Comparison of transverse single-spin asymmetries for forward π⁰ production in polarized pp, pAl and pAu collisions at nucleon pair c.m. energy √sNN=200 GeV

Journal Article · Fri Apr 16 00:00:00 EDT 2021 · Physical Review D

DOI:https://doi.org/10.1103/physrevd.103.072005· OSTI ID:1737436

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.; Calderón de la Barca Sánchez, M.; 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.; 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.; Koetke, D.  D.; Kosarzewski, L.  K.; Kramarik, L.; Kravtsov, P.; Krueger, K.; Kulathunga Mudiyanselage, N.; Kumar, L.; Kumar, S.; Kunnawalkam Elayavalli, R.; 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.; 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.

The STAR collaboration reports a measurement of the transverse single-spin asymmetries, $A_N$, for neutral pions produced in polarized proton collisions with protons ( $pp$), with aluminum nuclei ( $p\mathrm{Al}$) and with gold nuclei ( $p\mathrm{Au}$) at a nucleon-nucleon center-of-mass energy of 200 GeV. Neutral pions are observed in the forward direction relative to the transversely polarized proton beam, in the pseudorapidity region $2.7<\eta <3.8$. Results are presented for ${\pi }^0\mathrm{s}$ observed in the STAR forward meson spectrometer electromagnetic calorimeter in narrow Feynman x ( $x_F$) and transverse momentum ( $p_T$) bins, spanning the range $0.17<x_F<0.81$ and $1.7<p_T<6.0\mathrm{GeV}/c$. For fixed $x_F<0.47$, the asymmetries are found to rise with increasing transverse momentum. For larger $x_F$, the asymmetry flattens or falls as $p_T$ increases. Parametrizing the ratio $r\left(A\right)\equiv A_N\left(pA\right)/A_N\left(pp\right)=A^P$ over the kinematic range, the ratio $r\left(A\right)$ is found to depend only weakly on $A$, with $\left(P\right)=-0.027\pm 0.005$. No significant difference in $P$ is observed between the low- $p_T$ region, $p_T<2.5\mathrm{GeV}/c$, where gluon saturation effects may play a role, and the high- $p_T$ region, $p_T>2.5\mathrm{GeV}/c$. It is further observed that the value of $A_N$ is significantly larger for events with a large- $p_T$ isolated ${\pi }^0$ than for events with a nonisolated ${\pi }^0$ accompanied by additional jetlike fragments. The nuclear dependence $r\left(A\right)$ is similar for isolated and nonisolated ${\pi }^0$ events.

• Research Organization: Brookhaven National Lab. (BNL), Upton, NY (United States); Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
• Sponsoring Organization: USDOE Office of Science (SC), Nuclear Physics (NP)
• Contributing Organization: STAR Collaboration
• Grant/Contract Number: SC0012704; AC02-05CH11231
• OSTI ID: 1737436
• Alternate ID(s): OSTI ID: 1807496
• Report Number(s): BNL-220720-2020-JAAM; TRN: US2205316
• Journal Information: Physical Review D, Vol. 103, Issue 7; ISSN 2470-0010
• Publisher: American Physical Society (APS)
• Country of Publication: United States
• Language: English

Related Subjects

73 NUCLEAR PHYSICS AND RADIATION PHYSICS
Nucleon-nucleon interactions
particle interactions
particle production
polarization phenomena