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Recherche de nouveaux bosons légers en astronomie de haute énergie

Abstract : High-Energy astronomy studies the most violent phenomena in the universe with observations in a large spectrum of energies ranging from X rays to very high energy gamma rays (1 keV - 100 TeV). Such phenomena could be for instance supernovae explosions and their remnants, pulsars and pulsar wind nebulae or ultra relativistic jets formation by active galactic nuclei. Understanding these phenomena requires to use well-known particle physics processes. By means of high energy photons, studying such phenomena enables one to search for physics beyond the standard model. Concepts regarding the emission and propagation of high-energy photons are introduced and applied to study their emission by extragalactic sources and to constrain the extragalactic background light which affects their propagation. In this thesis, these high-energy extragalactic emitters are observed in order to search for new light bosons such as axion-like particles (ALPs). The theoretical framework of this family of hypothetical particles is reviewed as well as the associated phenomenology. In particular, because of their coupling to two photons, ALPs oscillate with photons in an external magnetic field. A new signature of such oscillations in turbulent magnetic fields, under the form of stochastic irregularities in the source energy spectrum, is introduced and discussed. A search for ALPs with the HESS telescopes with this new signature is presented, resulting in the first constraints on ALPs parameters coming from high-energy astronomy. Current constraints on ALPs at very low masses are improved by searching for the same signature in X-ray observations. An extension of these constraints to scalar field models for modified gravity in the framework of dark energy is then discussed. The potential of the search for ALPs with CTA, the prospected gamma-ray astronomy instrument, is eventually studied; in particular, a new observable is proposed that relies on the high number of sources that are expected to be discovered with this instrument.
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Submitted on : Thursday, September 18, 2014 - 12:57:13 PM
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  • HAL Id : tel-01065648, version 1

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Denis Wouters. Recherche de nouveaux bosons légers en astronomie de haute énergie. Autre [cond-mat.other]. Université Paris Sud - Paris XI, 2014. Français. ⟨NNT : 2014PA112141⟩. ⟨tel-01065648⟩

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