利用深度非弹性康普顿散射探索束缚质子的结构
Exploring the Structure of the Bound Proton with Deeply Virtual Compton Scattering.
作者信息
Hattawy M, Baltzell N A, Dupré R, Bültmann S, De Vita R, El Alaoui A, El Fassi L, Egiyan H, Girod F X, Guidal M, Hafidi K, Jenkins D, Liuti S, Perrin Y, Stepanyan S, Torayev B, Voutier E, Adhikari S, Angelini Giovanni, Ayerbe Gayoso C, Barion L, Battaglieri M, Bedlinskiy I, Biselli A S, Bossù F, Brooks W, Cao F, Carman D S, Celentano A, Chatagnon P, Chetry T, Ciullo G, Clark L, Cole P L, Contalbrigo M, Crede V, D'Angelo A, Dashyan N, De Sanctis E, Defurne M, Deur A, Diehl S, Djalali C, Ehrhart M, Eugenio P, Fegan S, Filippi A, Forest T A, Fradi A, Garçon M, Gavalian G, Gevorgyan N, Gilfoyle G P, Giovanetti K L, Golovatch E, Gothe R W, Griffioen K A, Harrison N, Hauenstein F, Hayward T B, Heddle D, Hicks K, Holtrop M, Ilieva Y, Ireland D G, Isupov E L, Jo H S, Johnston S, Keller D, Khachatryan G, Khachatryan M, Khanal A, Khandaker M, Kim C W, Kim W, Klein F J, Kubarovsky V, Kuhn S E, Lanza L, L Kabir M, Lenisa P, Livingston K, MacGregor I J D, Marchand D, Markov N, Mayer M, McKinnon B, Meziani Z E, Mineeva T, Mirazita M, Montgomery R A, Munoz Camacho C, Nadel-Turonski P, Niccolai S, Ostrovidov A I, Pappalardo L L, Paremuzyan R, Pasyuk E, Pogorelko O, Poudel J, Prok Y, Protopopescu D, Ripani M, Riser D, Rizzo A, Rosner G, Rossi P, Sabatié F, Salgado C, Schumacher R A, Sharabian Y G, Skorodumina Iu, Sokhan D, Soto O, Sparveris N, Strauch S, Taiuti M, Tan J A, Tyler N, Ungaro M, Voskanyan H, Wang R, Watts D P, Wei X, Weinstein L B, Wood M H, Zachariou N, Zhang J, Zhao Z W
机构信息
Argonne National Laboratory, Argonne, Illinois 60439, USA.
Institut de Physique Nucléaire, IN2P3-CNRS, Université Paris-Sud, Université Paris-Saclay, F-91406 Orsay, France.
出版信息
Phys Rev Lett. 2019 Jul 19;123(3):032502. doi: 10.1103/PhysRevLett.123.032502.
In the past two decades, deeply virtual Compton scattering of electrons has been successfully used to advance our knowledge of the partonic structure of the free proton and investigate correlations between the transverse position and the longitudinal momentum of quarks inside the nucleon. Meanwhile, the structure of bound nucleons in nuclei has been studied in inclusive deep-inelastic lepton scattering experiments off nuclear targets, showing a significant difference in longitudinal momentum distribution of quarks inside the bound nucleon, known as the EMC effect. In this Letter, we report the first beam spin asymmetry (BSA) measurement of exclusive deeply virtual Compton scattering off a proton bound in ^{4}He. The data used here were accumulated using a 6 GeV longitudinally polarized electron beam incident on a pressurized ^{4}He gaseous target placed within the CLAS spectrometer in Hall-B at the Thomas Jefferson National Accelerator Facility. The azimuthal angle (ϕ) dependence of the BSA was studied in a wide range of virtual photon and scattered proton kinematics. The Q^{2}, x_{B}, and t dependencies of the BSA on the bound proton are compared with those on the free proton. In the whole kinematical region of our measurements, the BSA on the bound proton is smaller by 20% to 40%, indicating possible medium modification of its partonic structure.
在过去二十年中，电子的深度虚拟康普顿散射已成功用于增进我们对自由质子部分子结构的了解，并研究核子内部夸克的横向位置与纵向动量之间的相关性。同时，通过对核靶进行的包容性深度非弹性轻子散射实验，研究了原子核中束缚核子的结构，结果表明束缚核子内部夸克的纵向动量分布存在显著差异，即所谓的EMC效应。在本信函中，我们报告了对束缚在⁴He中的质子进行的排他性深度虚拟康普顿散射的首次束流自旋不对称性（BSA）测量。这里使用的数据是利用6 GeV纵向极化电子束入射到位于托马斯·杰斐逊国家加速器设施B厅CLAS谱仪内的加压⁴He气态靶上积累得到的。在广泛的虚拟光子和散射质子运动学范围内研究了BSA的方位角（ϕ）依赖性。将束缚质子的BSA的Q²、xB和t依赖性与自由质子的进行了比较。在我们测量的整个运动学区域内，束缚质子的BSA小20%至40%，这表明其部分子结构可能受到介质的影响。
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