Description
Traditional positron scattering experiments are limited by their reliance on unpolarized, thermal atomic targets, which yield spin averaged cross-sections and obscure the underlying quantum exchange dynamics [1].This work addresses these limitations by employing a $^{87}$Rb Magneto-Optical Trap (MOT) to perform state-selective measurements of positron–atom interactions.
The selection of $^{87}$Rb is motivated by its low ionization potential (4.18 eV), which makes Ps formation (6.8 eV binding energy) an exothermic process with an energy release of 2.62 eV [2]. This favourable energy balance enables detailed investigations of scattering dynamics in the low-energy regime. By using optical pumping to achieve near-complete spin polarization, the experiment can selectively probe the singlet (para-Ps) and triplet (ortho-Ps) formation channels [3]. This unique capability permits direct measurements of spin-dependent asymmetries, providing tests of theoretical descriptions of spin-exchange, spin–orbit interactions and the branching ratios associated with Positronium (Ps) formation. As the MOT provides an ultracold atomic target, a high degree of control and state selectivity establishes a stringent benchmark to validate positron–atom scattering theories in the ultracold regime. Beyond its significance in antimatter physics, this work also aims to explore an important step towards the realization of a Positronium Bose–Einstein condensate (o-Ps BEC) [4]. Ps BECs have been theoretically proposed as a pathway to coherent gamma-ray(γ ray) lasing sources via self amplified annihilation of p-Ps atoms [5], with potential applications spanning precision measurements, materials science and advanced medical imaging technologies.
References
[1] M. Charlton and J. W. Humberston. Positron Physics. Cambridge University Press, 2001.
[2] Surdutovich, Anatoliy, et al. Physical Review A 53.4 (1996): 2861.
[3] Machacek, Joshua, et al. Physics Meeting Abstracts. Vol. 2023. 2023.
[4] Platzman, P. M., and A. P. Mills Jr. Physical Review B 49.1 (1994): 454.
[5] Avetissian, H. K., A. K. Avetissian, and G. F. Mkrtchian. Physical review letters 113.2 (2014): 023904.
| I am the presenting author | Yes |
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