Speaker
Description
Positronium atom (Ps), a fascinating purely leptonic system, serves as an excellent testbed for probing quantum electrodynamics (QED) in the bound state [1, 2]. Ps can manifest in one of two states, depending on the total spin number (S): a short-lived state with spin zero (para-Ps) and long-lived meta stable state with spin one (ortho-Ps). Prior to 1995, a significant discrepancy existed between experimentally measured and QED-predicted lifetimes values, termed as the ortho-Ps lifetime puzzle, which was later attributed to pickoff annihilations occurring during the thermalization process [3, 4]. Several groups have experimentally estimated the ortho-Ps decay rate in vacuum, yielding the most precise value of 𝜆$_{3𝛾}$ = 7.0401 ± 0.0007 μs$^{−1}$ [5]. However, this remains two orders of magnitude less precise than the theoretical prediction [6, 7].
This study proposes a novel methodology for estimating the ortho-Ps decay constant by measuring the 3$\gamma$ and 2$\gamma$ decay rates as a function of time utilizing J-PET, a multimodule detector capable of simultaneous multiphoton registration [8-10]. The primary aim of this investigation is to significantly improve the accuracy of determining the decay rate of ortho-Ps compared to previous measurements. The forthcoming presentation will emphasize the adapted analysis algorithm and highlight the results, which have already shown a precision that is an order of magnitude better than the best value measured so far.
References
[1] S.D. Bass, S. Mariazzi, P. Moskal and E. Stepien, Rev. Mod. Phy. 95, 021002 (2023)
[2] P. Moskal et al., Acta Phys. Polon. B 47, 509 (2016)
[3] R.S. Vallery, P.W. Zitzewitz and D.W. Gidley, Phys. Rev. Lett. 90, 203402 (2003)
[4] S. Asai, S. Orito and N. Shinohara, Phys. Lett. B 357, 475-480 (1995)
[5] Y. Kataoka, S. Asai, T. Kobayashi, Phys. Lett. B 671, 219-223 (2009)
[6] A. Ore and J.L Powell, Phys. Rev. 75, 1696 (1949)
[7] G. S. Adkins, Ann. Phys. (New York) 146, 78 (1983)
[8] P. Moskal et al., Science Advances 7, eabh4394 (2021)
[9] P. Moskal et al., Nature Comm. 12, 5658 (2021)
[10] P. Moskal et al., Nature Comm. 15, 78 (2024)
