Measurement of the Strong Coupling alpha s from Four-Jet Observables in e+e- Annihilation

Data from e+e- annihilation into hadrons at centre-of-mass energies between 91 GeV and 209 GeV collected with the OPAL detector at LEP, are used to study the four-jet rate as a function of the Durham algorithm resolution parameter ycut. The four-jet rate is compared to next-to-leading order calculations that include the resummation of large logarithms. The strong coupling measured from the four-jet rate is alphas(Mz0)= 0.1182+-0.0003(stat.)+-0.0015(exp.)+-0.0011(had.)+-0.0012(scale)+-0.0013(mass) in agreement with the world average. Next-to-leading order fits to the D-parameter and thrust minor event-shape observables are also performed for the first time. We find consistent results, but with significantly larger theoretical uncertainties.Comment: 25 pages, 15 figures, Submitted to Euro. Phys. J.

Higher harmonic anisotropic flow measurements of charged particles in Pb-Pb collisions at 2.76 TeV

We report on the first measurement of the triangular $v_3$, quadrangular $v_4$, and pentagonal $v_5$ charged particle flow in Pb-Pb collisions at 2.76 TeV measured with the ALICE detector at the CERN Large Hadron Collider. We show that the triangular flow can be described in terms of the initial spatial anisotropy and its fluctuations, which provides strong constraints on its origin. In the most central events, where the elliptic flow $v_2$ and $v_3$ have similar magnitude, a double peaked structure in the two-particle azimuthal correlations is observed, which is often interpreted as a Mach cone response to fast partons. We show that this structure can be naturally explained from the measured anisotropic flow Fourier coefficients.Comment: 10 pages, 4 figures, published version, figures at http://aliceinfo.cern.ch/ArtSubmission/node/387

Local convective heat flux to evaporating water droplets in micro-g to 2-g

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Δ\Delta(1232) Dalitz decay in proton-proton collisions at T=1.25 GeV measured with HADES at GSI

We report on the investigation of Δ(1232) production and decay in proton-proton collisions at a kinetic energy of 1.25 GeV measured with HADES. Exclusive dilepton decay channels ppe+e− and ppe+e−γ have been studied and compared with the partial-wave analysis of the hadronic ppπ0 channel. They allow to access both Δ+→pπ0(e+e−γ) and Δ+→pe+e− Dalitz decay channels. The perfect reconstruction of the well-known π0 Dalitz decay serves as a proof of the consistency of the analysis. The Δ Dalitz decay is identified for the first time and the sensitivity to N-Δ transition form factors is tested. The Δ(1232) Dalitz decay branching ratio is also determined for the first time; our result is (4.19 ± 0.62 syst. ± 0.34 stat.) ×10−5, albeit with some model dependence.Peer Reviewe

Search for excited quarks in the gamma plus jet final state in proton-proton collisions at root s=8 TeV

A search for excited quarks decaying into the gamma + jet final state is presented. The analysis is based on data corresponding to an integrated luminosity of 19.7 fb(-1) collected by the CMS experiment in proton-proton collisions at root s = 8 TeV at the LHC. Events with photons and jets with high transverse momenta are selected and the gamma + jet invariant mass distribution is studied to search for a resonance peak. The 95% confidence level upper limits on the product of cross section and branching fraction are evaluated as a function of the excited quark mass. Limits on excited quarks are presented as a function of their mass and coupling strength; masses below 3.5 TeV are excluded at 95% confidence level for unit couplings to their standard model partners