Search results for "Astrophysics - cosmology and nongalactic astrophysics"
showing 10 items of 607 documents
Direct neutralino searches in the NMSSM with gravitino LSP in the degenerate scenario
2011
In the present work a two-component dark matter model is studied adopting the degenerate scenario in the R-parity conserving NMSSM. The gravitino LSP and the neutralino NLSP are extremely degenerate in mass, avoiding the BBN bounds and obtaining a high reheating temperature for thermal leptogenesis. In this model both gravitino (absolutely stable) and neutralino (quasi-stable) contribute to dark matter, and direct detection searches for neutralino are discussed. Points that survive all the constraints correspond to a singlino-like neutralino.
Is the baryon asymmetry of the Universe related to galactic magnetic fields?
2009
A tiny hypermagnetic field generated before the electroweak phase transition (EWPT) associated to the generation of elementary particle masses can polarize the early Universe hot plasma at huge redshifts z >= 10(15). The anomalous violation of the right-handed electron current characteristic of the EWPT converts the lepton asymmetry into a baryon asymmetry. Under reasonable approximations, the magnetic field strength inferred by requiring such "leptogenic'' origin for the observed baryon asymmetry of the Universe matches the large-scale cosmological magnetic field strengths estimated from current astronomical observations.
Dark matter as the origin of neutrino mass in the inverse seesaw mechanism
2021
We propose that neutrino masses are "seeded" by a dark sector within the inverse seesaw mechanism. This way we have a new, "hidden", variant of the scotogenic scenario for radiative neutrino masses. We discuss both explicit and dynamical lepton number violation. In addition to invisible Higgs decays with majoron emission, we discuss in detail the pheneomenolgy of dark matter, as well as the novel features associated to charged lepton flavour violation, and neutrino physics.
Likelihood approach to the first dark matter results from XENON100
2011
Many experiments that aim at the direct detection of Dark Matter are able to distinguish a dominant background from the expected feeble signals, based on some measured discrimination parameter. We develop a statistical model for such experiments using the Profile Likelihood ratio as a test statistic in a frequentist approach. We take data from calibrations as control measurements for signal and background, and the method allows the inclusion of data from Monte Carlo simulations. Systematic detector uncertainties, such as uncertainties in the energy scale, as well as astrophysical uncertainties, are included in the model. The statistical model can be used to either set an exclusion limit or …
N_eff in low-scale seesaw models versus the lightest neutrino mass
2014
We evaluate the contribution to $N_{\rm eff}$ of the extra sterile states in low-scale Type I seesaw models (with three extra sterile states). We explore the full parameter space and find that at least two of the heavy states always reach thermalisation in the Early Universe, while the third one might not thermalise provided the lightest neutrino mass is below ${\mathcal O}(10^{-3}$eV). Constraints from cosmology therefore severely restrict the spectra of heavy states in the range 1eV- 100 MeV. The implications for neutrinoless double beta decay are also discussed.
Model-independent fit to Planck and BICEP2 data
2014
Inflation is the leading theory to describe elegantly the initial conditions that led to structure formation in our universe. In this paper, we present a novel phenomenological fit to the Planck, WMAP polarisation (WP) and the BICEP2 datasets using an alternative parameterisation. Instead of starting from inflationary potentials and computing the inflationary observables, we use a phenomenological parameterisation due to Mukhanov, describing inflation by an effective equation-of-state, in terms of the number of e-folds and two phenomenological parameters $\alpha$ and $\beta$. Within such a parametrisation, which captures the different inflationary models in a model-independent way, the valu…
Constraints on massive sterile neutrino species from current and future cosmological data
2011
Sterile massive neutrinos are a natural extension of the Standard Model of elementary particles. The energy density of the extra sterile massive states affects cosmological measurements in an analogous way to that of active neutrino species. We perform here an analysis of current cosmological data and derive bounds on the masses of the active and the sterile neutrino states as well as on the number of sterile states. The so-called (3+2) models with three sub-eV active massive neutrinos plus two sub-eV massive sterile species is well within the 95% CL allowed regions when considering cosmological data only. If the two extra sterile states have thermal abundances at decoupling, Big Bang Nucle…
Joint constraints on galaxy bias and σ8 through the N-pdf of the galaxy number density
2015
We present a full description of the N-probability density function of the galaxy number density fluctuations. This N-pdf is given in terms, on the one hand, of the cold dark matter correlations and, on the other hand, of the galaxy bias parameter. The method relies on the assumption commonly adopted that the dark matter density fluctuations follow a local non-linear transformation of the initial energy density perturbations. The N-pdf of the galaxy number density fluctuations allows for an optimal estimation of the bias parameter (e.g., via maximum-likelihood estimation, or Bayesian inference if there exists any a priori information on the bias parameter), and of those parameters defining …
Unveiling ν secrets with cosmological data: Neutrino masses and mass hierarchy
2017
Using some of the latest cosmological datasets publicly available, we derive the strongest bounds in the literature on the sum of the three active neutrino masses, $M_\nu$, within the assumption of a background flat $\Lambda$CDM cosmology. In the most conservative scheme, combining Planck cosmic microwave background (CMB) temperature anisotropies and baryon acoustic oscillations (BAO) data, as well as the up-to-date constraint on the optical depth to reionization ($\tau$), the tightest $95\%$ confidence level (C.L.) upper bound we find is $M_\nu0.06\,{\rm eV}$ from oscillations data would raise the quoted upper bounds by ${\cal O}(0.1\sigma)$ and would not affect our conclusions.
Direct limits on the interaction of antiprotons with axion-like dark matter
2019
Astrophysical observations indicate that there is roughly five times more dark matter in the Universe than ordinary baryonic matter, with an even larger amount of the Universe's energy content due to dark energy. So far, the microscopic properties of these dark components have remained shrouded in mystery. In addition, even the five percent of ordinary matter in our Universe has yet to be understood, since the Standard Model of particle physics lacks any consistent explanation for the predominance of matter over antimatter. Inspired by these central problems of modern physics, we present here a direct search for interactions of antimatter with dark matter, and place direct constraints on th…