Krambrich D, Zehr F, Fix A, Roca L, Aguar P, Ahrens J, Annand J R M, Arends H J, Beck R, Bekrenev V, Boillat B, Braghieri A, Branford D, Briscoe W J, Brudvik J, Cherepnya S, Codling R, Downie E J, Dexler P, Glazier D I, Grabmayr P, Gregor R, Heid E, Hornidge D, Jahn O, Kashevarov V L, Knezevic A, Kondratiev R, Korolija M, Kotulla M, Krusche B, Kulbardis A, Lang M, Lisin V, Livingston K, Lugert S, MacGregor I J D, Manley D M, Martinez M, McGeorge J C, Mekterovic D, Metag V, Nefkens B M K, Nikolaev A, Pedroni P, Pheron F, Polonski A, Prakhov S N, Price J W, Rosner G, Rost M, Rostomyan T, Schumann S, Sober D, Starostin A, Supek I, Tarbert C M, Thomas A, Unverzagt M, Walcher Th, Watts D P
Institut für Kernphysik, Johannes Gutenberg-Universität Mainz, Mainz, Germany.
Phys Rev Lett. 2009 Jul 31;103(5):052002. doi: 10.1103/PhysRevLett.103.052002. Epub 2009 Jul 30.
Beam-helicity asymmetries have been measured at the MAMI accelerator in Mainz in the three isospin channels gamma[over -->]p-->pi(+)pi(0)n, gamma[over -->]p-->pi(0)pi(0)p, and gamma[over -->]p-->pi(+)pi(-)p. The circularly polarized photons, produced from bremsstrahlung of longitudinally polarized electrons, were tagged with the Glasgow magnetic spectrometer. Charged pions and the decay photons of pi(0) mesons were detected in a 4pi electromagnetic calorimeter which combined the Crystal Ball detector with the TAPS detector. The precisely measured asymmetries are very sensitive to details of the production processes and are thus key observables in the modeling of the reaction dynamics.
在美因茨的MAMI加速器上，已经在三个同位旋通道γ[上标→]p→π⁺π⁰n、γ[上标→]p→π⁰π⁰p和γ[上标→]p→π⁺π⁻p中测量了束流螺旋度不对称性。由纵向极化电子的轫致辐射产生的圆偏振光子，用格拉斯哥磁谱仪进行标记。带电π介子和π⁰介子的衰变光子在一个4π电磁量能器中被探测到，该量能器将晶体球探测器与TAPS探测器结合在一起。精确测量的不对称性对产生过程的细节非常敏感，因此是反应动力学建模中的关键可观测量。
