Annihilation of low energy antiprotons in silicon

TL;DR

This paper reports the first direct measurement of low-energy antiproton annihilation in silicon, a crucial step for developing a detector to measure Earth's gravity on antimatter in the AEgIS experiment at CERN.

Contribution

It provides the first direct measurement of antiproton annihilation in segmented silicon and compares results with Monte Carlo simulations for energies below 5 MeV.

Findings

First direct measurement of antiproton annihilation in silicon.

Comparison with GEANT4 simulations shows good agreement.

Results inform design of a silicon detector for antimatter gravity measurement.

Abstract

The goal of the AE$\mathrm{\bar{g}}$IS experiment at the Antiproton Decelerator (AD) at CERN, is to measure directly the Earth's gravitational acceleration on antimatter. To achieve this goal, the AE$\mathrm{\bar{g}}$IS collaboration will produce a pulsed, cold (100 mK) antihydrogen beam with a velocity of a few 100 m/s and measure the magnitude of the vertical deflection of the beam from a straight path. The final position of the falling antihydrogen will be detected by a position sensitive detector. This detector will consist of an active silicon part, where the annihilations take place, followed by an emulsion part. Together, they allow to achieve 1$%$ precision on the measurement of $\bar{g}$ with about 600 reconstructed and time tagged annihilations. We present here, to the best of our knowledge, the first direct measurement of antiproton annihilation in a segmented silicon sensor, the first step towards designing a position sensitive silicon detector for the AE$\mathrm{\bar{g}}$IS experiment. We also present a first comparison with Monte Carlo simulations (GEANT4) for antiproton energies below 5 MeV