Figure 2: Antiproton fringe pattern.

(a) The spatial pattern of the antiprotons (highlighted as blue tracks) as detected by the emulsion detector in an exemplary area of 1 mm². The annihilation of an antiproton leads to a clear signal from which the annihilation vertex can be extracted with a precision of 2 μm by reconstruction analysing the emitted secondary particles. The image enlargement shows an exemplary annihilation star. (b) The fringe pattern after transmission through the moiré deflectometer setup reveals a visibility as high as (71±10) %. Since less than one antiproton is detected per lattice period, the pattern shown is obtained by binning the vertical positions modulo the extracted periodicity of the fringe pattern. The solid black line denotes the expected distribution. (c) The pattern behind a grating placed directly on the emulsion detector (‘contact’) is a simple shadow that is smeared out due to the finite resolution of the detection. The few background events are consistent with independently observed grating defects. This pattern is used as a reference with no force dependence since the transit time is zero. The position of the moiré fringe pattern (indicated as offset a) is measured using light.