44 research outputs found
Observation of Long-Lived Muonic Hydrogen in the 2S State
The kinetic energy distribution of ground state muonic hydrogen atoms
mu-p(1S) is determined from time-of-flight spectra measured at 4, 16, and 64
hPa H2 room-temperature gas. A 0.9 keV-component is discovered and attributed
to radiationless deexcitation of long-lived mu-p(2S) atoms in collisions with
H2 molecules. The analysis reveals a relative population of about 1%, and a
pressure-dependent lifetime (e.g. (30.4 +21.4 -9.7) ns at 64 hPa) of the
long-lived mu-p(2S) population, equivalent to a 2S-quench rate in mu-p(2S) + H2
collisions of (4.4 +2.1 -1.8) 10^11 s^-1 at liquid hydrogen density.Comment: 4 pages, 2 figures, accepted for publication in Physical Review
Letter
Improved X-ray detection and particle identification with avalanche photodiodes
Avalanche photodiodes are commonly used as detectors for low energy x-rays.
In this work we report on a fitting technique used to account for different
detector responses resulting from photo absorption in the various APD layers.
The use of this technique results in an improvement of the energy resolution at
8.2 keV by up to a factor of 2, and corrects the timing information by up to 25
ns to account for space dependent electron drift time. In addition, this
waveform analysis is used for particle identification, e.g. to distinguish
between x-rays and MeV electrons in our experiment.Comment: 6 pages, 6 figure
The Lamb shift in muonic hydrogen
The long quest for a measurement of the Lamb shift in muonic hydrogen is over. Last year we measured the 2S1/2F=1â2P3/2F=2 energy splitting (Pohl et al., Nature, 466, 213 (2010)) in ÎŒp with an experimental accuracy of 15 ppm, twice better than our proposed goal. Using current QED calculations of the fine, hyperfine, QED, and finite size contributions, we obtain a root-mean-square proton charge radius of rpâ=â0.841â84â(67) fm. This value is 10 times more precise, but 5 standard deviations smaller, than the 2006 CODATA value of rp. The origin of this discrepancy is not known. Our measurement, together with precise measurements of the 1Sâ2S transition in regular hydrogen and deuterium, gives improved values of the Rydberg constant, Rââ=â10â973â731.568â160â(16) mâ»Âč and the rms charge radius of the deuteron rdâ=â2.128â09â(31) fm
The size of the proton and the deuteron
We have recently measured the 2S1/2âŒÂč â 2P3/2 ⌠ÂČ energy splitting in the muonic hydrogen atom ÎŒp to be 49881.88 (76) GHz. Using recent QED calculations of the fine-, hyperfine, QED and finite size contributions we obtain a root-mean-square proton charge radius of rp = 0.84184 (67) fm. This value is ten times more precise, but 5 standard deviations smaller, than the 2006 CODATA value of rp = 0.8768 (69) fm. The source of this discrepancy is unknown. Using the precise measurements of the 1S-2S transition in regular hydrogen and deuterium and our value of rp we obtain improved values of the Rydberg constant, Râ = 10973731.568160 (16) mâ»Âčand the rms charge radius of the deuteron rd = 2.12809 (31) fm
The Lamb shift in muonic hydrogen 1
Abstract: The long quest for a measurement of the Lamb shift in muonic hydrogen is over. Last year we measured the energy splitting (Pohl et al., Nature, 466, 213 (2010)) in mp with an experimental accuracy of 15 ppm, twice better than our proposed goal. Using current QED calculations of the fine, hyperfine, QED, and finite size contributions, we obtain a rootmean-square proton charge radius of r p = 0.841 84 (67) fm. This value is 10 times more precise, but 5 standard deviations smaller, than the 2006 CODATA value of r p . The origin of this discrepancy is not known. Our measurement, together with precise measurements of the 1S-2S transition in regular hydrogen and deuterium, gives improved values of the Rydberg constant, R ? = 10 973 731.568 16
Measuring the α-particle charge radius with muonic helium-4 ions
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 2Sâ2P 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 scattering1, 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 puzzle2,3,4,5, in line with recent determinations of the proton charge radius6,7,8,9, and establishes spectroscopy of light muonic atoms and ions as a precise tool for studies of nuclear properties.ISSN:0028-0836ISSN:1476-468
Neutron radiography of a static density gradient of 3He gas at cryogenic temperatures
We demonstrate a stationary helium gas density gradient which is needed for a proposed novel low-energy ÎŒ+ beam line. In a closed system with constant pressure the corresponding density gradient is only a function of the temperature. In a neutron radiography experiment two gas cells with different geometries were filled with 3He gas at constant pressures of about 10 mbar. Temperatures in the range from 6 K to 40 K were applied and density distributions with a maximum to minimum density ratio of larger than 3 were realized. The distribution was investigated employing the strongly neutron absorbing isotope 3He. A simple one-dimensional approach derived from FourierŚłs law describes the obtained gas density with a deviation <2% .ISSN:0168-9002ISSN:1872-957