论文标题

在200和500 GEV横向极化质子 - 质子碰撞时,$π^0 $的横向单旋旋转不对称的测量和电磁射流的测量

Measurement of transverse single-spin asymmetries of $π^0$ and electromagnetic jets at forward rapidity in 200 and 500 GeV transversely polarized proton-proton collisions

论文作者

STAR Collaboration, Adam, J., Adamczyk, L., Adams, J. R., Adkins, J. K., Agakishiev, G., Aggarwal, M. M., Ahammed, Z., Alekseev, I., Anderson, D. M., Aparin, A., Aschenauer, E. C., Ashraf, M. U., Atetalla, F. G., Attri, A., Averichev, G. S., Bairathi, V., Barish, K., Behera, A., Bellwied, R., Bhasin, A., Bielcik, J., Bielcikova, J., Bland, L. C., Bordyuzhin, I. G., Brandenburg, J. D., Brandin, A. V., Butterworth, J., Caines, H., Sánchez, M. Calderón de la Barca, Cebra, D., Chakaberia, I., Chaloupka, P., Chan, B. K., Chang, F-H., Chang, Z., Chankova-Bunzarova, N., Chatterjee, A., Chen, D., Chen, J., Chen, J. H., Chen, X., Chen, Z., Cheng, J., Cherney, M., Chevalier, M., Choudhury, S., Christie, W., Chu, X., Crawford, H. J., Csanád, M., Daugherity, M., Dedovich, T. G., Deppner, I. M., Derevschikov, A. A., Didenko, L., Dilks, C., Dong, X., Drachenberg, J. L., Dunlop, J. C., Edmonds, T., Elsey, N., Engelage, J., Eppley, G., Esumi, S., Evdokimov, O., Ewigleben, A., Eyser, O., Fatemi, R., Fazio, S., Federic, P., Fedorisin, J., Feng, C. J., Feng, Y., Filip, P., Finch, E., Fisyak, Y., Francisco, A., Fulek, L., Gagliardi, C. A., Galatyuk, T., Geurts, F., Ghimire, N., Gibson, A., Gopal, K., Gou, X., Grosnick, D., Guryn, W., Hamad, A. I., Hamed, A., Harabasz, S., Harris, J. W., He, S., He, W., He, X. H., He, Y., Heppelmann, S., Heppelmann, S., Herrmann, N., Hoffman, E., Holub, L., Hong, Y., Horvat, S., Hu, Y., Huang, H. Z., Huang, S. L., Huang, T., Huang, X., Humanic, T. J., Huo, P., Igo, G., Isenhower, D., Jacobs, W. W., Jena, C., Jentsch, A., Ji, Y., Jia, J., Jiang, K., Jowzaee, S., Ju, X., Judd, E. G., Kabana, S., Kabir, M. L., Kagamaster, S., Kalinkin, D., Kang, K., Kapukchyan, D., Kauder, K., Ke, H. W., Keane, D., Kechechyan, A., Kelsey, M., Khyzhniak, Y. V., Kikoła, D. P., Kim, C., Kimelman, B., Kincses, D., Kinghorn, T. A., Kisel, I., Kiselev, A., Kocan, M., Kochenda, L., Kosarzewski, L. K., Kramarik, L., Kravtsov, P., Krueger, K., Mudiyanselage, N. Kulathunga, Kumar, L., Kumar, S., Elayavalli, R. Kunnawalkam, Kwasizur, J. H., Lacey, R., Lan, S., Landgraf, J. M., Lauret, J., Lebedev, A., Lednicky, R., Lee, J. H., Leung, Y. H., Li, C., Li, C., Li, W., Li, W., Li, X., Li, Y., Liang, Y., Licenik, R., Lin, T., Lin, Y., Lisa, M. A., Liu, F., Liu, H., Liu, P., Liu, P., Liu, T., Liu, X., Liu, Y., Liu, Z., Ljubicic, T., Llope, W. J., Longacre, R. S., Lukow, N. S., Luo, S., Luo, X., Ma, G. L., Ma, L., Ma, R., Ma, Y. G., Magdy, N., Majka, R., Mallick, D., Margetis, S., Markert, C., Matis, H. S., Mazer, J. A., Minaev, N. G., Mioduszewski, S., Mohanty, B., Mondal, M. M., Mooney, I., Moravcova, Z., Morozov, D. A., Nagy, M., Nam, J. D., Nasim, Md., Nayak, K., Neff, D., Nelson, J. M., Nemes, D. B., Nie, M., Nigmatkulov, G., Niida, T., Nogach, L. V., Nonaka, T., Nunes, A. S., Odyniec, G., Ogawa, A., Oh, S., Okorokov, V. A., Page, B. S., Pak, R., Pandav, A., Panebratsev, Y., Pawlik, B., Pawlowska, D., Pei, H., Perkins, C., Pinsky, L., Pintér, R. L., Pluta, J., Pokhrel, B. R., Porter, J., Posik, M., Pruthi, N. K., Przybycien, M., Putschke, J., Qiu, H., Quintero, A., Radhakrishnan, S. K., Ramachandran, S., Ray, R. L., Reed, R., Ritter, H. G., Rogachevskiy, O. V., Romero, J. L., Ruan, L., Rusnak, J., Sahoo, N. R., Sako, H., Salur, S., Sandweiss, J., Sato, S., Schmidke, W. B., Schmitz, N., Schweid, B. R., Seck, F., Seger, J., Sergeeva, M., Seto, R., Seyboth, P., Shah, N., Shahaliev, E., Shanmuganathan, P. V., Shao, M., Sheikh, A. I., Shen, W. Q., Shi, S. S., Shi, Y., Shou, Q. Y., Sichtermann, E. P., Sikora, R., Simko, M., Singh, J., Singha, S., Smirnov, N., Solyst, W., Sorensen, P., Spinka, H. M., Srivastava, B., Stanislaus, T. D. S., Stefaniak, M., Stewart, D. J., Strikhanov, M., Stringfellow, B., Suaide, A. A. P., Sumbera, M., Summa, B., Sun, X. M., Sun, X., Sun, Y., Sun, Y., Surrow, B., Svirida, D. N., Szymanski, P., Tang, A. H., Tang, Z., Taranenko, A., Tarnowsky, T., Thomas, J. H., Timmins, A. R., Tlusty, D., Tokarev, M., Tomkiel, C. A., Trentalange, S., Tribble, R. E., Tribedy, P., Tripathy, S. K., Tsai, O. D., Tu, Z., Ullrich, T., Underwood, D. G., Upsal, I., Van Buren, G., Vanek, J., Vasiliev, A. N., Vassiliev, I., Videbæk, F., Vokal, S., Voloshin, S. A., Wang, F., Wang, G., Wang, J. S., Wang, P., Wang, Y., Wang, Y., Wang, Z., Webb, J. C., Weidenkaff, P. C., Wen, L., Westfall, G. D., Wieman, H., Wissink, S. W., Witt, R., Wu, Y., Xiao, Z. G., Xie, G., Xie, W., Xu, H., Xu, N., Xu, Q. H., Xu, Y. F., Xu, Y., Xu, Z., Xu, Z., Yang, C., Yang, Q., Yang, S., Yang, Y., Yang, Z., Ye, Z., Ye, Z., Yi, L., Yip, K., Yu, Y., Zbroszczyk, H., Zha, W., Zhang, C., Zhang, D., Zhang, S., Zhang, S., Zhang, X. P., Zhang, Y., Zhang, Y., Zhang, Z. J., Zhang, Z., Zhang, Z., Zhao, J., Zhong, C., Zhou, C., Zhu, X., Zhu, Z., Zurek, M., Zyzak, M.

论文摘要

Star协作报告了横向单旋不对称(TSSA)的测量值$π^0 $在质量中心能量($ \ sqrt s $)中的200 GEV和500 GEV在pse​​udo-rapities 2.7至4.0的横向偏光质子化的质子proton-proton碰撞中。两个不同能量的结果表明,TSSA与Feynman-$ x $不断增加,与以前的测量相比,没有发现对$ \ sqrt S $从19.4 GEV到500 GEV的依赖。为了研究导致大型TSSA的潜在物理学,已经研究了不同的拓扑结构。 $π^0 $没有附近粒子的tssa往往高于包含$π^0 $。在初始状态下对Sivers敏感的包容性电磁射流的TSSA较小,但表现出与包含$π^0 $不对称的行为相同,作为Feynman-$ x $的函数。为了研究最终状态效应,已经测量了电磁喷气机内$π^0 $的柯林斯不对称性。分析了Collins的不对称性,其依赖于$π^0 $动量横向到射流推力轴及其对$π^0 $携带的射流能量分数的依赖性。在每种情况下,对于两个质量中心的能量,发现不对称性很小。将所有测量值与基于QCD的理论计算进行比较,以横向摩托明依赖性的Parton分布函数和碎片化函数。发现了一些差异,这表明可能涉及新机制。

The STAR Collaboration reports measurements of the transverse single-spin asymmetry (TSSA) of inclusive $π^0$ at center-of-mass energies ($\sqrt s$) of 200 GeV and 500 GeV in transversely polarized proton-proton collisions in the pseudo-rapidity region 2.7 to 4.0. The results at the two different energies show a continuous increase of the TSSA with Feynman-$x$, and, when compared to previous measurements, no dependence on $\sqrt s$ from 19.4 GeV to 500 GeV is found. To investigate the underlying physics leading to this large TSSA, different topologies have been studied. $π^0$ with no nearby particles tend to have a higher TSSA than inclusive $π^0$. The TSSA for inclusive electromagnetic jets, sensitive to the Sivers effect in the initial state, is substantially smaller, but shows the same behavior as the inclusive $π^0$ asymmetry as a function of Feynman-$x$. To investigate final-state effects, the Collins asymmetry of $π^0$ inside electromagnetic jets has been measured. The Collins asymmetry is analyzed for its dependence on the $π^0$ momentum transverse to the jet thrust axis and its dependence on the fraction of jet energy carried by the $π^0$. The asymmetry was found to be small in each case for both center-of-mass energies. All the measurements are compared to QCD-based theoretical calculations for transverse-momentum-dependent parton distribution functions and fragmentation functions. Some discrepancies are found, which indicates new mechanisms might be involved.

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