Measurement of the hyperfine structure of antihydrogen in a beam
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Measurement of the hyperfine structure of antihydrogen in a beam E. Widmann · M. Diermaier · B. Juhász · C. Malbrunot · O. Massiczek · C. Sauerzopf · K. Suzuki · B. Wünschek · J. Zmeskal · S. Federmann · N. Kuroda · S. Ulmer · Y. Yamazaki
Published online: 29 January 2013 © Springer Science+Business Media Dordrecht 2013
Abstract A measurement of the hyperfine structure of antihydrogen promises one of the best tests of CPT symmetry. We describe an experiment planned at the Antiproton Decelerator of CERN to measure this quantity in a beam of slow antihydrogen atoms. Keywords Antihydrogen · Precision spectroscopy · CPT
Supported by the European Research Council grant no. 291242-HBAR-HFS, the Austrian Ministry for Science and Research, and the Grant-in-Aid for Specially Promoted Research (19002004), JSPS. The 5th International Symposium on Symmetries in Subatomic Physics (SSP 2012), Groningen, The Netherlands, 18–22 June 2012. E. Widmann (B) · M. Diermaier · B. Juhász · C. Malbrunot · O. Massiczek · C. Sauerzopf · K. Suzuki · B. Wünschek · J. Zmeskal Stefan Meyer Institute for Subatomic Physics, Austrian Academy of Sciences, Boltzmanngasse 3, 1090 Vienna, Austria e-mail: [email protected] S. Federmann CERN, 1211 Geneva 23, Switzerland N. Kuroda Institute of Physics, University of Tokyo, 3-8-1 Komaba, Meguro-ku, Tokyo 153-8902, Japan S. Ulmer · Y. Yamazaki RIKEN Advanced Science Institute, Hirosawa, Wako, Saitama 351-0198, Japan Present Address: B. Juhász Lufthansa Systems Hungária Kft., Neumann János utca 1/E, Budapest 1117, Hungary
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1 Introduction Antihydrogen is the simplest atom consisting entirely of antimatter. Since its hydrogen counterpart is one of the most precisely measured atoms in physics, a comparison of antihydrogen and hydrogen offers one of the most sensitive tests of CPT symmetry. This project proposes to measure the ground state hyperfine splitting νHFS (H) of antihydrogen (H), which is known in hydrogen to be νHFS (H) = 1,420,405,751.768(1) Hz (relative precision 7 × 10−13 ) as determined in a hydrogen maser [1, 2]. It is the central part of the program of the ASACUSA collaboration at CERN-AD. Since the maser confines atoms in a teflon coated box which is currently not feasible for antimatter, the experimental method consists of the formation of an antihydrogen beam and a measurement using a spin-flip cavity and a sextupole magnet [3, 4] as spin analyzer like it was done initially for hydrogen. A major milestone was achieved in 2010 when antihydrogen was first synthesized by ASACUSA in a so-called cusp trap [5]. In the first phase of this proposal, an antihydrogen beam will be produced and the H hyperfine splitting will be measured to a precision of below 10−6 using a single microwave cavity. In a second phase, the Ramsey method of separated oscillatory fields will be used to increase the precision by about one order of magnitude. In parallel methods will be developed towards trapping and laser cooling the antihydrogen atoms. Letting the cooled antihydrogen escape in a field
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