Characterization of neutral trapped antihydrogen in the ALPHA experiment

• Main Author: Ahmadi, M.
• Other Authors: Joss, David
• Published: University of Liverpool 2018
• Online Access: https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.762853

One of the pivotal principles of physics is the C (charge) P (parity) T (time reversal) (CPT) theorem. One method for testing the CPT symmetry is to investigate the properties of antihydrogen. The Antihydrogen Laser PHysics Apparatus (ALPHA) experiment aims at creating, confining and applying spectroscopic techniques to probe the atomic structure of antihydrogen anti-atom with the same accuracy as that of the hydrogen atom. There are several non-trivial experimental challenges that must be overcome in antihydrogen studies. One major challenge is the detection of antihydrogen anti-atoms. This is done by identifying the antihydrogen annihilation. This thesis presents both a new method for identifying signal pulses from the background electric pulses of the silicon strips (Alternative Pedestal Analysis (APA), see Appendix A) as well as a completely new and enhanced vertex reconstruction method (Alternative Reconstruction Method (ARM), see Appendix C). The ARM is based on implementing a set of filtration mechanisms to identify the track candidates. Moreover, the reconstruction of the tracks is accomplished by adapting a numerical approach. Combining the APA and the ARM schemes has led to an increase in the vertex reconstruction efficiency by 1.5%. The alternative approaches for pedestal analysis and vertex reconstruction utilize a considerably more versatile algorithm. This feature allows greater control over variables and selection parameters employed for the reconstruction of vertices. The conclusive verifications of the performances of the new approaches are based on their visualization capabilities, the key aspect in devising the APA and the ARM, see Appendices B and D. The scripts in Appendices A-D haven been written solely by the author and are completely independent of pedestal and even vertex reconstruction algorithms currently implemented in the ALPHA experiment. The full commented versions of the scripts in Appendices A-D are available via the accompanying website.