Annihilation (physique)

Résumé

En physique, l’annihilation ou anéantissement correspond à la collision entre une particule sous-atomique et son antiparticule respective. Puisque l’énergie et la quantité de mouvement doivent être conservées, les particules ne se muent pas en rien, mais plutôt en nouvelles particules. Les antiparticules possèdent des nombres quantiques exactement opposés à ceux des particules, donc la somme des nombres quantiques du pair égale zéro. Ainsi, le processus peut donner naissance à n’importe quel jeu de particules dont la somme des nombres quantiques est égale à zéro, pourvu que la conservation d’énergie et de la quantité de mouvement soient respectées. Lors de la collision entre une particule et son antiparticule, leur énergie se transforme en particule porteuse de force, tel le boson W+/W-, porteuse de force W/Z ou un photon. Ces particules se transforment plus tard en autres particules. Lors d’une annihilation à faible énergie, la production des photons est favorisée, puisque ces part

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https://fr.wikipedia.org/wiki/Annihilation_(physique)

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This lecture describes advanced concepts and applications of quantum optics. It emphasizes the connection with ongoing research, and with the fast growing field of quantum technologies. The topics cover some aspects of quantum information processing, quantum sensing and quantum simulation.

Presentation of particle properties, their symmetries and interactions. Introduction to quantum electrodynamics and to the Feynman rules.

The goal of the course is to introduce relativistic quantum field theory as the conceptual and mathematical framework describing fundamental interactions.

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CMB photons shedding light on dark matter

Benjamin Audren, Gaëlle Giesen, Julien Lesgourgues

The annihilation or decay of Dark Matter (DM) particles could affect the thermal history of the universe and leave an observable signature in Cosmic Microwave Background (CMB) anisotropies. We update constraints on the annihilation rate of DM particles in the smooth cosmological background, using WMAP7 and recent small-scale CMB data. With a systematic analysis based on the Press-Schechter formalism, we also show that DM annihilation in halos at small redshift may explain entirely the reionization patterns observed in the CMB, under reasonable assumptions concerning the concentration and formation redshift of halos. We find that a mixed reionization model based on DM annihilation in halos as well as star formation at a redshift z similar or equal to 6.5 could simultaneously account for CMB observations and satisfy constraints inferred from the Gunn-Peterson effect. However, these models tend to reheat the inter-galactic medium (IGM) well above observational bounds: by including a realistic prior on the IGM temperature at low redshift and allowing most of the reionization to be due to star formation, we find stronger cosmological bounds on the annihilation cross-section than with the CMB alone.

Iop Publishing Ltd2012

Chargement

Recent analyses have shown that the inclusion of electroweak corrections can alter significantly the energy spectra of Standard Model particles originated from dark matter annihilations. We investigate the important situation where the radiation of electroweak gauge bosons has a substantial influence: a Majorana dark matter particle annihilating into two light fermions. This process is in p-wave and hence suppressed by the small value of the relative velocity of the annihilating particles. The inclusion of electroweak radiation eludes this suppression and opens up a potentially sizeable s-wave contribution to the annihilation cross section. We study this effect in detail and explore its impact on the fluxes of stable particles resulting from the dark matter annihilations, which are relevant for dark matter indirect searches. We also discuss the effective field theory approach, pointing out that the opening of the s-wave is missed at the level of dimension-six operators and only encoded by higher orders.

2011

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Electroweak lights from Dark Matter annihilations

Andrea De Simone

The energy spectra of Standard Model particles originated from Dark Matter annihilations can be significantly altered by the inclusion of electroweak gauge boson radiation from the final state. A situation where this effect is particularly important is when a Majorana Dark Matter particle annihilates into two light fermions. This process is in p-wave and hence suppressed by the small value of the relative velocity of the annihilating particles. The inclusion of electroweak radiation eludes this suppression and opens up a potentially sizeable s-wave contribution to the annihilation cross section. I will discuss the impact of this effect on the fluxes of stable particles resulting from the Dark Matter annihilations, which are relevant for Dark Matter indirect searches.

Iop Publishing Ltd2012

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