The impact of the ARGUS experiment to elementary particle physics is reviewed. More than ten years of data taking has allowed ARGUS to contribute significantly to our understanding of beauty and charmed hadrons, τ Leptons, ϒ mesons, ϒϒ interactions and fragmentation processes. In particular the ARGUS measurements of CKM matrix elements opened up a new window on the Standard Model.

We report a study of the decay τ−→τ−τ+τ−vτ using the ARGUS detector at the DORIS II storage ring. Tau pairs were produced bye+e− annihilation at centre-of-mass energies near 10 GeV. We have observed about 1,700 events, corresponding to a branching ratio for τ−→τ−τ+τ−vτ of (5.6±0.7)%. The dominant mode for this decay is observed to beρ0π− in aJ p =1+ spin state. Theρ0π− mass spectrum shows a broad enhancement near 1.10 GeV/c2, which has the properties expected for theA1.

Using the ARGUS detector at DORIS II, the decay of F+→K∗0K+, and the ratio BR(F+→K∗0K+)/BR(F+→ φπ+) is found to be 1.44±0.37. This is a substantial rate for a decay channel which cannot proceed via a colour-favoured diagram.

A search for two exotic decay modes of the ϒ(1S) meson has been made using the ARGUS detector at the e+e− storage ring DORIS II at DESY. The first was ϒ(1S) decays into weakly interacting particles, for which an upper limit of 2.3% at the 90% CL on the branching ratio is found. The second mode was ϒ(1S)→γa, where a is a neutral particle with mass less than 1.5GeV/c2, that either decays inside the detector or is sufficiently long-lived to escape detection. For short-lived particles a decaying into an e+e− pair, upper limits on the BR(ϒ(1S)→γa) of 3.1 × 10− at the 90% CL are found. The upper limit without restriction on the lifetime of a is found to be 1.3 × 10−3. Limits for other decay modes are also given.

Using the ARGUS detector at thee+e− storage ring DORIS II at DESY, we have studied the distribution of various topological quantities on the Υ(1S) resonance and in the nearby continuum. With the help of the second Fox-Wolfram moment we determine the two-jet contribution to direct Υ(1S) decays to be less than 5.3% with 95% confidence.

Using the ARGUS detector at the DORIS II e+e- storage ring, we have searched for gluinos (g), the supersymmetric partner of the gluon, by looking for secondary decay vertices in hadronic decays of χb(13P1) mesons. Events containing χb(13P1) states were selected by detecting the radiative transition from the ϒ (2S) in a data set corresponding to an integrated luminosity of 38.6 pb−1. The absence of secondary vertices from gluino decays into hadrons and a photino allows us to exclude gluinos in a mass range from 1 to 4.5 GeV/c2 and a lifetime range from 10−11 to 10−9 s.

Using the ARGUS detector at DORIS II, we have observed a signal of 36.7±8.0 events in the decay channel D0→Ks0φ. In the same data sample, we have observed the well established decay D0→Ks0π+π−, and find the ratio, Br(D)0→Ks0φ)Br(D)0→Ks0π+π−), to be 0.186±0.052. The substantial value of (0.99±0.32±0.17)% then derived for the branching ratio for D0→K0φ gives direct evidence that W exchange contributes D0 decay.

Using the ARGUS detector at the e+e− storage ring DORIS II, we have observed the colour suppressed decay B → Jψ X, with a branching ratio of (1.37+0.6−0.5)% for the mixture of charged and neutral B's produced on the ϒ(4S). From the momentum distribution of the Jψ we conclude that Br(B → Jψ X) < 0.7% (90% CL), for recoil masses, mx, less than 1 GeV/c2.

The production of antideuterons has been observed in electron-positron annihilations at center-of-mass energies around 10 GeV. Antideuterons have been identified unambiguously by their energy loss in the drift chamber, their time-of-flight and the pattern of their energy deposition in the shower counters of the ARGUS detector. The production rate in the momentum range (0.6−1.8) GeV/c is (1.6−0.7+1.0) × 10−5 per hadronic event.

Using the ARGUS detector at the e+e− storage ring DORIS II, we have measured the vτ energy spectrum in the decay π+π−π±vτ of τ leptons produced near s=10 GeV. From this energy spectrum, we derive an upper limit of m(vτ)<70MeVc2 at the 95% confidence level.

A search has been made for particles with charge Q = 13, Q = 23 and Q = 43 produced in e+e− annihilation using the ARGUS detector at the e+e− storage ring DORIS, operating at a centre of mass energy around 10 GeV. No candidate events were found in 84.5 pb−1 of collected data. Upper limits are established for the cross section for the production of fractionally charged particles with masses up to 4 GeVc2, improving on previously obtained limits.

We report the results of a search for monoenergetic photons in the decay of both theY(1S)- and theY(2S)-meson. Photons converted in the beam tube or the drift chamber inner wall, and photons detected with the barrel shower counters of the ARGUS detector, respectively, have been used in the analysis. No narrow peak is observed in the energy interval 0.5 GeV≦Ey≦4.0 GeV.

The ARGUS detector at the e+e− storage ring DORIS II has been used as a pair spectrometer to study the photon transitions in the reaction ϒ(2S)→γχb(13P2,1,0). Three photon lines were observed with energies (110.6±0.3±0.9) MeV, (131.7±0.3±1.1) MeV and (162.1±0.5±1.4) MeV, respectively. The corresponding branching ratios were found to be (9.8±2.1±2.4)%, (9.1±1.8±2.2)% and (6.4±1.4±1.6)%. Upper limits for full widths at the 90% confidence limit are 1.0 MeV for the χb(13P2) and 2.6 MeV for the other two states.

Using the ARGUS detector at thee+e− storage ring DORIS-II, we have observed the decays of γ(9,460) andΥ'(10,023) into muon pairs. The ratio of the two observed rates determines Bμμ(γ') largely independent of acceptance uncertainties and absolute luminosity calibration, ifBμμ(γ) is known. From data with an integrated luminosity of 6.11/pb on the γ and 9.93/pb on the γ, using the present world averageBμμ(γ)=(2.9±0.2)%, we obtainBμμ(γ)=(1.57±0.59±0.68)%.

We have investigated the ϒ→γττ using tagged ϒ mesons from the decay ϒ'→π+π−ϒ. The photon spectrum exhibits no monochromatic line corresponding to a narrow object decaying into a τ pair and is fully compatible with the expected background contributions. The branching ratio Br(ϒ→τ+τ− is determined to be (3.07±0.46±0.22)%.