Longitudinal double-spin asymmetries for π0s in the forward direction for 510 GeV polarized pp collisions

J Adam,A Lebedev,S Yang,R Lacey,N Xu,D Tlusty,J Sandweiss,N Yu,M Lomnitz,G Nigmatkulov,D Smirnov,K Kauder,P Federic,D Arkhipkin,A Gibson,B Pawlik,P Filip,L Ruan,N Chankova-Bunzarova,S Luo,L Didenko,J Pluta,D Grosnick,M Cherney,P Federicova,Y Panebratsev,R Witt,G Eppley,A Hamed,S Fazio,K Jiang,P Seyboth,O Rusnakova,L Krauth,Y Zhang,R Pak,W Solyst,T Niida,S Mioduszewski,I Vassiliev,E Finch,S Margetis,G Wang,J Porter,Y Guo,S Kabana,R Seto,D Kalinkin,M Posik,A Ogawa,G Odyniec,A Lipiec,Y Li,T Galatyuk,K Yip,N Herrmann,S Trentalange,A Attri,W Zha,S Siejka,C Dilks,T Todoroki,A Harlenderova,P Sorensen,I Bunzarov,H Caines,G Agakishiev,S Esumi,M Shao,J Engelage,F Videbæk,M Sergeeva,A Aparin,E Shahaliev,M Strikhanov,C Perkins,B Stringfellow,D Mallick,N Kulathunga,J Bryslawskyj,P Chaloupka,J Lauret,X Dong,W Christie,D Kapukchyan,R Ma,A Quintero,Z Chang,T Ullrich,Y Fisyak,M Tokarev,G Igo,N Schmitz,L Kochenda,K Krueger,J Cheng,S Ramachandran,D Keane,J Schambach,F Liu,R Aoyama,W Guryn,S Horvat,S Heppelmann,N Elsey,K Meehan,R Fatemi,A Kechechyan,A Vossen,D Cebra,B Tu,F Seck,T Tarnowsky,O Eyser,G Van Buren,B Huang,A Taranenko,X Huang,S B Nurushev ,I M Deppner ,L Kumar,L K Kosarzewski ,X Chen,H W Ke ,S Singha,M M Mondal ,P K Sahu ,V Bairathi,B Srivastava,A K Bhati ,S Zhang,Z Tang,A Jentsch,A Gupta,L Kramárik ,T Ljubičić ,P Szymański ,M Nie,J Putschke,M Simko,G L ,Z H Zhu ,Z Xu,J H Lee ,G Contin,J L Drachenberg ,J M Landgraf ,S Huang ,C Markert,Yi Yang ,B Mohanty,P V Shanmuganathan ,Y Wu,S B Oh ,Q Shou ,I Kisel,T J Humanic ,L Wen,C Kim,Q H Xu ,B Surrow,M Przybycień ,E P Sichtermann ,A J Bassill ,Xie Wang ,C A Tomkiel ,J Bielčík ,W Q Shen ,J D Brandenburg ,M Calderón De La Barca Sánchez,D B Nemes ,J Seger,O Matonoha,C Yang,Long Zhou ,I Alekseev,J D Negrete ,R E Tribble ,J K Adkins ,X Li,M U Ashraf ,C A Gagliardi ,I G Bordyuzhin ,David J Stewart ,C Zhou,J Mazer ,P Huo,J C Webb ,P Tribedy,C Flores ,N Sahoo ,T A Kinghorn ,Zhong Chen ,K N Barish ,A Kisiel,J W Harris ,K Oh,M Šumbera ,F Shen,S S Shi ,A N Vasiliev ,R Sikora,J Fedorišin ,J R Adams ,Д А Морозов ,Xiao Zhang ,A Schmah ,M Zyzak,A V Brandin ,L Zhang,A I Hamad ,G S Averichev ,L C Bland ,A F Kraishan ,T H Lin ,J Kvapil,N G Minaev ,B Summa,Z Ye,A Chatterjee,G D Westfall ,X Luo,W Li,J H Chen ,Md Nasim,H Pei,J Zhao,N Magdy,J L Romero ,Y Liu,David G Mayes ,L Holub,I K Yoo ,H S Matis ,A Hirsch,D G Underwood ,O V Rogachevskiy ,Xiaozhi Bai ,R Bellwied,M M Aggarwal ,П Кравцов ,O Evdokimov,A Bhasin,S W Wissink ,K Kang,R Lednický ,C Li,M A Lisa ,J Roberts ,R L Ray ,J C Mei ,L V Nogach ,B R Schweid ,Vitaly Okorokov ,I Mooney,J Lidrych,S A Voloshin ,H Liu,O D Tsai ,A R Timmins ,S Das,D P Kikoła ,E G Judd ,D S Brown ,J Ewigleben,F Wang,N K Pruthi ,Y G ,W J Llope ,N Shah,Q Yang,A H Tang ,T D S Stanislaus ,A A Derevschikov ,J M Nelson ,L G Efimov ,R S Longacre ,S K Radhakrishnan ,D Mishra,N N Ajitanand ,J M Butterworth ,W W Jacobs ,J Rusňák ,X P Zhang ,Y J Sun ,I Upsal,T Huang,J M Campbell ,S K Tripathy ,S Jowzaee,I Chakaberia,L Ma,N Smirnov,J C Dunlop ,Y Liang,B S Page ,S Chattopadhyay,F G Atetalla ,L Yi,Z Ahammed,H Zbroszczyk,S Vokál ,Santosh Kumar ,Jun Xu ,T G Dedovich ,D M Anderson ,D S Gunarathne ,H G Ritter ,Y Xu ,R Esha,H M Spinka ,P Liu,T Sugiura,H Wieman,R Reed,A Behera,H J Crawford ,X M Sun ,R Majka,Z Zhang,D N Svirida ,J Zhang,F-H Chang,D Olvitt,Y Wang,J Bielčíková ,S Salur,E C Aschenauer ,T Nonaka,Ł Fulek ,G Xie,L He,J Vaněk ,L Adamczyk,Alexandre Alarcon Do Passo Suaide ,J Jia,J H Kwasizur ,F J M Geurts ,H Z Huang ,W B Schmidke ,X Zhu,J H Thomas

doi:10.1103/physrevd.98.032013

Abstract

The STAR Collaboration reports measurements of the longitudinal double-spin asymmetry, $A_{LL}$, for neutral pions produced at forward directions in polarized proton-proton collisions, at a center-of-mass energy of $510$ GeV. Results are given for transverse momenta in the range $2<p_{T}<10$ GeV/$c$ within two regions of pseudorapidity that span $2.65<\eta<3.9$. These results are sensitive to the polarized gluon parton distribution function, $\Delta g(x)$, down to the region of Bjorken $x \sim 10^{-3}$. The asymmetries observed are less than $\pm 5 \cdot 10^{-3}$ in magnitude, and will help constrain the contribution to the spin of the proton from polarized gluons at low $x$, when combined with other measurements as part of a global analysis.

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