Double pi0 photoproduction off the proton at threshold

Kotulla, M. et al. (2004) Double pi0 photoproduction off the proton at threshold. Physics Letters B, 578(1-2), 63 -68. (doi: 10.1016/j.physletb.2003.10.056)

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The reaction gammap → pi(0)pi(0)p has been measured using the TAPS BaF2 calorimeter at the tagged photon facility of the Mainz Microtron accelerator. Chiral perturbation theory (ChPT) predicts that close to threshold this channel is significantly enhanced compared to double pion final states with charged pions. In contrast to other reaction channels, the lower order tree terms are strongly suppressed in 2pi(0) photoproduction. The consequence is the dominance of pion loops in the 2pi(0) channel close to threshold-a result that opens new prospects for the test of ChPT and in particular its inherent loop terms. The present measurement is the first which is sensitive enough for a conclusive comparison with the ChPT calculation and is in agreement with its prediction. The data also show good agreement with a calculation in the unitary chiral approach.

Item Type:Articles
Glasgow Author(s) Enlighten ID:McGeorge, Dr John and MacGregor, Professor Douglas and Annand, Dr John and Watts, Dr Daniel and Owens, Professor Robert
Authors: Kotulla, M., Ahrens, J., Annand, J.R.M., Beck, R., Hornidge, D., Janssen, S., Krusche, B., McGeorge, J.C., MacGregor, I.J.D., Messchendorp, J.G., Metag, V., Novotny, R., Pfeiffer, M., Owens, R.O., Rost, M., Schadmand, S., and Watts, D.P.
Subjects:Q Science > QC Physics
College/School:College of Science and Engineering > School of Physics and Astronomy
Journal Name:Physics Letters B
Publisher:Elsevier BV
ISSN (Online):1873-2445

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