Open Access

Jaroslav Adam, Leszek Adamczyk, Joseph R. Adams, J. Kevin Adkins, Geydar Agakishiev, Madan Mohan Aggarwal, Zubayer Ahammed, Igor G. Alekseev, Derek M. Anderson, Alexey Aparin, Elke Caroline Aschenauer, Muhammad Usman Ashraf, F. G. Atetalla, Anjali Attri, Georgy S. Averichev, Vipul Bairathi, Kenneth Barish, Arabinda Behera, Rene Bellwied, Anju Bhasin, Jaroslav Bielčík, Jana Bielčíková, Leslie C. Bland, Igor G. Bordyuzhin, James D. Brandenburg, Andrei V. Brandin, Joseph Butterworth, Helen Louise Caines, Manuel Calderón de la Barca Sánchez, Daniel A. Cebra, Irakli Chakaberia, Petr Chaloupka, B. K. Chan, F-H. Chang, Z. Chang, N. Chankova-Bunzarova, A. Chatterjee, D. Chen, J. Chen, J. H. Chen, X. Chen, Z. Chen, J. Cheng, Michael Gerard Cherney, M. Chevalier, Subikash Choudhury, William Christie, X. Chu, Henry J. Crawford, Máté Csanád, M. Daugherity, T. G. Dedovich, Ingo Martin Deppner, Anatoly A. Derevschikov, Lidia Didenko, Christopher Dilks, X. Dong, James Lucus Drachenberg, James C. Dunlop, Terrence Edmonds, Nicholas Elsey, Jon M. Engelage, Geary Wareham Eppley, ShinIchi Esumi, Olga Y. Evdokimov, A. Ewigleben, Kjeld Oleg Eyser, Renee H. Fatemi, Salvatore Fazio, Pavol Federič, Jan Fedorišin, C. J. Feng, Yicheng Feng, Peter Filip, Evan Finch, Yuri V. Fisyak, Audrey Francisco, Łukasz Fulek, Carl A. Gagliardi, Tetyana Galatyuk, Frank Geurts, N. Ghimire, Adam Gibson, Krishan Gopal, X. Gou, David P. Grosnick, Włodzimierz Guryn, A. I. Hamad, Ahmed M. Hamed, Szymon Harabasz, John W. Harris, S. He, W. He, X. H. He, Y. He, S. Heppelmann, S. Heppelmann, Norbert Herrmann, E. Hoffman, Lukáš Holub, Y. Hong, S. Horvat, Y. Hu, Huan Zhong Huang, Shengli Huang, T. Huang, X. Huang, Thomas J. Humanic, P. Huo, George J. Igo, D. Isenhower, William W. Jacobs, Chitrasen Jena, Alexander Jentsch, Yuanjing Ji, J. Jia, K. Jiang, S. Jowzaee, X. Ju, Eleanor G. Judd, Sonia Kabana, M. L. Kabir, Skipper Kagamaster, Dmitry Kalinkin, K. Kang, David Kapukchyan, Kolja Kauder, Hongwei Ke, Declan Keane, Armen Kechechyan, Matthew Kelsey, Y. V. Khyzhniak, Daniel P. Kikoła, C. Kim, B. Kimelman, D. Kincses, Todd Adler Kinghorn, Ivan Kisel, A. Kiselev, Michal Kocan, L. M. Kočenda, Leszek Krzysztof Kosarzewski, L. Kramarik, Peter Kravtsov, Keith William Krueger, Nalinda Kulathunga Mudiyanselage, Lokesh Kumar, Shyam Kumar, R. Kunnawalkam Elayavalli, Joseph H. Kwasizur, Roy Alphanso Lacey, Shaowei Lan, Jeffery M. Landgraf, Jerome Lauret, Alexei Lebedev, Richard Lednicky, J. H. Lee, Y. H. Leung, C. Li, C. Li, W. Li, W. Li, X. Li, Y. Li, Y. Liang, Robert Licenik, T. Lin, Y. Lin, Michael A. Lisa, F. Liu, H. Liu, P. Liu, P. Liu, T. Liu, X. Liu, Y. Liu, Z. Liu, Tonko A. Ljubicic, William Joseph Llope, Ronald S. Longacre, N. S. Lukow, S. Luo, X. Luo, G. L. Ma, L. Ma, R. Ma, Yu-Gang Ma, Niseem Magdy Abdelwahab Abdelrahman, Richard Daniel Majka, Dukhishyam Mallick, Spyridon Margetis, Christina Markert, Howard S. Matis, Joel Anthony Mazer, Nikolai G. Minaev, Saskia Mioduszewski, Bedangadas Mohanty, Mriganka Mouli Mondal, Isaac A. Mooney, Zuzana Moravcova, Dmitry A. Morozov, M. Nagy, J. D. Nam, Md. Nasim, Kishora Nayak, D. Neff, John M. Nelson, Daniel B. Nemes, M. Nie, Grigory A. Nigmatkulov, Takafumi Niida, Larisa V. Nogach, Toshihiro Nonaka, A. S. Nunes, G. Odyniec, Akio Ogawa, Saehanseul Oh, Vitaly A. Okorokov, Brian S. Page, R. Pak, A. Pandav, Yuri Panebratsev, Bogdan Pawlik, Diana Pawłowska, Hua Pei, Chris Perkins, Lawrence Pinsky, Roland Laszlo Pintér, Jan Marian Pluta, B. R. Pokhrel, Jeffrey Brent Porter, Matthew Posik, Navneet Kumar Pruthi, Mariusz Przybycien, Jörn H. Putschke, H. Qiu, Amilkar Quintero, Sooraj Krishnan Radhakrishnan, Suvarna Ramachandran, Robert L. Ray, Rosi Jan Reed, H. G. Ritter, Oleg V. Rogačevskij, Juan L. Romero, L. Ruan, Jan Rusnak, Nihar Ranjan Sahoo, H. Sako, Sevil Salur, Jack H. Sandweiss, S. Sato, William B. Schmidke, Norbert Schmitz, Benjamin R. Schweid, Florian Seck, Janet Elizabeth Seger, Maria Sergeeva, Richard Seto, Peter Seyboth, N. Shah, Ehtiram Shahaliev, Prashanth V. Shanmuganathan, M. Shao, Ashik Ikbal Sheikh, W. Q. Shen, S. S. Shi, Y. Shi, Q. Y. Shou, Ernst P. Sichtermann, Rafał Sikora, Miroslav Šimko, J. Singh, Subhash Singha, Nikolai Smirnov, William Solyst, Paul Richard Sorensen, Harold. M. Spinka, B. Srivastava, T. D. Shirvel Stanislaus, Maria Stefaniak, David J. Stewart, Michail Nikolaevič Strichanov, Blair Stringfellow, Alexandre Alarcon do Passo Suaide, Michal Šumbera, Branden Summa, X. M. Sun, X. Sun, Y. Sun, Y. Sun, Bernd Surrow, Dmitry N. Svirida, Paweł Szymański, Aihong Tang, Z. Tang, Arkadiy Taranenko, Terence J. Tarnowsky, James H. Thomas, Anthony Robert Timmins, David Tlusty, Mikhail V. Tokarev, C. A. Tomkiel, Stephen Trentalange, Robert E. Tribble, Prithwish Tribedy, Srikanta Kumar Tripathy, Oleg D. Tsai, Zhoudunming Tu, Thomas Ullrich, David G. Underwood, Isaac Upsal, Gene Van Buren, Jan Vanek, Alexander Nikolaevich Vasiliev, Iouri Vassiliev, Flemming Videbæk, Stanislav Vokal, Sergei Voloshin, F. Wang, G. Wang, J. S. Wang, P. Wang, Y. Wang, Y. Wang, Z. Wang, Jason C. Webb, Philipp Weidenkaff, L. Wen, Gary D. Westfall, Howard Wieman, Scott W. Wissink, Richard Witt, Y. Wu, Z. G. Xiao, Guannan Xie, W. Xie, H. Xu, N. Xu, Q. H. Xu, Y. F. Xu, Y. Xu, Z. Xu, Z. Xu, C. Yang, Q. Yang, S. Yang, Y. Yang, Z. Yang, Z. Ye, Z. Ye, L. Yi, K. Yip, Y. Yu, Hanna Paulina Zbroszczyk, W. Zha, C. Zhang, D. Zhang, S. Zhang, S. Zhang, X. P. Zhang, Y. Zhang, Y. Zhang, Z. J. Zhang, Z. Zhang, Z. Zhang, J. Zhao, C. Zhong, C. Zhou, X. Zhu, Z. Zhu, Maria Katarzyna Żurek, Maksym Zyzak

• The STAR Collaboration reports measurements of the transverse single-spin asymmetry (TSSA) of inclusive 𝜋0 at center-of-mass energies (√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 √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. 𝜋0 with no nearby particles tend to have a higher TSSA than inclusive 𝜋0. 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 𝜋0 asymmetry as a function of Feynman-𝑥. To investigate final-state effects, the Collins asymmetry of 𝜋0 inside electromagnetic jets has been measured. The Collins asymmetry is analyzed for its dependence on the 𝜋0 momentum transverse to the jet thrust axis and its dependence on the fraction of jet energy carried by the 𝜋0. 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.