Speaker
Description
The study of the nucleon's 3-D momentum and spin structure emerged from studies of both leading power (LP) and next-to-leading power (NLP) contributions to SIDIS observables. Although typically suppressed by $\Lambda_{\tiny QCD}/Q$, an understanding of the NLP TMD observables is essential for accurately describing SIDIS, and for properly extracting LP effects from SIDIS data. A key NLP observable, the $\cos\phi$ azimuthal modulation (Cahn effect), has been crucial in the development of the TMD field. Recent COMPASS measurements of the Cahn-effect have reaffirmed its importance in probing the nucleon’s 3-D structure. Additionally, the HERMES collaboration's observation of the Sivers effect via a power-suppressed target single-spin-asymmetries (SSA) for pion production underscored the importance of NLP contributions.
In this talk, I will review the phenomenology and theory of leading and next to leading power TMD observables in semi-inclusive scattering processes. I present our latest work on establishing TMD factorization at NLP, emphasizing the role of renormalization group consistency and the criteria for matching large and small transverse momenta in the cross section. Establishing TMD factorization at NLP is essential for 3-D imaging of hadrons in current and future DIS experiments, as well as for advancing global analyses of transverse SSA studies in the EIC era.
