Quarkonium Polarization using Jet Substructure

We discuss the jet energy dependence of the J/ψ production cross section using the Fragmenting Jet Function (FJF) aprroach. By comparing the cross sections for the different NRQCD production channels ( 1S08, 3S18, 3PJ8 and 3S11 ), we find that at fixed values of energy fraction z carried by the J/ψ, if the normalized cross section is a decreasing function of the jet energy, in particular for z > 0.5, then the depolarizing 1S08 must be the dominant channel. This makes the prediction made in [Baumgart et al., JHEP 1411, 003 (2014)] for the FJF’s also true for the cross section. We also make comparisons between the long distance matrix elements extracted by various groups.