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  • 2000-2004  (3)
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  • 1
    Electronic Resource
    Electronic Resource
    The pion–nucleon scattering lengths from pionic hydrogen and deuterium (2001)
    Springer
    The European physical journal 21 (2001), S. 473-488 
    Details
    ISSN: 1434-6052
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract. This is the final publication of the ETH Zurich–Neuchâtel–PSI collaboration on the pionic hydrogen and deuterium precision X-ray experiments. We describe the recent hydrogen 3p–1s measurement, report on the determination of the Doppler effect correction to the transition line width, analyze the deuterium shift measurement and discuss implications of the combined hydrogen and deuterium results. From the pionic hydrogen 3p–1s transition experiments we obtain the strong-interaction energy level shift $\varepsilon_{1s} = -7.108\pm0.013 (\mathrm{stat.})\pm0.034 (\mathrm{syst.})$ eV and the total decay width $\Gamma_{1s} = 0.868\pm0.040 (\mathrm{stat.})\pm0.038 (\mathrm{syst.})$ eV of the $1s$ state. Taking into account the electromagnetic corrections we find the hadronic $\pi N$ s-wave scattering amplitude $a_{\pi^{-}p\rightarrow\pi^{-}p} = 0.0883\pm0.0008 m_{\pi}^{-1}$ for elastic scattering and $a_{\pi^{-}p\rightarrow\pi^{0}n} = -0.128\pm0.006 m_{\pi} ^{-1}$ for single charge exchange, respectively. We then combine the pionic hydrogen results with the 1s level shift measurement on pionic deuterium and test isospin symmetry of the strong interaction: our data are still compatible with isospin symmetry. The isoscalar and isovector $\pi N$ scattering lengths (within the framework of isospin symmetry) are found to be $b_0 = -0.0001^{+0.0009}_{-0.0021} m_{\pi}^{-1}$ and $b_{1} = -0.0885^{+0.0010}_{-0.0021} m_{\pi} ^{-1}$ , respectively. Using the GMO sum rule, we obtain from $b_1$ a new value of the $\pi N$ coupling constant ( $g_{\pi N} = 13.21_{-0.05}^{+0.11}$ ) from which follows the Goldberger–Treiman discrepancy $\Delta_{\mathrm{{GT}}} =0.027_{-0.008}^{+0.012}$ . The new values of $b_0$ and $g_{\pi N}$ imply an increase of the nucleon sigma term by at least 9 MeV.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s100520100754
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  • 2
    Electronic Resource
    Electronic Resource
    Experiment to measure the Lamb shift in muonic hydrogen (2000)
    Springer
    Hyperfine interactions 127 (2000), S. 161-166 
    Details
    ISSN: 1572-9540
    Keywords: proton ; proton radius ; muon ; muonic hydrogen ; Lamb shift
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The contribution of the root mean square (RMS) proton charge radius to the Lamb shift (2S–2P energy difference) in muonic hydrogen (μp) amounts to 2%. Apart from the uncertainty on this charge radius, theory predicts the Lamb shift with a precision on the ppm level. We are going to measure ΔE (2 S1/2(F=1)–2 P3/2(F=2)) in a laser resonance experiment to a precision of 30 ppm (i.e., 10% of the natural linewidth) and to deduce the RMS proton charge radius with 10−3 relative accuracy, 20 times more precise than presently known. The most important requirement for the feasibility of such an experiment, namely the availability of a sufficient amount of long lived metastable μp atoms in the 2S state, has been investigated in a recent experiment at PSI. Our analysis shows that in the order of one percent of all muons stopped in low pressure hydrogen gas form a long lived μp(2S) with a lifetime of the order of 1 μs. The technical realization of our experiment involves a new high intensity low energy muon beam, an efficient low energy muon entrance detector, a randomly triggered 3 stage laser system providing the 0.5 mJ, 7 ns laser pulses at 6.02 μm wavelength, and a combination of a xenon gas proportional scintillation chamber (GPSC) and a microstrip gas chamber (MSGC) with a CsI coated surface to detect the 2 keV X rays from theμp(2P → 1S) transition.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1012679114531
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  • 3
    Electronic Resource
    Electronic Resource
    High resolution X ray spectroscopy in light antiprotonic atoms (2000)
    Springer
    Hyperfine interactions 127 (2000), S. 149-155 
    Details
    ISSN: 1572-9540
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract At the LEAR facility, CERN, antiprotonic Lα transitions in light elements have been investigated with a focussing crystal spectrometer. The high resolution of the experiment allowed for the first time to resolve in $${\bar p}$$ H the 23P0 state from the close lying states 23P2, 21P1, and 23P1. In $${\bar p}$$ D the corresponding transitions were found to be more than an order of magnitude broader. To a large extent the results for $${\bar p}$$ H support the meson exchange model.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1012675013623
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