GPU-based Online Reconstruction for J/ψ TSSA at SpinQuest experiment*

The E1039/SpinQuest experiment at Fermilab will measure the transverse single spin asymmetry (TSSA) in several processes such as J/ψ production and Drell-Yan di-muon pair production, exploiting the 120 GeV unpolarized proton beam from the Fermilab Main Injector on transversely polarized fixed targets of NH₃ and ND₃.

Such measurements are anticipated to provide knowledge on the Sivers function from the proton sea quarks and gluons. The Sivers function represents the correlation between the transverse momentum of a quark/gluon and the spin of the parent nucleon and gives hints about the orbital angular momenta of quarks and gluons, which are suspected to contribute significantly to the nucleon spin and thus are essential to solving the “proton spin puzzle”.

In pursuit of these asymmetry measurements, we have developed an online reconstruction algorithm exploiting the high throughput and mass parallelization capabilities of graphics processing units (GPU), which combined with adequate visualization tools will provide real-time data monitoring for the SpinQuest experiment. This talk will highlight the SpinQuest experiment and the projected measurements, uncertainties and efficiency studies for the J/ψ TSSA from its

first production data. The performance metrics of the GPU-based online reconstruction algorithm will also be discussed, along with the features and methods employed to reach successful real-time data visualization.