Linearly Polarized Gluons and the Higgs Transverse Momentum Distribution
  We study how gluons carrying linear polarization inside an unpolarized hadron contribute to the transverse momentum distribution of Higgs bosons produced in hadronic collisions. They modify the distribution produced by unpolarized gluons in a characteristic way that could be used to determine whether the Higgs boson is a scalar or a pseudoscalar particle. 
Daniel Boer, Wilco J. den Dunnen, Cristian Pisano, Marc Schlegel,   Werner Vogelsang
hep-ph