Gluon fragmentation into polarized charmonium

Abstract

Gluon fragmentation to x_cJ(1P) followed by single photon emission represents the dominant source of prompt J/ψ's at the Fermilab Tevatron for p⊥ ≳6 GeV. Since fragmenting gluons are approximately transverse, their products are significantly polarized. We find that gluon fragmentation populates the helicity levels of xc1, xc2, and J/ψ according to Dx_c1(h=0): D _xc1(|h|=1) ⋍ 1:1, D _xc2(h=0): D_xc2(|h|=1):D _xc2(|h|=2) ⋍1 : 2.9 : 6.0, and D _J/ψ(h=0) : D _{J/ψ(||h||=1)} ⋍ 1 : 3.4. We also speculate that gluon fragmentation to the radially excited xc2(2P) state followed by radiative decay could represent a large source of ψ'(2S)'s and potentially resolve the ψ'. A measurement of these states' polarizations would test this idea.