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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

J. Adam⁶, L. Adamczyk², J. R. Adams³³, J. K. Adkins⁵⁵, G. Agakishiev²², M. M. Aggarwal³⁴, Z. Ahammed⁶², I. Alekseev^3,28, D. M. Anderson⁴⁵ et al. (STAR Collaboration)

D. M. Anderson⁴⁵, A. Aparin²², E. C. Aschenauer⁶, M. U. Ashraf⁷, F. G. Atetalla²³, A. Attri³⁴, G. S. Averichev²², V. Bairathi²¹, K. Barish⁵⁰, A. Behera⁴², R. Bellwied⁵³, A. Bhasin⁵⁴, J. Bielcik⁹, J. Bielcikova³¹, L. C. Bland⁶, I. G. Bordyuzhin³, J. D. Brandenburg⁶, A. V. Brandin²⁸, J. Butterworth³⁷, H. Caines⁶⁵, M. Calderón de la Barca Sánchez⁴⁸, D. Cebra⁴⁸, I. Chakaberia^23,6, P. Chaloupka⁹, B. K. Chan⁴⁹, F-H. Chang³⁰, Z. Chang⁶, N. Chankova-Bunzarova²², A. Chatterjee⁷, D. Chen⁵⁰, J. Chen³⁹, J. H. Chen¹², X. Chen⁵⁷, Z. Chen³⁹, J. Cheng⁴⁶, M. Cherney⁸, M. Chevalier⁵⁰, S. Choudhury¹², W. Christie⁶, X. Chu⁶, H. J. Crawford⁴⁷, M. Csanád¹⁰, M. Daugherity¹, T. G. Dedovich²², I. M. Deppner⁵², A. A. Derevschikov³², L. Didenko⁶, C. Dilks³⁵, X. Dong²⁴, J. L. Drachenberg¹, J. C. Dunlop⁶, T. Edmonds³⁶, N. Elsey⁶⁴, J. Engelage⁴⁷, G. Eppley³⁷, S. Esumi⁵⁹, O. Evdokimov⁵¹, A. Ewigleben²⁵, O. Eyser⁶, R. Fatemi⁵⁵, S. Fazio⁶, P. Federic³¹, J. Fedorisin²², C. J. Feng³⁰, Y. Feng³⁶, P. Filip²², E. Finch⁴¹, Y. Fisyak⁶, A. Francisco⁶⁵, L. Fulek², C. A. Gagliardi⁴⁵, T. Galatyuk⁴³, F. Geurts³⁷, N. Ghimire⁴⁴, A. Gibson⁶¹, K. Gopal¹⁵, X. Gou³⁹, D. Grosnick⁶¹, W. Guryn⁶, A. I. Hamad²³, A. Hamed⁵, S. Harabasz⁴³, J. W. Harris⁶⁵, S. He⁷, W. He¹², X. H. He¹⁸, Y. He³⁹, S. Heppelmann⁴⁸, S. Heppelmann³⁵, N. Herrmann⁵², E. Hoffman⁵³, L. Holub⁹, Y. Hong²⁴, S. Horvat⁶⁵, Y. Hu¹², H. Z. Huang⁴⁹, S. L. Huang⁴², T. Huang³⁰, X. Huang⁴⁶, T. J. Humanic³³, P. Huo⁴², G. Igo^49,†, D. Isenhower¹, W. W. Jacobs¹⁷, C. Jena¹⁵, A. Jentsch⁶, Y. Ji⁵⁷, J. Jia^6,42, K. Jiang⁵⁷, S. Jowzaee⁶⁴, X. Ju⁵⁷, E. G. Judd⁴⁷, S. Kabana²¹, M. L. Kabir⁵⁰, S. Kagamaster²⁵, D. Kalinkin¹⁷, K. Kang⁴⁶, D. Kapukchyan⁵⁰, K. Kauder⁶, H. W. Ke⁶, D. Keane²³, A. Kechechyan²², M. Kelsey²⁴, Y. V. Khyzhniak²⁸, D. P. Kikoła⁶³, C. Kim⁵⁰, B. Kimelman⁴⁸, D. Kincses¹⁰, T. A. Kinghorn⁴⁸, I. Kisel¹¹, A. Kiselev⁶, M. Kocan⁹, L. Kochenda²⁸, L. K. Kosarzewski⁹, L. Kramarik⁹, P. Kravtsov²⁸, K. Krueger⁴, N. Kulathunga Mudiyanselage⁵³, L. Kumar³⁴, S. Kumar¹⁸, R. Kunnawalkam Elayavalli⁶⁴, J. H. Kwasizur¹⁷, R. Lacey⁴², S. Lan⁷, J. M. Landgraf⁶, J. Lauret⁶, A. Lebedev⁶, R. Lednicky²², J. H. Lee⁶, Y. H. Leung²⁴, C. Li³⁹, C. Li⁵⁷, W. Li³⁷, W. Li⁴⁰, X. Li⁵⁷, Y. Li⁴⁶, Y. Liang²³, R. Licenik³¹, T. Lin⁴⁵, Y. Lin⁷, M. A. Lisa³³, F. Liu⁷, H. Liu¹⁷, P. Liu⁴², P. Liu⁴⁰, T. Liu⁶⁵, X. Liu³³, Y. Liu⁴⁵, Z. Liu⁵⁷, T. Ljubicic⁶, W. J. Llope⁶⁴, R. S. Longacre⁶, N. S. Lukow⁴⁴, S. Luo⁵¹, X. Luo⁷, G. L. Ma⁴⁰, L. Ma¹², R. Ma⁶, Y. G. Ma⁴⁰, N. Magdy⁵¹, R. Majka^65,†, D. Mallick²⁹, S. Margetis²³, C. Markert⁵⁸, H. S. Matis²⁴, J. A. Mazer³⁸, N. G. Minaev³², S. Mioduszewski⁴⁵, B. Mohanty²⁹, M. M. Mondal¹⁹, I. Mooney⁶⁴, Z. Moravcova⁹, D. A. Morozov³², M. Nagy¹⁰, J. D. Nam⁴⁴, Md. Nasim¹⁴, K. Nayak⁷, D. Neff⁴⁹, J. M. Nelson⁴⁷, D. B. Nemes⁶⁵, M. Nie³⁹, G. Nigmatkulov²⁸, T. Niida⁵⁹, L. V. Nogach³², T. Nonaka⁵⁹, A. S. Nunes⁶, G. Odyniec²⁴, A. Ogawa⁶, S. Oh²⁴, V. A. Okorokov²⁸, B. S. Page⁶, R. Pak⁶, A. Pandav²⁹, Y. Panebratsev²², B. Pawlik²⁰, D. Pawlowska⁶³, H. Pei⁷, C. Perkins⁴⁷, L. Pinsky⁵³, R. L. Pintér¹⁰, J. Pluta⁶³, B. R. Pokhrel⁴⁴, J. Porter²⁴, M. Posik⁴⁴, N. K. Pruthi³⁴, M. Przybycien², J. Putschke⁶⁴, H. Qiu¹⁸, A. Quintero⁴⁴, S. K. Radhakrishnan²³, S. Ramachandran⁵⁵, R. L. Ray⁵⁸, R. Reed²⁵, H. G. Ritter²⁴, O. V. Rogachevskiy²², J. L. Romero⁴⁸, L. Ruan⁶, J. Rusnak³¹, N. R. Sahoo³⁹, H. Sako⁵⁹, S. Salur³⁸, J. Sandweiss^65,†, S. Sato⁵⁹, W. B. Schmidke⁶, N. Schmitz²⁶, B. R. Schweid⁴², F. Seck⁴³, J. Seger⁸, M. Sergeeva⁴⁹, R. Seto⁵⁰, P. Seyboth²⁶, N. Shah¹⁶, E. Shahaliev²², P. V. Shanmuganathan⁶, M. Shao⁵⁷, A. I. Sheikh²³, W. Q. Shen⁴⁰, S. S. Shi⁷, Y. Shi³⁹, Q. Y. Shou⁴⁰, E. P. Sichtermann²⁴, R. Sikora², M. Simko³¹, J. Singh³⁴, S. Singha¹⁸, N. Smirnov⁶⁵, W. Solyst¹⁷, P. Sorensen⁶, H. M. Spinka^4,†, B. Srivastava³⁶, T. D. S. Stanislaus⁶¹, M. Stefaniak⁶³, D. J. Stewart⁶⁵, M. Strikhanov²⁸, B. Stringfellow³⁶, A. A. P. Suaide⁵⁶, M. Sumbera³¹, B. Summa³⁵, X. M. Sun⁷, X. Sun⁵¹, Y. Sun⁵⁷, Y. Sun¹³, B. Surrow⁴⁴, D. N. Svirida³, P. Szymanski⁶³, A. H. Tang⁶, Z. Tang⁵⁷, A. Taranenko²⁸, T. Tarnowsky²⁷, J. H. Thomas²⁴, A. R. Timmins⁵³, D. Tlusty⁸, M. Tokarev²², C. A. Tomkiel²⁵, S. Trentalange⁴⁹, R. E. Tribble⁴⁵, P. Tribedy⁶, S. K. Tripathy¹⁰, O. D. Tsai⁴⁹, Z. Tu⁶, T. Ullrich⁶, D. G. Underwood⁴, I. Upsal^39,6, G. Van Buren⁶, J. Vanek³¹, A. N. Vasiliev³², I. Vassiliev¹¹, F. Videbæk⁶, S. Vokal²², S. A. Voloshin⁶⁴, F. Wang³⁶, G. Wang⁴⁹, J. S. Wang¹³, P. Wang⁵⁷, Y. Wang⁷, Y. Wang⁴⁶, Z. Wang³⁹, J. C. Webb⁶, P. C. Weidenkaff⁵², L. Wen⁴⁹, G. D. Westfall²⁷, H. Wieman²⁴, S. W. Wissink¹⁷, R. Witt⁶⁰, Y. Wu⁵⁰, Z. G. Xiao⁴⁶, G. Xie²⁴, W. Xie³⁶, H. Xu¹³, N. Xu²⁴, Q. H. Xu³⁹, Y. F. Xu⁴⁰, Y. Xu³⁹, Z. Xu⁶, Z. Xu⁴⁹, C. Yang³⁹, Q. Yang³⁹, S. Yang⁶, Y. Yang³⁰, Z. Yang⁷, Z. Ye³⁷, Z. Ye⁵¹, L. Yi³⁹, K. Yip⁶, Y. Yu³⁹, H. Zbroszczyk⁶³, W. Zha⁵⁷, C. Zhang⁴², D. Zhang⁷, S. Zhang⁵⁷, S. Zhang⁴⁰, X. P. Zhang⁴⁶, Y. Zhang⁵⁷, Y. Zhang⁷, Z. J. Zhang³⁰, Z. Zhang⁶, Z. Zhang⁵¹, J. Zhao³⁶, C. Zhong⁴⁰, C. Zhou⁴⁰, X. Zhu⁴⁶, Z. Zhu³⁹, M. Zurek²⁴, and M. Zyzak¹¹ (STAR Collaboration)

¹Abilene Christian University, Abilene, Texas 79699
²AGH University of Science and Technology, FPACS, Cracow 30-059, Poland
³Alikhanov Institute for Theoretical and Experimental Physics NRC “Kurchatov Institute”, Moscow 117218, Russia
⁴Argonne National Laboratory, Argonne, Illinois 60439
⁵American University of Cairo, New Cairo 11835, New Cairo, Egypt
⁶Brookhaven National Laboratory, Upton, New York 11973
⁷Central China Normal University, Wuhan, Hubei 430079
⁸Creighton University, Omaha, Nebraska 68178
⁹Czech Technical University in Prague, FNSPE, Prague 115 19, Czech Republic
¹⁰ELTE Eötvös Loránd University, Budapest H-1117, Hungary
¹¹Frankfurt Institute for Advanced Studies FIAS, Frankfurt 60438, Germany
¹²Fudan University, Shanghai 200433
¹³Huzhou University, Huzhou, Zhejiang 313000
¹⁴Indian Institute of Science Education and Research (IISER), Berhampur 760010, India
¹⁵Indian Institute of Science Education and Research (IISER) Tirupati, Tirupati 517507, India
¹⁶Indian Institute Technology, Patna, Bihar 801106, India
¹⁷Indiana University, Bloomington, Indiana 47408
¹⁸Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou, Gansu 730000
¹⁹Institute of Physics, Bhubaneswar 751005, India
²⁰Institute of Nuclear Physics PAN, Cracow 31-342, Poland
²¹Instituto de Alta Investigación, Universidad de Tarapacá, Arica 1000000, Chile
²²Joint Institute for Nuclear Research, Dubna 141 980, Russia
²³Kent State University, Kent, Ohio 44242
²⁴Lawrence Berkeley National Laboratory, Berkeley, California 94720
²⁵Lehigh University, Bethlehem, Pennsylvania 18015
²⁶Max-Planck-Institut für Physik, Munich 80805, Germany
²⁷Michigan State University, East Lansing, Michigan 48824
²⁸National Research Nuclear University MEPhI, Moscow 115409, Russia
²⁹National Institute of Science Education and Research, HBNI, Jatni 752050, India
³⁰National Cheng Kung University, Tainan 70101
³¹Nuclear Physics Institute of the CAS, Rez 250 68, Czech Republic
³²NRC “Kurchatov Institute”, Institute of High Energy Physics, Protvino 142281, Russia
³³Ohio State University, Columbus, Ohio 43210
³⁴Panjab University, Chandigarh 160014, India
³⁵Pennsylvania State University, University Park, Pennsylvania 16802
³⁶Purdue University, West Lafayette, Indiana 47907
³⁷Rice University, Houston, Texas 77251
³⁸Rutgers University, Piscataway, New Jersey 08854
³⁹Shandong University, Qingdao, Shandong 266237
⁴⁰Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai 201800
⁴¹Southern Connecticut State University, New Haven, Connecticut 06515
⁴²State University of New York, Stony Brook, New York 11794
⁴³Technische Universität Darmstadt, Darmstadt 64289, Germany
⁴⁴Temple University, Philadelphia, Pennsylvania 19122
⁴⁵Texas A&M University, College Station, Texas 77843
⁴⁶Tsinghua University, Beijing 100084
⁴⁷University of California, Berkeley, California 94720
⁴⁸University of California, Davis, California 95616
⁴⁹University of California, Los Angeles, California 90095
⁵⁰University of California, Riverside, California 92521
⁵¹University of Illinois at Chicago, Chicago, Illinois 60607
⁵²University of Heidelberg, Heidelberg 69120, Germany
⁵³University of Houston, Houston, Texas 77204
⁵⁴University of Jammu, Jammu 180001, India
⁵⁵University of Kentucky, Lexington, Kentucky 40506-0055
⁵⁶Universidade de São Paulo, São Paulo 05314-970, Brazil
⁵⁷University of Science and Technology of China, Hefei, Anhui 230026
⁵⁸University of Texas, Austin, Texas 78712
⁵⁹University of Tsukuba, Tsukuba, Ibaraki 305-8571, Japan
⁶⁰United States Naval Academy, Annapolis, Maryland 21402
⁶¹Valparaiso University, Valparaiso, Indiana 46383
⁶²Variable Energy Cyclotron Centre, Kolkata 700064, India
⁶³Warsaw University of Technology, Warsaw 00-661, Poland
⁶⁴Wayne State University, Detroit, Michigan 48201
⁶⁵Yale University, New Haven, Connecticut 06520

^†Deceased.

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Phys. Rev. D 103, 092009 – Published 27 May, 2021

DOI: https://doi.org/10.1103/PhysRevD.103.092009

Abstract

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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Phys. Rev. D 103, 092009– Published 27 May, 2021

Vol. 103, Iss. 9 — 1 May 2021

Received 21 December 2020
Accepted 29 March 2021

DOI: https://doi.org/10.1103/PhysRevD.103.092009

Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI. Funded by SCOAP³.

Published by the American Physical Society

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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

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Measurement of transverse single-spin asymmetries of π0 and electromagnetic jets at forward rapidity in 200 and 500 GeV transversely polarized proton-proton collisions

Abstract

Physics Subject Headings (PhySH)

Article Text

References (52)

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