Production of Z'-Boson Resonances with Large Width at the LHC

TL;DR

This paper investigates the production and detection of wide Z'-boson resonances at the LHC, employing advanced QCD resummation techniques to improve the modeling of signals with large widths.

Contribution

It introduces the use of NNLL QCD transverse momentum resummation with the reSolve program for studying wide Z' bosons, enhancing analysis methods beyond traditional narrow resonance searches.

Findings

Resonance shape and size are characterized at differential level.

QCD corrections are effectively modeled using resummation techniques.

Sensitivity estimates for Z' detection at LHC Run 3 and HL-LHC are provided.

Abstract

Di-lepton searches for Beyond the Standard Model (BSM) Z' bosons that rely on the analysis of the Breit-Wigner (BW) line shape are appropriate in the case of narrow resonances, but likely not sufficient in scenarios featuring Z' states with large widths. Conversely, alternative experimental strategies applicable to wide Z' resonances are much more dependent than the default bump search analyses on the modelling of QCD higher-order corrections to the production processes, for both signal and background. For heavy Z' boson searches in the di-lepton channel at the CERN Large Hadron Collider (LHC), the transverse momentum q_T of the di-lepton system peaks at q_T \ltap 10^{-2} M_{ll}, where M_{ll} is the di-lepton invariant mass. We exploit this to treat the QCD corrections by using the logarithmic resummation methods in M_{ll} / q_T to all orders in the strong coupling constant \alpha_s. We carry out studies of Z' states with large width at the LHC by employing the program {\tt reSolve}, which performs QCD transverse momentum resummation up to Next-to-Next-to-Leading Logarithmic (NNLL) accuracy. We consider two benchmark BSM scenarios, based on the Sequential Standard Model (SSM) and dubbed `SSM wide' and `SSM enhanced'. We present results for the shape and size of Z' boson signals at the differential level, mapped in both cross section (\sigma) and Forward-Backward Asymmetry (A_{\rm FB}), and perform numerical investigations of the experimental sensitivity at the LHC Run 3 and High-Luminosity LHC (HL-LHC).