Forward-backward asymmetry as a discovery tool for Z' bosons at the LHC

Abstract

The Forward-Backward Asymmetry (AFB) in Z? physics is commonly only perceived as the observable which possibly allows one to interpret a Z? signal appearing in the Drell-Yan channel by distinguishing different models of such (heavy) spin-1 bosons. In this paper, we revisit this issue, showing that the absence of any di-lepton rapidity cut, which is commonly used in the literature, can enhance the potential of the observable at the LHC. We moreover examine the ability of AFB in setting bounds on or even discovering a Z? at the Large Hadron Collider (LHC) concluding that it may be a powerful tool for this purpose. We analyse two different scenarios: Z?-bosons with a narrow and wide width, respectively. We find that, in the first case, the significance of the AFB search can be comparable with that of the ‘bump’ search usually adopted by the experimental collaborations; however, in being a ratio of (differential) cross sections, the AFB has the advantage of reducing experimental systematics as well as theoretical errors due to PDF uncertainties. In the second case, the AFB search can outperform the bump search in terms of differential shape, meaning the AFB distribution may be better suited for new broad resonances than the event counting strategy usually adopted in such cases.

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Identifiers

ORCID for Alexander Belyaev: orcid.org/0000-0002-1733-4408

ORCID for Stefano Moretti: orcid.org/0000-0002-8601-7246

ORCID for Alexander Belyaev: orcid.org/0000-0002-1733-4408

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