16041899
Measurement of the lifetime of the tau lepton
The tau lepton lifetime is measured with the L3 detector at LEP using the complete data taken at centre-of-mass energies around the Z pole resulting in $\tau_{\tau}\,=\,293.2\,\pm\,2.0~\mbox{(stat)}\,\pm\, 1.5~\mbox{(syst)}$ fs. The comparison of this result with the muon lifetime supports lepton universality of the weak charged current at the level of six per mille. Assuming lepton universality, the value of the strong coupling constant, $\alpha_s$ is found to be $\alpha_s(m_{\tau}^2)$ = 0.319 $\pm$ 0.015~\mbox{(exp)} $\pm$ 0.014~\mbox{(theory)}.
117839544
Search for a Higgs boson decaying into two photons at LEP
A Higgs particle produced in association with a Z boson and decaying into two photons is searched for in the data collected by the L3 experiment at LEP. All possible decay modes of the Z boson are investigated. No signal is observed in 447.5 pb^-1 of data recorded at centre-of-mass energies up to 209 GeV. Limits on the branching fraction of the Higgs boson decay into two photons as a function of the Higgs mass are derived. A lower limit on the mass of a fermiophobic Higgs boson is set at 105.4 GeV at 95% confidence level.
195317607
Search for excited fermions
Recent results on searches for excited fermions at the LEP, HERA and Tevatron colliders are reported. These results improve the limits on the masses and couplings of excited fermions. PACS: 12.60.Rc Composite models – 12.60.Cn Extensions of electroweak gauge sector – 13.66.Hk Production of non-standard model particles in e–e+ interactions – 13.60.Hb Total and inclusive cross sections (including deep-inelastic processes) – 13.85.Rm Limits on production of particles
54840976
In-beam tests of the AMS RICH prototype with 20 a GeV/c secondary ions
A prototype of the AMS Cherenkov imager (RICH) has been tested by means of a low intensity 20 GeV/c per nucleon ion beam coming from the fragmentation of a primary beam of Pb ions. Data have been collected for charges I < Z < ∼45 in various beam conditions and using different radiators. The charge Z and velocity /i resolution have been of the prototype investigated.
204860499
Flavour independent search for neutral Higgs bosons at LEP
Abstract A flavour independent search for the CP-even and CP-odd neutral Higgs bosons h and A is performed in 624 pb −1 of data collected with the L3 detector at LEP at centre-of-mass energies between 189 and 209 GeV . Higgs boson production through the e + e − →Zh and the e + e − →hA processes is considered and decays of the Higgs bosons into hadrons are studied. No significant signal is observed and 95% confidence level limits on the hZZ and hAZ couplings are derived as a function of the Higgs boson masses. Assuming the Standard Model cross section for the Higgs-strahlung process and a 100% branching fraction into hadrons, a 95% confidence level lower limit on the mass of the Higgs boson is set at 110.3 GeV.
209836116
Measurement of triple gauge boson couplings of the W boson at LEP
The CP-conserving triple-gauge-boson couplings, g(1)(Z), kappa(gamma), lambda(gamma), g(5)(Z), kappa(Z) and lambda(Z) are measured using hadronic and semi-leptonic W-pair events selected in 629 pb(-1) of data collected at LEP with the L3 detector at centre-of-mass energies between 189 and 209 GeV. The results are combined with previous L3 measurements based on data collected at lower centre-of-mass energies and with the results from single-W production and from events with a single-photon and missing energy. Imposing the constraints kappa(Z) = g(1)(Z) - tan(2) thetaw(kappa(gamma) - 1) and lambda(Z) = lambda(gamma), we obtain for the C and P conserving couplings the results:
118433859
Clustering of photometric luminous red galaxies – I. Growth of structure and baryon acoustic feature
The possibility of measuring redshift-space distortions (RSDs) using photometric data has been recently highlighted. This effect complements and significantly alters the detectability of baryon acoustic oscillations (BAO) in photometric surveys. In this paper we present measurements of the angular correlation function of luminous red galaxies (LRGs) in the photometric catalogue of the final data release [data release 7 (DR7)] of the Sloan Digital Sky Survey II (SDSS-II). The sample compromises ∼1.5 × 106 LRGs distributed in 0.45 < z < 0.65, with a characteristic photometric error of ∼0.05. Our measured correlation centred at z= 0.55 is in very good agreement with predictions from standard Λcold dark matter (ΛCDM) in a broad range of angular scales, 05 < θ < 6°. We find that the growth of structure can indeed be robustly measured, with errors matching expectations. The velocity growth rate is recovered as fσ8= 0.53 ± 0.42 when no prior is imposed on the growth factor and the background geometry follows a ΛCDM model with 7-year Wilkinson Microwave Anisotropy Probe (WMAP7)+SNIa priors. This is compatible with the corresponding General Relativity (GR) prediction fσ8= 0.45 for our fiducial cosmology. If we adopt a parametrization such that f=Ωγm(z), with γ≈ 0.55 in GR, and combine our fσ8 measurement with the corresponding ones from spectroscopic LRGs at lower redshifts, we obtain γ= 0.54 ± 0.17. In addition we find evidence for the presence of the baryon acoustic feature matching the amplitude, location and shape of ΛCDM predictions. The photometric BAO feature is detected with 98 per cent confidence level at z= 0.55.
14700133
First cosmological constraints on dark energy from the radial baryon acoustic scale.
We present cosmological constraints arising from the first measurement of the radial (line-of-sight) baryon acoustic oscillations (BAO) scale in the large scale structure traced by the galaxy distribution. Here we use these radial BAO measurements at z = 0.24 and z = 0.43 to derive new constraints on dark energy and its equation of state for a flat universe, without any other assumptions on the cosmological model: w = -1.14 + or - 0.39 (assumed constant), Omega(m) = 0.24(-0.05);(+0.06). If we drop the assumption of flatness and include previous cosmic microwave background and supernova data, we find w = -0.974 + or - 0.058, Omega(m) = 0.271 + or - 0.015, and Omega(k) = -0.002 + or - 0.006, in good agreement with a flat cold dark matter cosmology with a cosmological constant. To our knowledge, these are the most stringent constraints on these parameters to date under our stated assumptions.
28279200
Tracing the sound horizon scale with photometric redshift surveys
We propose a new method for the extraction cosmological parameters using the baryon acoustic oscillation (BAO) scale as a standard ruler in deep galaxy surveys with photometric determination of redshifts. The method consists in a simple empirical parametric fit to the angular two-point correlation function ω(θ). It is parametrized as a power law to describe the continuum and as a Gaussian to describe the BAO bump. The location of the Gaussian is used as the basis for the measurement of the sound horizon scale. This method, although simple, actually provides a robust estimation, since the inclusion of the power law and the use of the Gaussian remove the shifts which affect the local maximum. We discuss the effects of projection bias, non-linearities, redshift space distortions and photo-z precision and apply our method to a mock catalogue of the Dark Energy Survey, built upon a large N-body simulation provided by the MICE collaboration. We discuss the main systematic errors associated with our method and show that they are dominated by the photo-z uncertainty.
15111743
Measurement of the Fermi constant by FAST
An initial measurement of the lifetime of the positive muon to a precision of 16 parts per million (ppm) has been performed with the FAST1 detector at the Paul Scherrer Institute. The result is τμ=2.197083(32)(15)μs, where the first error is statistical and the second is systematic. The muon lifetime determines the Fermi constant, GF=1.166352(9)×10−5GeV−2 (8 ppm).