274 research outputs found
Search for Branons at LEP
We search, in the context of extra-dimension scenarios, for the possible
existence of brane fluctuations, called branons. Events with a single photon or
a single Z-boson and missing energy and momentum collected with the L3 detector
in e^+ e^- collisions at centre-of-mass energies sqrt{s}=189-209$ GeV are
analysed. No excess over the Standard Model expectations is found and a lower
limit at 95% confidence level of 103 GeV is derived for the mass of branons,
for a scenario with small brane tensions. Alternatively, under the assumption
of a light branon, brane tensions below 180 GeV are excluded
Search for Low Scale Gravity Effects in e+e- Collisions at LEP
Recent theories propose that quantum gravity effects may be observable at LEP
energies via gravitons that couple to Standard Model particles and propagate
into extra spatial dimensions. The associated production of a graviton and a
photon is searched for as well as the effects of virtual graviton exchange in
the processes: e+e- -> gamma gamma, ZZ, WW, mu mu, tau tau, qq and ee No
evidence for this new interaction is found in the data sample collected by the
L3 detector at LEP at centre-of-mass energies up to 183 GeV. Limits close to 1
TeV on the scale of this new scenario of quantum gravity are set
Search for Charginos with a Small Mass Difference with the Lightest Supersymmetric Particle at \sqrt{s} = 189 GeV
A search for charginos nearly mass-degenerate with the lightest
supersymmetric particle is performed using the 176 pb^-1 of data collected at
189 GeV in 1998 with the L3 detector. Mass differences between the chargino and
the lightest supersymmetric particle below 4 GeV are considered. The presence
of a high transverse momentum photon is required to single out the signal from
the photon-photon interaction background. No evidence for charginos is found
and upper limits on the cross section for chargino pair production are set. For
the first time, in the case of heavy scalar leptons, chargino mass limits are
obtained for any \tilde{\chi}^{+-}_1 - \tilde{\chi}^0_1 mass difference
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)
Search for R-parity Violating Decays of Supersymmetric Particles in e+e- Collisions at root(s)= 189 GeV
A search for chargino, neutralino and scalar lepton pair-production in e+e- collisions at the centre-of-mass energy of 189 GeV is performed under the assumptions that R-parity is not conserved in decays and only one of the coupling constants lambda_ijk, lambda'_ijk or lambda''_ijk is non-negligible. No signal is found in a data sample corresponding to an integrated luminosity of 176.4 pb-1. Limits on the production cross sections, on the Minimal Supersymmetric Standard Model parameters and on the masses of the supersymmetric particles are derived
Production of Single W Bosons at LEP
We report on the observation of single W boson production in a data sample collected by the L3 detector at LEP2. The signal consists of large missing energy final states with a single energetic lepton or two hadronic jets. The cross-section is measured to be at the centre of mass energy \sqrt{s}=172 \GeV{}, consistent with the Standard Model expectation. From this measurement the following limits on the anomalous WW gauge couplings are derived at 95\% CL: and
Measurement of the Average Lifetime of b-Hadrons in Z Decays
We present a measurement of the average b-hadron lifetime at the collider LEP. Using hadronic Z decays collected in the period from 1991 to 1994, two independent analyses have been performed. In the first one, the b-decay position is reconstructed as a secondary vertex of hadronic b-decay particles. The second analysis is an updated measurement of using the impact parameter of leptons with high momentum and high transverse momentum. The combined result is \begin{center} . \end{center} In addition, we measure the average charged b-decay multiplicity and the normalized average b-energy at LEP to be \begin{center} , \end{center} \begin{center} \end{center
Search for R-parity Violating Decays of Supersymmetric Particles in Collisions at LEP
A search, in collisions, for chargino, neutralino, scalar lepton and scalar quark pair-production is performed, without assuming R-parity conservation in decays, in the case that only one of the coupling constants or is non-negligible. No signal is found in data up to a centre-of-mass energy of 208 \GeV. Limits on the production cross sections and on the masses of supersymmetric particles are derived.A search, in e + e â collisions, for chargino, neutralino, scalar lepton and scalar quark pair-production is performed, without assuming R-parity conservation in decays, in the case that only one of the coupling constants λ or λ âł is non-negligible. No signal is found in data up to a centre-of-mass energy of 208 GeV. Limits on the production cross sections and on the masses of supersymmetric particles are derived.A search, in e^+e^- collisions, for chargino, neutralino, scalar lepton and scalar quark pair-production is performed, without assuming R-parity conservation in decays, in the case that only one of the coupling constants lambda_ijk or lambda''_ijk is non-negligible. No signal is found in data up to a centre-of-mass energy of 208GeV. Limits on the production cross sections and on the masses of supersymmetric particles are derived
Synthesis of 2-azidoethyl α-d-mannopyranoside orthogonally protected and selective deprotections
4 pĂĄginas, 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
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