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- Adlarson, Patrik, et al.
(author)
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Exclusive measurement of the eta -> pi(+) pi(-) gamma decay
- 2012
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In: Physics Letters B. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 707:2, s. 243-249
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Journal article (peer-reviewed)abstract
- An exclusive measurement of the decay eta -> pi(+) pi(-) gamma has been performed at the WASA facility at COSY. The eta mesons were produced in the fusion reaction pd -> He-3 X at a proton beam momentum of 1.7 GeV/c. Efficiency corrected differential distributions have been extracted based on 13 960 +/- 140 events after background subtraction. The measured pion angular distribution is consistent with a relative p-wave of the two-pion system, whereas the measured photon energy spectrum was found at variance with the simplest gauge invariant matrix element of eta -> pi(+) pi(-) gamma. A parameterization of the data can be achieved by the additional inclusion of the empirical pion vector form factor multiplied by a first-order polynomial in the squared invariant mass of the pi(+) pi(-) system.
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2. |
- Hanhart, C., et al.
(author)
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Dispersive analysis for eta ->gamma gamma*
- 2013
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In: European Physical Journal C. - : Springer Science and Business Media LLC. - 1434-6044 .- 1434-6052. ; 73:12, s. 2668-
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Journal article (peer-reviewed)abstract
- A dispersion integral is derived that connects data on eta ->pi (+) pi (-) gamma to the eta ->gamma gamma (au) transition form factor. A detailed analysis of the uncertainties is provided. We find for the slope of the eta transition form factor at the origin . Using an additional, plausible assumption, one finds for the corresponding slope of the eta' transition form factor, . Both values are consistent with all recent data, but differ from some previous theoretical analyses.
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5. |
- Stollenwerk, F., et al.
(author)
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Model-independent approach to η→π+π−γ and η′→π+π−γ
- 2012
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In: Physics Letters B. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 707:1, s. 184-190
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Journal article (peer-reviewed)abstract
- We present a new, model-independent method to analyze radiative decays of mesons to a vector, isovector pair of pions of invariant mass square below the first significant pi pi threshold in the vector channel. It is based on a combination of chiral perturbation theory and dispersion theory. This allows for a controlled inclusion of resonance physics without the necessity to involve vector meson dominance explicitly. As an example, the method is applied to an analysis of the reactions eta -> pi(+)pi(-)gamma and eta' -> pi(+)pi(-)gamma.
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