Preliminary insights from SpinQuest studies using the polarized target

SpinQuest is a high-luminosity Drell-Yan experiment utilizing transversely polarized ammonia (NH$_3$) and deuterated ammonia (ND$_3$) targets to measure the Sivers function for light sea quarks in nucleons. A non-vanishing sea quark Sivers function is evidence of their orbital angular momentum. The experiment also intends to measure transverse single-spin asymmetries (TSSA) in the production of $J/\psi$ particles, which are sensitive to the gluon Sivers function. Such studies are possible because of a polarized target with a 5~T split-pair magnet, a high-power 140~GHz microwave system and a high-power $^4$He evaporation refrigerator. The refrigerator, with a 17,000~liter/hr roots stack, has a cooling power of 5~W at 1~K.

With this setup, the expected average target polarization of about 80\% (32\%) for NH$_3$ (ND$_3$) will be achieved based on the dynamic nuclear polarization technique. In this talk, I will present the current status of the polarized target system, as well as dedicated efforts to benchmark the $J/\psi$ TSSA from the first SpinQuest data-taking period.