Electroweak measurements in electron–positron collisions at w-boson-pair energies at lep

Contains fulltext : 121524.pdf (preprint version ) (Open Access

Inclusive Σ+\Sigma^+ and Σ0\Sigma^0 Production in Hadronic Z Decays

We report on measurements of the inclusive production rate of $\Sigma^+$ and $\Sigma^0$ baryons in hadronic Z decays collected with the L3 detector at LEP. The $\Sigma^+$ baryons are detected through the decay $\Sigma^+ \rightarrow {\rm p} \pi^0$, while the $\Sigma^0$ baryons are detected via the decay mode $\Sigma^0 \rightarrow \Lambda \gamma$. The average numbers of $\Sigma^+$ and $\Sigma^0$ per hadronic Z decay are measured to be: \begin{eqnarray*} \left N_{\Sigma^+} \right + \left N_{\bar{\Sigma}^+} \right & = & 0.114 \pm 0.011_{\mbox{\it \small stat}} \pm 0.009_{\mbox{\it \small syst}} \\ \left N_{\Sigma^0} \right + \left N_{\bar{\Sigma}^0} \right & = & 0.095 \pm 0.015_{\mbox{\it \small stat}} \pm 0.013_{\mbox{\it \small syst}} \ \mbox{.} \end{eqnarray*} These rates are found to be higher than the predictions from Monte Carlo hadronization models and analytical parameterizations of strange baryon production

Comparison of energy flows in deep inelastic scattering events with and without a large rapidity gap

Energy flows in deep inelastic electron-proton scattering are investigated at a center-of-mass energy of 296 GeV for the range Q2 greater-than-or-equal-to 10 GeV2 using the ZEUS detector. A comparison is made between events with and without a large rapidity gap between the hadronic system and the proton direction. The energy flows, corrected for detector acceptance and resolution, are shown for these two classes of events in both the HERA laboratory frame and the Breit frame. From the differences in the shapes of these energy flows we conclude that QCD radiation is suppressed in the large-rapidity-gap events compared to the events without a large rapidity gap

Search for Charged Higgs bosons: Combined Results Using LEP Data

The four LEP collaborations, ALEPH, DELPHI, L3 and OPAL, have searched for pair-produced charged Higgs bosons in the framework of Two Higgs Doublet Models (2HDMs). The data of the four experiments are statistically combined. The results are interpreted within the 2HDM for Type I and Type II benchmark scenarios. No statistically significant excess has been observed when compared to the Standard Model background prediction, and the combined LEP data exclude large regions of the model parameter space. Charged Higgs bosons with mass below 80 GeV/c^2 (Type II scenario) or 72.5 GeV/c^2 (Type I scenario, for pseudo-scalar masses above 12 GeV/c^2) are excluded at the 95% confidence level