Collins and Sivers asymmetries in muonproduction of pions and kaons off transversely polarised protons

C Adolph,M Levillain,B Gobbo,F Klein,J Pretz,H Schmieden,G.V Khaustov,M Virius,T Matsuda,S Neubert,F Gautheron,F Kunne,P Jörg,F Herrmann,Yu Kisselev,S Sirtl,J Bisplinghoff,C Elia,A Rychter,G Sbrizzai,F Tessarotto,J Barth,M Stolarski,S Dalla Torre,R Akhunzyanov,L Wang,S Ishimoto,O.Yu Shevchenko,J.H Koivuniemi,S Goertz,M Schott,A Cicuttin,K Schmidt,S Platchkov,V Andrieux,S Grabmüller,C Braun,P Jasinski,Y Bedfer,M Zavertyaev,M Wilfert,A Bressan,G Meshcheryakov,W Dünnweber,R Jahn,F Balestra,M.L Crespo,R Geyer,Yu.A Khokhlov,J Marzec,L Silva,I Konorov,N Du Fresne Von Hohenesche,N Horikawa,C Schill,Y Miyachi,C Quintans,K Kurek,T Nagel,D.V Peshekhonov,O Kouznetsov,D Neyret,E.R Bielert,R Joosten,S Takekawa,S Sosio,D Von Harrach,P Schiavon,S Tessaro,E Kabuß,G Baum,A Sandacz,K Schönning,B Ketzer,M Quaresma,G Pesaro,A Lehmann,S.V Donskov,M Finger,B Parsamyan,C Franco,S Huber,A Guskov,V Duic,M Ostrick,S Uhl,P Bordalo,S Schopferer,K Königsmann,J Bernhard,V.N Kolosov,A.A Lednev,S Paul,A Martin,N Doshita,T Schlüter,M Faessler,W Eyrich,R Beck,A Austregesilo,T Weisrock,Ch Höppner,M Ziembicki,E Rocco,T Iwata,L Steiger,T Szameitat,A Amoroso,T Grussenmeyer,T Michigami,S Sarkar,F Nerling,H Fischer,N.S Rossiyskaya,D Panzieri,F Sozzi,W.-D Nowak,K Kondo,W Meyer,Z.V Kroumchtein,D.I Ryabchikov,J Pochodzalla,F Bradamante,V.A Polyakov,A Ferrero,Yu.V Mikhailov,D Hahne,G.K Mallot,H Wollny,K Bicker,E Zemlyanichkina,M Gorzellik,A Maggiora,A Srnka,R Windmolders,R Sulej,F Thibaud,M Chiosso,M Bodlak,L Capozza,C Regali,S Ramos,O.P Gavrichtchouk,S Gerassimov,N Makke,K Klimaszewski,R Birsa,I Uman,M Dziewiecki,J Lichtenstadt,B Grube,A Szabelski,N Kuchinski,G Reicherz,P.D Eversheim,M Krämer,R Panknin,A Nagaytsev,A Grasso,A Zink,S Dasgupta,I Gnesi,M Büchele,B Badełek,S Levorato,Yu Ivanshin,E Burtin,L Sinha,A Magnon,J Ter Wolbeek,A.M Kotzinian,Q Curiel,V.D Samoylenko,F Hinterberger,P Sznajder,J Bieling,В Аносов ,I Savin ,N D’hose ,Jan Matoušek ,Claude Marchand ,V Jarý ,J Nový ,В.ф Константинов ,R Kurjata ,Ryo Hashimoto ,О Денисов ,И Орлов ,M Slunečka ,A S Nunes ,А А Берлин ,S U Chung ,Hiromasa Suzuki ,M Šulc ,А.g Оlshevsky ,G D Alexeev ,А В Ефремов ,Hiroki Matsuda ,M Alexeev ,А Иванов ,V V Frolov ,Friedrich Jm ,F H Heinsius ,К Заремба ,Florian Haas ,M Boër

doi:10.1016/j.physletb.2015.03.056

Abstract

Measurements of the Collins and Sivers asymmetries for charged pions and charged and neutral kaons produced in semi-inclusive deep-inelastic scattering of high energy muons off transversely polarised protons are presented. The results were obtained using all the available COMPASS proton data, which were taken in the years 2007 and 2010. The Collins asymmetries exhibit in the valence region a non-zero signal for pions and there are hints of non-zero signal also for kaons. The Sivers asymmetries are found to be positive for positive pions and kaons and compatible with zero otherwise.

Highlights

The description of the nucleon spin structure is still one of the open issues in hadron physics
In the last decades major progress in this field has been made by an interplay between new experimental results and the development of non-collinear QCD
The complete description of quarks in the nucleon includes all possible correlations between quark spin, quark transverse momentum and nucleon spin [1,2]

Summary

Introduction

The description of the nucleon spin structure is still one of the open issues in hadron physics. We present results on the Collins and Sivers asymmetries for pions and kaons produced on transversely polarised protons in a NH3 target. Such measurements are in line with the set of measurements done by the COMPASS Collaboration in the last years. Of particular relevance for these measurements is the upgrade of the RICH detector [12], which led to improved efficiency and purity for the samples of identified particles, and the use of a new target solenoid magnet with a polar angle acceptance of 180 mrad as compared to the 70 mrad of the magnet used until 2005 Measurements of these asymmetries by the HERMES experiment exist [13,14] in a different kinematic range (measurements in a limited x range exist on neutron targets, see [15,16,17]). Comparison with these results are presented in the paper

Apparatus and data selection

Charged pions and kaons

K 0 identification

Results