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Toshi-Aki Shibata Tokyo Tech for HERMES Collaboration

Explore physics effects on a transversely polarized hydrogen target, analyzing Collins and Sivers effects, quark distribution functions, and more. The study includes the HERMES experiment and findings on quark transversity distributions. Conclusions indicate a significant separation of effects and promising outlook.

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Toshi-Aki Shibata Tokyo Tech for HERMES Collaboration

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  1. Single Spin Asymmetry with a Transversely Polarized Hydrogen Target at HERMES Toshi-Aki Shibata Tokyo Tech for HERMES Collaboration Contents: • Physics with DIS on Transversely Polarized Targets • HERMES Experiment • Separation of Collins Effect and Sivers Effect HAWAII05 T.-A. Shibata

  2. Airapetian et al, HERMES, • Phys. Rev. Lett. 94 (2005) 012002 • Single-Spin Asymmetries in Semi-inclusive Deep-Inelastic • Scattering on a Transversely-Polarized Hydrogen Target + update including the 2004 data HAWAII05 T.-A. Shibata

  3. Quark Distribution Functions At leading twist Quark Momentum Distribution Quark Helicity Distribution Quark Transversity Distribution Positivity Bound Soffer Bound HAWAII05 T.-A. Shibata

  4. Why Are Quark Transversity Distributions Interesting? proves Quark’s Relativistic Nature in the Nucleon Because of Lack of Transversity of Gluon, Q2 Evolution Should Be Different From That of and . Chiral Odd. So Far Never Measured initial quark transverse momentum final quark transverse momentum Sivers Effect: could be related to orbital motion of quarks The separation of the two effects was carried out for the first time. HAWAII05 T.-A. Shibata

  5. HERMES Detector e＋ 27.5 GeV Reconstruction Kinematical Range HAWAII05 T.-A. Shibata

  6. Two Azimuthal Angles in Semi-inclusive Measurement with a Transversely Polarized Target electron reaction plane hadron Target HAWAII05 T.-A. Shibata

  7. Azimuthal Single Spin Asymmetry Asymmetry around the virtual photon direction Collins Sivers means convolution Integral over initial (pT ) and final (kT ) quark transverse momentum Fourier Component Fit in 2-dimension in each x bin Collins Sivers HAWAII05 T.-A. Shibata

  8. Monte Carlo Test of Extraction Method • generate Collins and Sivers Asymmetries (Gaussian Ansatz in Pt2) • analyse MC data like experimental data and extract Asymmetries • Collins-Sivers cross contamination is negligible HAWAII05 T.-A. Shibata

  9. Collins Asymmetry Phys. Rev. Lett. 94 (2005) 012002 Positive Asymmetry Negative Asymmetry The magnitude is larger. HAWAII05 T.-A. Shibata

  10. Sivers Asymmetry Phys. Rev. Lett. 94 (2005) 012002 Positive Asymmetry Asymmetry is nearly 0 Effects of Exclusive Vector Meson Production were studied. HAWAII05 T.-A. Shibata

  11. Update including Data 2004 Collins Sivers HAWAII05 T.-A. Shibata

  12. Conclusions • The separation of Collins effect and Sivers effect was carried • out for the first time. • Non-zero asymmetry is observed for Collins asymmetry. • Positive asymmetry, negative asymmetry are compatible • with helicity distribution . But the amplitude of • asymmetry is large. • asymmetry is positive, and asymmetry is nearly 0 • for Sivers asymmetry. The effects of exclusive vector • meson production were investigated and found to be • negligible. outlook: Statistics will be about doubled by the end of 2005. HAWAII05 T.-A. Shibata

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