Polarized Target Operation in Fermilab SpinQuest Experiment and J/ψ Transverse Single Spin Asymmetry Analysis*

The SpinQuest (E1039) experiment at Fermilab is designed to perform the first measurement of the Sivers asymmetry in Drell-Yan proton-proton scattering arising from the sea quarks, including determining its sign. A non-zero Sivers asymmetry would constitute ‘smoking gun’ evidence that the seaquark orbital angular momentum contributes to the spin of the proton. The experiment will explore the transverse single-spin asymmetry (TSSA), A_N, in J/ψ production involving a transversely polarized solid-state NH₃/ND₃ target and a 120 GeV unpolarized proton beam. The target polarization is achieved using Dynamic Nuclear Polarization (DNP) in a 5 T magnetic field, driven by a 140 GHz Extended Interaction Oscillator (EIO) microwave source and the target system include a ⁴He evaporation refrigerator operating at 1 K, a 17,000 m³/hr roots pump system, and a Q-meter–based NMR setup for continuous polarization monitoring. The system has achieved polarization levels exceeding 90% and has successfully completed commissioning and production runs. A classification technique was developed to identify signal dimuon events using neural networks. The asymmetry is being investigated in low- and high-mass dimuon regions, where contributions from ψ' and Drell-Yan processes are relevant. In this talk I will talk about the Dynamic Nuclear Polarization, offline Polarization and the current status of the TSSA analysis.