Transverse Single Spin Asymmetry of Electromagnetic Jets for Inclusive and Single Diffractive Process at Forward Rapidity in p^{\uparrow}+p Collisions at \sqrt{s} = 200 GeV at STAR

There have been numerous attempts, in the last decades, to unravel the origin of the unexpectedly significant transverse single-spin asymmetry ($A_{N}$) observed in inclusive hadron productions at forward rapidities in transversely polarized $p^{\uparrow}$+$p$ collisions across various center-of-mass energies ($\sqrt{s}$). Theoretical frameworks proposed to explain this phenomenon include the twist-3 contributions in the collinear factorization framework, the transverse-momentum-dependent contributions from the initial-state quark and gluon Sivers functions, and/or final-state Collins fragmentation functions. Furthermore, recent studies at STAR hinted that such sizeable $A_{N}$ values may potentially arise from diffractive processes. We present a multi-dimensional investigation into the $A_{N}$ for electromagnetic jets (EM-jets) produced in inclusive processes using data collected with the Forward Meson Spectrometer in transversely polarized $p^{\uparrow}$ + $p$ collisions at $\sqrt{s} =$ 200 GeV at STAR in 2015. We also explore the photon-multiplicity-dependent EM-jet $A_{N}$ for single diffractive processes and rapidity gap events. The size of the EM-jet $A_{N}$ for inclusive processes, single diffractive process and the rapidity gap events are consistent within uncertainty. These results do not provide evidence to show the single diffractive process contributes to large $A_{N}$ in the inclusive processes.