Probing antimatter gravity – The AEGIS experiment at CERN

¹ Max-Planck-Institut für Kernphysik, Saupfercheckweg 1, 69117 Heidelberg, Germany
² Politecnico of Milano, Piazza Leonardo da Vinci 32, 20133 Milano Italy
³ INFN Milano, via Celoria 16, 20133 Milano, Italy
⁴ Laboratory for High Energy Physics, Albert Einstein Center for Fundamental Physics, University of Bern, 3012 Bern
⁵ Department of Mechanical and Industrial Engineering, Univ. of Brescia, via Branze 38, 25123 Brescia, Italy
⁶ INFN Pavia, via Bassi 6, 27100 Pavia Italy
⁷ Kirchhoff-Institut für Physik, Univ. of Heidelberg, Im Neuenheimer Feld 227, 69120 Heidelberg, Germany
⁸ Physics Department, CERN, 1211 Geneva 23 Switzerland
⁹ Department of Physics, University of Trento, via Sommarive 14, 38123 Povo, Trento, Italy
¹⁰ TIFPA/INFN Trento, via Sommarive 14, 38123 Povo, Trento Italy
¹¹ Laboratoire Aimé Cotton, University Paris-Sud, 91405 Orsay Cedex, France
¹² Department of Science, University of Insubria, via Valleggio 11, 22100 Como Italy
¹³ Department of Physics, University of Genova, via Dodecaneso 33, 16146 Genova, Italy
¹⁴ INFN Genova, via Dodecaneso 33, 16146 Genova Italy
¹⁵ Department of Physics, University of Milano, via Celoria 16, 20133 Milano, Italy
¹⁶ Czech Technical University, Prague, Brehová 7, 11519 Prague 1 Czech Republic
¹⁷ Institute of Physics and Technology, University of Bergen, Allégaten 55, 5007 Bergen, Norway
¹⁸ Department of Physics, University of Oslo, Sem Sælandsvei 24, 0371 Oslo Norway
¹⁹ Institute of Nuclear Physics, CNRS/IN2p3, University of Lyon 1, 69622 Villeurbanne, France
²⁰ Stefan Meyer Institute for Subatomic Physics, Austrian Academy of Sciences, Boltzmanngasse 3, 1090 Vienna Austria
²¹ Institute for Nuclear Research of the Russian Academy of Science, 117312 Moscow, Russia
²² Joint Institute for Nuclear Research, 141980 Dubna Russia
²³ INFN Padova, via Marzolo 8, 35131 Padova, Italy
²⁴ University of Bologna, viale Berti Pichat 6/2, 40126 Bologna Italy
²⁵ Department of Physics, University of Pavia, via Bassi 6, 27100 Pavia, Italy
²⁶ Department of Physics, University of Napoli Federico II, Complesso Universitario di Monte S. Angelo, 80126 Napoli Italy
²⁷ Research Council of Norway, Drammensveien 288, 0283 Oslo, Norway
²⁸ Physics Department, Technical University Berlin, Straße des 17. Juni 135, 10623 Berlin Germany
²⁹ Department of Civil Engineering, University of Brescia, via Branze 43, 25123 Brescia, Italy

^a e-mail: a.kellerbauer@cern.ch

Published online: 4 November 2016

Abstract

The weak equivalence principle states that the motion of a body in a gravitational field is independent of its structure or composition. This postulate of general relativity has been tested to very high precision with ordinary matter, but no relevant experimental verification with antimatter has ever been carried out. The AEGIS experiment will measure the gravitational acceleration of antihydrogen to ultimately 1% precision. For this purpose, a pulsed horizontal antihydrogen beam with a velocity of several 100 m s⁻¹ will be produced. Its vertical deflection due to gravity will be detected by a setup consisting of material gratings coupled with a position-sensitive detector, operating as a moiré deflectometer or an atom interferometer. The AEGIS experiment is installed at CERN’s Antiproton Decelerator, currently the only facility in the world which produces copious amounts of low-energy antiprotons. The construction of the setup has been going on since 2010 and is nearing completion. A proof-of-principle experiment with antiprotons has demonstrated that the deflection of antiparticles by a few μm due to an external force can be detected. Technological and scientific development pertaining to specific challenges of the experiment, such as antihydrogen formation by positronium charge exchange or the position-sensitive detection of antihydrogen annihilations, is ongoing.