Bochum 2009 – scientific programme

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HK: Fachverband Hadronen und Kerne

HK 67: Poster Session

HK 67.23: Poster

Thursday, March 19, 2009, 14:00–16:00, Audi-Max

Decay Rate and Photodetachment Cross Section Measurement of the Negative Positronium Ion^† — •Stefan Gärtner¹, Hubert Ceeh², Frank Fleischer³, Christoph Hugenschmidt², Klaus Schreckenbach², Dirk Schwalm⁴, and Peter Thirolf¹ — ¹Ludwig-Maximilians-Universität München, Garching, Germany — ²Technische Universität München and FRM II, Garching, Germany — ³University of Washington, Seattle, USA — ⁴Max-Planck-Institut für Kernphysik, Heidelberg, Germany

The preparations of a new decay rate measurement of the Ps⁻ ion (e⁺e⁻e⁻) at the NEPOMUC high flux positron source (≈ 10⁹ moderated positrons per second) at the FRM II reactor in Garching are shown. The setup, which was previously mounted in Heidelberg, utilizes ≈ 5 nm thin Diamond Like Carbon (DLC) foils for the Ps⁻ production as well as for stripping off the electrons, which takes place immediately after the acceleration across a variable length gap. The aim is to improve the most accurate decay rate measurement [1] of Γ = 2.089(15) ns⁻¹ by a factor of 5–10, thus allowing to test QED [2] for this fundamental leptonic three-body system. In a further step the photodetachment cross section of Ps⁻ will be measured at the two energies provided by the fundamental and second harmonic mode of a high power Nd:YAG laser for the first time. A photodetachment rate of the order of 40 s⁻¹ and 4 · 10⁴ s⁻¹ for continuous and Q-switched laser light, respectively, is expected. [1] F. Fleischer et al., Phys. Rev. Lett. 96, 063401 (2006). [2] M. Puchalski et al., Phys. Rev. Lett. 99, 203401 (2007). ^†Supported by DFG under contract HA1101/13-1.