arXiv subjects

Florian Beutler

Publications and source records attributed to Florian Beutler.

129 records · Page 8Linked to original sources

arXiv2011

The WiggleZ Dark Energy Survey: mapping the distance-redshift relation with baryon acoustic oscillations

We present measurements of the baryon acoustic peak at redshifts z = 0.44, 0.6 and 0.73 in the galaxy correlation function of the final dataset of the WiggleZ Dark Energy Survey. We combine our correlation function with lower-redshift measurements from the 6-degree Field Galaxy Survey and Sloan Digital Sky Survey, producing a stacked survey correlation function in which the statistical significance of the detection of the baryon acoustic peak is 4.9-sigma relative to a zero-baryon model with no peak. We fit cosmological models to this combined baryon acoustic oscillation (BAO) dataset comprising six distance-redshift data points, and compare the results to similar fits to the latest compilation of supernovae (SNe) and Cosmic Microwave Background (CMB) data. The BAO and SNe datasets produce consistent measurements of the equation-of-state w of dark energy, when separately combined with the CMB, providing a powerful check for systematic errors in either of these distance probes. Combining all datasets we determine w = -1.03 +/- 0.08 for a flat Universe, consistent with a cosmological constant model. Assuming dark energy is a cosmological constant and varying the spatial curvature, we find Omega_k = -0.004 +/- 0.006.

astro-ph.CO↗

arXiv2011

The 6dF Galaxy Survey: Baryon Acoustic Oscillations and the Local Hubble Constant

We analyse the large-scale correlation function of the 6dF Galaxy Survey (6dFGS) and detect a Baryon Acoustic Oscillation (BAO) signal. The 6dFGS BAO detection allows us to constrain the distance-redshift relation at z_{\rm eff} = 0.106. We achieve a distance measure of D_V(z_{\rm eff}) = 456\pm27 Mpc and a measurement of the distance ratio, r_s(z_d)/D_V(z_{\rm eff}) = 0.336\pm0.015 (4.5% precision), where r_s(z_d) is the sound horizon at the drag epoch z_d. The low effective redshift of 6dFGS makes it a competitive and independent alternative to Cepheids and low-z supernovae in constraining the Hubble constant. We find a Hubble constant of H_0 = 67\pm3.2 km s^{-1} Mpc^{-1} (4.8% precision) that depends only on the WMAP-7 calibration of the sound horizon and on the galaxy clustering in 6dFGS. Compared to earlier BAO studies at higher redshift, our analysis is less dependent on other cosmological parameters. The sensitivity to H_0 can be used to break the degeneracy between the dark energy equation of state parameter w and H_0 in the CMB data. We determine that w = -0.97\pm0.13, using only WMAP-7 and BAO data from both 6dFGS and \citet{Percival:2009xn}. We also discuss predictions for the large scale correlation function of two future wide-angle surveys: the WALLABY blind H{\sc I} survey (with the Australian SKA Pathfinder, ASKAP), and the proposed TAIPAN all-southern-sky optical galaxy survey with the UK Schmidt Telescope (UKST). We find that both surveys are very likely to yield detections of the BAO peak, making WALLABY the first radio galaxy survey to do so. We also predict that TAIPAN has the potential to constrain the Hubble constant with 3% precision.

astro-ph.CO↗

arXiv2009

Thermal description of hadron production in e+e- collisions

This thesis gives a comprehensive analysis of hadron production in $e^{+}e^{-}$ collisions at different center of mass energies in the framework of the Statistical Model of the hadron resonance gas. The model used for the analysis is formulated in the canonical ensemble with exact conservation of five quantum numbers. The corresponding canonical partition function in quantum statistics is derived and the canonical factor as the striking feature of the canonical framework will be investigated in detail. The parameters of the underlying model were determined using a fit to the average multiplicities of the latest measurements at $\sqrt{s}$=10, 29-35, 91 and 130-200 GeV. The measurements are compared to the pure thermal production like in heavy ion collisions as well as to the production in a second scenario accounting for hard collisions and the resulting enhancement of heavy quark. The results demonstrate that, within the accuracy of the experiments, none of the data sets is satisfactorily described with this approach, calling into question the notion that particle production in $e^{+}e^{-}$ collisions is thermal in origin. Nevertheless it is observed that the charm and bottom particle yields produced in hard collisions can be explained by large canonical enhancements of such particles in heavy jets, almost independent of the model parameters.

nucl-th↗