Recent results on cold-QCD from RHIC

Polarized proton-proton collisions at the Relativistic Heavy Ion Collider (RHIC) provide unique opportunities to study the spin structure of the nucleon. We will highlight recent results on the nucleon spin structure from the STAR and PHENIX experiments at RHIC: (1) A sizable gluon polarization in the proton is measured with longitudinal double spin asymmetries of jet and hadron production; (2) Longitudinal single spin asymmetries in W boson production improve constraints on the sea quark polarization. The new spin asymmetry results for W boson confirmed the SU(2) flavor asymmetry of the light sea quark polarization in the proton; (3) Transverse spin effects in hadronic systems offer new implications on parton distribution functions in the collinear and transverse momentum dependent frameworks. We will also discuss near term plans for the STAR forward detector upgrade and prospects for proton-proton and proton-ion collisions in the years beyond 2021 at STAR.Comment: Proceedings for plenary talk at XLIX International Symposium on Multiparticle Dynamics (ISMD2019

Spin alignment of vector meson in e+e- annihilation at Z0 pole

We calculate the spin density matrix of the vector meson produced in e+e- annihilation at Z^0 pole. We show that the data imply a significant polarization for the antiquark which is created in the fragmentation process of the polarized initial quark and combines with the fragmenting quark to form the vector meson. The direction of polarization is opposite to that of the fragmenting quark and the magnitude is of the order of 0.5. A qualitative explanation of this result based on the LUND string fragmentation model is given.Comment: 15 pages, 2 fgiures; submitted to Phys. Rev.

Spin Alignment of Vector Meson in High Energy Reactions

The recent data on the polarization of vector meson at LEP show that the vector mesons favor the helicity zero state. We calculate the helicity density matrix of vector meson which contains a polarized fragmenting quark by adding the spin of the fragmenting quark and that of the antiquark created in the fragmentation. The data at LEP imply a significant polarization for the antiquark in the opposite direction as that of the fragmenting quark. We extend the calculations to other reactions and make predictions for vector mesons in deeply inelastic lepton-nucleon scatterings and polarized $pp$ collisions.Comment: 4 pages,3 figures, Talk given at 3rd Circum-Pan-Pacific Symposium on "High Energy Spin Physics", Beijing, China, Oct.8-13, 200

Biholomorphic mappings on bounded starlike circular domains

AbstractLet Ω⊂Cn be a bounded starlike circular domain with 0∈Ω. In this paper, we introduce a class of holomorphic mappings Mg on Ω. Let f(z) be a normalized locally biholomorphic mapping on Ω such that Jf−1(z)f(z)∈Mg and z=0 is the zero of order k+1 of f(z)−z. We obtain a sharp growth theorem and sharp coefficient bounds for f(z). As applications, sharp distortion theorems for a subclass of starlike mappings are obtained. These results unify and generalize many known results