Measurement of event shape distributions and moments in e+e- -> hadrons at 91-209 GeV and a determination of alpha_s

We have studied hadronic events from e+e- annihilation data at centre-of-mass energies from 91 to 209 GeV. We present distributions of event shape observables and their moments at each energy and compare with QCD Monte Carlo models. From the event shape distributions we extract the strong coupling alpha_s and test its evolution with energy scale. The results are consistent with the running of alpha_s expected from QCD. Combining all data, the value of alpha_s(M_Z) is determined to be alpha_s(M_Z) = 0.1191 +- 0.0005 (stat.) +- 0.0010 (expt.) +- 0.0011 (hadr.) +- 0.0044 (theo.). The energy evolution of the moments is also used to determine a value of alpha_s with slightly larger errors: alpha_s(M_Z) = 0.1223 +- 0.0005 (stat.) +- 0.0014 (expt.) +- 0.0016 (hadr.) +0.0054 -0.0036 (theo.).Comment: 63 pages 26 fi

Searches for Gauge-Mediated Supersymmetry Breaking Topologies in e+e- collisions at LEP2

In gauge-mediated supersymmetry (SUSY) breaking (GMSB) models the lightest supersymmetric particle (LSP) is the gravitino and the phenomenology is driven by the nature of the next-to-lightest SUSY particle (NLSP) which is either the lightest neutralino, the stau or mass degenerate sleptons. Since the NLSP decay length is effectively unconstrained, searches for all possible lifetime and NLSP topologies predicted by GMSB models in e+e- collisions are performed on the data sample collected by OPAL at centre-of-mass energies up to 209 GeV at LEP. Results independent of the NLSP lifetime are presented for all relevant final states including direct NLSP pair-production and, for the first time, also NLSP production via cascade decays of heavier SUSY particles. None of the searches shows evidence for SUSY particle production. Cross-section limits are presented at the 95% confidence level both for direct NLSP production and for cascade decays, providing the most general, almost model independent results. These results are then interpreted in the framework of the minimal GMSB (mGMSB) model, where large areas of the accessible parameter space are excluded. In the mGMSB model, the NLSP masses are constrained to be larger than 53.5 GeV/c^2, 87.4 GeV/c^2 and 91.9 GeV/c^2 in the neutralino, stau and slepton co-NLSP scenarios, respectively. A complete scan on the parameters of the mGMSB model is performed, constraining the universal SUSY mass scale Lambda from the direct SUSY particle searches: Lambda > 40, 27, 21, 17, 15 TeV/c^2 for messenger indices N=1, 2, 3, 4, 5 respectively, for all NLSP lifetimes.Comment: 4 pages, 2 figures. To appear in Proceedings of SUSY06, the 14th International Conference on Supersymmetry and the Unification of Fundamental Interactions, UC Irvine, California, 12-17 June 200

Flavour Independent hA Search and Two Higgs Doublet Model Interpretation of Neutral Higgs Boson Searches at LEP

Upper limits on the cross-section of the pair-production process e+e- -> h0A0 assuming 100% decays into hadrons, are derived from a new search for the h0A0 -> hadrons topology, independent of the hadronic flavour of the decay products. Searches for the neutral Higgs bosons h0 and A0, are used to obtain constraints on the Type II Two Higgs Doublet Model (2HDM(11)) with no CP violation in the Higgs sector and no additional non Standard Model particles besides the five Higgs bosons. The analysis combines LEP1 and LEP2 data collected with the OPAL detctor up to the highest available centre-of-mass energies. The searches are sensitive to the h0, A0 -> qq, gg,tau+tau- and h0 -> A0A0 decay modes of the Higgs bosons. The 2HDM(II) parameter space is explored in a detailed scan. Large regions of the 2HDM(II) parameter space are excluded at the 95% CL in the (mh, mA), (mh, tanb) and (mA, tanb) planes, using both direct neutral Higgs boson searches and indirect limits derived from Standard Model high precision measurements. The region 1 lesssim mh lesssim 55 GeV and 3 lesssim mA lesssim 63 GeV is excluded at 95% CL independently of the choice of the 2HDM(II) parameters.Comment: 37 pages, 11 figures, Submitted to Eur. Phys. J.

La performance "vestita" di Peter Gabriel

Analisi sulla performance "vestita" degli anni settanta, con esame approfondito dell'attivit\ue0 di Peter Gabriel in in generale del contesto del "ritorno all'ordine"

Fisica in barca

Descrizione dell'iniziativa "Fisica in Barca" di divulgazione della fisica attraverso lo sport della vela e valenza nell'ambito della didattica della scienz

PROCEEDINGS OF THE XIV IFAEITALIAN MEETING ON HIGH ENERGY PHYSICS

ATTI INCONTRO DI FISICA DELLE ALTE ENERGI

The activity of nanopowder and mesoporous titanium catalysts for the analysis of fatty acids in triglycerides by pyrolysis methylation with dimethyl carbonate

The activity of Ti doped MCM-41 mesoporous materials towards pyrolysis transmethylation of triglycerides with dimethyl carbonate (DMC) was compared to that of titanium silicate and titanium oxide nanopowders. DMC solutions of soybean oil, utilised as test lipid material, were pyrolysed in the presence of few milligrams of active solids under off-line and on-line (Py-GC-MS) conditions. While the yields of fatty acid methyl esters (FAMEs) determined by off-line pyrolysis were negligible with undoped MCM-41, those of Ti-MCM-41 increased with increasing Ti content from 3.5% (at Ti/Si molar ratio 1/28) to 17% at Ti/Si molar ratio 1/9 becoming comparable to those of titanium silicate nanopowders (13%). Titania nanoparticles enriched in rutile or anatase were the most active solids (19–26%), while coarse TiO2 (NIST) was poorly active (0.7%). The best performing Ti-MCM-41 was more effective than nanopowder titanium silicate for profiling FAMEs by on-line Py-GC-MS, but caused a larger double bond isomerisation of linoleic acid with respect to TiO2 nanopowders. Although the accuracy of pyrolysis/methylation with DMC and Ti-MCM-41 was inferior to standard methods, the method is appealing in the field of green analytical chemistry for being essentially a simple one-step procedure utilising small quantity of non-toxic and non-corrosive reagents. The method was tested on real matrices using DMC to extract the lipid fraction and was further explored by preparative pyrolysis with a fixed bed reactor