Optical data transmission technology for fixed and drag-on STS payloads umbilicals. Volume 1: Executive summary

The feasibility of using optical data handling methods to transmit payload checkout and telemetry is discussed. Optical communications are superior to conventional communication systems for the following reasons: high data capacity optical channels; small and light weight optical cables; and optical signal immunity to electromagnetic interference. Task number one analyzed the ground checkout data requirements that may be expected from the payload community. Task number two selected the optical approach based on the interface requirements, the location of the interface, the amount of time required to reconfigure hardware, and the method of transporting the optical signal. Task number three surveyed and selected optical components for the two payload data link. Task number four makes a qualitative comparison of the conventional electrical communication system and the proposed optical communication system

Measurement of differential cross-sections of a top quark produced in association with a W boson at √s=13 TeV with ATLAS

The differential cross-section for the production of a W boson in association with a top quark is measured for several particle-level observables. The measurements are performed using 36.1fb−1 of pp collision data collected with the ATLAS detector at the LHC in 2015 and 2016. Differential cross-sections are measured in a fiducial phase space defined by the presence of two charged leptons and exactly one jet matched to a b-hadron, and are normalised with the fiducial cross-section. Results are found to be in good agreement with predictions from several Monte Carlo event generators

Search for direct top squark pair production in final states with two leptons in √s=13 TeV pp collisions with the ATLAS detector

The results of a search for direct pair production of top squarks in events with two opposite-charge leptons (electrons or muons) are reported, using 36.1 fb−1 of integrated luminosity from proton–proton collisions at √s=13 TeV collected by the ATLAS detector at the Large Hadron Collider. To cover a range of mass differences between the top squark t~ and lighter supersymmetric particles, four possible decay modes of the top squark are targeted with dedicated selections: the decay t~→bχ~1± into a b-quark and the lightest chargino with χ~1±→Wχ~10 , t~→tχ~10 into an on-shell top quark and the lightest neutralino, the three-body decay t~→bWχ~10 and the four-body decay t~→bℓνχ~10. No significant excess of events is observed above the Standard Model background for any selection, and limits on top squarks are set as a function of the t~ and χ~01 masses. The results exclude at 95% confidence level t~ masses up to about 720 GeV, extending the exclusion region of supersymmetric parameter space covered by previous searches

Gluing silicon with silicone

Problems and solutions concerning the gluing of silicon detectors are discussed. The R and D work for the HERA-B vertex detector system led to gluing studies with epoxy and silicone based adhesives used on ceramics and carbon fibre. The HERA-B solution using a silicone glue is presented. (orig.)11 refs.SIGLEAvailable from TIB Hannover: RR 2916(97-20) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman

Measurement of the B(s)0 lifetime

The lifetime of the Bs0 has been measured in a data sample of 8890000 hadronic events recorded with the ALEPH detector at LEP. After background subtraction 30.8 ± 6.9 events are attributed to the semileptonic decay of the Bs0 to a Ds− and an opposite-sign lepton. A maximum-likelihood fit to the distribution of the proper times of these events yields a Bs0 lifetime of τBs = 1.92−0.35+0.45 ± 0.04 ps

PRODUCTION OF CHARMED MESONS IN Z DECAYS

The production of charmed mesons D0(-), D+/-, and D*+/- is studied in a sample of 478,000 hadronic Z decays. The production rates are measured to be GAMMA(Z --> D*+/- X)/GAMMA(had) = 0.187 +/- 0.015 (exp.) +/- 0.013 (BR), GAMMA(Z --> D+/- X) = 0.251 +/- 0.026 (exp.) +/- 0.025 (BR), GAMMA(Z --> D0(-) X)/GAMMA(had) = 0.518 +/- 0.052 (exp.) +/- 0.035 (BR), where the errors from this analysis are separated from those coming from the D branching ratios (BR). The D *+/momentum distribution is extracted separately for Z --> cc and Z --> bbBAR events with the help of event shape variables. It is consistent with the prediction of the JETSET Monte Carlo program after adjustment of the charm fragmentation function. Constraining the shape of the Z --> bbBAR contribution, the average fraction of the beam energy taken by a D* meson produced in the fragmentation of a charm quark is extracted by a parametric fit to be [X(E)]c = 0.495 +/- 0.011 +/- 0.007. Evidence for D**0 (D1(2420)0 and/or D2*(2460)0) production is found in the D*+/-pi-/+ channel, accounting for a fraction (18 +/- 5 +/- 2)% of all D*+/- production. The relative production of vector and pseudoscalar mesons is dicussed, together with the possible effects of D** production. The c-quark forward-backward Z-pole asymmetry is determined from that of high momentum D*+/- to be A(FB)0,c = (7.7 +/- 4.4)%

K0 production in one prong tau decays

From a sample of about 75000 τ decays identified with the ALEPH detector, K0 production in 1-prong hadronic decays is investigated by tagging the KL0 component in a hadronic calorimeter. Results are given for the final states ντh−K0 and ντh−π0K0 where the h− is separated into π and K contributions by means of the dE/dx measurement in in the central detector. The resulting branching ratios are: (Bτ → ντπ−K0) = (0.88±0.14±0.09)%, (Bτ → ντK−K0) = (0.29±0.12±0.03)%, (Bτ → ντπ−π0K0) = (0.33±0.14±0.07)% aand (Bτ → ντK−π0K0) = (0.05±0.05±0.01)%. The K∗ decay rate in the K0π channel agrees with that in the Kπ0 mode: the combined value for the branching ratio is

Observation of mono - jet events and tentative interpretation

A data sample corresponding to almost two million hadronic Z decays collected by the ALEPH detector at LEP has been searched for monojet events. Three events were found, in agreement with the expectation from the process e+e- --> gamma*nunuBAR, with gamma* --> ffBAR. Two events are hadronic, the third one being an e+e- pair. All monojet masses are in excess of 3 GeV/c2, and two of the events have large transverse momenta: 18.5 and 20.3 GeV/c. These kinematic characteristics are quite unlikely in the process e+e- --> gamma*nunuBAR. The probability of their occurrence increases substantially when processes involving further Z or W exchanges are taken into account, but still remains at the 5% level

Search for excited neutrinos in Z decay

Excited neutrinos decaying into a neutrino and a photon are searched for in the ALEPH detector at LEP. No evidence is found for Z decay into v̄v∗ or v̄∗v∗ final states. Upper limits are derived on excited neutrino couplings up to excited neutrino masses close to the Z mass. Lower limits on the v∗ mass, independent of the v∗ decay modes, are deduced from the total Z width