A new determination of the γπ → ππ anomalous amplitude via πe- → π-e-π0 data

I. Giller*, A. Ocherashvili, T. Ebertshäuser, M. A. Moinester, S. Scherer

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

12 Scopus citations


We discuss the reaction π- e - → π- e -π0 with the purpose of obtaining information on the γπ → ππ anomalous amplitude ℱ . We compare a full calculation at script O sign (p 6) in chiral perturbation theory and various phenomenological predictions with the existing data of Amendolia et al. By integrating our theory results using Monte Carlo techniques, we obtain σ = 2.05 nb at script O sign (p 6) and σ = 2.17 nb after including the dominant electromagnetic correction. Both results are in good agreement with the experimental cross-section of σ = (2.11±0.47) nb. On the basis of the ChPT results one would extract from the experimental cross-section as amplitudes ℱ (0)extr = (9.9±1.1) GeV-3 and ℱ (0)extr = (9.6±1.1) GeV-3, respectively, which have to be compared with the low-energy theorem ℱ = e/(4π2 F π 3) = 9.72GeV-3. We emphasize the need for new data to allow for a comparison of experimental and theoretical distributions and to obtain ℱ with smaller uncertainty.

Original languageEnglish
Pages (from-to)229-240
Number of pages12
JournalEuropean Physical Journal A
Issue number2
StatePublished - Aug 2005


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