Chiral-odd Fragmentation Function Research Articles

Updated QCD global analysis of single transverse-spin asymmetries: Extracting H˜ , and the role of the Soffer bound and lattice QCD

We present an update to the QCD global analysis of single transverse-spin asymmetries presented in [J. Cammarota et al. (Jefferson Lab Angular Momentum Collaboration), Phys. Rev. D 102, 054002 (2020).] (JAM3D-20). JAM3D-20 simultaneously included transverse momentum dependent and collinear twist-3 observables, both of which are sensitive to quark-gluon-quark correlations in hadrons. In this study we extract for the first time the twist-3 chiral odd fragmentation function $\stackrel{\texttildelow{}}{H}$ by incorporating the $\mathrm{sin}{\ensuremath{\phi}}_{s}$ modulation data from semi-inclusive deep-inelastic scattering along with its contribution to the single transverse-spin asymmetry in pion production from proton-proton collisions. We also explore the impact of lattice QCD tensor charge calculations and the Soffer bound on our global analysis. We find that both constraints can be accommodated within our results, with $\stackrel{\texttildelow{}}{H}$ playing a key role in maintaining agreement with the data from proton-proton collisions.

The beam single spin asymmetry in semi-inclusive deep inelastic scattering

We study the beam single spin asymmetry in semi-inclusive hadron production in deep inelastic scattering at order 1/Q. There are two competing contributions: the leading order transverse momentum dependent parton distribution h1⊥(x,k⊥) convoluted with chiral-odd fragmentation function ê(z), and the chiral-odd distribution function e(x) convoluted with Collins fragmentation function H1⊥(z,k′⊥). We estimate this asymmetry and compare with the experimental measurements from CLAS and HERMES Collaborations.

Evidence for a single-spin azimuthal asymmetry in semi-inclusive pion electroproduction

Single-spin asymmetries for semi-inclusive pion production in deep-inelastic scattering have been measured for the first time. A significant target-spin asymmetry of the distribution in the azimuthal angle straight phi of the pion relative to the lepton scattering plane was formed for pi(+) electroproduction on a longitudinally polarized hydrogen target. The corresponding analyzing power in the sinstraight phi moment of the cross section is 0.022+/-0.005+/-0.003. This result can be interpreted as the effect of terms in the cross section involving chiral-odd spin distribution functions in combination with a chiral-odd fragmentation function that is sensitive to the transverse polarization of the fragmenting quark.