Towards a Measurement of the Lamb Shift in Muonic Hydrogen
Abstract
The availability of long-lived metastable muonic hydrogen atoms (7p) in the 2S state has been investigated in a recent series of experiments at PSI. From the low-energy part of the initial kinetic energy distribution of (1S) we determined the fraction of long-lived (2S) to be \char 126 1.5% for pressures between 1 and 64 hPa. Another analysis involving (1S) with a kinetic energy of \char 126 1 keV originating from quenching of thermalized (2S) via the resonant process mup(2S) + Htwo to \{ [(p p mu)^+]^* p e e \}^* to mup(1S) + p + dots + 2 keV gives the same result. This is the first direct observation of long-lived (2S) atoms. We are preparing a measurement of the 2S Lamb shift in muonic hydrogen, which will improve the uncertainty on the RMS proton charge radius by more than one order of magnitude. Technical aspects of our experiment are presented, including a new low-energy negative muon beam, an efficient low-energy muon entrance detector, a randomly triggered 3-stage laser system providing 0.5 mJ, 7 ns laser pulses at 6.02 7m wavelength, and a large solid angle xenon gas-proportional-scintillation-chamber (GPSC) read out by a microstrip-gas-chamber (MSGC) with a CsI-coated surface for the detection of 2 keV X-rays.
- Publication:
-
The Hydrogen Atom: Precision Physics of Simple Atomic Systems
- Pub Date:
- 2001
- Bibcode:
- 2001LNP...570..454P