II – Experimental investigation of transverse spin asymmetries in μ-p SIDIS processes: Sivers asymmetries
Articolo
Data di Pubblicazione:
2012
Abstract:
The COMPASS Collaboration at CERN has measured the transverse spin azimuthal asymmetry of charged hadrons produced in semi-inclusive deep inelastic scattering using a 160 GeV μ+ beam and a transversely polarised NH3 target. The Sivers asymmetry of the proton has been extracted in the Bjorken x range 0.003 < x < 0.7. The new measurements have small statistical and systematic uncertainties of a few percent and confirm with considerably better accuracy the previous COMPASS measurement. The
Sivers asymmetry is found to be compatible with zero for negative hadrons and positive for positive hadrons, a clear indication of a spin–orbit coupling of quarks in a transversely polarised proton. As compared to measurements at lower energy, a smaller Sivers asymmetry for positive hadrons is found in the region x > 0.03. The asymmetry is different from zero and positive also in the low x region, where sea-quarks dominate. The kinematic dependence of the asymmetry has also been investigated and results are given for various intervals of hadron and virtual photon fractional energy. In contrast to the
case of the Collins asymmetry, the results on the Sivers asymmetry suggest a strong dependence on the four-momentum transfer to the nucleon, in agreement with the most recent calculations.
Tipologia CRIS:
03A-Articolo su Rivista
Keywords:
COMPASS; SIDIS; spin asymmetries; Sivers asymmetries
Elenco autori:
C. Adolph;M.G. Alekseev;V.Yu. Alexakhin;Yu. Alexandrov;G.D. Alexeev;A. Amoroso;A.A. Antonov;A. Austregesilo;B. Badełek;F. Balestra;J. Barth;G. Baum;Y. Bedfer;J. Bernhard;R. Bertini;M. Bettinelli;K. Bicker;J. Bieling;R. Birsa;J. Bisplinghoff;P. Bordalo;F. Bradamante;C. Braun;A. Bravar;A. Bressan;M. Büchele;E. Burtin;L. Capozza;M. Chiosso;S.U. Chung;A. Cicuttin;M.L. Crespo;S. Dalla Torre;S. Das;S.S. Dasgupta;S. Dasgupta;O.Yu. Denisov;L. Dhara;S.V. Donskov;N. Doshita;V. Duic;W. Dünnweber;M. Dziewiecki;A. Efremov;C. Elia;P.D. Eversheim;W. Eyrich;M. Faessler;A. Ferrero;A. Filin;M. Finger;M. Finger;H. Fischer;C. Franco;N. du Fresne von Hohenesche;J.M. Friedrich;V. Frolov;R. Garfagnini;F. Gautheron;O.P. Gavrichtchouk;S. Gerassimov;R. Geyer;M. Giorgi;I. Gnesi;B. Gobbo;S. Goertz;S. Grabmüller;A. Grasso;B. Grube;R. Gushterski;A. Guskov;T. Guthörl;F. Haas;D. von Harrach;F.H. Heinsius;F. Herrmann;C. Heß;F. Hinterberger;N. Horikawa;Ch. Höppner;N. dʼHose;S. Huber;S. Ishimoto;O. Ivanov;Yu. Ivanshin;T. Iwata;R. Jahn;V. Jary;P. Jasinski;R. Joosten;E. Kabuß;D. Kang;B. Ketzer;G.V. Khaustov;Yu.A. Khokhlov;Yu. Kisselev;F. Klein;K. Klimaszewski;S. Koblitz;J.H. Koivuniemi;V.N. Kolosov;K. Kondo;K. Königsmann;I. Konorov;V.F. Konstantinov;A. Korzenev;A.M. Kotzinian;O. Kouznetsov;M. Krämer;Z.V. Kroumchtein;F. Kunne;K. Kurek;L. Lauser;A.A. Lednev;A. Lehmann;S. Levorato;J. Lichtenstadt;T. Liska;A. Maggiora;A. Magnon;N. Makke;G.K. Mallot;A. Mann;C. Marchand;A. Martin;J. Marzec;T. Matsuda;G. Meshcheryakov;W. Meyer;T. Michigami;Yu.V. Mikhailov;A. Morreale;A. Mutter;A. Nagaytsev;T. Nagel;T. Negrini;F. Nerling;S. Neubert;D. Neyret;V.I. Nikolaenko;W.-D. Nowak;A.S. Nunes;A.G. Olshevsky;M. Ostrick;A. Padee;R. Panknin;D. Panzieri;B. Parsamyan;S. Paul;E. Perevalova;G. Pesaro;D.V. Peshekhonov;G. Piragino;S. Platchkov;J. Pochodzalla;J. Polak;V.A. Polyakov;J. Pretz;M. Quaresma;C. Quintans;J.-F. Rajotte;S. Ramos;V. Rapatsky;G. Reicherz;A. Richter;E. Rocco;E. Rondio;N.S. Rossiyskaya;D.I. Ryabchikov;V.D. Samoylenko;A. Sandacz;M.G. Sapozhnikov;S. Sarkar;I.A. Savin;G. Sbrizzai;P. Schiavon;C. Schill;T. Schlüter;K. Schmidt;L. Schmitt;K. Schönning;S. Schopferer;M. Schott;W. Schröder;O.Yu. Shevchenko;L. Silva;L. Sinha;A.N. Sissakian;M. Slunecka;G.I. Smirnov;S. Sosio;F. Sozzi;A. Srnka;L. Steiger;M. Stolarski;M. Sulc;R. Sulej;H. Suzuki;P. Sznajder;S. Takekawa;J. Ter Wolbeek;S. Tessaro;F. Tessarotto;L.G. Tkatchev;S. Uhl;I. Uman;M. Vandenbroucke;M. Virius;N.V. Vlassov;L. Wang;M. Wilfert;R. Windmolders;W. Wiślicki;H. Wollny;K. Zaremba;M. Zavertyaev;E. Zemlyanichkina;M. Ziembicki;N. Zhuravlev;A. Zvyagin
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