Transverse Single Spin Asymmetry for Inclusive and Diffractive Electromagnetic Jets at Forward Rapidity in p↑+ p Collisions at √s = 200 GeV and 510 GeV at STAR

There have been numerous attempts, in the last decades, to unravel the origin of the unexpectedly significant transverse single-spin asymmetry (AN) observed in inclusive hadron productions at forward rapidities in transversely polarized p↑+p collisions across various center-of-mass energies (√s). The theoretical frameworks that explain this puzzle 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. Recent studies at STAR have also suggested that the prominent AN values may potentially arise from diffractive processes. We present detailed investigations into the AN for electromagnetic jets (EM-jets) produced in inclusive processes using the Forward Meson Spectrometer with transversely polarized p↑+ p data at √s = 200 GeV collected in 2015 at STAR. Additional studies are performed in order to isolate contributions from diffractive processes to the large inclusive AN. However, the negative and non-zero AN is observed for EM-jets in diffractive processes, which can not prove that the large AN in inclusive processes might come from diffractive processes. Finally, we present the statistical projections of the AN for inclusive and diffractive EM-jets utilizing p↑+ p data at √s = 510 GeV collected in 2017 at STAR. This dataset provides complementary measurements at a high value of √s with a substantial enhancement in statistical precision.