1,696 research outputs found
Towards Rapid Parameter Estimation on Gravitational Waves from Compact Binaries using Interpolated Waveforms
Accurate parameter estimation of gravitational waves from coalescing compact
binary sources is a key requirement for gravitational-wave astronomy.
Evaluating the posterior probability density function of the binary's
parameters (component masses, sky location, distance, etc.) requires computing
millions of waveforms. The computational expense of parameter estimation is
dominated by waveform generation and scales linearly with the waveform
computational cost. Previous work showed that gravitational waveforms from
non-spinning compact binary sources are amenable to a truncated singular value
decomposition, which allows them to be reconstructed via interpolation at fixed
computational cost. However, the accuracy requirement for parameter estimation
is typically higher than for searches, so it is crucial to ascertain that
interpolation does not lead to significant errors. Here we provide a proof of
principle to show that interpolated waveforms can be used to recover posterior
probability density functions with negligible loss in accuracy with respect to
non-interpolated waveforms. This technique has the potential to significantly
increase the efficiency of parameter estimation.Comment: 7 pages, 2 figure
Higher twist analysis of the proton g_1 structure function
We perform a global analysis of all available spin-dependent proton structure
function data, covering a large range of Q^2, 1 < Q^2 < 30 GeV^2, and calculate
the lowest moment of the g_1 structure function as a function of Q^2. From the
Q^2 dependence of the lowest moment we extract matrix elements of twist-4
operators, and determine the color electric and magnetic polarizabilities of
the proton to be \chi_E = 0.026 +- 0.015 (stat) + 0.021/-0.024 (sys) and \chi_B
= -0.013 -+ 0.007 (stat) - 0.010/+0.012 (sys), respectively.Comment: 6 pages, 2 figures, to appear in Phys. Lett.
Self-Consistent Data Analysis of the Proton Structure Function g1 and Extraction of its Moments
The reanalysis of all available world data on the longitudinal asymmetry A||
is presented. The proton structure function g1 was extracted within a unique
framework of data inputs and assumptions. These data allowed for a reliable
evaluation of moments of the structure function g1 in the Q2 range from 0.2 up
to 30 GeV2. The Q2 evolution of the moments was studied in QCD by means of
Operator Product Expansion (OPE).Comment: Proceeding of 3rd International Symposium on the
Gerasimov-Drell-Hearn Sum Rule and its extensions, Old Dominion University,
Norfolk, Virginia June 2-5, 200
Q^2 Evolution of Generalized Baldin Sum Rule for the Proton
The generalized Baldin sum rule for virtual photon scattering, the
unpolarized analogy of the generalized Gerasimov-Drell-Hearn integral, provides
an important way to investigate the transition between perturbative QCD and
hadronic descriptions of nucleon structure. This sum rule requires integration
of the nucleon structure function F_1, which until recently had not been
measured at low Q^2 and large x, i.e. in the nucleon resonance region. This
work uses new data from inclusive electron-proton scattering in the resonance
region obtained at Jefferson Lab, in combination with SLAC deep inelastic
scattering data, to present first precision measurements of the generalized
Baldin integral for the proton in the Q^2 range of 0.3 to 4.0 GeV^2.Comment: 4 pages, 3 figures, one table; text added, one figure replace
The impact of new neutrino DIS and Drell-Yan data on large-x parton distributions
New data sets have recently become available for neutrino and antineutrino
deep inelastic scattering on nuclear targets and for inclusive dimuon
production in pp pd interactions. These data sets are sensitive to different
combinations of parton distribution functions in the large-x region and,
therefore, provide different constraints when incorporated into global parton
distribution function fits. We compare and contrast the effects of these new
data on parton distribution fits, with special emphasis on the effects at large
x. The effects of the use of nuclear targets in the neutrino and antineutrino
data sets are also investigated.Comment: 24 pages, 13 figure
New parton distributions from large-x and low-Q^2 data
We report results of a new global next-to-leading order fit of parton
distribution functions in which cuts on W and Q are relaxed, thereby including
more data at high values of x. Effects of target mass corrections (TMCs),
higher twist contributions, and nuclear corrections for deuterium data are
significant in the large-x region. The leading twist parton distributions are
found to be stable to TMC model variations as long as higher twist
contributions are also included. The behavior of the d quark as x-->1 is
particularly sensitive to the deuterium corrections, and using realistic
nuclear smearing models the d-quark distribution at large x is found to be
softer than in previous fits performed with more restrictive cuts.Comment: 31 pages, 8 figures. Minor corrections. References added. To appear
in Phys.Rev.
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