Cross section and longitudinal single-spin asymmetry AL for forward W±→μ±ν production in polarized p+p collisions at s=510  GeV

A Adare,E Stenlund,B Xia,K Sedgwick,T Moon,B Meredith,K Deblasio,K Tanida,K Imai,M Towell,A Taranenko,R Lacey,S Yokkaichi,C Baumann,B Komkov,S Wolin,S Tarafdar,A Garishvili,M Slunečka,R Belmont,D Kawall,V Papavassiliou,B Azmoun,N Cronin,K Nakano,K Gainey,J Hanks,J Bryslawskyj,J Koster,I Nakagawa,H Ge,L Xue,M Stepanov,T Hachiya,J Klatsky,Y Akiba,D Kleinjan,M Skolnik,Z Rowan,A Bagoly,D Isenhower,S Nagamiya,E Vazquez-Zambrano,S Kanda,S Mizuno,A Iordanova,C Pinkenburg,F Wei,D Richford,A Isinhue,A Franz,N Riveli,R Seidl,N Novitzky,A Durum,A Mwai,E Kistenev,D Kincses,V Baublis,T Murakami,Y Sekiguchi,B Fadem,E Tennant,S Bathe,M Jezghani,V Cianciolo,O Drapier,A Bazilevsky,I Tserruya,B Sahlmueller,T Hester,K Okada,Y Imazu,S Zharko,T Engelmore,N Crossette,D Kotov,D Lynch,S Solano,I Shein,R Petti,I Younus,G David,M Mendoza,Y Nakamiya,M Patel,T Sumita,Y Tanaka,A Denisov,S Sawada,M Wysocki,P Montuenga,Y Goto,M Sarsour,M Gonin,V Babintsev,A Lebedev,A Vossen,M Chiu,T Ichihara,A Manion,Y Ikeda,E Richardson,A Drees,K Shoji,W Peng,A Dion,R Pak,M Beaumier,D Roach,R Seto,M Leitgab,A Taketani,T Koblesky,V Bumazhnov,T Todoroki,E Joo,A Veicht,R Granier De Cassagnac,D Kotchetkov,J Murata,J Seele,K Boyle,L Zou,V Canoa Roman,A Sexton,R Pinson,G Mitsuka,I Garishvili,S Butsyk,S Beckman,K Dehmelt,M Nihashi,I Ravinovich,Y Fukao,M Grosse Perdekamp,Y Berdnikov,M Virius,T Niida,A Meles,N Hotvedt,A Berdnikov,M Mccumber,A Ster,D Ivanishchev,S Zhou,A Hodges,A Timilsina,J Runchey,M Tomášek,R Yang,N Grau,M Rosati,E Vznuzdaev,D Jouan,Y Aramaki,A Enokizono,L Patel,K Kurita,N Feege,T Hoshino,K Kihara,T Majoros,C Gal,Y Riabov,J Sziklai,P Kline,S Esumi,A Deshpande,B Bannier,Y Watanabe,C Mckinney,A Yanovich,N A Lewis ,Y.-J Kim,Shoichi Hasegawa ,T Mibe,S K Park ,D Silvermyr,D Blau ,C E Perezlara ,H Sako,K Nagashima,Y Yamaguchi ,N Saito,D Mishra ,T A Shibata ,C Y ,Stephen Baumgart ,M Boër ,T O S Haseler ,H Qu,K Hashimoto,J D Osborn ,M Csanád,J Sun,K Shigaki,D Mcglinchey,S Yalcin,A Khanzadeev,Z Ji,S F Pate ,Y K Kim ,T Sugitate,M Makek,S Fokin ,V Khachatryan,A Datta,R P Pisani ,S Whitaker,W A Zajc ,X He,P V Radzevich ,B H Kang ,D E Fields ,K O Eyser ,J M Durham ,S P Stoll ,V Vrba,C A Ogilvie ,Yue Shi Lai ,Z Y You ,S Park,M J Leitch ,L Ding,J Rubin ,S I Morrow ,A Milov,A Takahara,K N Barish ,A J Miller ,R Vértesi,K M Kijima ,X R Wang ,J.-C Peng,J Yoo ,M Alfred,E.-J Kim,А Суханов ,V K Singh ,M Kim,Sanghoon Lim ,S Greene ,K R Nakamura ,T Fusayasu,J Perry,D P Morrison ,M J Tannenbaum ,B Jacak ,X Jiang,K B Lee ,R S Towell ,A Öskarsson ,C Kim,Jeongsu Bok ,M Inaba,D Yu Peressounko ,Y Gu,S Y Han ,R Akimoto,P L Mcgaughey ,B K Singh ,P Shukla,J Choi ,T Nagae,B Schaefer,J L Nagle ,Y I Makdisi ,S Campbell,J D Orjuela Koop ,M I Nagy ,М Фингер ,P Steinberg,J Jia,P W Stankus ,V Pantuev,Deirdre Black ,H Asano,J Velkovska,M Shimomura,T Gunji,H Torii,V Riabov,H En’Yo,J A Key ,W E Sondheim ,T Csörgõ ,B M Johnson ,X Gong,H Buesching,B Lewis,T C Awes ,R A Soltz ,J G Lajoie ,M L Purschke ,P Sett,E T Atomssa ,H Nakagomi,S D Rolnick ,Marc L Moskowitz ,C L Woody ,Kenneth Francis Read ,S Mohapatra,T K Hemmick ,A V Kazantsev ,A M Sickles ,A Sen,T Chujo,V Manko ,J Huang,D J Kim ,H Hamagaki,J Kamin,M R Stone ,Y Kwon,C.-H Chen,X Cai ,Q H Xu ,J T Mitchell ,J H ,J Alexander,D S Jumper ,C Maguire ,K Ozawa,E Mannel,R Nouicer,A K Mohanty ,F Fleuret,W Fan,S Miyasaka,Daisuke Watanabe ,D Reynolds,D Sharma,Z H Citron ,G D N Perera ,C L Silva ,K Watanabe,Sihyun Jeon ,M X Liu ,P K Khandai ,M Vargyas,T V Moukhanova ,E J Desmond ,A Zelenski,R Tieulent,M Kurosawa,P Christiansen,T Nakamura,T Sakaguchi,K A Drees ,S Choi,H Yu,J C Hill ,N S Bandara ,A D Frawley ,K S Lee ,C Nattrass,S H Lee ,R Hayano,N N Ajitanand ,B K Schmoll ,A Glenn,H W Van Hecke ,Y Miake,A Nyanin ,J S Haggerty ,Laurent D’orazio ,K Homma,I V Sourikova ,F Křížek ,D H Kim ,C P Wong ,J Lee,B Ujvári ,A Shaver,K I Hahn ,S Lökòs ,P K Netrakanti ,M L Brooks ,P Gallus,J S Kang ,X Li,I J Choi ,I E Yushmanov ,Y H Leung ,B Hong,Z Sun,S Huang,B Cole ,C P Singh ,R S Hollis ,J E Frantz ,H Oide,J Rak,H Guragain,Kazuo Aoki ,Timothy Thomas Rinn ,P Garg,G H Lee ,M Kofarago,S Sörensen ,Xiaozhi Bai ,Susumu Sato ,D V Perepelitsa ,M S Ryu ,E O’Brien,N Apadula,M Connors,J H Kang ,T Novák,H.-J Kim,K S Joo ,F Giordano,K K Hill ,C A Aidala ,M J Skoby ,D M Lee ,A C Mignerey ,I H Park ,I Yoon,V Samsonov,T W Danley ,D E Mihalik ,M Daugherity ,J Kapustinsky,Mei Bai

doi:10.1103/physrevd.98.032007

Abstract

We have measured the cross section and single spin asymmetries from forward $W^{\pm}\rightarrow\mu^{\pm}\nu$ production in longitudinally polarized $p$$+$$p$ collisions at $\sqrt{s}=510$ GeV using the PHENIX detector at the Relativistic Heavy Ion Collider. The cross sections are consistent with previous measurements at this collision energy, while the most forward and backward longitudinal single spin asymmetries provide new insights into the sea quark helicities in the proton. The charge of the W bosons provides a natural flavor separation of the participating partons.

Highlights

The spin of the proton and its decomposition is fundamentally important
The cross sections are consistent with previous measurements at this collision energy, while the most forward and backward longitudinal single spin asymmetries provide new insights into the sea quark helicities in the proton
Unlike what is naively expected from gluon splitting, the unpolarized light quark sea is found to be asymmetric with more antidown quarks than antiup quarks at small to intermediate Bjorken x < 0.2, where x is the parton momentum fraction in the infinite momentum frame

Summary

INTRODUCTION

The spin of the proton and its decomposition is fundamentally important. Understanding its origin is essential to explaining how the strong interaction, described by quantum chromodynamics (QCD), creates. An elegant alternative to access sea quark helicities is via the weak interaction Such processes are possible at the high scales proposed at a polarized electron-ion collider [8] or currently in polarized p þ p collisions at the Relativistic Heavy Ion Collider (RHIC) [9]. Building the difference of the W production cross sections for positive and negative helicities normalized by their sum, one arrives at the single longitudinal spin asymmetry, ApLp→Wþ. The corresponding single spin asymmetry for W− production becomes It accesses the other combination of light quark flavors. A data-driven approach has been employed to identify the contributions by the various backgrounds in the data sample to extract W production cross sections and the corresponding single spin asymmetries. VI before a summary of the measurements in the last section

DATA SETS

EVENT AND TRACK SELECTION CRITERIA

SIGNAL EXTRACTION AND BACKGROUNDS

SYSTEMATIC STUDIES

RESULTS

SUMMARY