Speaker
Description
Performing measurements on anti-matter atoms is an alluring proposition for studying the symmetries between matter and anti-matter; however, it presents a number of technical challenges. The ALPHA group has met these challenges and successfully trapped large numbers of anti-hydrogen atoms, opening the door for many such measurements. The new ALPHA-g experiment has the ability to measure the gravitational force exerted by the Earth on these anti-hydrogen atoms, by counterbalancing this force with precisely controlled magnetic fields. By relaxing only the confinement along the gravitational axis, the anti-atoms are released into two “up” and “down” regions separated by tens of centimetres. Here they annihilate, and the ratio of counts in the two regions describes the overall – magnetic plus gravitational – bias.
Charged pions resulting from these annihilations are tracked in a time projection chamber; these tracks are fit and extrapolated back to a common annihilation vertex. Our ability to reconstruct the position of these annihilation vertices into the correct region was previously one of the limiting factors of the experiment. Here I present the steps taken to improve our position resolution beyond that necessary for the experiment.
Furthermore, due to the low number of anti-atoms produced and slow experiment timescale, cosmic rays produce a sizeable background in our time projection chamber. To mitigate this, a second plastic scintillator-based detector system was implemented, called the “barrel veto”. This was used to discriminate against the cosmic ray background based on event topology in the first data-taking run in 2022. It has the additional possibility of using time-of-flight to further identify background events. Here I present the usage of the barrel veto to reject the cosmic ray background, and demonstrate the overall effectiveness of the ALPHA-g detector system.
| Keyword-1 | ALPHA |
|---|---|
| Keyword-2 | Anti-hydrogen |
