Single Spin Asymmetries from a Single Wilson Loop.

We study the leading-power gluon transverse-momentum-dependent distributions (TMDs) of relevance to the study of asymmetries in the scattering off transversely polarized hadrons. Next-to-leading-order perturbative calculations of these TMDs show that at large transverse momentum they have common dynamical origins but that in the limit of a small longitudinal momentum fraction x, only one origin remains. We find that in this limit, only the dipole-type gluon TMDs survive and become identical to each other. At small x, they are all given by the expectation value of a single Wilson loop inside the transversely polarized hadron, the so-called spin-dependent odderon. This universal origin of transverse spin asymmetries at small x is of importance to current and future experimental studies, paving the way to a better understanding of the role of gluons in the three-dimensional structure of spin-polarized protons.

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.

Bounding W-W' mixing with spin asymmetries at RHIC.

The W boson can obtain a small right-handed coupling to quarks and leptons through mixing with a hypothetical W^{'} boson that appears in many extensions of the standard model. Measuring or even bounding this coupling to the light quarks is very challenging. Only one model independent bound on the absolute value of the complex mixing parameter has been obtained to date. Here we discuss a method sensitive to both the real and CP-violating imaginary parts of the coupling, independent of assumptions on the new physics, and demonstrate quantitatively the feasibility of its measurement at RHIC.

Test of the universality of naive-time-reversal-odd fragmentation functions.

We investigate the "spontaneous" hyperon transverse polarization in e+ e- annihilation and semi-inclusive deep inelastic scattering processes as a test of the universality of the naive-time-reversal-odd transverse momentum dependent fragmentation functions. We find that universality implies definite sign relations among various observables. This provides a unique opportunity to study initial or final state interaction effects in the fragmentation process and test the associated factorization.