Double Collins effect in e+e−→ΛΛ¯

Abstract

We study the Collins function H ⊥ 1 of the Λ hyperon, which describes the fragmentation of a transversely polarized quark into an unpolarized Λ hyperon. We calculate H ⊥ 1 for light quarks of the Λ hyperon, in the diquark spectator model with a Gaussian form factor for the hyperon-quarkdiquark vertex. The model calculation includes contributions from both the scalar diquark and vector diquark spectators. Using the model result, we estimate the azimuthal asymmetry A 12 , which appears in the ratio of unlike-sign events to like-sign events contributed by double Collins effects, in the processes e þ e − → ΛΛX and e þ e − → ΛπX. The QCD evolution effects for the half k T moment of the Collins function and the unpolarized fragmentation function D 1 ðzÞ are also included. The results show that the asymmetries are sizable and measurable at the kinematical configurations of Belle and BABAR experiments. We also find that the evolution effects play an important role in the phenomenological analysis.

Azimuthal single- and double-spin asymmetries in semi-inclusive deep-inelastic lepton scattering by transversely polarized protons

“…a calculation in a diquark spectator model resulted in sizable Collins functions for up and down quarks into Λ hyperons [145]. While no such calculation is presented for the case of protons, it is not unplausible that it would result in a non-vanishing Collins effect, as hinted at by the data.…”

30 years of jet quenching

“…This approach can be applied to quark propagation in cold nuclei and hadron suppression in semiinclusive deeply inelastic scattering (SIDIS) off large nuclei [26,27] as well as hadron suppression due to jet propagation in QGP in heavy-ion collisions [28,29]. In the most recent study of multiple parton scattering in SIDIS off large nuclei and Drell-Yan dilepton production in p + A collisions at NLO within the higher-twist framework [30,31,32], the factorization is verified for the transversemomentum weighted cross section. The QCD evolution equation for twist-4 matrix elements for parton correlation or the jet transport coefficient, is also derived and its universality is demonstrated.…”

Effect of the nature of the nucleophile and solvent on an SNAr reaction

“…The authors have suggested that the attack at the carbon or sulphur centres depends on the reagent used, and the yield of S N Ar or S N products is strongly influenced by the solvent. Currently, solvent effect in S N Ar reactions has been studied in conventional organic solvents (COS) 10,12,[19][20][21][22][23][24] and room temperature ionic liquids (RTILs); 12,17,18,20,[25][26][27][28] this opens the discussion of the factors that determine selectivities, reaction rates, and mechanisms. For instance, D'anna et al 18 investigated the reaction of 2-substituted 5-nitrothiophenes with secondary amines.…”