5,655 research outputs found
SUSY Searches at LEP
Between 1995-2000, the LEP e+e- collider has been operated above the Z0 peak,
at centre-of-mass energies sqrt(s) = 130-209 GeV. Searches for supersymmetric
particles have been performed using these data samples. The results from the
four LEP experiments have been combined. Model independent limits on the
pair-production cross-sections of supersymmetric particles and constraints on
their masses are presented in the context of the Minimal Supersymmetric
Standard Model (MSSM) and in the context of gauge-mediated supersymmetry
breaking models (GMSB). Results assuming an R-parity violating scenario are
also reviewed.Comment: 4 pages, 6 figures, Proceedings of Moriond 03 - QCD wee
Other searches at LEP
During the year 2000, LEP has been operated at centre-of-mass energies up to
sqrt(s) = 209 GeV. New particle searches have been performed using these data
samples. Model independent limits on the production cross-sections and mass
limits in the context of the Minimal Supersymmetric Standard Model (MSSM)
assuming R-parity violation and in the context of gauge-mediated supersymmetry
breaking theories (GMSB) are presented. Searches for technicolor, excited
leptons and leptoquarks are also reviewed.Comment: Proceedings of the Conference: "QCD and High Energy Hadronic
Interactions", Rencontres de Moriond, 18-24 March 200
Sphalerons at finite temperature
We construct the sphaleron for several temperature dependent effective
potentials. We determine the sphaleron energy as a function of temperature and
demonstrate that the sphaleron energy at a given temperature is well
approximated by the sphaleron energy at temperature zero scaled by the ratio of
the vacuum expectation values of the Higgs field at temperatures and zero.
We address the cosmological upper bound on the Higgs mass.Comment: 14 pages, plain tex, 5 figures appended as postscript files at the
end of the paper. MONS-93/01, THU-93/0
Implementing and reasoning about hash-consed data structures in Coq
We report on four different approaches to implementing hash-consing in Coq
programs. The use cases include execution inside Coq, or execution of the
extracted OCaml code. We explore the different trade-offs between faithful use
of pristine extracted code, and code that is fine-tuned to make use of OCaml
programming constructs not available in Coq. We discuss the possible
consequences in terms of performances and guarantees. We use the running
example of binary decision diagrams and then demonstrate the generality of our
solutions by applying them to other examples of hash-consed data structures
Alignment of quasar polarizations with large-scale structures
We have measured the optical linear polarization of quasars belonging to
Gpc-scale quasar groups at redshift z ~ 1.3. Out of 93 quasars observed, 19 are
significantly polarized. We found that quasar polarization vectors are either
parallel or perpendicular to the directions of the large-scale structures to
which they belong. Statistical tests indicate that the probability that this
effect can be attributed to randomly oriented polarization vectors is of the
order of 1%. We also found that quasars with polarization perpendicular to the
host structure preferentially have large emission line widths while objects
with polarization parallel to the host structure preferentially have small
emission line widths. Considering that quasar polarization is usually either
parallel or perpendicular to the accretion disk axis depending on the
inclination with respect to the line of sight, and that broader emission lines
originate from quasars seen at higher inclinations, we conclude that quasar
spin axes are likely parallel to their host large-scale structures.Comment: Accepted for publication in Astronomy and Astrophysic
The different origins of high- and low-ionization broad emission lines revealed by gravitational microlensing in the Einstein cross
We investigate the kinematics and ionization structure of the broad emission
line region of the gravitationally lensed quasar QSO2237+0305 (the Einstein
cross) using differential microlensing in the high- and low-ionization broad
emission lines. We combine visible and near-infrared spectra of the four images
of the lensed quasar and detect a large-amplitude microlensing effect
distorting the high-ionization CIV and low-ionization H line profiles
in image A. While microlensing only magnifies the red wing of the Balmer line,
it symmetrically magnifies the wings of the CIV emission line. Given that the
same microlensing pattern magnifies both the high- and low-ionization broad
emission line regions, these dissimilar distortions of the line profiles
suggest that the high- and low-ionization regions are governed by different
kinematics. Since this quasar is likely viewed at intermediate inclination, we
argue that the differential magnification of the blue and red wings of
H favors a flattened, virialized, low-ionization region whereas the
symmetric microlensing effect measured in CIV can be reproduced by an emission
line formed in a polar wind, without the need of fine-tuned caustic
configurations.Comment: 11 pages, 4 figures, A&
Evidence for two spatially separated UV continuum emitting regions in the Cloverleaf broad absorption line quasar
Testing the standard Shakura-Sunyaev model of accretion is a challenging task
because the central region of quasars where accretion takes place is unresolved
with telescopes. The analysis of microlensing in gravitationally lensed quasars
is one of the few techniques that can test this model, yielding to the
measurement of the size and of temperature profile of the accretion disc. We
present spectroscopic observations of the gravitationally lensed broad
absorption line quasar H1413+117, which reveal partial microlensing of the
continuum emission that appears to originate from two separated regions: a
microlensed region, corresponding to the compact accretion disc; and a
non-microlensed region, more extended and contributing to at least 30\% of the
total UV-continuum flux. Because this extended continuum is occulted by the
broad absorption line clouds, it is not associated with the host galaxy, but
rather with light scattered in the neighbourhood of the central engine. We
measure the amplitude of microlensing of the compact continuum over the
rest-frame wavelength range 1000-7000 \AA. Following a Bayesian scheme, we
confront our measurements to microlensing simulations of an accretion disc with
a temperature varying as . We find a most likely source
half-light radius of cm (i.e., 0.002\,pc) at
0.18\,m, and a most-likely index of . The standard disc
() model is not ruled out by our data, and is found within the 95\%
confidence interval associated with our measurements. We demonstrate that, for
H1413+117, the existence of an extended continuum in addition to the disc
emission only has a small impact on the inferred disc parameters, and is
unlikely to solve the tension between the microlensing source size and standard
disc sizes, as previously reported in the literature.Comment: Accepted for publication in Astronomy and Astrophysics. 12 pages.
Minor changes w.r.t. v1 (language editing, Fig. 5-6
Microlensing of the broad-line region in the quadruply imaged quasar HE0435-1223
Using infrared spectra of the z = 1.693 quadruply lensed quasar HE0435-1223
acquired in 2009 with the spectrograph SINFONI at the ESO Very Large Telescope,
we have detected a clear microlensing effect in images A and D. While
microlensing affects the blue and red wings of the H{\alpha} line profile in
image D very differently, it de-magnifies the line core in image A. The
combination of these different effects sets constraints on the line-emitting
region; these constraints suggest that a rotating ring is at the origin of the
H{\alpha} line. Visible spectra obtained in 2004 and 2012 indicate that the
MgII line profile is microlensed in the same way as the H{\alpha} line. Our
results therefore favour flattened geometries for the low-ionization
line-emitting region, for example, a Keplerian disk. Biconical models cannot be
ruled out but require more fine-tuning. Flux ratios between the different
images are also derived and confirm flux anomalies with respect to estimates
from lens models with smooth mass distributions.Comment: 6 pages, 4 figures, 3 tables, accepted by A&A on 10 April 201
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