121613505
Status of the Dark Energy Survey Camera (DECam) project
The Dark Energy Survey Collaboration has completed construction of the Dark Energy Camera (DECam), a 3 square degree, 570 Megapixel CCD camera which will be mounted on the Blanco 4-meter telescope at CTIO. DECam will be used to perform the 5000 sq. deg. Dark Energy Survey with 30% of the telescope time over a 5 year period. During the remainder of the time, and after the survey, DECam will be available as a community instrument. All components of DECam have been shipped to Chile and post-shipping checkout finished in Jan. 2012. Installation is in progress. A summary of lessons learned and an update of the performance of DECam and the status of the DECam installation and commissioning will be presented.
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
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:
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.
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.
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.
118999783
Application of GPUs for the Calculation of Two Point Correlation Functions in Cosmology
In this work, we have explored the advantages and drawbacks of using GPUs instead of CPUs in the calculation of a standard 2-point correlation function algorithm, which is useful for the analysis of Large Scale Structure of galaxies. Taking into account the huge volume of data foreseen in upcoming surveys, our main goal has been to accelerate significantly the analysis codes. We find that GPUs offer a 100-fold increase in speed with respect to a single CPU without a significant deviation in the results. For comparison's sake, an MPI version was developed as well. Some issues, like code implementation, which arise from using this option are discussed.
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.
119258454
Clustering of photometric luminous red galaxies – II. Cosmological implications from the baryon acoustic scale
A new determination of the sound horizon scale is presented. It makes use of 1:5 10 6 luminous red galaxies, selected from the Sloan Digital Sky Survey imaging data, with photometric redshifts. The sample is selected at redshifts that go from 0.4 to 0.6. We nd evidence of the Baryon Acoustic Oscillations (BAO) signal at the 2:3 level, at the highest redshift to date, 0:50 < z < 0:60. We obtain a value of BAO(z = 0:55) = (3:90 0:38) for the angular BAO scale, including systematic errors. This is the rst direct measurement of the angular BAO signal. We show its complementarity with the radial determination and how the degeneracy in the determination of cosmological parameters is broken when both measurements (angular and radial) are combined. The measurement is in good agreement with the expectations from the WMAP7 best-t cosmology. Combining with previous measurements of the acoustic scale, we obtain a value of w0 = 1:03 0:16 for the equation of state parameter of the dark energy, or M = 0:26 0:04 for the matter density, when the other parameters are xed. Both values include systematic errors. We have also tested the sensitivity of current BAO measurements to a time varying dark energy equation of state, nding wa = 0:06 0:22, including systematics and with the other parametrs xed.
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).