Implementation of Beyond the Standard Model Z ′ models using reweighting tools applied on PowHeg and Sherpa

The Standard Model (SM) has been successful in describing the particles and interactions that we know of today with great precision. We know however that it is not the ultimate theory since it does not, for example, describe gravity nor accommodate dark matter. Among the various beyond Standard Model (BSM) theories, we concentrate on extensions which predict one or several neutral massive spin-1 gauge bosons, Z′. Monte Carlo simulations are important for making predictions and interpreting measurements based on data from the ATLAS detector at the LHC. A method called signal reweighting is used to produce a Z′ signal from an existing Drell-Yan simulation, thus avoiding simulating a large number of Z′ events based on various models depending on many parameters. The signal reweighting method is extended to use the next-to-leading order PowhegPythia8 Drell-Yan sample. We obtain promising results when comparing the signal reweighted Z′ sample to a fully simulated Pythia8 Z′ sample in Run 2 at √s = 13 TeV with 58.5 fb^{−1} of data. The signal reweighted Z′ samples are also used in Run 3 on top of data and SM backgrounds at √s = 13.6 TeV corresponding to 26.1 fb^{1} of data collected by ATLAS in 2022. An attempt to apply signal reweighting to a Sherpa Z + jets sample is also performed but the information from the event generator is found to be insuffcient.