Jun 22 – 27, 2023
Auditorium Maximum
Europe/Warsaw timezone

Laser spectroscopy of metastable pionic helium atoms at Paul Scherrer Institute

Jun 26, 2023, 5:10 PM
20m
Medium lecture hall (A) (Auditorium Maximum)

Medium lecture hall (A)

Auditorium Maximum

Speaker

Masaki Hori (Imperial College London and Johannes Gutenberg University Mainz and Max Planck Institute of Quantum Optics)

Description

Metastable pionic helium is a three-body exotic atom composed of a helium nucleus, electron, and negatively-charged pion occupying a highly-excited state with a principal and orbital angular momentum quantum numbers of n≈l-1≈17 [1-4]. The atom has a τ=7 ns lifetime. We used the 590 MeV ring cyclotron facility of PSI to synthesize π4He+ and irradiate the atoms with 800 ps-long resonant laser pulses of frequency ν=183760 GHz that induced a pionic transition (n,l)=(17,16)→(17,15) [1,2]. This laser transition triggered an electromagnetic cascade that resulted in the pion being absorbed into the helium nucleus [1-3]. The nucleus immediately underwent fission and the neutron, proton, and deuteron fragments were detected by an array of 140 plastic scintillation counters surrounding the target. This constitutes the first laser excitation and spectroscopy of an atom containing a meson.
By further improving the precision of the transition frequencies and comparing them with the results of three-body QED calculations [2,4], the pion mass may be determined to a high precision, as has been done for the case of metastable antiprotonic helium [5,6].

[1] M. Hori, H. Aghai-Khozani, A. Sótér, A. Dax, D. Barna, Nature, 581, 37 (2020).
[2] M. Hori, A. Sótér, V. I. Korobov, Phys. Rev. A, 89, 042515 (2014).
[3] B. Obreshkov and D. Bakalov, Phys. Rev. A, 93, 062505 (2016).
[4] Z.-D. Bai et al., Phys. Rev. Lett. 128, 183001 (2022).
[5] M. Hori et al., Nature, 475, 484 (2011).
[6] M. Hori et al., Science 354, 610 (2016).

Collaboration ASACUSA and PiHe

Primary authors

Andreas Dax (PSI) Anna Sótér (ETH Zurich) Dániel Barna (Wigner Research Centre) Hossein Aghai-Khozani (Max Planck Institue of Quantum Optics) Masaki Hori (Imperial College London and Johannes Gutenberg University Mainz and Max Planck Institute of Quantum Optics)

Presentation materials