Measuring the gravitational free-fall of antihydrogen

Antihydrogen holds the promise to test, for the first time, the universality of free-fall with a system composed entirely of antiparticles. The AEgIS experiment at CERN’s antiproton decelerator aims to measure the gravitational interaction between matter and antimatter by measuring the deflection of a beam of antihydrogen in the Earths gravitational field (g¯¯¯). The principle of the experiment is as follows: cold antihydrogen atoms are synthesized in a Penning-Malberg trap and are Stark accelerated towards a moiré deflectometer, the classical counterpart of an atom interferometer, and annihilate on a position sensitive detector. Crucial to the success of the experiment is the spatial precision of the position sensitive detector. We propose a novel free-fall detector based on a hybrid of two technologies: emulsion detectors, which have an intrinsic spatial resolution of 50 nm but no temporal information, and a silicon strip / scintillating fiber tracker to provide timing and positional information. In 2012 we tested emulsion films in vacuum with antiprotons from CERN’s antiproton decelerator. The annihilation vertices could be observed directly on the emulsion surface using the microscope facility available at the University of Bern. The annihilation vertices were successfully reconstructed with a resolution of 1–2 μmon the impact parameter. If such a precision can be realized in the final detector, Monte Carlo simulations suggest of order 500 antihydrogen annihilations will be sufficient to determine g¯¯¯with a 1 % accuracy. This paper presents current research towards the development of this technology for use in the AEgIS apparatus and prospects for the realization of the final detector.ISSN:0304-3843ISSN:0304-3834ISSN:1572-954

The AEgIS Experiment

The AEgIS experiment aims at performing the first test of the Weak Equivalence Principle of General Relativity in the antimatter sector by measuring the gravitational acceleration acting on a beam of cold antihydrogen to a precision of 1%. The installation of the apparatus is making good progress and large parts were taken into operation. Parasitic detector tests during the beamtime in December 2012 gave essential input for an optimal moiré deflectometer and the detector layout necessary to perform the gravity measurement.ISSN:0304-3843ISSN:0304-3834ISSN:1572-954