Semi-inclusive π0 target and beam-target asymmetries from 6 GeV electron scattering with CLAS

S S Jawalkar ,S S Jawalkar ,M Mayer,W Kim,S Bültmann,C Hanretty,D Riser,Y Ghandilyan,M Osipenko,G Rosner,Y Prok,S Boiarinov,G Niculescu,K Hicks,E Golovatch,B Mckinnon,A El Alaoui,M Ripani,G Ciullo,G Ddoge,G Hollis,G Khachatryan,M Khandaker,H Avakian,M Hattawy,N Dashyan,S Strauch,E Voutier,L El Fassi,M Mirazita,W Kim,F Sabatié,O Pogorelko,E De Sanctis,P Eugenio,N Guler,W Gohn,W Gohn,I Niculescu,Z Akbar,K Livingston,V Batourine,H Voskanyan,M Ungaro,L Lanza,M Guidal,M Khachatryan,E Seder,T Mineeva,S Anefalos Pereira,A Fradi,S Pisano,Iu Skorodumina,E Pasyuk,P Lenisa,C Djalali,W Phelps,S Koirala,R Paremuzyan,Y Ilieva,D Protopopescu,D Adikaram,E Phelps,M Contalbrigo,D Heddle,M Battaglieri,D Sokhan,S Niccolai,A Movsisyan,A Deur,M Taiuti,A Celentano,H Hakobyan,I Bedlinskiy,H Egiyan,A Simonyan,L Colaneri,N Markov,A Filippi,S Joosten,G Charles,W Phelps,M Holtrop,M Garçon,R De Vita,O Cortes,N A Baltzell ,J Pierce,M E Mccracken ,D P Watts ,M H Wood ,R A Schumacher ,L B Guo ,I J D Macgregor ,H Lu ,K S Joo ,S Adhikari,J W Price ,Y G Sharabian ,D I Sober ,J Ball,B A Raue ,J Brock,S M Hughes ,J Brock,Volker Burkert ,R Dupré ,A Klein,A S Biselli ,X Wei,K A Griffioen ,M J Amaryan ,N Sparveris,K Park,J Brock,K P Adhikari ,K P Adhikari ,W K Brooks ,P L Cole ,J Zhang,S Fegan,J Pierce,R A Montgomery ,N Harrison,N Zachariou,Б С Ишханов ,J Zhang,T Chetry,F Cao ,P Bosted,L B Weinstein ,J Brock,V Kubarovsky,D G Ireland ,L Elouadrhiri,S E Kuhn ,C Muñoz Camacho ,Ivana Stanković ,K L Giovanetti ,A I Ostrovidov ,P Bosted,G P Gilfoyle ,A Rizzo,P Rossi,D S Carman ,L A Net ,J Pierce,J Ball,V Credé ,R W Gothe ,Hao Jiang ,J Pierce,Carlos A Salgado ,J Zhang,A D’angelo ,J A Fleming ,F X Girod ,G D Smith ,J Zhang,C Carlin,V Mokeev,C A Meyer ,C Gleason,A Kim,R Fersch,D Keller,J Ball,M Defurne,Ф Клейн ,G Fedotov,K A Griffioen ,P Bosted,C Keith,T A Forest ,J Ball,W J Briscoe ,S V Kuleshov ,L Clark,E L Isupov ,N K Walford ,D Jenkins,P Nadel-Turoński ,Z W Zhao

doi:10.1016/j.physletb.2018.06.014

Abstract

We present precision measurements of the target and beam-target spin asymmetries from neutral pion electroproduction in deep-inelastic scattering (DIS) using the CEBAF Large Acceptance Spectrometer (CLAS) at Jefferson Lab. We scattered 6-GeV, longitudinally polarized electrons off longitudinally polarized protons in a cryogenic 14NH3 target, and extracted double and single target spin asymmetries for ep→e′π0X in multidimensional bins in four-momentum transfer (1.0<Q2<3.2 GeV2), Bjorken-x (0.12<x<0.48), hadron energy fraction (0.4<z<0.7), transverse pion momentum (0<PT<1.0 GeV), and azimuthal angle ϕh between the lepton scattering and hadron production planes. We extracted asymmetries as a function of both x and PT, which provide access to transverse-momentum distributions of longitudinally polarized quarks. The double spin asymmetries depend weakly on PT. The sin⁡2ϕh moments are zero within uncertainties, which is consistent with the expected suppression of the Collins fragmentation function. The observed sin⁡ϕh moments suggest that quark gluon correlations are significant at large x.

Highlights

Contents lists available at ScienceDirectSemi-inclusive π 0 target and beam-target asymmetries from 6 GeV electron scattering with CEBAF Large Acceptance Spectrometer (CLAS)
We present precision measurements of the target and beam-target spin asymmetries from neutral pion electroproduction in deep-inelastic scattering (DIS) using the CEBAF Large Acceptance Spectrometer (CLAS) at Jefferson Lab
In this Letter we report results of unprecedented accuracy in measurements of spin-azimuthal asymmetries in neutral pion production in semi-inclusive DIS (SIDIS), which provides important information on the quark structure of the proton, complementary to that from charged pions

Summary

Contents lists available at ScienceDirect

Semi-inclusive π 0 target and beam-target asymmetries from 6 GeV electron scattering with CLAS. Large spin-azimuthal asymmetries were observed at JLab using a longitudinally polarized beam [21,22] in one case and a transversely polarized 3He target in the other [23] These results are consistent with the corresponding HERMES [24] and COMPASS [25] measurements, which were interpreted in terms of higher-twist contributions related to quark–gluon correlations. Polarized beams and targets give access to longitudinal target SSAs and the longitudinal DSAs as a function of φh , 4-momentum transfer Q 2, Bjorken x, transverse hadron momentum P T , and hadron energy fraction z These spin asymmetries are defined in the laboratory frame, for which beam and target polarizations are along the beam-line (L) or unpolarized (U). From the φh-dependence of these asymmetries (defined on the left-hand side of Eq (1) for SSAs and Eq (2) for DSAs) we can extract the experimental azimuthal moments (given on the right-hand side of Eqs. (1) and (2)) using the φh -dependence:

ALL cos LL

Collins fragmentation functions

Recently the effects of the