Search results for " Background"
showing 10 items of 316 documents
GEANT4 simulation of the neutron background of the C6D6 set-up for capture studies at n_TOF
2014
The neutron sensitivity of the C6D6 detector setup used at n_TOF facility for capture measurements has been studied by means of detailed GEANT4 simulations. A realistic software replica of the entire n_TOF experimental hall, including the neutron beam line, sample, detector supports and the walls of the experimental area has beeni mplemented in the simulations. The simulations have been analyzed in the same manner as experimental data, in particular by applying the Pulse Height Weighting Technique. The simulations have been validated against a measurement of the neutron background performed with anatC sample, showing an excellent agreement above 1 keV. At lower energies, an additional compo…
Modeling quitessential inflation
2001
We develop general criteria to construct unified frameworks for inflation and quintessence which employ a unique scalar field to drive both. By using such a minimal theoretical framework we avoid having to fine-tune couplings and mass-scales. In particular the initial conditions for quintessence are already fixed at the end of the inflationary epoch. We provide concrete realizations of the method which meet all inflationary and quintessence requirements, such as the COBE normalization and the resulting spectral index n = 0.97, which is in excellent agreement with the latest CMB data.
The roughness of the last scattering surface
1999
We propose an alternative analysis of the microwave background temperature anisotropy maps that is based on the study of the roughness of natural surfaces. We apply it to large angle anisotropies, such as those measured by COBE-DMR. We show that for a large signal to noise experiment, the spectral index can be determined independently of the normalization. We then analyze the 4 yr COBE map and find for a flat $\Omega=1$ universe, that the best-fitting value for the spectral index is $n = 1.15^{+0.39}_{-0.34}$ and for the amplitude $Q_{rms-PS}= 14.1^{+3.9}_{-3.5}\mu K$. For $n=1$, the best-fitting normalization is $Q_{rms-PS}|_{n=1}= 16.2^{+1.4}_{-1.3}\mu K$.
Probing neutrino masses with future galaxy redshift surveys
2004
We perform a new study of future sensitivities of galaxy redshift surveys to the free-streaming effect caused by neutrino masses, adding the information on cosmological parameters from measurements of primary anisotropies of the cosmic microwave background (CMB). Our reference cosmological scenario has nine parameters and three different neutrino masses, with a hierarchy imposed by oscillation experiments. Within the present decade, the combination of the Sloan Digital Sky Survey (SDSS) and CMB data from the PLANCK experiment will have a 2-sigma detection threshold on the total neutrino mass close to 0.2 eV. This estimate is robust against the inclusion of extra free parameters in the refer…
Constraints on neutrino masses from Planck and Galaxy clustering data
2013
We present here bounds on neutrino masses from the combination of recent Planck cosmic microwave background (CMB) measurements and galaxy clustering information from the Baryon Oscillation Spectroscopic Survey, part of the Sloan Digital Sky Survey-III. We use the full shape of either the photometric angular clustering (Data Release 8) or the 3D spectroscopic clustering (Data Release 9) power spectrum in different cosmological scenarios. In the Lambda CDM scenario, spectroscopic galaxy clustering measurements improve significantly the existing neutrino mass bounds from Planck data. We find Sigma m(v) < 0.39 eV at 95% confidence level for the combination of the 3D power spectrum with Planck C…
Neutrino and dark radiation properties in light of recent CMB observations
2013
Recent cosmic microwave background measurements at high multipoles from the South Pole Telescope and from the Atacama Cosmology Telescope seem to disagree in their conclusions for the neutrino and dark radiation properties. In this paper we set new bounds on the dark radiation and neutrino properties in different cosmological scenarios combining the ACT and SPT data with the nine-year data release of the Wilkinson Microwave Anisotropy Probe (WMAP-9), baryon acoustic oscillation data, Hubble Telescope measurements of the Hubble constant, and supernovae Ia luminosity distance data. In the standard three massive neutrino case, the two high multipole probes give similar results if baryon acoust…
Model independent constraints on mass-varying neutrino scenarios
2009
Models of dark energy in which neutrinos interact with the scalar field supposed to be responsible for the acceleration of the Universe usually imply a variation of the neutrino masses on cosmological time scales. In this work we propose a parametrization for the neutrino mass variation that captures the essentials of those scenarios and allows one to constrain them in a model independent way, that is, without resorting to any particular scalar field model. Using WMAP 5 yr data combined with the matter power spectrum of SDSS and 2dFGRS, the limit on the present value of the neutrino mass is m(0) equivalent to m(nu)(z = 0) 0), totally consistent with no mass variation. These stringent bounds…
Probing neutrino masses with CMB lensing extraction
2005
We evaluate the ability of future cosmic microwave background (CMB) experiments to measure the power spectrum of large scale structure using quadratic estimators of the weak lensing deflection field. We calculate the sensitivity of upcoming CMB experiments such as BICEP, QUaD, BRAIN, ClOVER and PLANCK to the non-zero total neutrino mass M_nu indicated by current neutrino oscillation data. We find that these experiments greatly benefit from lensing extraction techniques, improving their one-sigma sensitivity to M_nu by a factor of order four. The combination of data from PLANCK and the SAMPAN mini-satellite project would lead to sigma(M_nu) = 0.1 eV, while a value as small as sigma(M_nu) = 0…
Neutrino Mass from Cosmology
2012
Neutrinos can play an important role in the evolution of the Universe, modifying some of the cosmological observables. In this contribution we summarize the main aspects of cosmological relic neutrinos and we describe how the precision of present cosmological data can be used to learn about neutrino properties, in particular their mass, providing complementary information to beta decay and neutrinoless double-beta decay experiments. We show how the analysis of current cosmological observations, such as the anisotropies of the cosmic microwave background or the distribution of large-scale structure, provides an upper bound on the sum of neutrino masses of order 1 eV or less, with very good p…
Probing interactions within the dark matter sector via extra radiation contributions
2013
The nature of dark matter is one of the most thrilling riddles for both cosmology and particle physics nowadays. While in the typical models the dark sector is composed only by weakly interacting massive particles, an arguably more natural scenario would include a whole set of gauge interactions which are invisible for the standard model but that are in contact with the dark matter. We present a method to constrain the number of massless gauge bosons and other relativistic particles that might be present in the dark sector using current and future cosmic microwave background data, and provide upper bounds on the size of the dark sector. We use the fact that the dark matter abundance depends…