Abstract
Precision determinations of Standard Model (SM) Electro-Weak (EW) parameters at the Large Hadron Collider (LHC) are dominated by uncertainties due to Parton Distribution Functions (PDFs). Reweighting and profiling techniques are routinely employed to treat this. We explore approaches based on combining measurements of charged current and neutral current Drell-Yan (DY) asymmetries to improve PDF uncertainties. We present the results of a numerical analysis performed with the open-source platform xFitter. PDF uncertainties are examined for lepton-charge and forward-backward asymmetries in regions of transverse and invariant masses near the vector-boson peak, based on LHC Run III and HL-LHC luminosity scenarios. We discuss the complementarity of the asymmetries in reducing PDF uncertainties in observables relevant to both SM and Beyond the SM (BSM) physics.
Highlights
The Large Hadron Collider (LHC), having completed its Runs I and II, has recently provided determinations of the weak mixing angle θW [1,2,3] and W boson mass mW [4,5] which are competitive in accuracy with previous determinations from lepton colliders [6] and Tevatron [7,8]
We introduce the enhanced Sequential Standard Model (SM) (SSM) model as in Ref. [48], which follows the original SSM [49] and features in its spectrum an extra Z and a W characterised by the same chiral couplings as the SM gauge bosons, but in this case the overall Beyond the SM (BSM) gauge coupling is enhanced by a factor 3 with respect to the SM one
We have explored the potential of approaches using the combination of asymmetry measurements in the neutral-current and charged-current DY channels to improve our knowledge of Parton Distribution Functions (PDFs) and reduce the corresponding uncertainties
Summary
The LHC, having completed its Runs I and II, has recently provided determinations of the weak mixing angle θW [1,2,3] and W boson mass mW [4,5] which are competitive in accuracy with previous determinations from lepton colliders [6] and Tevatron [7,8]. In the framework of QCD collinear hard-scattering factorisation for inclusive pp production processes [13], such contributions are embodied in quark and gluon PDFs. The successful completion of the precision EW physics programme at the LHC and HL-LHC calls for careful scrutiny of the PDFs, including understanding their correlations with the measured EW parameters, the associated uncertainties as well as looking for methods to improve the latter. Using xFitter, we analyze the separate and combined impact of high-statistics AFB and AW asymmetry measurements in the mass region near the vector boson pole on PDF uncertainties. The differences with respect to the AW central value curve (μF and μR unchanged) are at the permille level, confirming the reliability of the calculations with respect to this systematic uncertainty
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