Reconstructed Weak Bosons in p - p Collisions at 3 √ s = 500 − 510 GeV at RHIC

We present the status and preliminary results of the analysis of kinematically fully reconstructed weak bosons at the STAR experiment. The transverse single-spin asymmetry (AN) has been measured in transversely polarized proton-proton collisions at √ s = 500 GeV, with a recorded integrated luminosity of 25 pb−1. The measured observable is sensitive to the non-universality of the Sivers function, a fundamental prediction from the gauge invariance of QCD, and can provide a direct verification of transverse momentum dependent (TMD) distribution factorization. Furthermore, it provides an ideal tool to study the spin-flavor structure of valence and sea quarks inside the proton and to test the TMD evolution. The W+/W− cross section ratio has been measured in unpolarized proton-proton collisions at √ s = 500 and 510 GeV, with a recorded integrated luminosity of 110 pb−1. The observable is sensitive to the flavor asymmetry of sea quarks, providing an independent constraint on the large flavor asymmetry observed in Drell-Yan experiments, without the assumption of charge symmetry required in fitting the Drell-Yan data.