Transverse spin-dependent azimuthal correlations of charged pion pairs measured in p↑ + p collisions at [formula omitted

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

doi:10.1016/j.physletb.2018.02.069

Abstract

The transversity distribution, which describes transversely polarized quarks in transversely polarized nucleons, is a fundamental component of the spin structure of the nucleon, and is only loosely constrained by global fits to existing semi-inclusive deep inelastic scattering (SIDIS) data. In transversely polarized p↑+p collisions it can be accessed using transverse polarization dependent fragmentation functions which give rise to azimuthal correlations between the polarization of the struck parton and the final state scalar mesons.This letter reports on spin dependent di-hadron correlations measured by the STAR experiment. The new dataset corresponds to 25 pb−1 integrated luminosity of p↑+p collisions at s=500 GeV, an increase of more than a factor of ten compared to our previous measurement at s=200 GeV. Non-zero asymmetries sensitive to transversity are observed at a Q2 of several hundred GeV and are found to be consistent with the former measurement and a model calculation. We expect that these data will enable an extraction of transversity with comparable precision to current SIDIS datasets but at much higher momentum transfers where subleading effects are suppressed.

Highlights

The proton is the fundamental bound state of quantum chromodynamics (QCD)
The analysis presented here investigates a channel in which transversity couples to the spin dependent di-hadron FF H1 (z, M) [8,9,10], which, for historical reasons, is known as the interference fragmentation function (IFF)
The results presented in this letter at s = 500 GeV use more than 10 times th√e integrated luminosity than our previously reported result at s = 200 GeV [29], where a significant signal of transversity was observed in an exploratory measurement of dipion correlations

Summary

Introduction

The proton is the fundamental bound state of quantum chromodynamics (QCD). In spite of its importance for our understanding of this theory, our knowledge of the proton structure remains incomplete [1]. The third one, the transversity distribution h1(x), does not appear at leading twist in the inclusive DIS cross-section since it is connected to a chiral-odd helicity-flip amplitude Instead, it is accessed in processes where it couples to the chiral-odd transverse spin dependent fragmentation function (FF) [7]. A comparison between di-hadron asymmetries, with measurements of azimuthal asymmetries of pions in jets by STAR [32], will provide further tests of universality and factorization The former asymmetries can be described in a collinear framework, while the latter include an explicit dependency on intrinsic transverse momenta (for more details see [33,34]). The collinear framework is well understood and describes the unpolarized p + p cross-section well [35], but the transverse momentum dependent (TMD) framework is still being developed, and questions remain about universality, factorization and evolution

Experiment

Analysis

Results

Conclusions