The Magnetic Moment of the Anti-Proton

In the Standard Model of particle physics, fundamental forces are successfully described by Lorentz invariant, local quantum field theories. By the CPT theorem, Lorentz invariance is strongly tied to CPT symmetry of combined charge conjugation (C), parity (P), and time reversal (T). While all of these three discrete symmetries have been shown to be broken individually, the symmetry of CPT has thus far withstood all experimental tests. Indeed, CPT is consistent with measurements at a remarkable precision performed with mesons (2 parts in 1018), leptons (2 parts in 1012), or baryons (9 parts in 1011). However, any violation of CPT would imply the breakdown of Lorentz invariance and would hence challenge our current formulation of particle physics all together. Given the implications, the absence of knowledge in which sector CPT violation might arise, and the accuracy of other tests of CPT, the current precision of the magnetic moment of the anti-proton at a level of only 103 is disturbing, but offers challenge and potential for significant discovery. No more stringent comparison to the protons equivalent has been made, which according to CPT should be of opposite sign, but of identical absolute value. As previous techniques to determine the anti-protons magnetic moment have reached their limitations, this project is to follow a novel method which could ultimately establish a million-fold improvement over the current literature value. It aims to observe a spin-flip of an anti-proton suspended in a Penning trap. Recent experimental progress in Penning trap techniques suggests that such a measurement could yield a thousand-fold better precision for the magnetic moment of the anti-proton. To perform a precision experiment with a million-fold improvement, it will be further necessary to advance the resolution of the technique to non- destructively detect a single proton spin- flip. For this purpose, a dedicated setup is be coupled to an existing anti-proton trapping facility. To date, low energy anti-protons are uniquely available at CERN`s Antiproton Decelerator (AD). There, the group of Prof. Gabrielse at Harvard University leads the ATRAP collaboration which routinely traps anti-protons delivered by the AD for anti- matter research. Owing to its knowledge and experience regarding Penning traps where the electrons magnetic moment has recently been improved by a similar technique, the Harvard group hence represents the optimal starting point for this project. Prof. Gabrielse is enthusiastic to support this project by providing experimental resources and full access to the required equipment at the host institution. Thus, with enough creativity and tenacity, a million fold improvement in the precision of the anti-proton magnetic moment is achievable.