Energy dependence of hadron polarization ine+e−→hXat high energies

Abstract

The longitudinal polarization of hyperon in e + e − annihilation at high energies depends on the longitudinal polarization of the quark produced at the e + e − annihilation vertex whereas the spin alignment of vector mesons is independent of it. They exhibit very different energy dependences. We use the longitudinal polarization of Lambda hyperon and the spin alignment of K * as representative examples to present numerical results of energy dependences and demonstrate such distinct differences. We present the results at the leading twist with perturbative QCD evolutions of fragmentation functions at the leading order.

Spin alignment of vector mesons in high energy pp collisions

“…In this paper, we follow the same procedure of Ref. [65] and make parametrizations of D 1LL in two different scenarios for K Ã0 and ρ 0 from different flavors of quarks, antiquarks, and gluon and evolve them using the DGLAP equation. We apply the results obtained to pp → VX and make predictions for the spin alignment of vector mesons at RHIC and LHC energies.…”

“…In the first scenario, we follow the same strategy employed in Ref. [65] and differentiate between favored and unfavored fragmentations, i.e.,…”

“…Recently, progresses in the theoretical study have been achieved in particular in the formal QCD description of the spin dependence of FFs [57][58][59][60][61][62][63][64][65][66][67]. In the QCD field theory, FFs are defined via Lorentz decompositions of the quark-quark correlator.…”

“…Correspondingly, the first attempt to extract D 1LL ðzÞ from the LEP data [1][2][3] has been performed in Ref. [65].…”

Parity-odd fragmentation functions

“…In electron-positron annihilation process, the quarkantiquark transverse polarization correlation is defined as [27] c q nn ≡ |m n++ | 2 + |m n−− | 2 − |m n+− | 2 − |m n−+ | 2 |m n++ | 2 + |m n−− | 2 + |m n+− | 2 + |m n−+ | 2 ,…”