Search

The forward-backward charge asymmetry (AFB) at hadron colliders is sensitive to both the electroweak (EW) symmetry breaking represented by the effective weak mixing angle sin2θeffℓ, and the proton structure information in the initial state modeled by the parton distribution functions (PDFs). Due to their strong correlation, the precisions of determination on sin2θeffℓ and PDFs using the measured AFB spectrum are limited. In this paper, we define a set of structure parameters which factorize the unique proton information of the relative difference between quarks and antiquarks in the AFB observation. Other than the conventional way of extracting sin2θeffℓ from the convolution of PDF and EW calculations, we propose a new method to simultaneously determine the value of sin2θeffℓ and the proton structure terms by fitting to the observed AFB distribution, and point out the necessity of specifying additional observations to further reduce the uncertainties on the proton structure terms, respectively, so that model-independent high precision sin2θeffℓ and proton structure measurements can be achieved at the future LHC experiments.

In an earlier publication, we introduced the software package, {\tt \texttt{ePump}} (error PDF Updating Method Package), that can be used to update or optimize a set of parton distribution functions (PDFs), including the best-fit PDF set and Hessian eigenvector pairs of PDF sets (i.e., error PDFs), and to update any other set of observables, in the Hessian approach. Here, we validate the {\tt \texttt{ePump}} program with a detailed comparison against a full global analysis, and we demonstrate the potential of {\tt \texttt{ePump}} by presenting selected phenomenological applications relevant to the Large Hadron Collider. For example, we use the package to estimate the impact of the recent LHC data of the measurements of $W$, $Z$ boson and top quark pair differential distributions on the CT14HERA2 PDFs.

Uncertainties in the parametrization of parton distribution functions (PDFs) are becoming a serious limiting systematic uncertainty in Large Hadron Collider (LHC) searches for beyond the standard model physics. This is especially true for measurements at high scales induced by quark and anti-quark collisions, where Drell-Yan continuum backgrounds are dominant. Tools are recently available which enable exploration of PDF fitting strategies and emulate the effects of new data in a future global fit. ePump is such a tool and it is shown that judicious selection of measurable kinematical quantities can reduce the assigned systematic PDF uncertainties by significant factors. This will be made possible by the huge statistical precision of future LHC standard model datasets.