Determining the Higgs spin and parity in the diphoton decay channel.

We calculate the diphoton distribution in the decay of arbitrary spin-0 and spin-2 bosons produced from gluon fusion, taking into account the fact that gluons inside an unpolarized proton are generally linearly polarized. The gluon polarization brings about a difference in the transverse momentum distribution of positive and negative parity states. At the same time, it causes the azimuthal distribution of the photon pair to be nonisotropic for several spin-2 coupling hypotheses, allowing one to distinguish these from the isotropic scalar and pseudoscalar distributions.

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.

Direct probes of linearly polarized gluons inside unpolarized hadrons.

We show that linearly polarized gluons inside unpolarized hadrons can be directly probed in jet or heavy quark pair production in electron-hadron collisions. We discuss the simplest cos2ϕ asymmetries and estimate their maximal value, concluding that measurements of the unknown linearly polarized gluon distribution in the proton should be feasible in future Electron-Ion Collider or Large Hadron electron Collider experiments. Analogous asymmetries in hadron-hadron collisions suffer from factorization breaking contributions and would allow us to quantify the importance of initial- and final-state interactions.