Measurement of the structure function of the nearly free neutron using spectator tagging in inelastic $^2$H(e, e'p)X scattering with CLAS
S. Tkachenko, N. Baillie, S. E. Kuhn, J. Zhang, J. Arrington, P. Bosted, S. Bültmann, M. E. Christy, D. Dutta, R. Ent, H. Fenker, K. A. Griffioen, M. Ispiryan, … 展开作者
S. Tkachenko, N. Baillie, S. E. Kuhn, J. Zhang, J. Arrington, P. Bosted, S. Bültmann, M. E. Christy, D. Dutta, R. Ent, H. Fenker, K. A. Griffioen, M. Ispiryan, N. Kalantarians, C. E. Keppel, W. Melnitchouk, V. Tvaskis, K. P. Adhikari, M. Aghasyan, M. J. Amaryan, S. Anefalos Pereira, H. Avakian, J. Ball, N. A. Baltzell, M. Battaglieri, I. Bedlinskiy, A. S. Biselli, W. J. Briscoe, W. K. Brooks, V. D. Burkert, D. S. Carman, A. Celentano, S. Chandavar, G. Charles, P. L. Cole, M. Contalbrigo, O. Cortes, V. Crede, A. D'Angelo, N. Dashyan, R. De Vita, E. De Sanctis, A. Deur, C. Djalali, G. E. Dodge, D. Doughty, R. Dupre, H. Egiyan, A. El Alaoui, L. El Fassi, L. Elouadrhiri, P. Eugenio, G. Fedotov, J. A. Fleming, B. Garillon, N. Gevorgyan, Y. Ghandilyan, G. P. Gilfoyle, K. L. Giovanetti, F. X. Girod, J. T. Goetz, E. Golovatch, R. W. Gothe, M. Guidal, L. Guo, K. Hafidi, H. Hakobyan, C. Hanretty, N. Harrison, M. Hattawy, K. Hicks, D. Ho, M. Holtrop, C . E. Hyde, Y. Ilieva, D. G. Ireland, B. S. Ishkhanov, H. S. Jo, D. Keller, M. Khandaker, A. Kim, W. Kim, P. M. King, A. Klein, F. J. Klein, S. Koirala, V. Kubarovsky, S. V. Kuleshov, P. Lenisa, S. Lewis, K. Livingston, H. Lu, M. MacCormick, I. J. D. MacGregor, N. Markov, M. Mayer, B. McKinnon, T. Mineeva, M. Mirazita, V. Mokeev, R. A. Montgomery, H. Moutarde, C. Munoz Camacho, P. Nadel-Turonski, S. Niccolai, G. Niculescu, I. Niculescu, M. Osipenko, L. L. Pappalardo, R. Paremuzyan, K. Park, E. Pasyuk, J. J. Phillips, S. Pisano, O. Pogorelko, S. Pozdniakov, J. W. Price, S. Procureur, D. Protopopescu, A. J . R. Puckett, D. Rimal, M. Ripani, A. Rizzo, G. Rosner, P. Rossi, P. Roy, F. Sabatié, D. Schott, R. A. Schumacher, E. Seder, I. Senderovich, Y. G. Sharabian, A. Simonyan, G. D. Smith, D. I. Sober, D. Sokhan, S. Stepanyan, S. S. Stepanyan, S. Strauch, W. Tang, M. Ungaro, A. V. Vlassov, H. Voskanyan, E. Voutier, N. K. Walford, D. Watts, X. Wei, L. B. Weinstein, M. H. Wood, L. Zana, I. Zonta
备注：
28 pages, 22 figures; published in Phys. Rev. C. Revised to include three authors inadvertently left off the original version: D. Dutta, R. Ent, and M. Ispiryan
Much less is known about neutron structure than that of the proton due to the absence of free neutron targets. Neutron information is usually extracted from data on nuclear targets such as deuterium, requiring corrections for nuclear binding and nucleon off-shell effects. These corrections are model dependent and have significant uncertainties, especially for large values of the Bjorken scaling variable x. The Barely Off-shell Nucleon Structure (BONuS) experiment at Jefferson Lab measured the inelastic electron deuteron scattering cross section, tagging spectator protons in coincidence with the scattered electrons. This method reduces nuclear binding uncertainties significantly and has allowed for the first time a (nearly) model independent extraction of the neutron structure function. A novel compact radial time projection chamber was built to detect protons with momentum between 70 and 150 MeV/c. For the extraction of the free neutron structure function $F_{2n}$, spectator protons at backward angle and with momenta below 100 MeV/c were selected, ensuring that the scattering took place on a nearly free neutron. The scattered electrons were detected with Jefferson Lab's CLAS spectrometer. The extracted neutron structure function $F_{2n}$ and its ratio to the deuteron structure function $F_{2d}$ are presented in both the resonance and deep inelastic regions. The dependence of the cross section on the spectator proton momentum and angle is investigated, and tests of the spectator mechanism for different kinematics are performed. Our data set can be used to study neutron resonance excitations, test quark hadron duality in the neutron, develop more precise parametrizations of structure functions, as well as investigate binding effects (including possible mechanisms for the nuclear EMC effect) and provide a first glimpse of the asymptotic behavior of d/u as x goes to 1.
Spectator-Tagged Deeply Virtual Compton Scattering on Light Nuclei
质子中夸克和胶子的三维图像将通过深度虚康普顿散射来揭示，而一维图像中一个至关重要的难题仍然存在，即EMC效应的起源。非相干核DVCS，即核内核子的DVCS，可以揭示束缚核子的三维部分子结构，为EMC效应提供新的解释。然而，费米运动的打击核子，离壳效应和最终状态的相互作用（FSI）复杂的部分子水平的解释。我们在这里提出了一个测量的不相干DVCS的反冲旁观者系统（核A-1）的标签，系统地控制核效应。通过观察者标记的DVCS，一个完全检测到的最终状态提供了一个独特的机会，系统地研究这些核效应，并干净地观察核子夸克分布的可能修改。我们建议测量$^4$ He和氘靶上的DVCS束流自旋不对称性（BSA）。反应$^4$ He $(e,e^{\prime}γ\,p\,^3$ H $)$与一个完全检测到的最终状态具有罕见的能力，同时量化FSI，测量初始核子动量，并提供一个敏感的探针，在部分子水平上的其他核效应。在一个（准自由）中子上的DVCS BSA将通过用氘靶标记旁观质子来测量。类似地，束缚中子测量检测离开$^4$ He靶的旁观者$^3$ He。这两个观测值将允许中子偏离前向EMC效应的独立测量。
Semi-inclusive Deep Inelastic Scattering off Few-Nucleon Systems: Tagging the EMC Effect and Hadronization Mechanisms with Detection of Slow Recoiling Nuclei
Measurements of Beam Spin Asymmetries of $π^\pmπ^0$ dihadrons at CLAS12
University of York（约克大学）；Christopher Newport University（克里斯托弗纽波特大学）；Universit’e Paris-Saclay, CNRS/IN2P3, IJCLab（巴黎萨克雷大学）；Old Dominion University（老道明大学）；Argonne National Laboratory（阿贡国家实验室）；Temple University（天普大学）；Thomas Jefferson National Accelerator Facility（托马斯杰斐逊国家加速设施）；INFN, Sezione di Ferrara（意大利国家核物理研究所费拉拉分部）；INFN, Sezione di Genova（意大利国家核物理研究所热那亚分部）；Duquesne University（杜肯大学）；Universit‘a degli Studi di Brescia（布雷西亚大学）；INFN, Sezione di Pavia（意大利国家核物理研究所帕维亚分部）；Fairfield University（费尔菲尔德大学）；II Physikalisches Institut der Universitaet Giessen（吉森大学第二物理研究所）；IRFU, CEA, Universit’e Paris-Saclay（法国原子能和替代能源委员会）；The George Washington University（乔治华盛顿大学）
