Photoproduction of neutral pion pairs from the proton

M. Wolf; J. Ahrens; R. Beck; V. Hejny; J.D. Kellie; M. Kotulla; B. Krusche; V. Kuhr; R. Leukel; V. Metag; J.C. Nacher; R. Novotny; V. Olmos de León; R.O. Owens; F. Rambo; A. Schmidt; M. Schumacher; U. Siodlaczek; H. Ströher; J. Weiß; F. Wissmann

doi:doi:10.1007/s100500070048

2021 Impact factor 3.131

Hadrons and Nuclei

Eur. Phys. J. A 9, 5-8

Short note

Photoproduction of neutral pion pairs from the proton

M. Wolf¹ - J. Ahrens² - R. Beck² - V. Hejny¹ - J.D. Kellie³ - M. Kotulla¹ - B. Krusche¹ - V. Kuhr⁴ - R. Leukel² - V. Metag¹ - J.C. Nacher⁶ - R. Novotny¹ - V. Olmos de León² - R.O. Owens³ - F. Rambo⁴ - A. Schmidt² - M. Schumacher⁴ - U. Siodlaczek⁵ - H. Ströher¹ - J. Weiß¹ - F. Wissmann⁴

¹ II. Physikalisches Institut, Universität Gießen, D-35392 Gießen, Germany
² Institut für Kernphysik, Johannes-Gutenberg-Universität Mainz, D-55099 Mainz, Germany
³ Department of Physics and Astronomy, University of Glasgow, Glasgow G128QQ, UK
⁴ II. Physikalisches Institut, Universität Göttingen, D-37073 Göttingen, Germany
⁵ Physikalisches Institut, Universität Tübingen, D-72076 Tübingen, Germany
⁶ Departamento de Física Teórica and IFIC, Universidad de Valencia, 46100 Burjassot, Spain

Received: 6 June 2000 / Revised version: 27 July 2000
Communicated by Th. Walcher

Abstract
Double neutral pion photoproduction from the proton has been measured at MAMI for photon energies between threshold and 820 MeV. The reaction was identified by an invariant mass and missing mass analysis. From threshold up to 370 MeV the total cross-section does not exceed 30 nb. For higher energies it shows a smooth rise until it reaches a maximum of about 10 $\mu$ b at $E_\gamma = 740$ MeV. Dalitz plots of $m^2(\pi^0,\pi^0)$ versus $m^2(p,\pi^0)$ for seven bins of incident photon energy have been analysed. For $E_\gamma >610$ MeV, a strong contribution of a sequential decay is observed with the $\Delta(1232)$ -resonance as intermediate state. A comparison to model calculations shows that these sequential decays presumably originate from the D₁₃(1520)- and also the P₁₁(1440)-resonance.