High Energy
and Nuclear Physics
The DOE Office of High Energy
and Nuclear Physics sponsors major experimental facilities
and theoretical studies, as well as computational simulations
and analyses of experimental data.
In 2002 the MAXIMA data analysis
team documented their successful approach to recovering a
map of the cosmic microwave background (CMB); their methods
will be applicable to other CMB experiments. Accomplishments
in nuclear physics included the only quantum Monte Carlo calculations
of 6- through 10-nucleon systems that use realistic interactions
and are accurate to 1–2% for the binding energies
Research in lattice quantum chromodynamics
(QCD) included the first simulations to explore the finite
temperature phase diagram with an improved staggered fermion
action; a study of chiral properties of pseudoscalar mesons
with overlap fermions; and simulations of lattice QCD at finite
isospin density..
Making Maps of the Cosmic Microwave Background
The cosmic microwave background (CMB), a “snapshot”
of the Universe as it was only 300,000 years after the Big
Bang, provides the most powerful discriminant between different
cosmological models. To date, CMB datasets have ruled out
an entire class of models (based on topological defects) for
the generation of primordial density perturbations in the
Universe; have demonstrated the spatial flatness of the Universe
as a whole; and, coupled with supernova data, have given a
first measurement of the overall mass-energy budget for the
Universe.
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Figure
1 Pixel domain correlations of the
noise projected on the sky. All three panels show a level
of the correlations relative to the rms value of the noise
for the same pixel, which is marked with an x. This pixel
was observed twice during the MAXIMA-I flight. The noise
correlations for the first observation are shown in the
left panel, and these for the second one in the middle
panel. The right panel shows the final co-added noise
correlations. Due to the MAXIMA-I scanning strategy and
the presence of the noise correlations in the time domain,
the noise correlation pattern in pixel domain is highly
anisotropic and strongly correlated as a result of any
single observation of a pixel. However, the combined noise
for all pixels that were observed twice is significantly
less correlated and more isotropic. (Click on image
for larger version.) |
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There is much more information still to be mined from CMB
data, especially from current and future satellite missions
(MAP and Planck), but the size of the datasets presents new
challenges for timely and precise data analysis. Stompor et
al. have documented how those challenges were met successfully
in the analysis of data from the MAXIMA-I balloon-borne experiment,
which required improvement of existing methods and tools as
well as development and testing of new ones.
The MAXIMA collaborators present a comprehensive, consistent
approach to recovering a map of the sky and estimating its
error matrix in realistic circumstances. Their approach includes
data preprocessing and noise estimation; a suite of different
map-making methods that simultaneously produce both a map
and a corresponding pixel-pixel noise correlation matrix (Figure
1); ways of handling systematic effects within the general
framework of maximum likelihood map making; iterative algorithms
for time-domain noise estimation; and numerical tests for
checking the consistency of the analysis. Their methods are
expected to be applicable to other current and future CMB
experiments.
INVESTIGATORS
J. D. Borrill and G. F. Smoot, Lawrence Berkeley National
Laboratory and University of California, Berkeley; R. Stompor,
University of California, Berkeley and Copernicus Astronomical
Center, Warsaw; A. H. Jaffe, A. T. Lee, S. Oh, B. Rabii, P.
L. Richards, C. D. Winant, and J. H. P. Wu, University of
California, Berkeley; A. Balbi, Università Tor Vergata,
Rome; P. G. Ferreira, University of Oxford; S. Hanany, University
of Minnesota.
PUBLICATION
R. Stompor, A. Balbi, J. D. Borrill, P. G. Ferreira, S. Hanany,
A. H. Jaffe, A. T. Lee, S. Oh, B. Rabii, P. L. Richards, G.
F. Smoot, C. D. Winant, and J. H. P. Wu, “Making maps
of the cosmic microwave background: The MAXIMA example,”
Phys. Rev. D 65, 022003 (2001).
URL
http://www.nersc.gov/~borrill/
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