1 Department of Physics and Astronomy, Science and Technology, Aarhus University2 York University3 Simon Fraser University4 University of California at Berkeley5 Swansea University6 CERN7 Universidade Federal Do Rio de Janeiro8 University of Calgary9 4004 Wesbrook Mall10 University of British Columbia11 Stockholm University12 University of Liverpool13 Auburn University14 NRCN-Nuclear Research Center Negev15 Department of Physics and Astronomy, Science and Technology, Aarhus University
Physicists have long wondered whether the gravitational interactions between matter and antimatter might be different from those between matter and itself. Although there are many indirect indications that no such differences exist and that the weak equivalence principle holds, there have been no direct, free-fall style, experimental tests of gravity on antimatter. Here we describe a novel direct test methodology; we search for a propensity for antihydrogen atoms to fall downward when released from the ALPHA antihydrogen trap. In the absence of systematic errors, we can reject ratios of the gravitational to inertial mass of antihydrogen >75 at a statistical significance level of 5%; worst-case systematic errors increase the minimum rejection ratio to 110. A similar search places somewhat tighter bounds on a negative gravitational mass, that is, on antigravity. This methodology, coupled with ongoing experimental improvements, should allow us to bound the ratio within the more interesting near equivalence regime.