Laser spectroscopy of muonic deuterium Pohl, Randolf; Nez, François; Fernandes, Luis M. P. ...
Science (American Association for the Advancement of Science),
08/2016, Letnik:
353, Številka:
6300
Journal Article
Recenzirano
Odprti dostop
The deuteron is the simplest compound nucleus, composed of one proton and one neutron. Deuteron properties such as the root-mean-square charge radius rd and the polarizability serve as important ...benchmarks for understanding the nuclear forces and structure. Muonic deuterium μd is the exotic atom formed by a deuteron and a negative muon μ⁻. We measured three 2S-2P transitions in μd and obtain rd = 2.12562(78) fm, which is 2.7 times more accurate but 7.5σ smaller than the CODATA-2010 value rd = 2.1424(21) fm. The μd value is also 3.5σ smaller than the rd value from electronic deuterium spectroscopy. The smaller rd, when combined with the electronic isotope shift, yields a "small" proton radius rp, similar to the one from muonic hydrogen, amplifying the proton radius puzzle.
Accurate knowledge of the charge and Zemach radii of the proton is essential, not only for understanding its structure but also as input for tests of bound-state quantum electrodynamics and its ...predictions for the energy levels of hydrogen. These radii may be extracted from the laser spectroscopy of muonic hydrogen (μp, that is, a proton orbited by a muon). We measured the $2{\mathrm{S}}_{1/2}^{\mathrm{F}=0}-2{\mathrm{P}}_{3/2}^{\mathrm{F}=1}$ transition frequency in μp to be 54611.16(1.05) gigahertz (numbers in parentheses indicate one standard deviation of uncertainty) and reevaluated the $2{\mathrm{S}}_{1/2}^{\mathrm{F}=1}-2{\mathrm{P}}_{3/2}^{\mathrm{F}=1}$ transition frequency, yielding 49881.35(65) gigahertz. From the measurements, we determined the Zemach radius, r Z = 1.082(37) femtometers, and the magnetic radius, r M = 0.87(6) femtometer, of the proton. We also extracted the charge radius, r E = 0.84087(39) femtometer, with an order of magnitude more precision than the 2010-CODATA value and at 7σ variance with respect to it, thus reinforcing the proton radius puzzle.
The energy levels of hydrogen-like atomic systems can be calculated with great precision. Starting from their quantum mechanical solution, they have been refined over the years to include the ...electron spin, the relativistic and quantum field effects, and tiny energy shifts related to the complex structure of the nucleus. These energy shifts caused by the nuclear structure are vastly magnified in hydrogen-like systems formed by a negative muon and a nucleus, so spectroscopy of these muonic ions can be used to investigate the nuclear structure with high precision. Here we present the measurement of two 2S-2P transitions in the muonic helium-4 ion that yields a precise determination of the root-mean-square charge radius of the α particle of 1.67824(83) femtometres. This determination from atomic spectroscopy is in excellent agreement with the value from electron scattering
, but a factor of 4.8 more precise, providing a benchmark for few-nucleon theories, lattice quantum chromodynamics and electron scattering. This agreement also constrains several beyond-standard-model theories proposed to explain the proton-radius puzzle
, in line with recent determinations of the proton charge radius
, and establishes spectroscopy of light muonic atoms and ions as a precise tool for studies of nuclear properties.
Reach-through avalanche photodiodes (RT-APDs) from Hamamatsu Photonics, with different active areas, 5 × 5 and 3 × 3 mm 2 , were investigated to evaluate their suitability for the muonic helium Lamb ...shift experiment. The gain has been determined as a function of voltage and temperature for both prototypes. As expected, it increases with increasing bias voltage and with decreasing temperature. The gain variation with temperature is smaller than per -2% °C even for higher bias voltages applied to the RT-APD. The non-linearity between gain obtained for X-rays and visible light pulses has been investigated for different temperatures. The non-linearity was found to increase with decreasing temperature. For example at 350 V, it is as high as 25% at -20 °C and about 10% at 20 °C. The RT-APDs performance for the detection of 8 keV X-rays has been investigated. The best energy resolution was achieved for the larger prototype for a temperature of 0 °C. The minimum energy resolution values, between 9.2 and 9.9%, were obtained for gains between 55 and 80. The minimum detectable energy observed is about 0.2 keV for the higher gain region, for both RT-APDs, investigated, with no significant improvement at lower temperatures.
Laser spectroscopy of muonic hydrogen Pohl, Randolf; Antognini, Aldo; Amaro, Fernando D. ...
Annalen der Physik,
09/2013, Letnik:
525, Številka:
8-9
Journal Article
Recenzirano
Odprti dostop
Muonic hydrogen (μp) is a very sensitive probe of the proton structure. Laser spectroscopy of two 2S‐2P transitions in μp was used to determine both the Lamb shift and the hyperfine splitting of the ...2S state in μp. The rms charge radius of the proton, Rch=0.84087(39) fm, was extracted from the Lamb shift. The Zemach radius of the proton, RZ=1.082(37) fm, was obtained from the 2S‐hyperfine splitting. This article summarizes the previously published findings.
Muonic hydrogen (μp) is a very sensitive probe of the proton structure. Laser spectroscopy of two 2S‐2P transitions in μp was used to determine both the Lamb shift and the hyperfine splitting of the 2S state in μp. The rms charge radius of the proton, Rch = 0.84087(39) fm, was extracted from the Lamb shift. The Zemach radius of the proton, RZ = 1.082(37) fm, was obtained from the 2S‐hyperfine splitting. This article summarizes the previously published findings.
Reach-through APDs for X-ray detection Gouvea, Andrea L.; Fernandes, Luis M. P.; dos Santos, Joaquim M. F. ...
2012 IEEE Nuclear Science Symposium and Medical Imaging Conference Record (NSS/MIC),
2012-Oct.
Conference Proceeding
The performance of two reach-through avalanche photodiodes (RT-APO) manufactured by Hamamatsu Photonics with different active areas, 5×5 and 3×5 mm 2 , has been investigated. In order to evaluate ...their suitability for the muonic helium Lamb shift experiment already being prepared. The gain was determined as a function of voltage and temperature for the 5×5 RT-APO prototype. The gain non-linearity between X-rays and light was found to be as high as 15% for the 5 × 5 prototype and 20% for the 3 × 5 prototype for gains between 70 and 200 at 20°C. The energy resolution and the minimum detectable energy (MOE) were also determined. The best energy resolution obtained for 8 keY X-rays was 9.3% for a gain of 30 at -20°C. The MOE achieved was 0.2keV obtained for a gain of 100 and for a temperature of -20°C.
Avalanche photodiodes (APDs) will be used in the muonic helium Lamb shift experiment for detection of 8 keY Xrays. Reach-through APDs (RT-APDs) from Hamamatsu Photonics have been investigated for ...X-ray detection as an alternative to conventional APDs. In order to understand the behavior of the energy resolution obtained in a RT-APD for 8 keY X-rays, the APD response to visible light pulses from a LED has also been investigated. The gain non-uniformity is determined from the comparison of the energy resolution obtained for X-rays and light pulses. In addition, the measurement of the electronic noise contribution allows the determination of the excess noise factor. Results at different temperatures are shown.
Hydrogen-like light muonic ions, in which one negative muon replaces all the electrons, are extremely sensitive probes of nuclear structure, because the large muon mass increases tremendously the ...wave function overlap with the nucleus. Using pulsed laser spectroscopy we have measured three 2S-2P transitions in the muonic helium-3 ion (\(\mu^3\)He\(^+\)), an ion formed by a negative muon and bare helium-3 nucleus. This allowed us to extract the Lamb shift \(E(2P_{1/2}-2S_{1/2})= 1258.598(48)^{\rm exp}(3)^{\rm theo}\) meV, the 2P fine structure splitting \(E_{\rm FS}^{\rm exp} = 144.958(114)\) meV, and the 2S-hyperfine splitting (HFS) \(E_{\rm HFS}^{\rm exp} = -166.495(104)^{\rm exp}(3)^{\rm theo}\) meV in \(\mu^3\)He\(^+\). Comparing these measurements to theory we determine the rms charge radius of the helion (\(^3\)He nucleus) to be \(r_h\) = 1.97007(94) fm. This radius represents a benchmark for few nucleon theories and opens the way for precision tests in \(^3\)He atoms and \(^3\)He-ions. This radius is in good agreement with the value from elastic electron scattering, but a factor 15 more accurate. Combining our Lamb shift measurement with our earlier one in \(\mu^4\)He\(^+\) we obtain \(r_h^2-r_\alpha^2 = 1.0636(6)^{\rm exp}(30)^{\rm theo}\) fm\(^2\) to be compared to results from the isotope shift measurements in regular He atoms, which are however affected by long-standing tensions. By comparing \(E_{\rm HFS}^{\rm exp}\) with theory we also obtain the two-photon-exchange contribution (including higher orders) which is another important benchmark for ab-initio few-nucleon theories aiming at understanding the magnetic and current structure of light nuclei.
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