Quasi-free photoproduction from the bound nucleon

K. Kossert; M. Camen; F. Wissmann; J. Ahrens; J. R. M. Annand; H.-J. Arends; R. Beck; G. Caselotti; P. Grabmayr; O. Jahn; P. Jennewein; M. I. Levchuk; A. I. L’vov; J. C. McGeorge; A. Natter; V. Olmos de León; V. A. Petrun’kin; G. Rosner; M. Schumacher; B. Seitz; F. Smend; A. Thomas; W. Weihofen; F. Zapadtka

doi:10.1140/epja/i2003-10130-3

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2023 Impact factor 2.6

Hadrons and Nuclei

Eur. Phys. J. A (2004) 19: 391-399
https://doi.org/10.1140/epja/i2003-10130-3

Quasi-free $\pi^0$ photoproduction from the bound nucleon

K. Kossert¹, M. Camen¹, F. Wissmann¹, J. Ahrens², J. R. M. Annand³, H.-J. Arends², R. Beck², G. Caselotti², P. Grabmayr⁴, O. Jahn², P. Jennewein², M. I. Levchuk⁵, A. I. L’vov⁶, J. C. McGeorge³, A. Natter⁴, V. Olmos de León², V. A. Petrun’kin⁶, G. Rosner³, M. Schumacher¹^*, B. Seitz¹, F. Smend¹, A. Thomas², W. Weihofen¹ and F. Zapadtka¹

¹ II. Physikalisches Institut, Universität Göttingen, D-37073, Göttingen, Germany
² Institut für Kernphysik, Universität Mainz, D-55099, Mainz, Germany
³ Department of Physics and Astronomy, University of Glasgow, G12 8QQ, Glasgow, UK
⁴ Physikalisches Institut, Universität Tübingen, D-72076, Tübingen, Germany
⁵ B.I. Stepanov Institute of Physics, Belarussian Academy of Sciences, 220072, Minsk, Belarus
⁶ P.N. Lebedev Physical Institute, 119991, Moscow, Russia

^* e-mail: schumacher@physik2.uni-goettingen.de

Abstract

Differential cross-sections for quasi-free $\pi^0$ photoproduction from the proton and neutron bound in the deuteron have been measured for $E_\gamma = 200\mbox{--}400$ MeV at $\theta_\gamma^{\rm lab} = 136.2^\circ$ using the Glasgow photon tagger at MAMI, the Mainz 48 cm $\clubsuit\times 64$ cm NaI(Tl) photon detector and the Göttingen SENECA recoil detector. For the proton measurements made with both liquid-deuterium and liquid-hydrogen targets allow direct comparison of “free” $\pi^0$ photoproduction cross-sections as extracted from the bound-proton data with experimental free cross-sections which are found to be in reasonable agreement below 320 MeV. At higher energies the “free” cross-sections extracted from quasi-free data are significantly smaller than the experimental free cross-sections and theoretical predictions based on multipole analysis. For the first time, “free” neutron cross-section have been extracted in the $\Delta$ -region. They are also in agreement with the predictions from multipole analysis up to 320 MeV and significantly smaller at higher photon energies.