Transversity from Single-Hadron TSSAs and Dihadron Fragmentation Theory Developments

I report on a QCD global analysis of transverse single-spin asymmetries (TSSAs) involving transverse momentum dependent (TMD)/collinear twist-3 (CT3) observables where single-hadron fragmentation functions (FFs) enter. I further explore the impact of lattice QCD tensor charge calculations on the results. A byproduct of this study is the extraction of the transversity PDFs and calculation of the nucleon tensor charges, where comparisons are made to previous phenomenological analyses. I also discuss new developments in the theory of dihadron fragmentation functions (DiFFs), where a definition is introduced that maintains a number density interpretation in a parton model framework (just as one has for single-hadron FFs). The associated evolution equations for these DiFFs are also derived.