Large transverse single-spin asymmetries (TSSAs) in inclusive hadron production at forward ra-
pidities have persisted as a major puzzle in QCD spin physics. To further explore the origin of these
asymmetries, we measure the analyzing power 𝐴 𝑁 of electromagnetic (EM) jets reconstructed
from photons detected by the Forward Meson Spectrometer (FMS) at STAR. Using data from
√
transversely polarized $𝑝^{\uparrow}$ + 𝑝 collisions collected at 𝑠 = 200 GeV in 2015 and 510 GeV in 2017,
we study the dependence of 𝐴 𝑁 on kinematic variables, photon multiplicity, and event topology
to probe possible diffractive contributions. We find that 𝐴 𝑁 increases with 𝑥 𝐹 , decreases with
√
photon multiplicity, shows little dependence on 𝑠, and is similar across inclusive and diffractive-
enriched samples, indicating that diffractive processes are not the dominant source of the large
observed asymmetries.