Experiment to measure the Lamb shift in muonic hydrogen

• Main Author: Pohl, R.
• Publication Date: 2000
• Other Authors: Biraben, F., Conde, C. A. N., Gay, C. Donche, Hänsch, T. W., Hartmann, F. J., Hauser, P., Hughes, V. W., Huot, O., Indelicato, P., Knowles, P., Kottmann, F., Liu, Y.-W., Mulhauser, F., Nez, F., Petitjean, C., Rabinowitz, P., Santos, J. M. F. dos, Schaller, L. A., Schneuwly, H., Schott, W., Simons, L. M., Taqqu, D., Trehin, F., Veloso, J. F. C. A.
• Format: Article
• Language: eng
• Source: Repositórios Científicos de Acesso Aberto de Portugal (RCAAP)
• Download full: https://hdl.handle.net/10316/7691; https://doi.org/10.1023/A:1012679114531

Abstract The contribution of the root mean square (RMS) proton charge radius to the Lamb shift (2S–2P energy difference) in muonic hydrogen (µp) amounts to 2%. Apart from the uncertainty on this charge radius, theory predicts the Lamb shift with a precision on the ppm level. We are going to measure ?E (2 S1/2(F=1)–2 P3/2(F=2)) in a laser resonance experiment to a precision of 30 ppm (i.e., 10% of the natural linewidth) and to deduce the RMS proton charge radius with 10-3 relative accuracy, 20 times more precise than presently known. The most important requirement for the feasibility of such an experiment, namely the availability of a sufficient amount of long lived metastable µp atoms in the 2S state, has been investigated in a recent experiment at PSI. Our analysis shows that in the order of one percent of all muons stopped in low pressure hydrogen gas form a long lived µp(2S) with a lifetime of the order of 1 µs. The technical realization of our experiment involves a new high intensity low energy muon beam, an efficient low energy muon entrance detector, a randomly triggered 3 stage laser system providing the 0.5 mJ, 7 ns laser pulses at 6.02 µm wavelength, and a combination of a xenon gas proportional scintillation chamber (GPSC) and a microstrip gas chamber (MSGC) with a CsI coated surface to detect the 2 keV X rays from theµp(2P ? 1S) transition.