Measurement of the formation rate and the radiative decay of the muonic molecules (pμ^{3}He)^{} and (pμ^{4}He)^{} (original) (raw)
Related papers
Excited State Muon Transfer in Hydrogen/Deuterium Mixtures
Physical Review Letters, 1996
We report the rst direct observation of excited state muon transfer in hydrogen/deuterium mixtures by direct measurement o f q 1s , the probability that a p atom, which is initially formed in an excited state, reaches the 1s ground state. The dependence of q 1s on deuterium concentration c d was measured for two dierent densities at cryogenic temperatures using charge coupled devices (CCDs) to detect the muonic X rays. First results based on the analysis of the K-lines of the two isotopes are presented.
Physics Letters A, 2020
We report the first measurement of the temperature dependence of muon transfer rate from muonic hydrogen atoms to oxygen between 100 and 300 K. Data were obtained from the X-ray spectra of delayed events in a gaseous target, made of a H 2 /O 2 mixture, exposed to a muon beam. This work sets constraints on theoretical models of muon transfer and is of fundamental importance for the measurement of the hyperfine splitting of muonic hydrogen ground state as proposed by the FAMU collaboration.
The FAMU experiment at RIKEN-RAL to study the muon transfer rate from hydrogen to other gases
Journal of Instrumentation
The aim of the FAMU (Fisica degli Atomi Muonici) experiment is to realize the first measurement of the hyperfine splitting (hfs) in the 1S state of muonic hydrogen ∆E h f s 1S , by using the RIKEN-RAL intense pulsed muon beam and a high-energy mid-infrared tunable laser. This requires a detailed study of the muon transfer mechanism at different temperatures and hence at different epithermal states of the muonic system. The experimental setup involves a cryogenic pressurized gas target and a detection system based on silicon photomultipliers-fiber beam hodoscopes and high purity Germanium detectors and Cerium doped Lanthanium Bromide crystals, for X-rays detection at energies around 100 keV. Simulation, construction and detector performances of the FAMU apparatus at RAL are reported in this paper. K : Muonic atoms; Detection systems; Precision spectroscopy Contents 1 Introduction 1 2 The FAMU experimental setup 2 2.1 The 1 mm pitch beam hodoscope 4 2.2 The cryogenic target system 4 2.2.1 Cooling system 7 2.3 The Ce:LaBr 3 X-ray detectors with PMT readout 7 2.4 Compact X-rays detectors with SiPM array readout 8 2.5 The HPGe X-ray detectors 9 2.6 Beam momentum tuning and detectors positioning 10 3 Raw data handling 12 3.1 Structure of offline data processing 13 4 Experimental operations and performances 16 4.1 Target operations 16 4.2 Beam characterisation with the 1 mm pitch hodoscope 17 4.3 Detection of characteristic X-rays with Ce:LaBr 3 with PMT readout 18 4.4 Detection of characteristic X-rays with crystals with SiPM array readout 21 4.5 Detection of characteristic X-rays with HPGe detectors 23 5 Conclusions 26
Measurement of the energy dependence of the muon transfer rate from hydrogen to higher-Z gases
The recent Lamb shift experiment at PSI and the apparent incompatibility of the proton radii extracted using different methods revived the interest in the measurement of the hyperfine splitting in the ground state of muonic hydrogen as an alternative possibility for the experimental comparison of ordinary and muonic hydrogen spectroscopy data about the proton electromagnetic structure. The efficiency of the method developed for this measurement has been shown to critically depend on the energy dependence of the rate of muon transfer from hydrogen to heavier gases in the epithermal range. The available experimental data provide only qualitative information on the energy dependence, and the detailed theoretical predictions have not yet been tested. The present paper outlines an experimental method for the quantitative measurement of the muon transfer rate based on a series of repeated measurements of the muon transfer rate in a mixture of hydrogen and the gas of interest with appropri...
Observation of Long-Lived Muonic Hydrogen in the 2S State
Physical Review Letters, 2006
The kinetic energy distribution of ground state muonic hydrogen atoms µp(1S) is determined from time-of-flight spectra measured at 4, 16, and 64 hPa H2 room-temperature gas. A 0.9 keVcomponent is discovered and attributed to radiationless deexcitation of long-lived µp(2S) atoms in collisions with H2 molecules. The analysis reveals a relative population of about 1 %, and a pressuredependent lifetime (e.g. 30.4 +21.4 −9.7 ns at 64 hPa) of the long-lived µp(2S) population, equivalent to a 2S-quench rate in µp(2S)+H2 collisions of 4.4 +2.1 −1.8 × 10 11 s −1 at liquid hydrogen density.
Measurement of the muon transfer rate from muonic hydrogen to oxygen in the range 70-336 K
2021
The first measurement of the temperature dependence of the muon transfer rate from muonic hydrogen to oxygen was performed by the FAMU collaboration in 2016. The results provide evidence that the transfer rate rises with the temperature in the range 104-300 K. This paper presents the results of the experiment done in 2018 to extend the measurements towards lower (70 K) and higher (336 K) temperatures. The 2018 results confirm the temperature dependence of ΛpO observed in 2016 and sets firm ground for comparison with the theoretical predictions.
Resonant enhancement of the formation of hydrogen–helium muonic molecules
Physics Letters A, 2010
Formation of muonic molecules (4 Heμp) ++ J =1 and (3 Heμd) ++ J =0,1,2 , where J is rotational quantum number, in electron conversion process is investigated at collision energies between 0.004 eV and 50 eV. Corresponding reaction rates are calculated in adiabatic approximation for the three-body Coulomb problem. Significant enhancement of the rates for (4 Heμp) ++ 1 and (3 Heμd) ++ 2 is found near 7 eV and 30 eV, respectively. It is shown that the enhancement is due to resonances present in elastic (pμ) 1s + 4 He ++ and (dμ) 1s + 3 He ++ scattering at these energies. Acceleration of dμ atoms up to the resonant energy could be realized in triple H-D-3 He mixture due to the muon transfer from protium to deuterium. Experimental investigation of d-3 He ++ nuclear synthesis from (3 Heμd) ++ 0 molecular state directly formed in the mixture is suggested.
First FAMU observation of muon transfer from μp atoms to higher-Z elements
Journal of Instrumentation
The FAMU experiment aims to accurately measure the hyperfine splitting of the ground state of the muonic hydrogen atom. A measurement of the transfer rate of muons from hydrogen to heavier gases is necessary for this purpose. In June 2014, within a preliminary experiment, a pressurized gas-target was exposed to the pulsed low-energy muon beam at the RIKEN RAL muon facility (Rutherford Appleton Laboratory, U.K.). The main goal of the test was the characterization of both the noise induced by the pulsed beam and the X-ray detectors. The apparatus, to some extent rudimental, has served admirably to this task. Technical results have been published that prove the validity of the choices made and pave the way for the next steps. This paper presents the results of physical relevance of measurements of the muon transfer rate to carbon dioxide, oxygen, and argon from non-thermalized excited µp atoms. The analysis methodology and the approach to the systematics errors are useful for the subsequent study of the transfer rate as function of the kinetic energy of the µp currently under way.
The influence of spectator nuclear motion on the nonresonant formation of muonic hydrogen molecules
Journal of Physics B: Atomic, Molecular and Optical Physics
A model for description of nonresonant formation of the muonic molecules in collisions of the muonic hydrogen atoms with the hydrogenic molecules has been developed with taking into account the internal motion of all nuclei. It has been shown that such a motion leads to a significant smearing of the calculated energy-dependent formation rates at low collision energies. In particular, this effect is strong in the ddµ and dtµ formation. An appreciable isotopic effect in the case of nonresonant ddµ formation in dµ collisions with the molecules D 2 and HD has been found. All these effects are of importance for many experimental researches in low-energy muon physics.