Bose-Einstein Correlations of Three Charged Pions in Hadronic Z^0 Decays

Bose-Einstein Correlations (BEC) of three identical charged pions were studied in 4 x 10^6 hadronic Z^0 decays recorded with the OPAL detector at LEP. The genuine three-pion correlations, corrected for the Coulomb effect, were separated from the known two-pion correlations by a new subtraction procedure. A significant genuine three-pion BEC enhancement near threshold was observed having an emitter source radius of r_3 = 0.580 +/- 0.004 (stat.) +/- 0.029 (syst.) fm and a strength of \lambda_3 = 0.504 +/- 0.010 (stat.) +/- 0.041 (syst.). The Coulomb correction was found to increase the \lambda_3 value by \~9% and to reduce r_3 by ~6%. The measured \lambda_3 corresponds to a value of 0.707 +/- 0.014 (stat.) +/- 0.078 (syst.) when one takes into account the three-pion sample purity. A relation between the two-pion and the three-pion source parameters is discussed.Comment: 19 pages, LaTeX, 5 eps figures included, accepted by Eur. Phys. J.

First Measurement of Z/gamma* Production in Compton Scattering of Quasi-real Photons

We report the first observation of Z/gamma* production in Compton scattering of quasi-real photons. This is a subprocess of the reaction e+e- to e+e-Z/gamma*, where one of the final state electrons is undetected. Approximately 55 pb-1 of data collected in the year 1997 at an e+e- centre-of-mass energy of 183 GeV with the OPAL detector at LEP have been analysed. The Z/gamma* from Compton scattering has been detected in the hadronic decay channel. Within well defined kinematic bounds, we measure the product of cross-section and Z/gamma* branching ratio to hadrons to be (0.9+-0.3+-0.1) pb for events with a hadronic mass larger than 60 GeV, dominated by (e)eZ production. In the hadronic mass region between 5 GeV and 60 GeV, dominated by (e)egamma* production, this product is found to be (4.1+-1.6+-0.6) pb. Our results agree with the predictions of two Monte Carlo event generators, grc4f and PYTHIA.Comment: 18 pages, LaTeX, 5 eps figures included, submitted to Physics Letters

Measurement of the Production Rate of Charm Quark Pairs from Gluons in Hadronic Z0Z^{0} Decays

The rate of secondary charm-quark-pair production has been measured in 4.4 million hadronic Z0 decays collected by OPAL. By selecting events with three jets and tagging charmed hadrons in the gluon jet candidate using leptons and charged D* mesons, the average number of secondary charm-quark pairs per hadronic event is found to be (3.20+-0.21+-0.38)x10-2

Total hadronic cross-section of photon-photon interactions at OPAL

The total hadronic cross-section sigma /sub gamma gamma / for the interaction of real photons, gamma gamma to hadrons, is extracted from a measurement of the cross-section of the process e/sup +/e/sup -/ to e/sup +/e/sup -/ gamma * gamma * to e/sup +/e/sup -/+hadrons using a luminosity function for the photon flux and form factors for extrapolating to Q/sup 2/=0. The data was taken with the OPAL detector at LEP at e/sup +/e/sup -/ centre-of-mass energies square root (s/sub ee/)=161 GeV, 172 GeV and 183 GeV. In the energy range 10<or=W<or=110 GeV the total hadronic gamma gamma cross-section sigma /sub gamma gamma / is consistent with the Regge behaviour of the total cross-section observed in gamma p and hadron-hadron interactions. (23 refs)

Optimized detection and decoding of 4D signals for the nonlinear fiber-optical channel

We review multistage bit-wise coded modulation to overcome the rate-loss encountered in typical bit-interleaved coded modulation with non-Gray 4D signal sets. Optimized decoding metrics are assessed using an end-to-end perturbation-based fiber model

Notes on a stick: use and acceptability of woman-held maternity notes

OBJECTIVE: To provide expectant mothers with a USB stick containing their maternity notes, including ultrasound images, and to assess its use and acceptability versus conventional care with exclusively hospital-held notes. STUDY DESIGN: USB group: 200 women attending Zurich University Hospital Obstetrics Department for antenatal-to-postnatal care in 2006-2007. Controls: 200 women attending the Obstetrics Department for delivery only, after receiving conventional antenatal care elsewhere. Women were interviewed using an essentially identical postpartum questionnaire for each group, with minor wording differences. Main outcome measures: Overall satisfaction with pregnancy and delivery, feeling of safety, interest in the pregnancy, partner involvement, usefulness of USB stick in emergencies, impact on smoking behaviour, data confidentiality concerns, pregnancy and infant outcome. Stepwise multiple regression was used to identify determinants of overall impressions of pregnancy and delivery. RESULTS: Of the USB group, 98.5% wished to repeat the USB experience in a subsequent pregnancy; of the controls, 86.5% would have appreciated the experience, and 18.0% could think of situations in their pregnancy (vacation, emergencies) where the stick would have helped; 7.5% of the USB group shared their stick data with a doctor outside the Department, and 80.5% felt safer having the stick available. Along with preterm delivery and mode of delivery, the USB stick was a significant determinant of the overall positive impression of pregnancy. Primary caesarean section was (inexplicably) more frequent in the USB group. CONCLUSION: The questionnaire confirmed that issuing women with their maternity notes on a USB stick is a major advance in patient empowerment, satisfaction and safety

External high-Quality-factor Resonator tunes up nuclear magnetic resonance

The development of powerful sensors for the detection of weak electromagnetic fields is crucial for many spectroscopic applications, in particular for nuclear magnetic resonance (NMR). Here, we present a comprehensive theoretical model for boosting the NMR signal-to-noise ratio, validated by liquid-state 1H, 129Xe and 6Li NMR experiments at low frequencies, using an external resonator with a high quality-factor combined with a low-quality-factor input coil. In addition to an enhanced signal-to-noise ratio, this approach exhibits striking features such as a high degree of flexibility with respect to input coil parameters and a square-root dependence on the sample volume, and signifies an important step towards compact NMR spectroscopy at low frequencies with small and large coils

Measurement of the τ−→h − h + h − v τ and τ−→h − h + h −≥1π0 v τ branching ratios

Contains fulltext : 124548.pdf (preprint version ) (Open Access