66 research outputs found
Using CMB lensing to constrain the multiplicative bias of cosmic shear
Weak gravitational lensing is one of the key probes of cosmology. Cosmic
shear surveys aimed at measuring the distribution of matter in the universe are
currently being carried out (Pan-STARRS) or planned for the coming decade (DES,
LSST, EUCLID, WFIRST). Crucial to the success of these surveys is the control
of systematics. In this work a new method to constrain one such family of
systematics, known as multiplicative bias, is proposed. This method exploits
the cross-correlation between weak lensing measurements from galaxy surveys and
the ones obtained from high resolution CMB experiments. This cross-correlation
is shown to have the power to break the degeneracy between the normalization of
the matter power spectrum and the multiplicative bias of cosmic shear and to be
able to constrain the latter to a few percent.Comment: 5 pages, 1 figur
Magnification as a Tool in Weak Lensing
Weak lensing surveys exploit measurements of galaxy ellipticities. These
measurements are subject to errors which degrade the cosmological information
that can be extracted from the surveys. Here we propose a way of using the
galaxy data themselves to calibrate the measurement errors. In particular, the
cosmic shear field, which causes the galaxies to appear elliptical, also
changes their sizes and fluxes. Information about the sizes and fluxes of the
galaxies can be added to the shape information to obtain more robust
information about the cosmic shear field. The net result will be tighter
constraints on cosmological parameters such as those which describe dark
energy.Comment: 4 pages, 2 figure
The Interplay Between Collider Searches For Supersymmetric Higgs Bosons and Direct Dark Matter Experiments
In this article, we explore the interplay between searches for supersymmetric
particles and Higgs bosons at hadron colliders (the Tevatron and the LHC) and
direct dark matter searches (such as CDMS, ZEPLIN, XENON, EDELWEISS, CRESST,
WARP and others). We focus on collider searches for heavy MSSM Higgs bosons
(, , ) and how the prospects for these searches are impacted by
direct dark matter limits and vice versa. We find that the prospects of these
two experimental programs are highly interrelated. A positive detection of ,
or at the Tevatron would dramatically enhance the prospects for a
near future direct discovery of neutralino dark matter. Similarly, a positive
direct detection of neutralino dark matter would enhance the prospects of
discovering heavy MSSM Higgs bosons at the Tevatron or the LHC. Combining the
information obtained from both types of experimental searches will enable us to
learn more about the nature of supersymmetry.Comment: 22 pages, 28 figure
Inelastic Dark Matter As An Efficient Fuel For Compact Stars
Dark matter in the form of weakly interacting massive particles is predicted
to become gravitationally captured and accumulate in stars. While the
subsequent annihilations of such particles lead to the injection of energy into
stellar cores, elastically scattering dark matter particles do not generally
yield enough energy to observably impact stellar phenomenology. Dark matter
particles which scatter inelastically with nuclei (such that they reconcile the
annual modulation reported by DAMA with the null results of CDMS and other
experiments), however, can be captured by and annihilate in compact stars at a
much higher rate. As a result, old white dwarf stars residing in high dark
matter density environments can be prevented from cooling below several
thousand degrees Kelvin. Observations of old, cool white dwarfs in dwarf
spheroidal galaxies, or in the inner kiloparsec of the Milky Way, can thus
potentially provide a valuable test of the inelastic dark matter hypothesis.Comment: 6 pages, 2 figur
Neutralino Dark Matter and Trilepton Searches in the MSSM
Searches for supersymmetry are among the most exciting physics goals at Run
II of the Tevatron. In particular, in supersymmetric models with light
charginos, neutralinos and sleptons, associated chargino--neutralino production
can potentially be observed as multi-lepton events with missing energy. We
discuss how, in the generic TeV-scale MSSM, the prospects for these
chargino-neutralino searches are impacted by cosmological considerations,
namely the neutralino relic abundance and direct detection limits. We also
discuss what an observation of chargino-neutralino production at the Tevatron
would imply for the prospects of future direct dark matter searches without
assuming specific patterns of supersymmetry breaking.Comment: 13 pages, 14 figure
A ground-based 21cm Baryon acoustic oscillation survey
Baryon acoustic oscillations (BAO) provide a robust standard ruler with which
to measure the acceleration of the Universe. The BAO feature has so far been
detected in optical galaxy surveys. Intensity mapping of neutral hydrogen
emission with a ground-based radio telescope provides another promising window
for measuring BAO at redshifts of order unity for relatively low cost. While
the cylindrical radio telescope (CRT) proposed for these measurements will have
excellent redshift resolution, it will suffer from poor angular resolution (a
few arcminutes at best). We investigate the effect of angular resolution on the
standard ruler test with BAO, using the Dark Energy Task Force Figure of Merit
as a benchmark. We then extend the analysis to include variations in the
parameters characterizing the telescope and the underlying physics. Finally, we
optimize the survey parameters (holding total cost fixed) and present an
example of a CRT BAO survey that is competitive with Stage III dark energy
experiments. The tools developed here form the backbone of a publicly available
code that can be used to obtain estimates of cost and Figure of Merit for any
set of parameters.Comment: ApJ accepted version. Important changes in section 2 and 3 - uses a
more realistic instrument response model and removed the discussion of
aliasing effect. The conclusions remain the same. Typos fixed (including eq
5). 11 emulated apj pages with 7 figures and 1 tabl
The WIMP Forest: Indirect Detection of a Chiral Square
The spectrum of photons arising from WIMP annihilation carries a detailed
imprint of the structure of the dark sector. In particular, loop-level
annihilations into a photon and another boson can in principle lead to a series
of lines (a WIMP forest) at energies up to the WIMP mass. A specific model
which illustrates this feature nicely is a theory of two universal extra
dimensions compactified on a chiral square. Aside from the continuum emission,
which is a generic prediction of most dark matter candidates, we find a
"forest" of prominent annihilation lines that, after convolution with the
angular resolution of current experiments, leads to a distinctive (2-bump plus
continuum) spectrum, which may be visible in the near future with the Fermi
Gamma-Ray Space Telescope (formerly known as GLAST).Comment: 11 pages, 4 figure
Lenses in the forest: cross-correlation of the Lyman-alpha flux with CMB lensing
We present a theoretical estimate for a new observable: the cross-correlation
between the Lyman-alpha flux fluctuations in quasar (QSO) spectra and the
convergence of the cosmic microwave background (CMB) as measured along the same
line-of-sight. As a first step toward the assessment of its detectability, we
estimate the signal-to-noise ratio using linear theory. Although the
signal-to-noise is small for a single line-of-sight and peaks at somewhat
smaller redshifts than those probed by the Lyman-alpha forest, we estimate a
total signal-to-noise of 9 for cross-correlating QSO spectra of SDSS-III with
Planck and of 20 for cross-correlating with a future polarization based CMB
experiment. The detection of this effect would be a direct measure of the
neutral hydrogen-matter cross-correlation and could provide important
information on the growth of structures at large scales in a redshift range
which is still poorly probed by observations.Comment: 5 pages, 4 figures, matches published versio
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