References of "Payez, Alexandre"
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See detailConstraining ALPs with linear and circular polarisation measurements of quasar light
Payez, Alexandre ULg

in 9th Patras Workshop on Axions, WIMPs and WISPs (in press)

We discuss the constraints derived on the mixing of photons with light pseudoscalars using the distributions of good-quality linear and circular polarisation measurements of light from the least polarised ... [more ▼]

We discuss the constraints derived on the mixing of photons with light pseudoscalars using the distributions of good-quality linear and circular polarisation measurements of light from the least polarised classes of quasars. We also provide the dependence of our limit on the average electron density in the local supercluster for nearly massless particles. [less ▲]

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See detailA fresh look on the limit on light ALPs from SN1987A
Payez, Alexandre ULg; Evoli, Carmelo; Fischer, Tobias et al

Poster (2014, July 03)

We revisit the limit on very light axion-like particles from the absence of coincidental gamma rays with the neutrino burst from SN1987A. This is done using an updated supernova simulation, an updated ... [more ▼]

We revisit the limit on very light axion-like particles from the absence of coincidental gamma rays with the neutrino burst from SN1987A. This is done using an updated supernova simulation, an updated model for the magnetic field inside the Galaxy, and a Primakoff cross section which takes into account proton degeneracy. [less ▲]

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See detailLarge-scale alignments of quasar polarisations: a detailed study of the spinless-particle scenario
Payez, Alexandre ULg

Doctoral thesis (2013)

The main motivation for our work has been a puzzling observation concerning quasars. No one expected the existence of correlations in the polarisation of visible light coming from objects separated by ... [more ▼]

The main motivation for our work has been a puzzling observation concerning quasars. No one expected the existence of correlations in the polarisation of visible light coming from objects separated by gigaparsecs, until they were first reported in the form of a redshift-dependent effect that has become more and more significant with the growth of the data sample. In close connexion with the observational group, we have studied in detail the most widely considered scenario, involving axion-photon mixing in extragalactic magnetic fields. After a systematic investigation, we conclude that it is very unlikely that these observations can be accounted for by axion-like particles, given current data and constraints. We also derive new limits on the parameters describing these particles. This thesis gives in particular a detailed account of the consequences of axion-photon mixing on polarisation, studies the influence of averages over the frequency (including a wave-packet treatment of the mixing), and discusses the consequences of different magnetic-field morphologies. [less ▲]

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See detailNew polarimetric constraints on axion-like particles
Payez, Alexandre ULg; Cudell, Jean-René ULg; Hutsemekers, Damien ULg

in Journal of Cosmology and Astroparticle Physics [= JCAP] (2012), 1207

We show that the parameter space of axion-like particles can be severly constrained using high-precision measurements of quasar polarisations. Robust limits are derived from the measured bounds on optical ... [more ▼]

We show that the parameter space of axion-like particles can be severly constrained using high-precision measurements of quasar polarisations. Robust limits are derived from the measured bounds on optical circular polarisation and from the distribution of linear polarisations of quasars. As an outlook, this technique can be improved by the observation of objects located behind clusters of galaxies, using upcoming space-borne X-ray polarimeters. [less ▲]

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See detailCornering the axionlike particle explanation of quasar polarizations
Payez, Alexandre ULg

in Physical Review. D : Particles and Fields (2012), 85(8), 087701

In a series of papers, it has been shown that the distribution of polarization position angles for visible light from quasars is not random in extremely large regions of the sky. As explained in a recent ... [more ▼]

In a series of papers, it has been shown that the distribution of polarization position angles for visible light from quasars is not random in extremely large regions of the sky. As explained in a recent article, the measurement of vanishing circular polarization for such quasars is an important problem for a mechanism involving the mixing with axionlike particles in external magnetic fields. In this paper, we stress that a recent report of similar coherent orientations of polarization in radio waves further disfavors the need for such particles, as an effect at these wavelengths would be extremely suppressed or would directly contradict data. [less ▲]

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See detailNew constraints on very light pseudoscalars
Payez, Alexandre ULg; Cudell, Jean-René ULg; Hutsemekers, Damien ULg

in Zioutas, K. (Ed.) 7th Patras Workshop on Axions, WIMPs and WISPs (2012, January 01)

Nearly massless axion-like particles are of interest for astrophysical observations, and some constraints on their parameter space do exist in the literature. Here, we propose to put new constraints on ... [more ▼]

Nearly massless axion-like particles are of interest for astrophysical observations, and some constraints on their parameter space do exist in the literature. Here, we propose to put new constraints on these particles using polarisation and, in particular, the polarisation differences observed between different quasar classes. [less ▲]

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See detailCan axionlike particles explain the alignments of the polarizations of light from quasars?
Payez, Alexandre ULg; Cudell, Jean-René ULg; Hutsemekers, Damien ULg

in Physical Review. D : Particles and Fields (2011), 84

The standard axion-like particle explanation of the observed large-scale coherent orientations of quasar polarisation vectors is ruled out by the recent measurements of vanishing of circular polarisation ... [more ▼]

The standard axion-like particle explanation of the observed large-scale coherent orientations of quasar polarisation vectors is ruled out by the recent measurements of vanishing of circular polarisation. We introduce a more general wave-packet formalism and show that, although decoherence effects between waves of different frequencies can reduce significantly the amount of circular polarisation, the axion-like particle hypothesis is disfavoured given the bandwidth with which part of the observations were performed. Finally, we show that a more sophisticated model of extragalactic fields does not lead to an alignment of polarisations. [less ▲]

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See detailLarge-scale coherent orientations of quasar polarisation vectors: interpretation in terms of axion-like particles
Payez, Alexandre ULg; Hutsemekers, Damien ULg; Cudell, Jean-René ULg

in AIP Conference Proceedings (2010), 1274,

The observation of redshift-dependent coherent orientations of quasar polarisation vectors over cosmological distances in some regions of the sky is reviewed. Based on a good-quality sample of 355 ... [more ▼]

The observation of redshift-dependent coherent orientations of quasar polarisation vectors over cosmological distances in some regions of the sky is reviewed. Based on a good-quality sample of 355 measured quasars, this observation seems to infer the existence of a new effect acting on light propagation on such huge distances. A solution in terms of nearly massless axion-like particles has been proposed in the literature and its current status is discussed. [less ▲]

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See detailAxions et polarisation des quasars
Payez, Alexandre ULg

in Barillon, Pierre (Ed.) Journées Jeunes Chercheurs 2008 (2010)

[Français] Je présente rapidement l'objet de mes recherches et tente ensuite l'exercice consistant à exposer - le plus clairement possible - les idées et considérations physiques ayant amené à la ... [more ▼]

[Français] Je présente rapidement l'objet de mes recherches et tente ensuite l'exercice consistant à exposer - le plus clairement possible - les idées et considérations physiques ayant amené à la proposition de l'existence de l'axion. [less ▲]

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See detailOn the circular polarisation of light from axion-photon mixing
Payez, Alexandre ULg; Cudell, Jean-René ULg; Hutsemekers, Damien ULg

in Alimi, Jean-Michel; Füzfa, André (Eds.) INVISIBLE UNIVERSE: Proceedings of the Conference. AIP Conference Proceedings 1241. (2010)

From the analysis of measurements of the linear polarisation of visible light coming from quasars, the existence of large-scale coherent orientations of quasar polarisation vectors in some regions of the ... [more ▼]

From the analysis of measurements of the linear polarisation of visible light coming from quasars, the existence of large-scale coherent orientations of quasar polarisation vectors in some regions of the sky has been reported. Here, we show that this can be explained by the mixing of the incoming photons with nearly massless pseudoscalar (axion-like) particles in extragalactic magnetic fields. We present a new treatment in terms of wave packets and discuss its implications for the circular polarisation. [less ▲]

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See detailAxion-like particles and circular polarisation of active galactic nuclei
Payez, Alexandre ULg; Cudell, Jean-René ULg; Hutsemekers, Damien ULg

in Jaeckel, Joerg; Lindner, Axel; Redondo, Javier (Eds.) Proceedings of the 5th Patras Workshop on Axions, WIMPs and WISPs PATRAS 2009 (2010)

The measurements of the linear polarisation of visible light from quasars give strong evidence for large-scale coherent orientations of their polarisation vectors in some regions of the sky. We show that ... [more ▼]

The measurements of the linear polarisation of visible light from quasars give strong evidence for large-scale coherent orientations of their polarisation vectors in some regions of the sky. We show that these observations can be explained by the mixing of the photons with very light pseudoscalar (axion-like) particles in extragalactic magnetic fields during their propagation. We present a new treatment in terms of wave packets and discuss the circular polarisation. [less ▲]

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See detailAxions & Polarisation of Quasars
Payez, Alexandre ULg; Cudell, Jean-René ULg; Hutsemekers, Damien ULg

Poster (2008, May 21)

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See detailAxions and polarisation of quasars
Payez, Alexandre ULg; Cudell, Jean-René ULg; Hutsemekers, Damien ULg

in AIP Conference Proceedings (2008), 1038

We present results showing that, thanks to axion-photon mixing in external magnetic fields, it is actually possible to produce an effect similar to the one needed to explain the large-scale coherent ... [more ▼]

We present results showing that, thanks to axion-photon mixing in external magnetic fields, it is actually possible to produce an effect similar to the one needed to explain the large-scale coherent orientations of quasar polarisation vectors in visible light that have been observed in some regions of the sky. [less ▲]

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See detailAxions et polarisation des quasars
Payez, Alexandre ULg

Master's dissertation (2007)

Suite à l’observation de la polarisation de la lumière provenant de quasars, une tendance à l’alignement des vecteurs de polarisation de ces lointains objets fut détectée dans certaines régions du ciel ... [more ▼]

Suite à l’observation de la polarisation de la lumière provenant de quasars, une tendance à l’alignement des vecteurs de polarisation de ces lointains objets fut détectée dans certaines régions du ciel, celle-ci restant inexplicable par des effets locaux et semblant mettre en évidence l’existence de corrélations à très grande échelle, sur des distances cosmologiques. L’objet de ce travail, qui s’inscrit à l’interface entre la physique des particules et l’astrophysique, sera de se pencher sur ce problème et de déterminer dans quelle mesure l’existence d’un certain type de particules encore hypothétiques, nommées axions, pourrait permettre de rendre compte de ce phénomène ; les propriétés prédites pour celles-ci incluant un couplage (faible, mais les distances entrant en jeu étant très grandes, les effets de ce couplage pourraient malgré tout être observables) avec la lumière. [less ▲]

Detailed reference viewed: 84 (49 ULg)