# DIS 2015 - XXIII. International Workshop on Deep-Inelastic Scattering and Related Subjects

27 April 2015 to 1 May 2015
US/Central timezone

## Measurement of transverse single-spin asymmetry and cross-section ratios of kinematically fully reconstructed weak bosons in p+p collisions at $\sqrt{s}=500-510$~GeV at RHIC

28 Apr 2015, 16:40
25m
BALLROOM EAST ()

### BALLROOM EAST

WG1 Structure Functions and Parton Densities

### Speaker

Dr Salvatore Fazio (Brookhaven National Laboratory)

### Description

We present the status and preliminary results on the analysis of kinematically fully reconstructed weak bosons at the STAR experiment. The transverse single spin asymmetry ($A_{N}$) has been measured in transversely polarized proton-proton collisions at $\sqrt{s} = 500$~GeV, with a recorded integrated luminosity of $25~\text{pb}^{-1}$. 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) distributions 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 evolution of parton distributions. The $W^{+}/W^{-}$ cross section ratio has been measured in unpolarized proton-proton collisions at $\sqrt{s} = 500-510$~GeV, with a recorded integrated luminosity of $110~\text{pb}^{-1}$. The observable is sensitive to the flavor asymmetry in sea anti-quarks for Bjorken-$x > 0.1$ accessible at RHIC, 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. In addition, the future opportunities for a precise measurement of $A_{N}$ in weak boson production at STAR will be discussed as well as other observables sensitive to the non universality of the Sivers function, i.e. direct photon $A_N$.

### Primary author

Dr Salvatore Fazio (Brookhaven National Laboratory)

 Slides