9 research outputs found
Hadronic shift in pionic hydrogen
The hadronic shift in pionic hydrogen has been redetermined to be
\,eV by X-ray
spectroscopy of ground state transitions applying various energy calibration
schemes. The experiment was performed at the high-intensity low-energy pion
beam of the Paul Scherrer Institut by using the cyclotron trap and an
ultimate-resolution Bragg spectrometer with bent crystals.Comment: 10 pages, 6 figure
Erratum to: Hadronic shift in pionic hydrogen
After publication of the paper, the authors have noticed an error. Its correction is given in this erratum
The strong interaction shift and width of the ground state of pionic hydrogen
The 3p-1s transition in pionic hydrogen was investigated with a high-resolution crystal spectrometer system. From the precisely measured transition energy, together with the (calculated) electromagnetic energy, the strong interaction shift of the 1s state was obtained as Ï”1s = â7.127 ± 0.028(stat.)± 0.036(syst.) eV (attractive). From the natural line width, measured for the first time, we determine the decaywidth of the 1s state: Î1s(decay) = 0.97 ± 0.10(stat.)± 0.05(syst.) eV. With the recently calculated electromagnetic corrections the s-wave scattering lengths of an isospin symmetric strong interaction are deduced. The scattering length for elastic scattering of a negative pion on a proton is aÏâpâÏâph = 0.0885±0.00003(stat.)±0.0006(syst.)mÏâ1. The scattering lengthe for single charge exchange is found to be aÏâpâÏ0nh = â0.136 ± 0.007(stat.) ± 0.003(syst.)mÏâ1.The experiment was performed at the Paul Scherrer Institute (PSI) in Switzerland. A focussing crystal spectrometer with an array of bent crystals, the cyclotron trap (a magnetic system designed to increase the particle stop density) and a CCD (charge-coupled device) detector system were employed. The results from the pionic hydrogen experiment â together with those from the pionic deuterium experiment â were used to test the isospin symmetry of the strong interaction. The present data are still consistent with isospin sysmmetry
X-ray spectroscopy of the pionic deuterium atom
The low energy X-rays of the pionic deuterium 3P-1S transition were measured using a high resolution crystal spectrometer, together with a cyclotron trap (a magnetic device to increase the pion stopping density) and a CCD (charge-coupled device) detector system. The spectrometer resolution was 0.65 eV FWHM for a measured energy of approximately 3075 eV. This energy was measured with a precision of 0.1 eV. Compared to conventional methods, the cyclotron trap allowed for a gain in stopping density of about an order of magnitude. The CCDs had excellent spatial and energy resolutions. Non-X-ray background could therefore be almost completely eliminated. The 1S strong interaction shift Ï”1S and total decay width Î1S were determined from the position and line shape of the X-ray peak. They areÏ”1S(shift) = 2.43 ± 0.10eV(repulsive), Î1S(width) = 1.02 ± 0.21eV, where the statistical and systematic errors were added linearly. The total (complex) pionic deuterium S-wave scattering length aÏâd was deduced:aÏâd= â0.0259(±0.0011) +i0.0054(±0.0011)mÏâ1. From the real part of aÏâd a constraint in terms of the isoscalar and isovector ÏNâČ scattering lengths b0 and b1 was deduced. From Im aÏâd we determined the isoscalar coupling constant for Ïâ absorption: |g0| = (2.6 ± 0.3) 10â2mÏâ2. The experiments of the pionic hydrogen and deuterium S-wave scattering lengths were analyzed within the framework of a search for i isospin symmetry violation. The data are still compatible with isospin conservation. The scattering lengths deduced from the Karlsruhe-Helsinki phase shift analysis disagree with the present results
Measurement of absolute yields of Lyman transitions in pionic hydrogen and deuterium as a function of pressure
Pionic hydrogen and deuterium
The strong-interaction effects both in pionic hydrogen and deuterium atoms have been re-determined with improved precision. The hadronic shift and width in pionic hydrogen together with the hadronic shift in pionic deuterium constitute a one-fold constraint for the two independent pion-nucleon scattering lengths. Furthermore, the hadronic width in pionic deuterium measures the transition strength of s-wave pions on an isoscalar nucleon-nucleon pair which is an independent quantity not related to the pion-nucleon scattering lengths. The experiment was performed at the Paul Scherrer Institute by stopping a high-intensity low-energy pion beam in gaseous targets using the cyclotron trap. The X-rays emitted by the ÏH and ÏD atoms were analysed with a high resolution Bragg spectrometer equipped with spherically bent crystals. The pion-nucleon scattering lengths and other physical quantities extracted from the atom data are in good agreement with the results obtained from pionnucleon and nucleon-nucleon scattering experiments and confirm that a consistent picture is achieved for the low-energy pion-nucleon sector with respect to the expectations of chiral perturbation theory