Transverse-single-spin asymmetries of charged pions at midrapidity in transversely polarized p+p collisions at s=200  GeV

U Acharya ,S H Lee ,Q H Xu ,B Mulilo ,R Nouicer ,T Sumita ,I Tserruya ,M Daugherity ,R Seto ,C P Wong ,Y Yamaguchi ,D Ivanishchev ,A Timilsina ,I Shein ,N Grau ,M Chiu ,A Yanovich ,S Yalcin ,B Blankenship ,J D Osborn ,K Shigaki ,Y Berdnikov ,C Y ,A Pun ,S Lökòs ,Timothy Thomas Rinn ,M Patel ,V Andrieux ,D Kotov ,C Gal ,H Yu ,M Giles ,K I Hahn ,K Lovász ,W Peng ,Y Akiba ,T Hoshino ,P Montuenga ,V Samsonov ,T Murakami ,I J Choi ,M Makek ,S Park ,M Jezghani ,A M Sickles ,W A Zajc ,V Manko ,R Seidl ,G Mitsuka ,Sanghoon Lim ,J T Mitchell ,S Esumi ,D Larionova ,M Tomášek ,I Yoon ,L Xue ,D S Fitzgerald ,V Pantuev ,H Asano ,A Khatiwada ,Y Riabov ,J C Hill ,Iu Mitrankov ,Z Sun ,S P Sørensen ,Y I Makdisi ,D E Fields ,Y Kwon ,K Nagashima ,M Sarsour ,J Bryslawskyj ,V Canoa Roman ,N Ramasubramanian ,D Isenhower ,R Belmont ,V Babintsev ,M Mitrankova ,A Enokizono ,P W Stankus ,B Azmoun ,K Kurita ,Y Goto ,F Giordano ,W E Sondheim ,V Bumazhnov ,S Bathe ,M Potekhin ,H Sako ,A Lebedev ,D Yu Peressounko ,E Kistenev ,K A Drees ,S Tarafdar ,K Ozawa ,V Khachatryan ,X R Wang ,M Mendoza ,G Tarnai ,M M Mondal ,A Safonov ,H Ge ,N Feege ,T Hachiya ,S Miyasaka ,A Drees ,J S Haggerty ,A V Kazantsev ,C Kim ,H En’yo ,E Mannel ,C Nattrass ,P V Radzevich ,T K Hemmick ,J G Lajoie ,M Slunečka ,S D Rolnick ,P Garg ,R Corliss ,D Reynolds ,R Esha ,J L Nagle ,R S Hollis ,A Sen ,N Vukman ,K N Barish ,M J Leitch ,B Hong ,D Kincses ,V Papavassiliou ,J Velkovska ,T Gunji ,L Zou ,S Greene ,X He ,M Rosati ,T Nagashima ,K Imai ,H Hamagaki ,T Koblesky ,J Choi ,G Nukazuka ,I Nakagawa ,A S Nyanin ,T Niida ,S Lee ,I V Sourikova ,G David ,J H Kang ,E.-J Kim ,D V Perepelitsa ,A D Frawley ,M Finger ,Y Watanabe ,P Kline ,J Huang ,K Dehmelt ,T O S Haseler ,J D Orjuela Koop ,M Shimomura ,A Bazilevsky ,D Lynch ,C A Ogilvie ,J M Durham ,W Fan ,M Beaumier ,N Apadula ,A Khanzadeev ,M Csanád ,L Bichon ,C L Towell ,Z Ji ,I E Yushmanov ,E O’brien ,D Sharma ,A Milov ,J Perry ,B Schaefer ,J Hanks ,J Sziklai ,J Sun ,A Deshpande ,P Gallus ,G D N Perera ,R Tieulent ,Hiroshi Yamamoto ,M Connors ,T Kim ,N A Lewis ,M Virius ,N Cronin ,Y H Leung ,D Kawall ,C E Perezlara ,M Harvey ,A Berdnikov ,B M Johnson ,C L Woody ,K Deblasio ,T Shioya ,A Taranenko ,S Kudo ,J Runchey ,A Öskarsson ,J Murata ,R Petti ,S Fokin ,S Y Han ,S Campbell ,V.-R Loggins ,N Novitzky ,M Snowball ,Jeongsu Bok ,S Zharko ,A Dion ,N S Bandara ,D A Loomis ,Susumu Sato ,T Novák ,T W Danley ,V Vrba ,A Sexton ,T Sugitate ,D Richford ,T Sakaguchi ,K Tanida ,T A Shibata ,E J Desmond ,D Jouan ,V.s Borisov ,K Nakano ,C Mckinney ,Y Fukuda ,S Nelson ,X Li ,Z H Citron ,J S Park ,M I Nagy ,C L Silva ,A Sukhanov ,K Smith ,J Klatsky ,M J Tannenbaum ,M W Phipps ,H W Van Hecke ,D K Mishra ,M L Purschke ,A Denisov ,Z Rowan ,B V Jacak ,V Riabov ,H F Hamilton ,A Zelenski ,L Kovács ,M Kim ,M Mccumber ,B Ujvári ,R P Pisani ,M Inaba ,P L Mcgaughey ,C J Xu ,J H ,J Yoo ,P Shukla ,A C Mignerey ,D S Jumper ,M Grosse Perdekamp ,M X Liu ,T Csörgõ ,T Moon ,A Durum ,K F Read ,H Guragain ,R A Soltz ,J E Frantz ,D Silvermyr ,A Kingan ,T Todoroki ,D Mcglinchey ,D Kapukchyan ,K Sedgwick ,Dhruv Utpalkumar Dixit ,S Hasegawa ,C A Aidala ,N Hotvedt ,A Iordanova ,M L Brooks ,T Majoros ,C Pinkenburg ,S Mizuno ,B Fadem ,K Homma ,M Alfred ,S F Pate ,G J Ottino ,A Franz ,S P Stoll ,V K Singh ,D P Morrison ,A Hodges ,C P Singh ,B K Singh ,S Karthas ,D Blau ,R Cervantes ,Y Ueda ,K Nagai ,K K Hill ,X Jiang ,B K Schmoll ,R S Towell ,Null Author_Id

doi:10.1103/physrevd.105.032003

Abstract

In 2015, the PHENIX collaboration has measured single-spin asymmetries for charged pions in transversely polarized proton-proton collisions at the center of mass energy of $\sqrt{s}=200$ GeV. The pions were detected at central rapidities of $|\eta|<0.35$. The single-spin asymmetries are consistent with zero for each charge individually, as well as consistent with the previously published neutral-pion asymmetries in the same rapidity range. However, they show a slight indication of charge-dependent differences which may suggest a flavor dependence in the underlying mechanisms that create these asymmetries.

Highlights

Single-spin asymmetries have been measured in hadronic collisions over a wide range of energies for a number of final state particles [1–4] and at various rapidity regions
Calculations that were based entirely on perturbative quantum chromodynamics expected such asymmetries to be suppressed as they generally required a helicity flip which would be proportional to the parton mass over the hard scale of the scattering process [5], though recent calculations suggest that perturbative contributions may be possible [6]
Two different mechanisms were suggested to describe these asymmetries that attribute the effect to the nonperturbative parts of either the parton distribution functions [7] or the fragmentation functions [8]

Summary

INTRODUCTION

Single-spin asymmetries have been measured in hadronic collisions over a wide range of energies for a number of final state particles [1–4] and at various rapidity regions. Global fits of asymmetry measurements from SIDIS and hadron collisions have become possible and provide additional precision on the underlying functions of interest such as the quark transversity [15] or the Sivers [7] function in the proton The latest of these comes from [16], in which are found sizeable contributions from both initial- and finalstate effects. 032003-3 pion asymmetries provide different flavor sensitivity via the fragmentation functions and could test whether such cancellations happen, as the dominant hard process at the transverse momenta of this measurement is given by quark-gluon scattering. The PHENIX detector at RHIC has measured charged pion single-spin asymmetries at central rapidities in transversely ppoffiffilarized p þ p collisions at a center-of-mass energy of s 1⁄4 200 GeV. The documentation of the charged pion selection criteria, reconstruction efficiencies and various background corrections follow before evaluating the various systematic uncertainties for the asymmetry results which are discussed

DATASETS

EVENT AND PARTICLE SELECTION CRITERIA

ASYMMETRY EXTRACTION

SYSTEMATIC STUDIES AND CROSS CHECKS

RESULTS

SUMMARY