Carruth, Celeste

Date:   Monday, Nov. 26, 2018
Time:   11:00
Place:   ETH Zurich, Hönggerberg, HPF G 6
Host:    Jonathan Home

Testing CPT Symmetry with Antihydrogen at ALPHA

Celeste Carruth
University of California, Berkeley, USA

The observed imbalance of matter and antimatter in the universe is one of the biggest unanswered questions in physics. Charge-Parity-Time Symmetry requires that particles and their corresponding antiparticles should have the same energy levels, and a violation of CPT symmetry could lead to an explanation for the missing antimatter. Direct high-precision tests of CPT can be performed by comparing energy level transitions of antihydrogen and hydrogen; this is the main goal of the ALPHA (Antihydrogen Laser PHYsics Apparatus) experiment at CERN. At ALPHA, tens of thousands of antihydrogen atoms are synthesized by mixing cold plasmas of antiprotons and positrons prepared in Penning-Malmberg traps, but atoms are trapped only if colder than 0.54K. Prior to 2016, we could trap only 1 atom at a time, but during the 2016-2017 runs, developing new plasma manipulation techniques in our Penning traps we increased this to an average of nearly 20 atoms per trapping cycle and further developed the ability to accumulate up to several hundred atoms in the trap with a lifetime of tens of hours. We then performed the first measurements of the 1s-2s spectroscopy, Lyman-alpha spectroscopy, and hyperfine transitions in antihydrogen and found the results confirming CPT symmetry to a precision of 2*10^-12. This talk will provide an overview of CPT symmetry, our antihydrogen synthesis and trapping procedures, and discuss the measurement techniques and results.