Exclusive measurement of two-pion production in the dd --> 4Hepipi reaction
S. Keleta, Chr. Bargholtz, M. Bashkanov, M. Berlowski, D. Bogoslawsky, H. Calen, H. Clement, L. Demirors, C. Ekstrom, K. Fransson, L. Geren, L. Gustafsson, B. H… 展开作者
S. Keleta, Chr. Bargholtz, M. Bashkanov, M. Berlowski, D. Bogoslawsky, H. Calen, H. Clement, L. Demirors, C. Ekstrom, K. Fransson, L. Geren, L. Gustafsson, B. Hoistad, G. Ivanov, M. Jacewicz, E. Jiganov, T. Johansson, O. Khakimova, F. Kren, S. Kullander, A. Kupsc, A. Kuzmin, K. Lindberg, P. Marciniewski, B. Morosov, W. Oelert, C. Pauly, H. Petren, Y. Petukhov, A. Povtorejko, A. Pricking, R. J. M. Y. Ruber, K. Schonning, W. Scobel, R. Shafigullin, B. Shwartz, T. Skorodko, V. Sopov, J. Stepaniak, P. -E. Tegner, P. Thorngren Engblom, V. Tikhomirov, A. Turowiecki, G. J. Wagner, C. Wilkin, M. Wolke, J. Zabierowski, I. Zartova, J. Zlomanczuk
The results from the first kinematically complete measurement of the dd --> 4Hepipi reaction are reported. The aim was to investigate a long standing puzzle regarding the origin of the peculiar pipi-invariant mass distributions appearing in double pion production in light ion collisions, the so-called ABC effect. The measurements were performed at the incident deuteron energies of 712 MeV and 1029 MeV, with the WASA detector assembly at CELSIUS in Uppsala, Sweden. We report the observation of a characteristic enhancement at low pipi-invariant mass at 712 MeV, the lowest energy yet. At the higher energy, in addition to confirming previous experimental observations, our results reveal a strong angular dependence of the pions in the overall centre of mass system. The results are qualitatively reproduced by a theoretical model, according to which the ABC effect is described as resulting from a kinematical enhancement in the production of the pion pairs from two parallel and independent NN--> dpi sub-processes.
First exclusive measurements of the K^-pp state - populated in the pp to K^+ Lambda p reaction at 2.85 GeV
我们分析了在T_p = 2.85 $ GeV to search for a K^-pp (= X) nuclear bound state to be formed in the pp to K^+ + X reaction. The deviation spectra of the K^+ missing-mass MM (K^+) and Lambda p invariant-mass M(Lambda-p) with selection of large-angle proton emission revealed a structure with M_X = 2265 +- 2 MeV/c2 and Gamma_X = 118 +- 8$ MeV时，从pp到K^+ λ p的排它过程的DISTO实验数据。
Accessing proton generalized parton distributions and pion distribution amplitudes with the exclusive pion-induced Drell-Yan process at J-PARC
广义部分子分布（GPD）编码的强子部分子结构的多维信息出现在硬排斥反应的因式分解描述的积木。核子GPD是通过轻子束的深虚康普顿散射和深虚介子产生来实现的。与强子束互补的探测是π介子诱导的Drell-Yan过程。在本文中，我们讨论了最近的理论进展，描述这一过程的核子GPD和π分布振幅。此外，我们解决的可行性测量专有π介子诱导的Drell-Yan过程$π^- p \to μ^+μ^- n$通过光谱仪在高动量光束线正在建设中的日本J-PARC。在J-PARC实现这样的测量将提供一个新的测试微扰QCD描述的一类新的硬排斥反应。它还将提供在大型类时虚拟环境中实验性地访问核子GPD的可能性。
Hard exclusive pion electroproduction at backward angles with CLAS
我们报告的第一次测量的横截面独家深虚拟π电生产的质子，$e p \to e^\prime n π^+$，以上的共振区在向后π质心角。测量了$φ^*_π$依赖的截面，从中我们提取了质子的三种结构函数组合。我们的结果与基于核子到π介子跃迁分布振幅（TDAs）的计算结果是一致的，并为核子结构提供了新的解释。
