Determining the antiproton-to-electron mass ratio by laser spectroscopy of antiprotonic helium atoms
by
DrMasaki Hori(MPQ)
→
Europe/Berlin
Auditorium (MPI Meeting rooms)
Auditorium
MPI Meeting rooms
Description
An antiprotonic helium atom is a 3-body Coulomb system composed of a helium nucleus, antiproton, and electron
that retains microsecond-scale lifetimes against antiproton annihilation in the helium nucleus.
The ASACUSA collaboration at CERN carries out precise laser spectroscopy of this object to measure
the characteristic frequencies of transitions of the antiproton within this atom. By comparing the results
with three-body QED calculations, the antiproton-to-electron mass ratio was recently determined to a
fractional precision of 800 parts per trillion. The results agreed with the known proton-to-electron value.
In this experiment we used the technique of buffer gas cooling, i.e., to lower the temperature of our
samples of antiprotonic helium atoms to T=1.5 - 1.7 Kelvin by simply allowing the antiprotonic atoms
to collide with normal helium atoms at cryogenic temperatures.