298393
Cosmological constant and advanced gravitational wave detectors
Interferometric gravitational wave detectors could measure the frequency sweep of a binary inspiral (characterized by its chirp mass) to high accuracy. The observed chirp mass is the intrinsic chirp mass of the binary source multiplied by (1+z), where z is the redshift of the source. Assuming a nonzero cosmological constant, we compute the expected redshift distribution of observed events for an advanced LIGO detector. We find that the redshift distribution has a robust and sizable dependence on the cosmological constant; the data from advanced LIGO detectors could provide an independent measurement of the cosmological constant. {copyright} {ital 1997} {ital The American Physical Society}
15326079
Wavelets and WMAP non-Gaussianity
We study the statistical properties of the first-year Wilkinson Microwave Anisotropy Probe (WMAP) data on different scales using the spherical Mexican hat wavelet transform. Consistent with the 2004 results of Vielva et al., we find a deviation from Gaussianity in the form of kurtosis of wavelet coefficients on 3-4 scales in the southern Galactic hemisphere. This paper extends the work of Vielva et al. as follows: We find that the non-Gaussian signal shows up more strongly in the form of a larger than expected number of cold pixels and also in the form of scale-scale correlations among wavelet coefficients. We establish the robustness of the non-Gaussian signal under more wide-ranging assumptions regarding the Galactic mask applied to the data and the noise statistics. This signal is unlikely to be due to the usual quadratic term parameterized by the nonlinearity parameter fNL. We use the skewness of the spherical Mexican hat wavelet coefficients to constrain fNL with the first-year WMAP data. Our results constrain fNL to be 50+/-80 at 68% confidence and less than 280 at 99% confidence.
1842861
Dark Energy Constraints from Baryon Acoustic Oscillations
Baryon acoustic oscillations (BAOs) in the galaxy power spectrum allow us to extract the scale of the comoving sound horizon at recombination, a cosmological standard ruler accurately determined by the cosmic microwave background anisotropy data. We examine various issues important in the use of BAOs to probe dark energy. We find that if we assume a flat universe and priors on ?m, ?mh2, and ?bh2 as expected from the Planck mission, the constraints on dark energy parameters (w0, w') scale much less steeply with survey area than (area)-1/2 for a given redshift range. The constraints on the dark energy density ?X(z), however, do scale roughly with (area)-1/2 due to the strong correlation between H(z) and ?m (which reduces the effect of priors on ?m). Dark energy constraints from BAOs are very sensitive to the assumed linear scale of matter clustering and the redshift accuracy of the survey. For a BAO survey with 0.5 ? z ? 2, ? (R) = 0.4 [corresponding to kmax (z = 0) = 0.086 h Mpc-1], and ?z/ (1 + z) = 0.001, we find = (0.115,0.183) and (0.069, 0.104) for survey areas of 1000 and 10,000 deg2, respectively. We find that it is critical to minimize the bias in the scale estimates in order to derive reliable dark energy constraints. For a 1000 (10,000) deg2 BAO survey, a 1 ? bias in ln H (z) leads to a 2 ? (3 ?) bias in w'. The bias in w' due to the same scale bias from ln DA (z) is slightly smaller and opposite in sign. The results from this paper will be useful in assessing different proposed BAO surveys and guiding the design of optimal dark energy detection strategies.
119244043
A robust distance measurement and dark energy constraints from the spherically averaged correlation function of Sloan Digital Sky Survey luminous red Galaxies
We measure the effective distance to z = 0.26, DV (0.26), and mh 2 from the overall shape of the spherically-averaged two-point correlati on function of the Sloan Digital Sky Survey (SDSS) Data Release 7 (DR7) volume-limited luminous red galaxy (LRG) sample, without assuming a dark energy model or a flat Universe. We giv e the mean and covariance matrix of DV (0.26), mh 2 , bh 2 , and ns. We show that these provide an efficient and accurate summary of the volume-limited LRG data. With flat priors on bh 2 and ns (7σWMAP7), we find mh 2 = 0.131 ± 0.020, and rs/DV (0.26) = 0.1466 +0.0068 0.0073 (the ratio of the sound horizon at the drag epoch to the effective distance to z = 0.26). We find that measurements of mh 2 or m are biased low if flux-limited (instead of volume-limited) L RG sample is used. By scaling the spherically-averaged correlation fun ction, we find the Hubble parameter H(0.26) = 79 +12 13 km s 1 Mpc 1 and the angular diameter distance DA(0.26) = 848 +86 88 Mpc. Combining our results with the cosmic microwave background and supernova data, we obtain k = 0.0059 +0.0092 0.0093 andw = 1.023 +0.054 0.053 (assuming a constant dark energy equation of state). We use LasDamas SDSS mock catalogs to compute the covariance matrix of the correlation function, and investigate the use of lognormal catal ogs as an alternative. We find that the input correlation function can be accurately recovered from lognormal catalogs, although they give larger errors on all scales (especially on small sc ales) compared to the mock catalogs derived from cosmological N-body simulations.
42895334
Dark Energy Search with Supernovae
Abstract To determine the nature of dark energy from observational data, it is important that we use model-independent and optimal methods. We should probe dark energy using its density (allowed to be a free function of cosmic time) instead of its equation of state. We should minimize gravitational lensing effect on supernovae by flux-averaging. We need to include complementary data (for example, from the cosmic microwave background (CMB) and large scale structure (LSS)) in a consistent manner to help break the degeneracy between the dark energy density and the matter density fraction. We should push for ambitious future supernova surveys that can observe a large number of supernovae at the highest possible redshifts. I discuss these and other issues that will be important in our quest to unravel the mystery of the nature of dark energy. Current supernova, CMB, and LSS data already rule out dark energy models with dark energy densities that vary greatly with time; with the cosmological constant model providing an excellent fit to the data. A precise measurement of dark energy density as a free function of cosmic time will have a fundamental impact on particle physics and cosmology.
11940938
Constraints on generalized extended inflationary models.
We study the physical constraints on generalized extended inflationary theories, in which the Brans-Dicke field {Phi} couples to the inflaton sector in the form of two arbitrary power-law functions of {Phi}. We find that the most stringent constraints arise from the need to suppress large bubbles and from considerations of the density perturbations generated during extended inflation. We find that there are sizable portions of the parameter spaces in which all the constraints are satisfied.
6846086
PLANS FOR A 2 ND INSERTION DEVICE IN CAMD
To allow the possible installation of a 2 nd Insertion Device in the CAMD Light Source, the lattice optic needs to be changed. The present configuration has a small vertical beta function in the long straight section containing the 7 Tesla wiggler. The new optic will give a small vertical beta at two long straight sections which are diametrically opposite. Test results with the new optic are presented together with the measured beam parameters. These data are used to predict the photon beam performance for an Insertion Device which could be installed. nd generation facility of moderate brightness using a 4 cell Chasman-Green lattice. The normal beam operating energy is 1.3 GeV. At the injection energy of 200 MeV the lattice is operated in a fully symmetric zero dispersion mode, which is also used during the energy ramp. In 1998 a 3 pole wavelength shifter (3) was installed whose maximum field is 7 Tesla. This is used to provide hard X-rays for ultra-deep lithography, protein crystallography and other hard X-ray science. To increase the brightness, after the energy ramp is completed the optic is changed to one with finite dispersion in the long straights. This reduces the natural horizontal emittance by about a factor of 2 to 150 nm.rads. In addition the optic is configured to produce a small value of the vertical beta function at the center of the wiggler in order to increase the flux density of the source point. This is known as the minibeta optic.(4) The wavelength shifter is located in one of the 4 long straights which each have a free length of about 2.5 m. One of these straights contains the injection septum magnet and another contains the single RF cavity. The remaining straight is not presently used. These features may be seen in fig 1 which is a diagram of the CAMD facility. To enable the lattice to operate in the minibeta configuration, the F and D quadrupoles in the wavelength shifter straight are connected to independent power supplies. In addition these quadrupoles are adjusted to compensate for the focusing effects of the wavelength shifter and so maintain the beta values close to the optimum minibeta. At the end of the energy ramp the settings for the minibeta are applied smoothly in synchronism as the wavelength shifter is energized without loss of beam current.
119450128
Anti-d / anti-u asymmetry and the origin of the nucleon sea
The Drell-Yan cross section ratios, {sigma}(p+d)/{sigma}(p+p), measured in Fermilab E866, have led to the first determination of {bar d}(x)/{bar u}(x), {bar d}(x){minus}{bar u}(x), and the integral of {bar d}(x){minus}{bar u}(x) for the proton over the range 0.02{le}x{le}0.345. The E866 results are compared with predictions based on parton distribution functions and various theoretical models. The relationship between the E866 results and the NMC measurement of the Gottfried integral is discussed. The agreement between the E866 results and models employing virtual mesons indicates that these non-perturbative processes play an important role in the origin of the {bar d},{bar u} asymmetry in the nucleon sea. {copyright} {ital 1998} {ital The American Physical Society}
122101803
First results on the hybrid photodiode tube
Abstract The performance of a new breed of light detectors based on a photocathode followed by a planar silicon diode working in the bombarding mode is reported. This detector was developed by the LAA project in order to produce a fast light detector capable of covering a span of the more than 4 orders of magnitude of linearity required by the scintillating fibre and lead (“spaghetti”) calorimeter. Linear signals from single, to more than 10 6 photoelectrons per pulse were measured. The general characteristics of this detector are reported here.
119228702
Cosmological evolution of the Fanaroff–Riley type II source population
By combining a model for the evolution of the radio luminosity of an individual source with the radio luminosity function, we perform a multidimensional Monte Carlo simulation to investigate the cosmological evolution of the Fanaroff–Riley type II (FR II) radio galaxy population by generating large artificial samples. The properties of FR II sources are required to evolve with redshift in the artificial samples to fit the observations. Either the maximum jet age or the maximum density of the jet environment or both evolve with redshift. We also study the distribution of FR II source properties as a function of redshift. From currently available data we cannot constrain the shape of the distribution of environment density or age, but jet power is found to follow a power-law distribution with an exponent of approximately −2. This power-law slope does not change with redshift out to z = 0.6. We also find the distribution of the pressure in the lobes of FR II sources to evolve with redshift up to z ∼ 1.2.
18308235
Search for new particles in hadronic events with isolated photons
Abstract A search for the neutral Higgs boson in the processes e + e − → Z → H 0 γ → q q γ and e + e − → Z → Z ∗ H 0 → q q γγ has been performed using 2.8 million hadronic Z decays collected with the L3 detector at LEP from 1991 through 1994. No evidence for these processes has been observed. Upper limits at 95% confidence level for the corresponding cross sections have been set and the results have been compared with theoretical predictions beyond the Standard Model.