[NT/RBRC seminar] Quark Sivers Function at Small x: Spin-Dependent Odderon and the Sub-Eikonal Evolution

by Mr Gabriel Santiago (Ohio state university)

Friday 7 Jan 2022, 09:00 → 11:00 US/Eastern

https://bnl.zoomgov.com/j/1607303224?pwd=OHN4aHV2Zk9CcitZU29tUjV4TE1lZz09

The Sivers function is a leading-twist transverse momentum dependent parton distribution function (TMD) which encodes the spin-orbit coupling between the transverse motion of quarks and gluons and the spin of a transversely polarized hadron. The small-$x$ evolution of this TMD brings together several facets of QCD research, as it touches on the spin and angular momentum structure of hadrons, the sea quark and gluon dynamics which dominate at small-$x$, and even the QCD odderon. In this talk I will discuss a general formalism for deriving the small-$x$ evolution of quark TMDs and the application of this formalism to the quark Sivers function. I will show that the leading small-$x$ behavior of the quark Sivers function is given by
\begin{align*}
f_{1 \: T}^{\perp \: q} (x, k_T^2) = C_O (x, k_T^2) \, \frac{1}{x} + C_1 (k_T^2) \, \left( \frac{1}{x} \right)^0 + \ldots
\end{align*}
where the dominant term which grows as $1/x$ comes from the spin-dependent odderon and the $x$-independent term from the sub-eikonal correction. These asymptotics may be testable at the future Electron-Ion Collider (EIC). The sub-eikonal ($C_1$) term may provide the background in searches for the spin-dependent odderon in transverse spin asymmetries.