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CALIOPE, A Search for CPT-Violation in Positronium

Chelsea Bartram, University of Washington
Thursday, June 20, 2019 - 3:45pm
NPL 178

We present the results of a search for CPT-violation in the charged lepton sector by studying ortho-positronium decays with CALIOPE, or CPT Aberrant Leptons in Ortho-Positronium Experiment. Positronium, a bound state of an electron and positron, occurs in both a singlet and triplet state. The triplet state, ortho-positronium, decays primarily into three gamma rays. CPT-violation could potentially manifest itself in angular correlations between the directions of the three photons and the spin of the ortho-positronium (o-Ps). The APEX annular array consists of 24 NaI(Tl) bars arranged cylindrically and provides 75% angular coverage with a source placed at its center. We used the APEX array at Triangle Universities Nuclear Laboratory (TUNL) to acquire data for CALIOPE continuously for several months. We present the results of 16 weeks of data-taking, in addition to a comprehensive systematics study. We suggest improvements that would make such a search competitive with the most sensitive CPT-violation searches in o-Ps performed to date and discuss the possibility of a search for CP-violation.

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