Andrzej Adamczak

Steps towards the hyperfine splitting measurement of the muonic hydrogen ground state: pulsed muon beam and detection system characterization

The high precision measurement of the hyperfine splitting of the muonic-hydrogen atom ground state with pulsed and intense muon beam requires careful technological choices both in the construction of a gas target and of the detectors. In June 2014, the pressurized gas target of the FAMU experiment was exposed to the low energy pulsed muon beam at the RIKEN RAL muon facility. The objectives of the test were the characterization of the target, the hodoscope and the X-ray detectors. The apparatus consisted of a beam hodoscope and X-rays detectors made with high purity Germanium and Lanthanum Bromide crystals. In this paper the experimental setup is described and the results of the detector characterization are presented.

THERMALIZATION OF MUONIC HYDROGEN IN HYDROGEN TARGETS

The thermalization of pµ atoms in protium and dµ atoms in deuterium is considered. Monte Carlo calculations are performed for gaseous (300 K) and solid (3 K) protium and deuterium targets. Complete sets of the total and differential cross sections for the scattering of pµ on protium targets and dµ on deuterium targets are used as an input to the Monte Carlo simulations. At 300 K, muonic atom scattering from single molecules of H2 and D2 is considered. In the case of solid hydrogen the correlation effects from all molecules of the sample are taken into account. In particular, the Bragg and phonon scattering cross sections are calculated. The spin states and average energy of the muonic atoms are shown as functions of time. It is shown that at energies below about 0.01 eV the solid-state effects influence strongly the calculated cross sections, and therefore the deceleration processes in the solids are much slower than in the gaseous targets. It is shown that the neutron spectrum due to ddµ formation and subsequent dd fusion is significantly affected by slow dµ thermalization in solid deuterium.

Measuring the size of the proton

The size of an atom’s nucleus is roughly five orders of magnitude smaller than the size of the atom. Consequently, the nuclear corrections to atomic energy levels are very tiny. However, these corrections have become important in recent highprecision measurements of transitions in the hydrogen atom, which are being performed to test quantum electrodynamics (QED) and to determine related fundamental constants. Today, the interpretation of this data is only limited by the uncertainties in the size of the nucleus, which in the case of hydrogen is a single proton. The charge radius rp of the proton is a physical parameter that characterizes important aspects of the effective size of the proton. Its value is used together with the Rydberg constant in the calculations of bound-state QED involving hydrogen atoms as well as muonic hydrogen atoms that have a muon orbiting the nucleus rather than the electron. (Muons are like electrons but 200 times heavier.) A recent spectroscopic study of muonic hydrogen resulted in a new measurement of the proton root mean square (rms) charge radius.1 The reported value, rp D 0:84184.67/fm, differs by 5 standard deviations from (and is a factor of 10 more precise than) previous determinations. These earlier values come from three very different methods that are based mostly on electronic hydrogen data. Specifically, a compilation of physical constants (CODATA) gives rp D 0:8768.69/fm,2 the Lamb shift of electronic hydrogen results in rp D 0:883.14/fm,3, 4 and electron scattering from hydrogen yields rp D 0:895.18/fm.5 It is noteworthy that QED considerations show6 that the electron scattering experiments and the atomic hydrogen spectroscopy determine the same Figure 1. Block diagram of the layout of the first approach to a dedicated nonlinear laser source.

Resonantddμformation in condensed deuterium

The rate of

On the Use of a H2–O2 Gas Target in Muonic Hydrogen Atom Hyperfine Splitting Experiments

dd\mu

Deceleration of muonic hydrogen atoms in solid hydrogens

muonic molecule resonant formation in

Differential cross sections for muonic hydrogen scattering on hydrogen molecules

d\mu

Theoretical and computational study of the energy dependence of the muon transfer rate from hydrogen to higher- Z gases

atom collision with a condensed deuterium target is expressed in terms of a single-particle response function. In particular,

Shift and broadening of resonance lines of antiprotonic helium atoms in solid helium

dd\mu

Monte Carlo simulations of the μCF processes kinetics in deuterium gas

formation in solid deuterium at low pressures is considered. Numerical calculations of the rate in the case of fcc polycrystalline deuterium at 3 K have been performed using the isotropic Debye model of solid. It is shown that the energy-dependent