Collins effect ( Sin( φ h + φ S ) ) Access to transversity Artru model

1. Neutron (e,e’π±) Target Single-Spin Asymmetry in Semi-inclusive DIS on a Transversely Polarized 3He Target - Kalyan Allada, Chiranjib Dutta, Mitra Shabestari, Xin Qian On the behalf of Transversity Collaboration Two experiments with the highest scientific rate: A Nucleon Structure Characteristics of Transversity Detector system & 3He Target • Beam • - 6Gev, 15 microA electron beam • Target Well Known, since first measurement at 70s. • Nucleon anomalous magnetic moment (Stern, Nobel Prize 1943) • Electromagnetic form factor from electron scattering (Hofstadter, Nobel Prize 1961) • Deep-in-elastic scattering, quark underlying structure of the nucleon (Freedman, Kendell, Taylor, Nobel Prize 1990) Reasonable Known with 20 years effort. Transversity, business just started. HALL-A 3He Target • 40-cm long Rb-K spin-exchange hybrid cell at 10 atm . • ~42% target polarization with spin-flip frequency of 20 minutes. • A third set of Helmholtz coil will be added together with the laser optics to allow vertical polarization of the 3He target. • Some characteristics of transversity : • h1T = g1Lfor non-relativistic quarks • In non-relativistic case, boosts and rotations commute. • Important inequalities: |h1Tq| ≤ f1q ; |h1Tq| ≤ (f1q + g1Lq )/2. • h1T and gluons do not mix • Q2-evolution for h1T and g1L are different • Chiral-odd → • not accessible in inclusive DIS HRS HRS Understanding the underlying nucleon structure (Spin, flavor, charge, current distribution) from quantum chromodynamics (confinement region) is essential. q q Helicity state Electronuclear Scattering ------ A powerful tool to study nuclear structure • Target Polarimetry • NMR and EPR will be used to measure the target polarization. N N + - Spectrum: Inclusive: (the main tool) detecting electron only Semi-inclusive: (providing additional information) detecting electron and one of the hadrons coincidently • Hall-A Setup • It takes two Chiral-odd objects to measure transversity • Drell-Yan (Doubly transversely polarized p-p collision) • Semi-inclusive DIS Chiral-odd distributions function (transversity) Chiral-odd fragmentation function (Collins function) Asymmetry in Semi-Inclusive DIS with polarized target • Collins and Sivers Asymmetry • Electron detection - BigBite spectrometer, solid angle = 64msr, at 300 What is Semi-Inclusive Deep Inelastic Scattering (SIDIS) • Collins effect ( Sin(φh+ φS) ) • Access to transversity • Artru model • Based on LUND fragmentation picture. Scattering plane Parton distribution Function (PDF) • Charged pion detection - Hall-A High Resolution Spectrometer, at -160 Projections • First direct data on neutron AUT • At high-x • Clear separation of Collins and Sivers effect. • Statistical uncertainty dominates. • Kinematics comparable to the HERMES experiment. Fragmentation function (FF) DXs~PDF*FF The kinematics and coordinate • Sivers effect ( Sin(φh- φS) ) • A new type of PDF, T-odd, depends on intrinsically quark transverse momentum quark orbital momentum • E’ is the energy of scattered electron • θe is the scattering angle • ν =E-E’ is the energy transfer. • kT: quark transverse momentum HERMES: 3 years COMPASS: 1 year Beam direction Into the page DIS: Q2 (1/λ) and ν is large, but x is finite. HALL A: 29 days