17,145 research outputs found
Improving reconstruction of the baryon acoustic peak : the effect of local environment
Precise measurements of the baryon acoustic oscillation (BAO) scale as a
standard ruler in the clustering pattern of large-scale structure is a central
goal of current and future galaxy surveys. The BAO peak may be sharpened using
the technique of density-field reconstruction, in which the bulk displacements
of galaxies are estimated using a Zel'dovitch approximation. We use numerical
simulations to demonstrate how the accuracy of this approximation depends
strongly on local environment, and how this information may be used to
construct an improved BAO measurement through environmental re-weighting and
using higher-order perturbation theory. We outline further applications of the
displacement field for testing cosmological models.Comment: 13 pages, 14 figure
Report of the Working Group on `W Mass and QCD' (Phenomenology Workshop on LEP2 Physics, Oxford, April 1997)
The W Mass and QCD Working Group discussed a wide variety of topics relating
to present and future measurements of M(W) at LEP2, including QCD backgrounds
to W+W- production. Particular attention was focused on experimental issues
concerning the direct reconstruction and threshold mass measurements, and on
theoretical and experimental issues concerning the four jet final state. This
report summarises the main conclusions.Comment: 43 pages LaTeX and 15 encapsulated postscript figures. Uses epsfig
and ioplppt macros. Full Proceedings to be published in Journal of Physics
Removing beam asymmetry bias in precision CMB temperature and polarisation experiments
Asymmetric beams can create significant bias in estimates of the power
spectra from CMB experiments. With the temperature power spectrum many orders
of magnitude stronger than the B-mode power spectrum any systematic error that
couples the two must be carefully controlled and/or removed. Here, we derive
unbiased estimators for the CMB temperature and polarisation power spectra
taking into account general beams and general scan strategies. A simple
consequence of asymmetric beams is that, even with an ideal scan strategy where
every sky pixel is seen at every orientation, there will be residual coupling
from temperature power to B-mode power if the orientation of the beam asymmetry
is not aligned with the orientation of the co-polarisation. We test our
correction algorithm on simulations of two temperature-only experiments and
demonstrate that it is unbiased. The simulated experiments use realistic scan
strategies, noise levels and highly asymmetric beams. We also develop a
map-making algorithm that is capable of removing beam asymmetry bias at the map
level. We demonstrate its implementation using simulations and show that it is
capable of accurately correcting both temperature and polarisation maps for all
of the effects of beam asymmetry including the effects of temperature to
polarisation leakage.Comment: 18 pages, 9 figure
Removing beam asymmetry bias in precision CMB temperature and polarisation experiments
Asymmetric beams can create significant bias in estimates of the power
spectra from CMB experiments. With the temperature power spectrum many orders
of magnitude stronger than the B-mode power spectrum any systematic error that
couples the two must be carefully controlled and/or removed. Here, we derive
unbiased estimators for the CMB temperature and polarisation power spectra
taking into account general beams and general scan strategies. A simple
consequence of asymmetric beams is that, even with an ideal scan strategy where
every sky pixel is seen at every orientation, there will be residual coupling
from temperature power to B-mode power if the orientation of the beam asymmetry
is not aligned with the orientation of the co-polarisation. We test our
correction algorithm on simulations of two temperature-only experiments and
demonstrate that it is unbiased. The simulated experiments use realistic scan
strategies, noise levels and highly asymmetric beams. We also develop a
map-making algorithm that is capable of removing beam asymmetry bias at the map
level. We demonstrate its implementation using simulations and show that it is
capable of accurately correcting both temperature and polarisation maps for all
of the effects of beam asymmetry including the effects of temperature to
polarisation leakage.Comment: 18 pages, 9 figure
Top-quark mass measurements: review and perspectives
The top quark is the heaviest elementary particle known and its mass () is a fundamental parameter of the Standard Model (SM). The
value affects theory predictions of particle production cross-sections required
for exploring Higgs-boson properties and searching for New Physics (NP). Its
precise determination is essential for testing the overall consistency of the
SM, to constrain NP models, through precision electroweak fits, and has an
extraordinary impact on the Higgs sector, and on the SM extrapolation to
high-energies. The methodologies, the results, and the main theoretical and
experimental challenges related to the measurements and
combinations at the Large Hadron Collider (LHC) and at the Tevatron are
reviewed and discussed. Finally, the prospects for the improvement of the
precision during the upcoming LHC runs are briefly outlined.Comment: 18 pages, 2 figures, Preprint submitted to Reviews in Physics (REVIP
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