Real-time antiproton annihilation vertexing with sub-micron resolution

CERN-AEgIS. Characterization measurements for the detection of low-energy antiprotons using commercial complementary metal-oxide semiconductor (CMOS) optical image sensors (https://doi.org/10.1126/sciadv.ads1176). The device is the Sony IMX219 with 8 megapixels and a 3.67 mm by 2.76 mm sensitive area, originally developed for mobile applications and which has already been shown to be capable of imaging low-energy positrons with exceptional efficiency and resolution, with a cost that is three orders of magnitude lower than that of bespoke detectors such as Timepix3. Its 1.12 μm by 1.12 μm pixels are 50 times smaller than that of Timepix3 and of size similar to that of nuclear emulsions grains. We have now experimentally observed that the annihilation of antiprotons on the surface of the CMOS sensor results in the secondary charged particles leaving detectable signals in the exposed images. By reconstructing the vertex lying at the intersection of the tracks, the position of the antiproton annihilation can be determined with submicrometer accuracy. Since antihydrogen is an antiproton having only an extra positron bound to it, our detector is expected to be an antihydrogen annihilation vertexer as well and thus enable $\mathrm{\bar{H}}$ gravity measurements.