Excited State Muon Transfer in Hydrogen/Deuterium Mixtures (original) (raw)
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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.
Muon capture in hydrogen and deuterium
Hyperfine Interactions, 2009
We report on a new generation of muon lifetime experiments at PSI to measure the nuclear muon capture rate in hydrogen and deuterium with ≤1% accuracy. The goals are to determine in μp capture the induced pseudoscalar coupling g P predicted in HBchPT, and in μd capture the axial two-body current term L 1A described by modern EFT's. For the μp experiment a hydrogen TPC was developed as active muon stop detector, surrounded by cylindrical wire chambers and a plastic hodoscope as electron detector. Ultra-high purity of the hydrogen isotope 1 H 1 at levels below 10 −8 was achieved with a specially developed gas circulation and purification system, and with a novel isotope separation column. About 2 • 10 10 events were collected which are now in final analysis. Data from the first production run result in g P = 7.3 ± 1.1 in good agreement with theory. The μd experiment is in development. It requires measurements in ultra-pure, cold deuterium gas at ∼30K. For this we are constructing a new Cryo-TPC.
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...
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.
First FAMU observation of muon transfer from mu-p atoms to higher-Z elements
2017
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, UK). 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 mu-p atoms. The analysis methodology and the approach to the systematics errors are useful for the subse...
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
Physical Review A, 1998
Formation and decay of the (p 3 He͒* and (p 4 He͒* molecules have been studied in binary-gas mixtures of H 2 ϩ 3 He and H 2 ϩ 4 He at 30 K. The muon ground-state transfer rates from hydrogen to the two helium isotopes were extracted from the time distribution of the 7-keV decay x rays of the muonic hydrogen-helium molecules, measured with a Ge detector. The obtained transfer rates are p 3 He ϭ(0.46Ϯ0.15)ϫ10 8 s Ϫ1 and p 4 He ϭ(0.42Ϯ0.07)ϫ10 8 s Ϫ1. The radiative branching ratios of the decay of the (p 3 He͒* and (p 4 He͒* molecules were determined by comparing the yields of the Lyman series of muonic hydrogen with the one of the 7-keV line with charge-coupled-device detectors. The ratios are in agreement with theoretical predictions. Muon transfer from excited states of muonic hydrogen to both helium isotopes was also observed.