Impact of the Photon-Initiated process on Z'-boson searches in di-lepton final states at the LHC

TL;DR

This paper evaluates how photon-initiated processes influence Z'-boson searches in dilepton channels at the LHC, highlighting the importance of photon PDFs and their uncertainties for accurate signal interpretation.

Contribution

It provides a comparative analysis of photon PDF sets and quantifies their impact on Z'-boson search sensitivities, including the effects of PDF uncertainties.

Findings

Photon-initiated processes significantly affect Z'-boson search results.

Different photon PDF sets yield varying predictions for PI contributions.

Including PDF uncertainties alters the confidence in exclusion limits.

Abstract

We discuss the effect of the Photon Initiated (PI) process on the dilepton channel at the LHC. Adopting various QED PDF sets, we evaluate the contribution produced by two resolved photons which is not included in the Equivalent Photon Approximation (EPA). We compare the PI central value as predicted by the CTEQ, MRST and NNPDF collaborations. With the NNPDF2.3QED set of replicas we also estimate the PDF uncertainties on the PI central value. We show the effect of the inclusion of the PI contribution and its PDF uncertainties on neutral heavy Z'-boson searches. We explore the two scenarios of narrow and broad resonances, including in the analysis the reconstructed Forward-Backward Asymmetry observable, the latter being less affected by systematics effects.