Search for Charged Higgs Bosons in e+e- Collisions at \sqrt{s} = 189 GeV

A search for pair-produced charged Higgs bosons is performed with the L3 detector at LEP using data collected at a centre-of-mass energy of 188.6 GeV, corresponding to an integrated luminosity of 176.4 pb^-1. Higgs decays into a charm and a strange quark or into a tau lepton and its associated neutrino are considered. The observed events are consistent with the expectations from Standard Model background processes. A lower limit of 65.5 GeV on the charged Higgs mass is derived at 95 % confidence level, independent of the decay branching ratio Br(H^{+/-} -> tau nu)

Synthesis of 2-azidoethyl α-d-mannopyranoside orthogonally protected and selective deprotections

4 páginas, 1 figura, 2 esquemas.We present the synthesis of a fully orthogonally protected mannosyl glycoside 1 and the corresponding methods for selective deprotections. Mannosyl glycoside 1 contains a functionalized linker at the anomeric position to allow for the attachment of carbohydrate units to scaffolds in order to prepare carbohydrate multivalent systems.We would like to thank FIS (PI030093), for financial supportPeer reviewe

Precision Measurement of the Helium Flux in Primary Cosmic Rays of Rigidities 1.9 GV to 3 TV with the Alpha Magnetic Spectrometer on the International Space Station

Knowledge of the precise rigidity dependence of the helium flux is important in understanding the origin, acceleration, and propagation of cosmic rays. A precise measurement of the helium flux in primary cosmic rays with rigidity (momentum/charge) from 1.9 GV to 3 TV based on 50 million events is presented and compared to the proton flux. The detailed variation with rigidity of the helium flux spectral index is presented for the first time. The spectral index progressively hardens at rigidities larger than 100 GV. The rigidity dependence of the helium flux spectral index is similar to that of the proton spectral index though the magnitudes are different. Remarkably, the spectral index of the proton to helium flux ratio increases with rigidity up to 45 GV and then becomes constant; the flux ratio above 45 GV is well described by a single power law.</p

A Measurement of Pi-Polarization at Lep

Contains fulltext : 26223.pdf (publisher's version ) (Open Access

Measurement of hadron and lepton-pair production at 161 GeV<root s<172 GeV at LEP

Contains fulltext : 26256.pdf (publisher's version ) (Open Access

Measurement of the branching ratios b -&gt; e nu Chi, mu nu Chi, tau nu Chi, and nu Chi

The inclusive semileptonic branching ratios b --&gt; e nu X, mu nu X, tau nu X and nu X have been measured at LEP with the L3 detector. The analysis is based on 2-jet hadronic Z decays obtained in the data collected between 1991 and 1992. Three separate event samples are analysed, containing electrons, muons and large missing energy (neutrinos), respectively. From the electron sample, we measure Br(b --&gt; e nu X) = (10.89+/-0.20+/-0.51)% and, from the muon sample, Br(b --&gt; mu nu X) = (10.82+/-0.15+/-0.59)%, where the first error is statistical and the second is systematic. From the missing energy sample, we measure Br(b --&gt; nu X) = (23.08+/-0.77+/-1.24)%, assuming the relative semileptonic decay rates e:mu:tau = 1:1:(0.25+/-0.05), according to theoretical expectations. From a combined analysis of all three samples and constraining the relative semileptonic rates, we measure Br(b --&gt; e nu X) = Br(b --&gt; mu nu X) = (10.68+/-0.11+/-0.46)%. Alternatively, we can remove the constraint on the relative semileptonic rates and measure Br(b --&gt; tau nu X) = (1.7+/-0.5+/-1.1)%