Neutral pion cross section and spin asymmetries at intermediate pseudorapidity in polarized proton collisions ats=200  GeV

L Adamczyk ,C Perkins,P Chaloupka,L Eun,Y Li,R Varma,F Videbæk,W Guryn,Y Fisyak,I Sakrejda,P Djawotho,P Sorensen,I Bunzarov,W Peryt,A Szanto De Toledo,A Bridgeman,C Dilks,I Koralt,D Arkhipkin,P Bhattarai,W Zha,S Margetis,E Sangaline,P Seyboth,S Fazio,M Pachr,S Mioduszewski,E Finch,G Igo,P Filip,K Kauder,D Smirnov,A Kechechyan,N Schmitz,G Eppley,J Konzer,W Christie,D Cebra,P Yepes,P Huck,W Borowski,H Masui,D Kalinkin,A Hamed,J Takahashi,A Sandacz,I Kulakov,G Wang,O Hajkova,A Kesich,T Ullrich,R Fatemi,R Cendejas,J Balewski,B Stringfellow,B Pawlik,A Aparin,H Caines,J Deng,A Davila Leyva,J Pluta,Y Guo,R Corliss,A Chikanian,E Shahaliev,R Manweiler,L Kotchenda,N Xu,A Dion,J Porter,A Banerjee,T Pawlak,J Cheng,P Pile,T Tarnowsky,R Haque,Y Zoulkarneeva,M Cherney,B Huang,S Horvat,S Ramachandran,J Sandweiss,Y Zhang,A Ogawa,G Odyniec,S Bültmann,S Trentalange,R Witt,J Schambach,K Xin,G Webb,D Solanki,R Derradi De Souza,G Van Buren,M Shao,J Engelage,D Grosnick,S Heppelmann,J Alford,A Gibson,G Van Nieuwenhuizen,R Stock,A Vossen,D Garand,K Yip,F Ding,B Haag,J Turnau,L Didenko,J Lauret,Y Pandit,K Krueger,A Lebedev,X Dong,Z Chang,Y Panebratsev,S Kabana,M Tokarev,D Keane,S Dhamija,L Ruan,J Bouchet,B Di Ruzza,M Strikhanov,D Tlusty,H Bichsel,M Naglis,G Agakishiev,Y Zawisza,F Liu,E G Judd ,P V Shanmuganathan ,S Y Noh ,J L Romero ,C A Gagliardi ,Y P Viyogi ,R S Longacre ,A A Derevschikov ,B S Page ,J K Adkins ,H G Ritter ,J C Dunlop ,I G Bordyuzhin ,R L Ray ,L C De Silva ,W W Jacobs ,G S Averichev ,W B Schmidke ,P M Nord ,L G Efimov ,T J M Symons ,T K Nayak ,Z P Zhang ,G D Westfall ,T J Humanic ,J E Draper ,A K Bhati ,A M Poskanzer ,R E Tribble ,D P Mahapatra ,S K Pal ,L C Bland ,R G Fersch ,S B Nurushev ,C K Riley ,M J Levine ,O V Rogachevskiy ,J M Nelson ,K S Engle ,E C Aschenauer ,D G Underwood ,W J Llope ,N G Minaev ,T P Burton ,J W Harris ,N K Pruthi ,A H Tang ,J L Drachenberg ,D D Koetke ,T S Mcshane ,L M Lima ,T G Dedovich ,M J Skoby ,E W Oldag ,H W Ke ,M J M Codrington ,M A Lisa ,H J Crawford ,I K Yoo ,R P Scharenberg ,J G Cramer ,U G Desouza ,L V Nogach ,G M.s Vasconcelos ,O D Tsai ,D N Svirida ,J A Vanfossen ,D R Gangadharan ,A V Brandin ,C M Du ,L E Dunkelberger ,E P Sichtermann ,H M Spinka ,L Han ,S W Wissink ,H Z Huang ,S S Shi ,M M Mondal ,K D Landry ,J M Landgraf ,J Bielčík ,N Smirnov ,X Luo ,Zhong Chen ,R Raniwala ,A Roy ,C Pruneau ,S Salur ,A Vasiliev ,I Alekseev ,Z M Li ,B A Trzeciak ,J Butterworth ,Y J Sun ,Y Wang ,J Bielčíková ,T Ljubičić ,P K Sahu ,S Das ,J Fedorišin ,M Calderón De La Barca Sánchez ,X M Sun ,C Flores ,A Hirsch ,K Kang ,M M Aggarwal ,Z Ahammed ,M Przybycień ,P R Pujahari ,W Korsch ,J H Chen ,Y Xu ,C Li ,R Bellwied ,J P Hays-Wehle ,J H Thomas ,F Wang ,H Qiu ,П Кравцов ,X P Zhang ,William J Pochron ,C Markert ,Y X Pan ,S Chattopadhyay ,W A Leight ,M K Mustafa ,H F Chen ,Д А Морозов ,A Sarkar ,D Mcdonald ,X Zhu ,M A.c Lamont ,W Xie ,Q Shou ,H Xu ,B K Nandi ,M G Munhoz ,A Gupta ,Md Nasim ,B Srivastava ,G L ,J Rusňák ,S Gupta ,N Sahoo ,R Debbe ,B Mohanty ,B Sharma ,Z Sun ,S Zhang ,Q Wang ,J R Stevens ,L Yi ,W Li ,N Shah ,W He ,J C Webb ,J F Ross ,I Selyuzhenkov ,Z Barnovska ,Benjamin Barber ,D M M D Madagodagettige Don ,M Planinić ,R A Negrao De Oliveira ,Z Xu ,T Kollegger ,L Kumar ,X L Wang ,S Raniwala ,J Seger ,W Xu ,O Evdokimov ,J Roberts ,Xiao Zhang ,A Schmah ,J Novák ,W Q Shen ,M Betancourt ,H Zbroszczyk ,J B Zhang ,G W Hoffmann ,N Poljak ,Martin Girard ,Y F Wu ,H Pei ,K Oh ,A R Timmins ,C Anson ,S A Voloshin ,B Surrow ,J J Chwastowski ,Y G ,Q H Xu ,P Tribedy ,Yan Wang ,H Wieman ,A Bhasin ,I Kisel ,Z Tang ,Y Yang ,R Majka ,Z Ye ,J Putschke ,L Chen ,M Wada ,D Plyku ,F J M Geurts ,M Walker ,R Vértesi ,X Li ,H Wang ,J H Lee ,S Vokál ,D J Hofman ,D P Kikoła ,R Lednický ,R A Kycia ,X Cui ,C Jena ,A Ohlson ,C B Powell ,R Singaraju ,S Gliske ,Z H Khan ,D Olson ,Alexandre Alarcon Do Passo Suaide ,A Peterson ,V Okorokov ,M Šumbera ,J Zhao ,D Beavis ,Y Zhu ,A Kisiel ,C Yang ,J S Wang ,J Schaub ,Feng Zhao ,M C Cervantes ,H J Jang ,H S Matis ,S G Brovko ,T D S Stanislaus ,M Zyzak

doi:10.1103/physrevd.89.012001

Abstract

The differential cross section and spin asymmetries for neutral pions produced within the intermediate pseudorapidity range 0.8<η<2.0 in polarized proton-proton collisions at s=200 GeV are presented. Neutral pions were detected using the end cap electromagnetic calorimeter in the STAR detector at RHIC. The cross section was measured over a transverse momentum range of 5<pT<16 GeV/c and is found to agree with a next-to-leading order perturbative QCD calculation. The longitudinal double-spin asymmetry ALL is measured in the same pseudorapidity range and spans a range of Bjorken-x down to x≈0.01. The measured ALL is consistent with model predictions for varying degrees of gluon polarization. The parity-violating asymmetry AL is also measured and found to be consistent with zero. The transverse single-spin asymmetry AN is measured over a previously unexplored kinematic range in Feynman-x and pT. Such measurements may aid our understanding of the onset and kinematic dependence of the large asymmetries observed at more forward pseudorapidity (η≈3) and their underlying mechanisms. The AN results presented are consistent with a twist-3 model prediction of a small asymmetry over the present kinematic range.2 MoreReceived 6 September 2013DOI:https://doi.org/10.1103/PhysRevD.89.012001© 2014 American Physical Society

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