Systematic effects in the measurement of the negatively charged pion mass using laser spectroscopy of pionic helium atoms

Abstract

The collision-induced shift and broadening of selected dipole transition lines of pionic helium in gaseous helium at low temperatures up to $T=12$ K and pressure up to a few bar are calculated within variable phase function approach. We predict blue shift of the resonance frequencies of the $(n,l)=(16,15)\to (16,14)$ and $(16,15)\to (17,14)$ unfavored transitions and red shift for the favored transition $(17,16)\to (16,15)$. The result may be helpful in reducing the systematic error in proposed future experiments for determination of the negatively charged pion mass from laser spectroscopy of metastable pionic helium atoms.

Comments: 7 pages, 3 tables, 1 figure, Proceedings of the 35th International Workshop on Nuclear Theory, Rila Mountains (Bulgaria), June 26 - July 2, 2016. To appear in "Nuclear Theory", vol.35, Eds. M.Gaidarov, N. Minkov, Heron Press, Sofia