408 research outputs found
Reliable source of conditional non-Gaussian states from single-mode thermal fields
We address both theoretically and experimentally the generation of pulsed
non-Gaussian states from classical Gaussian ones by means of conditional
measurements. The setup relies on a beam splitter and a pair of linear
photodetectors able to resolve up to tens of photons in the two outputs. We
show the reliability of the setup and the good agreement with the theory for a
single-mode thermal field entering the beam splitter and present a thorough
characterization of the photon statistics of the conditional states.Comment: 18 pages, 12 figure
Measurement of the Cross Section of W-boson pair production at LEP
The cross section of W-boson pair-production is measured with the L3 detector
at LEP. In a data sample corresponding to a total luminosity of 629.4/pb,
collected at centre-of-mass energies ranging from 189 to 209 GeV, 9834
four-fermion events with W bosons decaying into hadrons or leptons are
selected. The total cross section is measured with a precision of 1.4 % and
agrees with the Standard Model expectation. Assuming charged-lepton
universality, the branching fraction for hadronic W-boson decays is measured to
be: Br(W-->hadrons) = 67.50 +- 0.42 (stat.) +- 0.30(syst.) %, in agreement with
the Standard Model. Differential cross sections as a function of the W-
production angle are also measured for the semi-leptonic channels qqev and
qqmv
A new application of emulsions to measure the gravitational force on antihydrogen
We propose to build and operate a detector based on the emulsion film
technology for the measurement of the gravitational acceleration on antimatter,
to be performed by the AEgIS experiment (AD6) at CERN. The goal of AEgIS is to
test the weak equivalence principle with a precision of 1% on the gravitational
acceleration g by measuring the vertical position of the anni- hilation vertex
of antihydrogen atoms after their free fall in a horizontal vacuum pipe. With
the emulsion technology developed at the University of Bern we propose to
improve the performance of AEgIS by exploiting the superior position resolution
of emulsion films over other particle de- tectors. The idea is to use a new
type of emulsion films, especially developed for applications in vacuum, to
yield a spatial resolution of the order of one micron in the measurement of the
sag of the antihydrogen atoms in the gravitational field. This is an order of
magnitude better than what was planned in the original AEgIS proposal.Comment: 17 pages, 14 figure
The Spitzer c2d survey of Large, Nearby, Interstellar Clouds. V. Chamaeleon II Observed with IRAC
We present IRAC (3.6, 4.5, 5.8, and 8.0 micron) observations of the
Chamaeleon II molecular cloud. The observed area covers about 1 square degree
defined by . Analysis of the data in the 2005 c2d catalogs reveals a
small number of sources (40) with properties similar to those of young
stellaror substellar objects (YSOs). The surface density of these YSO
candidates is low, and contamination by background galaxies appears to be
substantial, especially for sources classified as Class I or flat SED. We
discuss this problem in some detail and conclude that very few of the candidate
YSOs in early evolutionary stages are actually in the Cha II cloud. Using a
refined set of criteria, we define a smaller, but more reliable, set of 24 YSO
candidates.Comment: 19 pages, 10 figures, in press Ap
"TNOs are Cool": A survey of the trans-Neptunian region VI. Herschel/PACS observations and thermal modeling of 19 classical Kuiper belt objects
Trans-Neptunian objects (TNO) represent the leftovers of the formation of the
Solar System. Their physical properties provide constraints to the models of
formation and evolution of the various dynamical classes of objects in the
outer Solar System. Based on a sample of 19 classical TNOs we determine
radiometric sizes, geometric albedos and beaming parameters. Our sample is
composed of both dynamically hot and cold classicals. We study the correlations
of diameter and albedo of these two subsamples with each other and with orbital
parameters, spectral slopes and colors. We have done three-band photometric
observations with Herschel/PACS and we use a consistent method for data
reduction and aperture photometry of this sample to obtain monochromatic flux
densities at 70.0, 100.0 and 160.0 \mu m. Additionally, we use Spitzer/MIPS
flux densities at 23.68 and 71.42 \mu m when available, and we present new
Spitzer flux densities of eight targets. We derive diameters and albedos with
the near-Earth asteroid thermal model (NEATM). As auxiliary data we use
reexamined absolute visual magnitudes from the literature and data bases, part
of which have been obtained by ground based programs in support of our Herschel
key program. We have determined for the first time radiometric sizes and
albedos of eight classical TNOs, and refined previous size and albedo estimates
or limits of 11 other classicals. The new size estimates of 2002 MS4 and 120347
Salacia indicate that they are among the 10 largest TNOs known. Our new results
confirm the recent findings that there are very diverse albedos among the
classical TNOs and that cold classicals possess a high average albedo (0.17 +/-
0.04). Diameters of classical TNOs strongly correlate with orbital inclination
in our sample. We also determine the bulk densities of six binary TNOs.Comment: 21 pages, 9 figures, accepted for publication in Astronomy and
Astrophysic
Search for Doubly-Charged Higgs Bosons at LEP
Doubly-charged Higgs bosons are searched for in e^+e^- collision data
collected with the L3 detector at LEP at centre-of-mass energies up to 209 GeV.
Final states with four leptons are analysed to tag the pair-production of
doubly charged Higgs bosons. No significant excess is found and lower limits at
95% confidence level on the doubly-charged Higgs boson mass are derived. They
vary from 95.5 GeV to 100.2 GeV, depending on the decay mode. Doubly-charged
Higgs bosons which couple to electrons would modify the cross section and
forward-backward asymmetry of the e^+e^- -> e^+e^- process. The measurements of
these quantities do not deviate from the Standard Model expectations and
doubly-charged Higgs bosons with masses up to the order of a TeV are excluded
The Spitzer c2d Survey of Large, Nearby, Interstellar Clouds. I. Chamaeleon II Observed with MIPS
We present maps of over 1.5 square degrees in Chamaeleon (Cha) II at 24, 70,
and 160 micron observed with the Spitzer Space Telescope Multiband Imaging
Photometer for Spitzer (MIPS) and a 1.2 square degree millimeter map from SIMBA
on the Swedish-ESO Submillimetre Telescope (SEST). The c2d Spitzer Legacy
Team's data reduction pipeline is described in detail. Over 1500 24 micron
sources and 41 70 micron sources were detected by MIPS with fluxes greater than
10-sigma. More than 40 potential YSOs are identified with a MIPS and 2MASS
color-color diagram and by their spectral indices, including two previously
unknown sources with 24 micron excesses. Our new SIMBA millimeter map of Cha II
shows that only a small fraction of the gas is in compact structures with high
column densities. The extended emission seen by MIPS is compared with previous
CO observations. Some selected interesting sources, including two detected at 1
mm, associated with Cha II are discussed in detail and their SEDs presented.
The classification of these sources using MIPS data is found to be consistent
with previous studies.Comment: 44 pages, 12 figures (1 color), to be published in Ap
Z Boson Pair-Production at LEP
Events stemming from the pair-production of Z bosons in e^+e^- collisions are
studied using 217.4 pb^-1 of data collected with the L3 detector at
centre-of-mass energies from 200 GeV up to 209 GeV. The special case of events
with b quarks is also investigated.
Combining these events with those collected at lower centre-of-mass energies,
the Standard Model predictions for the production mechanism are verified. In
addition, limits are set on anomalous couplings of neutral gauge bosons and on
effects of extra space dimensions
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