A Position Detector for AEGIS - Anti-matter Experiment for Gravity, Interferometry and Spectroscopy

The goal of the AEGIS experiment at the Antimatter Decelerator (AD) at CERN, is to measure directly the Earth's gravitational acceleration on antimatter. To achieve this, the AEGIS collaboration will produce a pulsed cold (100 mK) antihydrogen beam with a velocity of few 100 m/s and measure the magnitude of the 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 consists of an active silicon part, where the annihilations take place and which we are responsible for developing, followed by an emulsion part (new), together allowing to achieve 1% precision on the measurement of g bar with about 600 reconstructed and time tagged annihilations. The main achievements of this RCN project is so far: - The first direct measurement of antiproton annihilation in a segmented silicon sensor to our knowledge, an important step towards designing a position sensitive silicon detector for the AEgIS experiment. - Results from Monte Carlo simulations (GEANT4) for antiproton energies below 5 MeV shows important discrepancies with data. To improve and study antiproton annihilations in more details at low energies a separate beam line is prepared to further understand the annihilation process - Prototype, mechanical tests and design review have been successful as well as first testbeam for the final detector in Autumn 2015, continuing during testbeam 2016. The Norwegian AEGIS project and Project leader has been subject of four evaluations - in 2012, 2013 and twice in 2014 (spring and fall) all with excellent outcome.

The weak equivalence principle (WEP) implies that the gravitational interactions of matter and anti-matter are exactly identical. This assertion, being a fundamental consequence of general relativity, has never been experimentally verifed; in fact the gra vitational force on anti-matter system has never been directly observed. Consequently, a first, even modest precision measurement of the gravitational interactions of anti-matter is very interesting. Observing the gravitational effects on anti-Hydrogen is a substantial experimental challenge, and a successful experiment will require the integration of techniques from two distinct fields within the broader discipline of experimental physics: atomic physics, and particle detectors. The across-discipline a pproach is reflected in this project, the participants having their respective backgrounds in atomic and particle physics. The groups at the University of Oslo (UoO) and the University of Bergen (UoB) have extensive experience with the development, constr uction and deployment of semiconductor tracking detectors as well as atomic research. The AEGIS collaboration initially approached the Norwegian groups, inviting us to participate in the experiment and take the main responsibility for its position sensi tive detector, a silicon detector which is a cruicial part of the apparatus. Pursuing this opportunity will allow us to capitalise on our silicon tracker expertise and play a major role in an international collaboration. The AEGIS project has a time fra me of four years, starting in 2012 and running through 2015. Contrasting with the much longer spans of typical experiments in the bordering field of high energy physics, a PhD student in AEGIS will have the opportunity to follow a medium-size physics expe riment virtually from conception to completion. Finally, this project present a unique opportunity for our industrial partners who are very interested in developing detectors and ASICs for cryogenic temperatures