Jet Charge: A Flavor Prism for Spin Asymmetries at the Electron-Ion Collider

Abstract

We propose the jet charge observable as a novel probe of flavor structure in the nucleon spin program at the Electron Ion Collider (EIC). We show that jet charge measurements can substantially enhance the sensitivity of spin asymmetries to different partonic flavors in the nucleon. This sensitivity can be further improved by constructing the jet charge using only a subset of hadron species (pions or kaons) in the jet. As an example, we use the Sivers asymmetry in back-to-back electron-jet production at the EIC to show that the jet charge can be a unique tool in constraining the Sivers function for different partonic flavors.

The Sivers asymmetry in hadronic dijet production

“…In order to achieve jet flavor separation mentioned above, one possible method is applying the electric charge information of jets, which has been proposed in [50,58,120]. In this paper, we will use the standard jet electric charge definition given in [121,122]…”

“…where z h is the transverse momentum ratio between hadrons and the jet. κ is an input parameter, which is fixed by κ = 0.3 [58] in our calculations. As shown in [58], after measuring the jet charge information, the theory formula is slightly modified by replacing the jet function J i (P ⊥ R, µ) in eq.…”

“…The index i denotes the parton species initiating the more forward jet. Here we use the same jet charge bins defined in [58], where +, − and 0 indicate Q κ > 0.25, Q κ < −0.25 and |Q κ | < 0.25 bins, separately. Such jet charge bin fraction can be fitted from the unpolarized cross section for back-toback dijet events at the RHIC.…”

“…Theoretically, there have been efforts in performing QCD resummation in back-to-back dijet [53,54] and vector boson-jet production [55][56][57]. At the same time, a theoretical framework has been developed to study spin asymmetries in specific jet charge JHEP02(2021)066 bin [58], which would facilitate the analysis of the dijet spin asymmetries by the STAR collaboration. In light of all these activities, we set out to develop a resummation formalism for studying the Sivers asymmetry in back-to-back dijet production in transversely polarized proton-proton collisions.…”

Angularity in DIS at next-to-next-to-leading log accuracy

“…They were also extensively studied in DIS [28]. Improved theoretical predictions [29,30] and new predictions [31][32][33][34] for event shapes that JHEP11(2021)026…”