arXiv subjects

G. Bertone

Publications and source records attributed to G. Bertone.

26 records · Page 2Linked to original sources

arXiv2007

WIMP identification through a combined measurement of axial and scalar couplings

We study the prospects for detecting Weakly Interacting Massive Particles (WIMPs), in a number of phenomenological scenarios, with a detector composed of a target simultaneously sensitive to both spin-dependent and spin-independent couplings, as is the case of COUPP (Chicagoland Observatory for Underground Particle Physics). First, we show that sensitivity to both couplings optimizes chances of initial WIMP detection. Second, we demonstrate that in case of detection, comparison of the signal on two complementary targets, such as in COUPP CF3I and C4F10 bubble chambers, allows a significantly more precise determination of the dark matter axial and scalar couplings. This strategy would provide crucial information on the nature of the WIMPs, and possibly allow discrimination between neutralino and Kaluza-Klein dark matter.

astro-ph↗

arXiv2005

Statistics of Magnification Perturbations by Substructure in the Cold Dark Matter Cosmological Model

We study the statistical properties of magnification perturbations by substructures in strong lensed systems using linear perturbation theory and an analytical substructure model including tidal truncation and a continuous substructure mass spectrum. We demonstrate that magnification perturbations are dominated by perturbers found within a tidal radius of an image, and that sizable magnification perturbations may arise from small, coherent contributions from several substructures within the lens halo. We find that the root-mean-square (rms) fluctuation of the magnification perturbation is 10% to 20% and both the average and rms perturbations are sensitive to the mass spectrum and density profile of the perturbers. Interestingly, we find that relative to a smooth model of the same mass, the average magnification in clumpy models is lower (higher) than that in smooth models for positive (negative) parity images. This is opposite from what is observed if one assumes that the image magnification predicted by the best-fit smooth model of a lens is a good proxy for what the observed magnification would have been if substructures were absent. While it is possible for this discrepancy to be resolved via nonlinear perturbers, we argue that a more likely explanation is that the assumption that the best-fit lens model is a good proxy for the magnification in the absence of substructure is not correct. We conclude that a better theoretical understanding of the predicted statistical properties of magnification perturbations by CDM substructure is needed in order to affirm that CDM substructures have been unambiguously detected.

astro-ph↗

arXiv2004

Annihilation Radiation of Dark Matter in Heterotic Orbifold Models

Direct and indirect dark matter searches can potentially lead to the discovery of Supersymmetry. In the specific context of heterotic orbifold compactification scenarios, it is even possible to get some clues on the SUSY breaking mechanism of the more fundamental underlying theory. In this paper, we investigate the prospects for indirect detection of neutralino dark matter via gamma-ray (continuum and line) and synchrotron radiation from the Galactic center, in the context of AMSB scenarios in an effective heterotic framework, which constitutes a consistent SUSY model between high energy theory and low energy phenomenology.

hep-ph↗

arXiv2003

Ultra-High Energy Cosmic Rays from Quasar Remnants

One of the models recently proposed to explain the origin of the ultra high energy cosmic rays assumes that these particles may be accelerated by the electromotive force around presently inactive quasar remnants. We study predictions for large and small scale ultra high energy cosmic ray arrival direction anisotropies in a scenario where the particles are injected with a mono-energetic spectrum by a discrete distribution of such sources. We find that known quasar remnants are typically distributed too anisotropically to explain the isotropic ultra high energy cosmic ray flux except in the unrealistic case where extragalactic magnetic fields of ~0.1 microGauss extend over many Mpc.

astro-ph↗

arXiv2001

Relativistic Thomas-Fermi Model at Finite Temperatures

We briefly review the Thomas-Fermi statistical model of atoms in the classical non-relativistic formulation and in the generalised finite-nucleus relativistic formulation. We then discuss the classical generalisation of the model to finite temperatures in the non-relativistic approximation and present a new relativistic model at finite temperatures, investigating how to recover the existing theory in the limit of low temperatures. This work is intended to be a propedeutical study for the evaluation of equilibrium configurations of relativistic ``hot'' white dwarfs.

astro-ph↗

arXiv2001

Astrophysical Limits on Massive Dark Matter

Annihilations of weakly interacting dark matter particles provide an important signature for the possibility of indirect detection of dark matter in galaxy halos. These self-annihilations can be greatly enhanced in the vicinity of a massive black hole. We show that the massive black hole present at the centre of our galaxy accretes dark matter particles, creating a region of very high particle density. Consequently the annihilation rate is considerably increased, with a large number of $e^+e^-$ pairs being produced either directly or by successive decays of mesons. We evaluate the synchrotron emission (and self-absorption) associated with the propagation of these particles through the galactic magnetic field, and are able to constrain the allowed values of masses and cross sections of dark matter particles.

astro-ph↗

arXiv2000

Annihilations from the Galactic Centre

A massive black hole is present at the centre of our galaxy and inevitably accretes dark matter particles, creating a region of very high particle density. The annihilation rate is enhanced with a large number of e+e- pairs produced either directly or by successive decays of mesons. We evaluate the synchrotron emission (and self-absorption) associated with the propagation of these particles through the galactic magnetic field and give constraints on the values of mass and cross section of the dark matter particles.

astro-ph↗

arXiv2000

Equilibrium configurations of relativistic White Dwarfs

The Feynman-Metropolis-Teller treatment for compressed atoms is here reconsidered in the framework of the relativistic generalised Fermi-Thomas model, obtained by Ruffini et al. Physical properties of a zero temperature plasma is thus investigated and the resulting equation of state, which keeps into account quantum, relativistic and electromagnetic effects, is applied to the study of equilibrium configurations of relativistic White Dwarfs. It is shown that numerical evaluation of such configuration leads, for the same central density $ρ_c$, to smaller values of radius R and of mass M than in the classical works of Chandrasekhar and Salpeter, the deviations being most marked at the lowest densities (up to 30% from the Chandrasekhar model and 10% from the Salpeter one for $ρ_c \sim 10^6g/cm^3$, corresponding to $M \sim 0.2 M_{\odot}$). At high densities we considered the occurrence of inverse beta decays, whose effect is to introduce gravitational instability of the configurations. We consequently find the maximum mass of White Dwarfs, which, for an Oxygen and an Iron WD, is respectively $1.365 M_{\odot}$ and $1.063 M_{\odot}$.

astro-ph↗