Jeudi 12 Avril
Résumé :
Antihydrogen (\rm \overline{H}) is the simplest anti-atom. It consists of a positron bound to an antiproton, just as an ordinary hydrogen atom (H) consists of an electron bound to a proton. The quest to produce, trap, and study dates back at least a quarter of a century. It is motivated in part by the idea that precise comparisons of corresponding atomic and anti-atomic spectra (e.g. those of H and \rm \overline{H}) should yield stringent tests of fundamental symmetries. If a difference were to be observed, it could provide a clue to aid in understanding the baffling fact that our universe seems to be almost entirely devoid of antimatter.
Significant progress towards the realization of antihydrogen spectroscopy has been reported by the CERN-based ALPHA collaboration over the last 18 months. In November 2010, we reported the first magnetic confinement of neutral antihydrogen atoms [1]. In June 2011, we showed that these newly synthesized and trapped anti-atoms rapidly decay to their ground state where they can be held for long periods of time [2]. Now, in our most recent report, we have used microwave radiation to induce spin flip transitions between hyperfine levels of the trapped positronic ground state [3]. These manipulations yield the first, albeit crude, spectroscopic measurements performed on a pure anti-atom.
During this talk I will describe the methods we use to produce, trap, detect, and interrogate atoms. I will also try to give an impression of the challenges with which one is faced in working with neutral anti-atoms, as well as a sense for how these experiments might evolve in the future.
[1] Trapped Antihydrogen : Nature 468, 673-676 (2010).
[2] Confinement of antihydrogen for 1,000s : Nature Physics 7, 558-564 (2011).
[3] Resonant quantum transitions in trapped antihydrogen atoms : Nature 483, 439-443 (2012).
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Le département de physique
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