Gluon polarization in the nucleon from quasi-real photoproduction of high-[formula omitted] hadron pairs

E.S Ageev,J Marzec,K Königsmann,Yu.A Khokhlov,S Paul,M Colantoni,I Ludwig,A.M Kotzinian,R Hermann,V.I Tretyak,L Dhara,V.D Samoylenko,D.V Peshekhonov,S.V Donskov,I Konorov,A Korzenev,R De Masi,G.K Mallot,M Fabro,R Windmolders,T Matsuda,F Sozzi,A Mielech,B Ketzer,H Schmitt,J Franz,M Wiesmann,N.I Jouravlev,A Srnka,G Piragino,A Amoroso,A Sandacz,C Heß,P Schiavon,S Panebianco,P Berglund,S Gerassimov,J Ball,N Takabayashi,O Nähle,M Virius,C Bernet,M Maggiora,F Hinterberger,W Dünnweber,M Stolarski,S Koblitz,T Toeda,A.A Shishkin,D Von Harrach,N Doshita,B Grube,O.A Grajek,M.E Ladygin,R Geyer,M Ostrick,P Bordalo,C Ilgner,E Saller,G Brona,J Pochodzalla,F Balestra,Y Bedfer,R Sulej,A Bressan,S Trousov,D Panzieri,L Cerini,E Burtin,D Thers,A.M Dinkelbach,S Ishimoto,J Ehlers,F Kunne,M Varanda,Yu Kisselev,W Wiślicki,A.M Rozhdestvensky,A Maggiora,V.N Kolosov,P.D Eversheim,J Zhao,K Kondo,N Dedek,R Jahn,G.V Khaustov,N.V Vlassov,V.A Polyakov,W Kastaun,J Pretz,S Goertz,F Klein,J Lichtenstadt,J.H Koivuniemi,A Cicuttin,V.P Sugonyaev,D Kang,S Platchkov,P Fauland,Q Weitzel,B Gobbo,S Procureur,J Marroncle,R Joosten,S Neliba,C Quintans,U Wiedner,S Ramos,L Schmitt,W Eyrich,F Tessarotto,J Bisplinghoff,E Kabuß,J Nassalski,N Horikawa,G.V Krivokhizhin,O.Yu Shevchenko,Z.V Kroumchtein,V.V Tchalishev,T Hasegawa,M Von Hodenberg,M Finger,V Diaz,R Birsa,W Meyer,G.I Smirnov,K Kurek,A Grasso,G Reicherz,M Leberig,L Sinha,M Sans,F Stinzing,T Iwata,R Garfagnini,M Lamanna,A.S Korentchenko,A.I Ioukaev,M.P Bussa,A Magnon,N.A Koutchinski,A Grünemaier,A Ferrero,M.L Crespo,V Falaleev,A Zvyagin,J Hannappel,E Rondio,S Costa,L Ferrero,J Reymann,O.P Gavrichtchouk,K Kowalik,A Bravar,A Janata,F Bradamante,C Schill,F Gautheron,S Horikawa,G Baum,Yu Alexandrov,A Padee,M Faessler,F Karstens,E Weise,A Martin,K Platzer,S Dalla Torre,S Hedicke,V Duic,S Wirth,E.V Komissarov,H Fischer,R Bertini,Yu.V Mikhailov,A Chapiró ,A Colavita ,A N Skachkova ,A Zanetti ,Andreas Teufel ,B Badełek ,Claude Marchand ,Friedrich Jm ,H W Siebert ,Klaus Rith ,M A Giorgi ,M Slunečka ,M Šulc ,Mathias Wagner ,N D’hose ,Paolo Pagano ,R Ijaduola ,Ralf Kühn ,Richard Webb ,Robert Ziegler ,T Liška ,Th Schmidt ,V A Kalinnikov ,V D Peshekhonov ,V V Frolov ,А.g Оlshevsky ,В.ф Константинов ,К Заремба ,О N Ivanov ,О Денисов ,S Dasgupta ,A Maximov ,A Nozdrin ,A Popov ,A Sadovski ,A Sissakian ,G D Alexeev ,I Savin ,K Medved ,L G Tkatchev ,M G Sapozhnikov ,N P Kravchuk ,N V Khomutov ,V Alexakhin ,V Bytchkov ,F H Heinsius ,H Pereira ,D Neyret ,J M Le Goff ,P Rebourgeard ,A Dolgopolov ,A Gorin ,A Konoplyannikov ,I Manuilov ,V Dorofeev ,V Nikolaenko ,V Obraztsov ,M A Moinester

doi:10.1016/j.physletb.2005.11.049

Abstract

We present a determination of the gluon polarization ΔG/G in the nucleon, based on the helicity asymmetry of quasi-real photoproduction events, Q2<1 (GeV/c)2, with a pair of large transverse-momentum hadrons in the final state. The data were obtained by the COMPASS experiment at CERN using a 160 GeV polarized muon beam scattered on a polarized 6LiD target. The helicity asymmetry for the selected events is 〈A∥/D〉=0.002±0.019(stat)±0.003(syst). From this value, we obtain in a leading-order QCD analysis ΔG/G=0.024±0.089(stat)±0.057(syst) at xg=0.095 and μ2≃3 (GeV/c)2.

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