Open Access

Mohamed Samy Abdallah, Bassam Aboona, Jaroslav Adam, Leszek Adamczyk, Joseph R. Adams, J. Kevin Adkins, Geydar Agakishiev, Ishu Aggarwal, Madan Mohan Aggarwal, Zubayer Ahammed, A. Aitbaev, Igor G. Alekseev, Derek M. Anderson, Alexey Aparin, Elke Caroline Aschenauer, Muhammad Usman Ashraf, F. G. Atetalla, Georgy S. Averichev, Vipul Bairathi, W. Baker, Jonathan Gonzalo Ball Cap, Kenneth Barish, Arabinda Behera, Rene Bellwied, Pratibha Bhagat, Anju Bhasin, Jaroslav Bielčík, Jana Bielčíková, Igor G. Bordyuzhin, James D. Brandenburg, Andrei V. Brandin, Xiang-Zhou Cai, Helen Louise Caines, Manuel Calderón de la Barca Sánchez, Daniel A. Cebra, Irakli Chakaberia, Petr Chaloupka, B. K. Chan, F-H. Chang, Z. Chang, A. Chatterjee, S. Chattopadhyay, D. Chen, J. Chen, J. H. Chen, X. Chen, Z. Chen, J. Cheng, Subikash Choudhury, William Christie, X. Chu, Henry J. Crawford, Máté Csanád, M. Daugherity, T. G. Dedovich, Ingo Martin Deppner, Anatoly A. Derevschikov, A. Dhamija, L. Di Carlo, Lidia Didenko, Prabhupada Dixit, X. Dong, James Lucus Drachenberg, Emilie Duckworth, James C. Dunlop, Jon M. Engelage, Geary Wareham Eppley, ShinIchi Esumi, Olga Y. Evdokimov, A. Ewigleben, Kjeld Oleg Eyser, Renee H. Fatemi, F. M. Fawzi, Salvatore Fazio, C. J. Feng, Yicheng Feng, Evan Finch, Yuri V. Fisyak, Audrey Francisco, C. Fu, Carl A. Gagliardi, Tetyana Galatyuk, Frank Geurts, Navagyan Ghimire, Adam Gibson, Krishan Gopal, X. Gou, David P. Grosnick, Anik Gupta, Włodzimierz Guryn, Ahmed M. Hamed, Y. Han, Szymon Harabasz, Matthew D. Harasty, John W. Harris, Hannah Harrison, S. He, W. He, X. H. He, Y. He, S. Heppelmann, Norbert Herrmann, E. Hoffman, Lukáš Holub, C. Hu, Q. Hu, Y. Hu, H. Huang, Huan Zhong Huang, Shengli Huang, T. Huang, X. Huang, Y. Huang, Thomas J. Humanic, D. Isenhower, M. Isshiki, William W. Jacobs, Chitrasen Jena, Alexander Jentsch, Yuanjing Ji, Jiangyong Jia, K. Jiang, Xin-Yue 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, Daniel P. Kikoła, B. Kimelman, D. Kincses, Ivan Kisel, A. Kiselev, Anders Garritt Knospe, H. S. Ko, L. M. Kočenda, A. Korobitsin, Leszek Krzysztof Kosarzewski, L. Kramarik, Peter Kravtsov, 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, N. Lewis, C. Li, C. Li, W. Li, X. Li, Y. Li, X. Liang, Y. Liang, Robert Licenik, T. Lin, Y. Lin, Michael A. Lisa, F. Liu, H. Liu, H. Liu, P. Liu, T. Liu, X. Liu, Y. Liu, Z. Liu, Tonko A. Ljubicic, William Joseph Llope, Ronald S. Longacre, E. Loyd, T. Lu, N. S. Lukow, X. F. Luo, L. Ma, R. Ma, Yu-Gang Ma, Niseem Magdy Abdelwahab Abdelrahman, Dukhishyam Mallick, S. L. Manukhov, Spyridon Margetis, Christina Markert, Howard S. Matis, Joel Anthony Mazer, Nikolai G. Minaev, Saskia Mioduszewski, Bedangadas Mohanty, Mriganka Mouli Mouli, Isaac A. Mooney, Dmitry A. Morozov, A. Mukherjee, M. Nagy, J. D. Nam, Md. Nasim, Kishora Nayak, D. Neff, John M. Nelson, Daniel B. Nemes, M. Nie, Grigory A. Nigmatkulov, Takafumi Niida, R. Nishitani, Larisa V. Nogach, Toshihiro Nonaka, A. S. Nunes, Grazyna Janina Odyniec, Akio Ogawa, Saehanseul Oh, Vitaly A. Okorokov, K. Okubo, Brian S. Page, Robert Pak, Jinjin Pan, Ashish Pandav, Ashutosh Kumar Pandey, Yuri Panebratsev, P. Parfenov, A. Paul, Bogdan Pawlik, Diana Pawłowska, Chris Perkins, Jan Marian Pluta, B. R. Pokhrel, Jeffrey Brent Porter, Matthew Posik, V. Prozorova, Navneet Kumar Pruthi, Mariusz Przybycien, Jörn H. Putschke, H. Qiu, Amilkar Quintero, Cameron Racz, Sooraj Krishnan Radhakrishnan, N. Raha, Robert L. Ray, Rosi Jan Reed, Hans Georg Ritter, Monika Robotkova, Juan L. Romero, D. Roy, L. Ruan, A. K. Sahoo, Nihar Ranjan Sahoo, H. Sako, Sevil Salur, E. Samigullin, Jack H. Sandweiss, Susumu Sato, William B. Schmidke, Norbert Schmitz, Benjamin R. Schweid, Florian Seck, Janet Elizabeth Seger, Richard Seto, Peter Seyboth, N. Shah, Ehtiram Shahaliev, Prashanth V. Shanmuganathan, M. Shao, T. Shao, R. Sharma, Ashik Ikbal Sheikh, D. Y. Shen, Shusu Shi, Y. Shi, Q. Y. Shou, Ernst P. Sichtermann, Rafał Sikora, J. Singh, Subhash Singha, P. Sinha, Michael J. Skoby, Nikolai Smirnov, Yannick Söhngen, William Solyst, Y. Song, 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, X. M. Sun, Xu Sun, Y. Sun, Y. Sun, Bernd Surrow, Dmitry N. Svirida, Zachary W. Sweger, Paweł Szymański, Aihong Tang, Z. Tang, Arkadiy Taranenko, Terence J. Tarnowsky, James H. Thomas, Anthony Robert Timmins, David Tlusty, Takahito Todoroki, Mikhail V. Tokarev, C. A. Tomkiel, Stephen Trentalange, Robert E. Tribble, Prithwish Tribedy, Srikanta Kumar Tripathy, Tomas Truhlar, Barbara Antonina Trzeciak, Oleg D. Tsai, Zhoudunming Tu, Thomas Ullrich, David G. Underwood, Isaac Upsal, Gene Van Buren, Jan Vanek, Alexander Nikolaevich Vasiliev, Iouri Vassiliev, Veronica Verkest, Flemming Videbæk, Stanislav Vokal, Sergei Voloshin, F. Wang, G. Wang, J. S. Wang, P. Wang, X. Wang, Y. Wang, Y. Wang, Z. Wang, Jason C. Webb, Philipp Weidenkaff, Gary D. Westfall, Howard Wieman, Scott W. Wissink, Richard Witt, J. Wu, J. Wu, Y. Wu, B. Xi, Z. G. Xiao, Guannan Xie, W. Xie, H. Xu, N. Xu, Q. H. Xu, Y. Xu, Z. Xu, Z. Xu, G. Yan, C. Yang, Q. Yang, S. Yang, Y. Yang, Z. Ye, Z. Ye, L. Yi, K. Yip, Y. Yu, Hanna Paulina Zbroszczyk, Wangmei Zha, C. Zhang, D. Zhang, J. Zhang, S. Zhang, S. Zhang, Y. Zhang, Y. Zhang, Y. Zhang, Z. J. Zhang, Z. Zhang, Z. Zhang, F. Zhao, J. Zhao, M. Zhao, C. Zhou, Y. Zhou, X. Zhu, Maria Katarzyna Żurek, Maksym Zyzak

• The strong force, as one of the four fundamental forces at work in the universe, governs interactions of quarks and gluons, and binds together the atomic nucleus. Notwithstanding decades of progress since Yukawa first developed a description of the force between nucleons in terms of meson exchange, a full understanding of the strong interaction remains a major challenge in modern science. One remaining difficulty arises from the non-perturbative nature of the strong force, which leads to the phenomenon of quark confinement at distance scales on the order of the size of the proton. Here we show that in relativistic heavy-ion collisions, where quarks and gluons are set free over an extended volume, two species of produced vector (spin-1) mesons, namely ϕ and K∗0, emerge with a surprising pattern of global spin alignment. In particular, the global spin alignment for ϕ is unexpectedly large, while that for K∗0 is consistent with zero. The observed spin-alignment pattern and magnitude for the ϕ cannot be explained by conventional mechanisms, while a model with strong force fields accommodates the current data. This is the first time that the strong force field is experimentally supported as a key mechanism that leads to global spin alignment. We extract a quantity proportional to the intensity of the field of the strong force. Within the framework of the Standard Model, where the strong force is typically described in the quark and gluon language of Quantum Chromodynamics, the field being considered here is an effective proxy description. This is a qualitatively new class of measurement, which opens a new avenue for studying the behaviour of strong force fields via their imprint on spin alignment.