Longitudinal Z-boson polarization and the Higgs boson production cross section at the Large Hadron Collider

S Amoroso,J Fiaschi,F Giuli,A Glazov,F Hautmann,O Zenaiev

doi:10.1016/j.physletb.2021.136613

Abstract

Charged lepton pairs are produced copiously in high-energy hadron collisions via electroweak gauge boson exchange, and are one of the most precisely measured final states in proton-proton collisions at the Large Hadron Collider (LHC). We propose that measurements of lepton angular distributions can be used to improve the accuracy of theoretical predictions for Higgs boson production cross sections at the LHC. To this end, we exploit the sensitivity of the lepton angular coefficient associated with the longitudinal Z-boson polarization to the parton density function (PDF) for gluons resolved from the incoming protons, in order to constrain the Higgs boson cross section from gluon fusion processes. By a detailed numerical analysis using the open-source platform xFitter, we find that high-statistics determinations of the longitudinally polarized angular coefficient at the LHC Run III and high-luminosity HL-LHC improve the PDF systematic uncertainties of the Higgs boson cross section predictions by 50% over a broad range of Higgs boson rapidities.

Highlights

Precision studies in the Higgs sector of the Standard Model (SM) are central to current [1] and forthcoming [2] physics programs at the Large Hadron Collider (LHC), and provide a portal to searches for beyond-Standard-Model (BSM) physics
Coupling αs, the theoretical systematic uncertainties affecting the predictions for gluon fusion processes receives essential contributions from the non-perturbative gluon parton density function
We have so far exploited the sensitivity of the longitudinal electroweak boson polarization to the gluon parton density function (PDF) and singled out A0 as a perturbatively stable observable, which can be built via diagonal elements of the polarization density matrix and is measurable via the lepton polar angle θ

Summary

Introduction

Precision studies in the Higgs sector of the Standard Model (SM) are central to current [1] and forthcoming [2] physics programs at the Large Hadron Collider (LHC), and provide a portal to searches for beyond-Standard-Model (BSM) physics. The DY cross section summed over the electroweak boson polarizations has the angular distribution 1 + cos2 θ and is sensitive to the gluon PDF for finite pT .

Results

Conclusion