Extraction of beam-spin asymmetries from the hard exclusive $π^{+}$ channel off protons in a wide range of kinematics
S. Diehl, K. Joo, A. Kim, H. Avakian, P. Kroll, K. Park, D. Riser, K. Semenov-Tian-Shansky, K. Tezgin, K. P. Adhikari, S. Adhikari, M. J. Amaryan, G. Angelini, … 展开作者
S. Diehl, K. Joo, A. Kim, H. Avakian, P. Kroll, K. Park, D. Riser, K. Semenov-Tian-Shansky, K. Tezgin, K. P. Adhikari, S. Adhikari, M. J. Amaryan, G. Angelini, G. Asryan, H. Atac, L. Barion, M. Battaglieri, I. Bedlinskiy, F. Benmokhtar, A. Bianconi, A. S. Biselli, F. Boss`u, S. Boiarinov, W. J. Briscoe, W. K. Brooks, D. Bulumulla, V. D. Burkert, D. S. Carman, J. C. Carvajal, A. Celentano, P. Chatagnon, T. Chetry, G. Ciullo, L. Clark, P. L. Cole, M. Contalbrigo, V. Crede, A. D'Angelo, N. Dashyan, R. De Vita, M. Defurne, A. Deur, C. Dilks, C. Djalali, R. Dupre, H. Egiyan, M. Ehrhart, A. El Alaoui, L. El Fassi, P. Eugenio, A. Filippi, T. A. Forest, Y. Ghandilyan, G. P. Gilfoyle, K. L. Giovanetti, F. X. Girod, D. I. Glazier, E. Golovatch, R. W. Gothe, K. A. Griffioen, M. Guidal, L. Guo, H. Hakobyan, N. Harrison, M. Hattawy, T. B. Hayward, D. Heddle, K. Hicks, M. Holtrop, Y. Ilieva, D. G. Ireland, B. S. Ishkhanov, E. L. Isupov, D. Jenkins, H. S. Jo, S. Joosten, D. Keller, M. Khachatryan, A. Khanal, M. Khandaker, C. W. Kim, W. Kim, V. Kubarovsky, S. E. Kuhn, L. Lanza, M. Leali, P. Lenisa, K. Livingston, I. J. D. MacGregor, D. Marchand, N. Markov, L. Marsicano, V. Mascagna, B. McKinnon, Z. E. Meziani, T. Mineeva, M. Mirazita, V. Mokeev, C. Munoz Camacho, P. Nadel-Turonski, G. Niculescu, M. Osipenko, M. Paolone, L. L. Pappalardo, E. Pasyuk, W. Phelps, O. Pogorelko, J. W. Price, Y. Prok, B. A. Raue, M. Ripani, A. Rizzo, P. Rossi, J. Rowley, F. Sabatie, C. Salgado, A. Schmidt, R. A. Schumacher, Y. G. Sharabian, U. Shrestha, O. Soto, N. Sparveris, S. Stepanyan, P. Stoler, I. I. Strakovsky, S. Strauch, J. A. Tan, N. Tyler, M. Ungaro, L. Venturelli, H. Voskanyan, E. Voutier, D. P. Watts, X. Wei, M. H. Wood, N. Zachariou, J. Zhang, Z. W. Zhao
我们已经测量了光束自旋不对称性提取$\sinϕ$时刻$A_{LU}^{\sinϕ}$从硬排他性$\vec{e} p \to e^\prime n π^+$反应以上的共振区域，第一次几乎完全覆盖从向前到向后的角度在质心。在$-t$中，测量了$A_{LU}^{\sinϕ}$矩，能量高达6.6 GeV $^{2}$，同时涵盖了广义部分子分布（GPD）和重子-介子跃迁分布振幅（TDA）的运动学区域。正向运动学的实验结果表明，手征奇，手征偶GPD的敏感性。在TDA框架适用的非常向后的运动学中，我们发现$A_{LU}^{\sinϕ}$为负，而在质量中心的90 $^\circ$附近观察到符号变化。本文中提出的独特的结果将提供关键的限制，建立反应机制，可以帮助进一步发展的GPD和TDA框架。
英文摘要：
We have measured beam-spin asymmetries to extract the $\sinϕ$ moment $A_{LU}^{\sinϕ}$ from the hard exclusive $\vec{e} p \to e^\prime n π^+$ reaction above the resonance region, for the first time with nearly full coverage from forward to backward angles in the center-of-mass. The $A_{LU}^{\sinϕ}$ moment has been measured up to 6.6 GeV$^{2}$ in $-t$, covering the kinematic regimes of Generalized Parton Distributions (GPD) and baryon-to-meson Transition Distribution Amplitudes (TDA) at the same time. The experimental results in very forward kinematics demonstrate the sensitivity to chiral-odd and chiral-even GPDs. In very backward kinematics where the TDA framework is applicable, we found $A_{LU}^{\sinϕ}$ to be negative, while a sign change was observed near 90$^\circ$ in the center-of-mass. The unique results presented in this paper will provide critical constraints to establish reaction mechanisms that can help to further develop the GPD and TDA frameworks.
Single-Transverse-Spin Asymmetries in Exclusive Photo-production of J/psi in Ultra-Peripheral Collisions in the Fixed-Target Mode at the LHC and in the Collider Mode at RHIC
Target and beam-target spin asymmetries in exclusive pion electroproduction for $Q^2>1$ GeV$^2$. II. $e p \rightarrow e π^0 p$
测量了专用$π^0$电生成反应$γ^* p \to p π^0$的束靶双自旋不对称性和靶单自旋不对称性，扩展了来自同一实验的$γ^* p \to n π^+$反应的分析。这些结果是用杰斐逊实验室的CEBAF大型接收谱仪从6 GeV的纵向极化电子与纵向极化质子的散射中得到的。所涵盖的运动学范围是$1.1<W<3$ GeV和$1<Q^2<6$ GeV $^2$。在$W$、$Q^2$、\cthcm和$ϕ^*$中获得了约5700个箱的结果。发现波束-目标不对称性通常大于零，具有相对适度的\phicmsp依赖性。靶不对称性表现出非常强的\phicmsp依赖性，与$π^+$电产生相反，在低$W$和高$W$下的结果之间发生符号变化。合理的协议，发现与现象学适合以前的数据$W<1.6$ GeV，但显着差异，在较高的$W$。当结合横截面测量，以及$π^+$观测值，目前的结果将提供强大的约束在中等和大的$Q^2$值的核子共振振幅，共振质量高达2.4 GeV。
