Angular Momentum and Polarization in Hadron Collisions up to LHC Energies

Gary R Goldstein,Simonetta Liuti

doi:10.1142/s2010194515600381

Abstract

Longstanding puzzles in spin physics can be confronted at the high energies of the LHC. Heavy quarks will be produced with significant polarization, both as single spin asymmetries and through polarization correlations. Lower energy proton accelerator and leptoproduction data suggest various mechanisms within QCD for polarization phenomena that can be tested at higher energies. Observation of strange and charm hadron polarization reveals important aspects of QCD spin physics. Top quark polarization is predicted to be significant, and polarization correlations will reveal important aspects of the gluon distributions of the hadrons.

Highlights

(But the combinations of helicities that correspond to transversity remain unchanged under boosts along the particle’s 3-momentum direction.) In TMDs or GPDs for which the transversity of the nucleon or the quark is fixed, the associated distribution must involve helicity flip
The kinematic dependence of these results favored small pT. If this hard process is the source of measured hyperon polarization, that polarization must be enhanced through soft process hadronization
This was accomplished in [3] through an ad hoc simple ansatz for that soft process by analogy with the “Thomas precession” mechanism [4] to boost the xF to xF while enhancing the scale of the polarization. This scheme could explain the systematic behavior of Λ and Σ polarization, including [5] the behavior of the Λc data from Fermilab experiment E791 [6], the need to introduce a soft mechanism beyond the Next to Leading Order (NLO) PQCD treatment suggests a more rigorous QCD based formulation [7]

Summary

Introduction

(But the combinations of helicities that correspond to transversity remain unchanged under boosts along the particle’s 3-momentum direction.) In TMDs or GPDs for which the transversity of the nucleon or the quark is fixed, the associated distribution must involve helicity flip. For the “observation” of a single quark or nucleon with definite transversity there has to be a chiral odd function. The pdf h1(x) is a measure of the transfer of transversity from the nucleon to the quark - it is a double polarization correlation.

Results

Conclusion