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Soutenance de thèse/ Séminaires/ HDR


Soutenance de thèse

Pas de soutenance a annoncer actuellement.

Séminaire

Niels Madsen, de Swansea university, donnera un séminaire le 15 novembre 2018 à 11h00 à l’Observatoire de Paris, Salle Denisse.

Le titre du séminaire est : « Antihydrogen Spectroscopy and Beyond ».

Voici l’abstract :

Antihydrogen, the bound state of an antiproton and a positron, is a very attractive system for probing a number of fundamental symmetries of physics such as the CPT theorem and the weak equivalence principle. The attractiveness stems from it being the only bound system of antimatter readily available, its neutrality and the detailed understanding of its matter counterpart, hydrogen, both theoretically and experimentally [1]. The ALPHA experiment produces and traps antihydrogen in order to subject it to precise measurements of e.g. its internal energy levels. According to the CPT theorem the transitions in antihydrogen must mirror those of hydrogen. I will present ALPHAs start-of-the-art antihydrogen production and trapping system [2] as well as discuss the first precise measurements on the internal states of antihydrogen [3, 4]. One example is ALPHAs most recent measurement of one hyperfine component of the 1S-2S transition in Antihydrogen to a precision of 2 parts in 1012, currently the most precise and accurate measurement on antimatter [4]. I will further discuss ALPHA‘s ongoing expansion with an experiment to probe the gravitational to inertial mass of antihydrogen, and I will discuss, various efforts that we believe will both increase the number of anti-atoms trapped as well as lower their temperature, allowing measurements whose precision will compete with that of hydrogen (e.g. Ref. [6]). [1] Antiproton physics in the ELENA era (eds. N. Madsen), Phil. Trans. Roy. Soc. A, 376 (2018). [2] Antihydrogen accumulation for fundamental symmetry tests, M. Ahmadi et al., Nat. Comm. 8, 681 (2017). [3] Observation of the hyperfine spectrum of antihydrogen, M. Ahmadi et al., Nature 548, 66 (2017) [4] Characterization of the 1S-2S transition in antihydrogen, M. Ahmadi et al., Nature 557, 71 (2018). [5] Observation of the 1S-2P Lyman- transition in antihydrogen, M. Ahmadi et al., Nature 561, 211 (2018). [6] Antihydrogen trapping assisted by sympathetically cooled positrons, N. Madsen, F. Robicheaux and S. Jonsell, N. J. Phys 16, 063046 (2014).