论文标题

在共振区域上方的向后角度独家PI0生产

Backward-angle Exclusive pi0 Production above the Resonance Region

论文作者

Li, W. B., Huber, G. M., Stevens, J. R., Semenov-Tian-Shansky, K., Szymanowski, L., Pire, B., Amaryan, M., Androic, D., Aniol, K., Armstrong, D., Averett, T., Gayoso, C. Ayerbe, Boeglin, W., Boer, M., Camsonne, A., Chen, J., Dusa, S. Covrig, Deconinck, W., Defurne, M., Delcarro, F., Diefenthaler, M., Diehl, S., Elaasar, M., Fanelli, C., Fegan, S., Fuchey, E., Gaskell, D., Hansen, O., Hauenstein, F., Higinbotham, D., Blin, A. Hiller, Hurley, A., Hyde, C., Joo, K., Junaid, M., Kalantarians, N., Kay, S., Khachatryan, M., King, P., Kumar, V., Lersch, D., Lorenti, L., Markowitz, P., McCaughan, M., Mkrtchyan, A., Mkrtchyan, H., Niculescu, G., Niculescu, I., Papandreou, Z., Paremuzyan, R., Park, K., Paudyal, D., Roche, J., Rodas, A., Sawatzky, B., Schertz, A., Smith, G., Strakovsky, I., Tadevosyan, V., Usman, A., Voskanyan, H., Yero, C.

论文摘要

所提出的测量是对共振区域上方的向后角度(U通道过程)中的专用电源过程1H(E,E'P)PI0的专门研究。生产的PI0与虚拟光子动量相反180度。这项研究还旨在应用众所周知的Rosenbluth分离技术,该技术在从未探索过的U通道运动区域提供了独立于模型的差异横截面。目前,U通道介子生产中的“软性过渡”仍然是一个有趣且尚未探索的主题。可用的理论框架为观察到的向后角截面峰提供了竞争解释。在“软”的HADRONIC REGGE交换描述中,向后的介子产生来自核子交换与通过核中重新散射产生的介子之间的干扰。尽管在“硬”类似GPD的向后分线化分解方案中,散射幅度将其分解为硬式子过程振幅,并将重子分解为中介子过渡分布振幅(TDAS),另有称为超级偏斜的Parton分布(SUPERSPDS)。 TDA和SPD都是仅通过向后角运动学访问的核子结构的通用非扰动对象。分离的横截面:Q2 = 2-6 GEV2时的Sigma_T,Sigma_l和T/L比,对TDA模型的两个预测提供了直接测试。分离的横截面的幅度和U依赖性也为重新分散的regge图片提供了直接连接。在不同Q2处提取的相互作用半径(来自U依赖性)可用于研究U通道运动学中的软性转变。这些数据的获取将是验证核子结构功能的向后分解方案的存在并建立其适用的运动范围的重要一步。

The proposed measurement is a dedicated study of the exclusive electroproduction process,1H(e,e'p)pi0, in the backward-angle regime (u-channel process) above the resonance region. The produced pi0 is emitted 180 degrees opposite to the virtual-photon momentum. This study also aims to apply the well-known Rosenbluth separation technique that provides the model-independent differential cross-sections at the never explored u-channel kinematics region. Currently, the "soft-hard transition" in u-channel meson production remains an interesting and unexplored subject. The available theoretical frameworks offer competing interpretations for the observed backward-angle cross section peaks. In a "soft" hadronic Regge exchange description, the backward meson production comes from the interference between nucleon exchange and the meson produced via re-scattering within the nucleon. Whereas in the "hard" GPD-like backward collinear factorization regime, the scattering amplitude factorizes into a hard subprocess amplitude and baryon to meson transition distribution amplitudes (TDAs), otherwise known as super skewed parton distributions (SuperSPDs). Both TDAs and SPDs are universal non-perturbative objects of nucleon structure accessible only through backward-angle kinematics. The separated cross sections:sigma_T,sigma_L and T/L ratio at Q2=2-6 GeV2, provide a direct test of two predictions from the TDA model. The magnitude and u-dependence of the separated cross sections also provide a direct connection to the re-scattering Regge picture. The extracted interaction radius (from u-dependence) at different Q2 can be used to study the soft-hard transition in the u-channel kinematics. The acquisition of these data will be an important step forward in validating the existence of a backward factorization scheme of the nucleon structure function and establishing its applicable kinematic range.

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