Speaker
Description
Discrete symmetries ( reflection in space (P), reversal in time (T) and charge conjugation (C)) are violated in weak interactions only. Charge conjugation transforms a particle into antiparticle and vice versa by changing its internal quantum numbers. Positronium atom (Ps) which is the meta-stable bound system of particle (e-) and its antiparticle (e+) can be an excellent tool for studying the charge symmetry violation [1-3]. In 1967, Mills and Berko measured the C-forbidden decays of the singlet state (1S0: p-Ps) by estimating the ratio (R) of its decays 3γ / 2γ with best limit so far (R~2.6x10-6 at 68% confidence level ) [4].
J-PET is the PET device built from 192 plastic scintillators of dimension 500 X19 X 7 mm3 which are arranged axially in 3-layers [5-8]. It can be used to investigate the C-forbidden decays of the positronium atoms (p-Ps → 3γ) and estimating the branching ratio between 3γ to 2γ [2]. The event wise registration of the annihilation photons emitting from the decay of positronium atoms allows to distinguish between photons originating from the long-lived (o-Ps in range of ns) or short-lived (p-Ps in range of ps) atoms [9-10]. Furthermore, the angular correlation between the annihilated photons can also be used as a signature to differentiate between the decays from singlet (p-Ps) or triplet (o-Ps) states of the Ps atoms. The plastic scintillators used in J-PET offers an excellent time and high angular resolution and thus the value of R is expected to be measured with better sensitivity [5]. The status and preliminary results from the studies will be discussed and presented.
References:
1] W. Bernreuther et al., Z. Phys. C 41, 143 (1998)
[2] P. Moskal et al., Acta Phys. Polon. B 47, 509 (2017)
[3] E. Czerwinski et al., Acta Phys. Polon. B 48, 1961 (2017)
[4] A. P. Mills et al., Phys. Rev. Lett. 18, 420 (1967)
[5]P. Moskal et al., Nucl. Instr. Meth. A 764, 317 (2014)
[7] P. Moskal et al., Phys. In Med. And Bio. 61 , 2025 (2016)
[8] S. Niedzwiecki et al., Acta. Phys. Polon. B 48, 1567, (2017)
[9] B. Jasinska et al. Acta. Phys. Polon. B 47, 453 (2016)
[10] K. Dulski et al., Hyperfine Interaction 40 , 1 (2018)
