Measurement of the Inclusive and Fiducial Cross-Section of Single Top-Quark tt-Channel Events in pppp Collisions at s\sqrt{s} = 8 TeV

This article presents the measurement of a $t$-channel single top-quark production fiducial cross-section in the lepton+jets channel with 20.3 fb$^{-1}$ of 8 TeV data using a neural-network discriminant. A fiducial cross-section quoted within the detector acceptance of $\sigma_{\rm fid} = 3.37 \pm 0.05 \, (\mathrm{stat.}) \pm 0.47 \, (\mathrm{syst.}) \pm 0.09 \, (\mathrm{lumi.})~\text{pb}$ is obtained. The total inclusive $t$-channel cross-section is calculated using the acceptance predicted by various Monte Carlo generators. If the acceptance from the a MC@NLO + Herwig event generator is used, a value of $\sigma_t = 82.6 \pm 1.2 \, (\mathrm{stat.}) \pm 11.4 \, (\mathrm{syst.}) \pm 3.1 \, (\mathrm{PDF}) \pm 2.3 \, (\mathrm{lumi.})~\text{pb}$ is obtained, consistent with the Standard Model prediction. Using the ratio of the measured inclusive cross-section to the predicted cross-section and assuming that the top-quark-related CKM matrix elements obey the relation $|V_{tb}|\gg |V_{ts}|, |V_{td}|$, the coupling strength at the $W$-$t$-$b$ vertex is determined to be $|V_{tb}|=0.97^{+0.09}_{-0.10}$. Assuming that $|V_{tb}|\leq 1$ a lower limit of $|V_{tb}|>0.78$ is obtained at the 95% confidence level.Comment: 4 pages, 3 figures, Top 2014 Conferencs Proceeding

One year into office, Austria’s grand coalition is under pressure from the growing popularity of the far-right Freedom Party

Austria held a general election in 2013, with the centre-left SPÖ and centre-right ÖVP ultimately forming a ‘grand coalition’. Philipp Decker assesses the government’s first year in office and where it stands in the context of current public opinion in Austria. He writes that the two mainstream parties are increasingly coming under pressure from the Freedom Party of Austria (FPÖ), which has effectively positioned itself in opposition to the governing parties on issues such as the military, European integration, and the government’s approach to Islam

Scanning Quantum Dot Microscopy

Interactions between atomic and molecular objects are to a large extent defined by the nanoscale electrostatic potentials which these objects produce. We introduce a scanning probe technique that enables three-dimensional imaging of local electrostatic potential fields with sub-nanometer resolution. Registering single electron charging events of a molecular quantum dot attached to the tip of a (qPlus tuning fork) atomic force microscope operated at 5 K, we quantitatively measure the quadrupole field of a single molecule and the dipole field of a single metal adatom, both adsorbed on a clean metal surface. Because of its high sensitivity, the technique can record electrostatic potentials at large distances from their sources, which above all will help to image complex samples with increased surface roughness.Comment: main text: 5 pages, 4 figures, supplementary information file: 4 pages, 2 figure

Was die Physik mit Lehramtsstudierenden macht

Im Rahmen des Projekts „Ko-WADiS“ wurde in einem domänenübergreifenden Ansatz die Erkenntnisgewinnungskompetenz von Lehramtsstudierenden und Fachstudierenden in den drei naturwissenschaftlichen Fächern Biologie, Chemie und Physik modelliert. Die Besonderheit dieses Projektansatzes, durch das es sich auch gegenüber anderen Studien abgrenzt, ist die postulierte fachübergreifende Erkenntnisgewinnungskompetenz. Dazu wurde ein Kompetenzmodell mit sieben Zellen adaptiert. Die hier dargestellten Ergebnisse beziehen sich auf die ausschließlich auf Physikstudierende (Lehramt und Mono). Die Auswertung erfolgt mit einem 1PL (Rasch)-Model. Es zeigt sich, dass bestimmte Effekte, die für die Gesamtkohorte nachgewiesen werden konnten [1], nicht für die Physikkohorte gelten