来自核子的π⁰ 对光生过程的螺旋度相关截面
Helicity-Dependent Cross Sections for the Photoproduction of π^{0} Pairs from Nucleons.
作者信息
Dieterle M, Witthauer L, Fix A, Abt S, Achenbach P, Adlarson P, Afzal F, Aguar Bartolome P, Ahmed Z, Annand J R M, Arends H J, Bashkanov M, Beck R, Biroth M, Borisov N, Braghieri A, Briscoe W J, Cividini F, Collicott C, Costanza S, Denig A, Dolzhikov A S, Downie E J, Drexler P, Gardner S, Ghosal D, Glazier D I, Gorodnov I, Gradl W, Günther M, Gurevich D, Heijkenskjöld L, Hornidge D, Huber G M, Käser A, Kashevarov V L, Kay S, Keshelashvili I, Kondratiev R, Korolija M, Krusche B, Lazarev A, Lisin V, Livingston K, Lutterer S, MacGregor I J D, Manley D M, Martel P P, Metag V, Meyer W, Middleton D G, Miskimen R, Mornacchi E, Mullen C, Mushkarenkov A, Neganov A, Neiser A, Oberle M, Ostrick M, Otte P B, Paudyal D, Pedroni P, Polonski A, Powell A, Prakhov S N, Reicherz G, Ron G, Rostomyan T, Sarty A, Sfienti C, Sokhoyan V, Spieker K, Steffen O, Strakovsky I I, Strub T, Supek I, Thiel A, Thiel M, Thomas A, Unverzagt M, Usov Yu A, Wagner S, Walford N K, Watts D P, Werthmüller D, Wettig J, Wolfes M, Zana L A
机构信息
Department of Physics, University of Basel, CH-4056 Basel, Switzerland.
Laboratory of Mathematical Physics, Tomsk Polytechnic University, 634034 Tomsk, Russia.
出版信息
Phys Rev Lett. 2020 Aug 7;125(6):062001. doi: 10.1103/PhysRevLett.125.062001.
The double-polarization observable E and helicity-dependent cross sections σ_{1/2}, σ_{3/2} have been measured for the photoproduction of π^{0} pairs off quasifree protons and neutrons at the Mainz MAMI accelerator with the Crystal Ball/TAPS setup. A circularly polarized photon beam was produced by bremsstrahlung from longitudinally polarized electrons and impinged on a longitudinally polarized deuterated butanol target. The reaction products were detected with an almost 4π covering calorimeter. The results reveal for the first time the helicity- and isospin-dependent structure of the γN→Nπ^{0}π^{0} reaction. They are compared to predictions from reaction models in view of nucleon resonance contributions and also to a refit of one model that predicted results for the proton and for the neutron target. The comparison of the prediction and the refit demonstrates the large impact of the new data.
利用晶体球/ TAPS装置，在美因茨MAMI加速器上测量了准自由质子和中子上产生π⁰对的双极化可观测量E以及与螺旋度相关的截面σ₁/₂、σ₃/₂。通过纵向极化电子的轫致辐射产生圆极化光子束，并将其入射到纵向极化的氘代丁醇靶上。用几乎覆盖4π的量热计探测反应产物。结果首次揭示了γN→Nπ⁰π⁰反应中与螺旋度和同位旋相关的结构。鉴于核子共振贡献，将它们与反应模型的预测进行了比较，并且还与一个预测质子和中子靶结果的模型的重新拟合进行了比较。预测与重新拟合的比较证明了新数据的巨大影响。
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