6.80± 0.27±0.57)%, and Br (D 0 → K 0 π + π − )=(5.03±0.39±0.49)% .

Study ofD0 andD+ decays into final states with two or three kaons

Using the ARGUS detector at thee+e− storage ring DORIS II, we have studied Cabibbo-suppressedD0 decay modes resulting in theK+K−π+π− final state and two-bodyD0 decay modes with a ϕ meson in the final state. TheBR(D0→KS0KS0π+π− was measured for the first time. We also present a measurement of theD+→KS0KS0K+ branching ratio. The values are compared with other experimental results and model predictions.

Tau decays into K* mesons

AbstractUsing the ARGUS detector at the storage ring DORIS II we have measured τ decays into three charged mesons containingK* mesons. Exploiting the good particle identification capabilities of the detector we have determined the following branching ratios:

Measurement of the absolute branching fractions for D0 decays into K- pi+, K- pi+ pi+ pi-, anti-K0 pi+ pi-

Br\left( {\tau ^ - \to \overline {K^{*0} } \pi ^ - v_\tau } \right) = \left( {0.25 \pm 0.10 \pm 0.05} \right)\%