The physics of hadron single transverse spin asymmetries is discussed. Possible measurements of both the quark and gluon Sivers functions are proposed.

Transverse Momentum Dependent Distributions (TMDs) describe the spin structure of the proton. At leading twist spin structure of spin-1/2 hadron can be described by 8 TMDs. TMDs reveal three-dimensional distribution of partons inside polarised nucleon. Experimentally these functions can be studied in polarised experiments using Spin Asymmetries in particular Single Spin Asymmetries (SSAs). We d...

Azimuthal asymmetries in semi-inclusive production of positive (h) and negative hadrons (h) have been measured by scattering of 160 GeV muons off longitudinally polarised deuterons at CERN. The asymmetries were decomposed in several terms, according to their expected modulation as a function of the outgoing hadron azimuthal angle φ. Each term receives contributions from one or several spin and ...

Acceleration of polarized protons in Relativistic Heavy Ion Collider (RHIC) provides unique tool to study the spin structure of the nucleon. We give a brief overview of the PHENIX program to investigate poorly known gluon and flavor decomposed see quark polarization in the proton, utilizing polarized proton collisions at RHIC. We report PHENIX first results on transverse single-spin asymmetry i...

We present a calculation of single and double spin asymmetries for inclusive hadron production in hadronic collisions. Our approach is based on Leading Order (LO) perturbative QCD and generalized factorization theorems, with full account of intrinsic parton momentum, k⊥, effects. This leads to a new class of spin and k⊥dependent distribution and fragmentation functions. Limiting ourselves to co...

We show how to observe sizable angular correlations between the decay products of the top quark and those of the anti-top quark in top quark pair production and decay at hadron colliders. These correlations result from the large asymmetry in the rate for producing like-spin versus unlike-spin top quark pairs provided the appropriate spin axes are used. The effects of new physics at production o...

We discuss the spin properties of top quark pairs produced at hadron colliders at next-to-leading order in the coupling constant αs of the strong interaction. Specifically we present, for some decay channels, results for differential angular distributions that are sensitive to tt̄ spin correlations. PACS number(s): 12.38.Bx, 13.88.+e, 14.65.Ha