The 750 GeV diphoton LHC excess and Extra Z's in Heterotic-String Derived Models

TL;DR

This paper explores how heterotic-string derived Z' models could explain recent 750 GeV diphoton and 1.9 TeV diboson excesses at the LHC, linking them to string-inspired new physics and dark matter candidates.

Contribution

It proposes a string-theoretic framework connecting LHC excesses with Z' bosons, scalar singlets, and dark matter, highlighting the role of Wilson line breaking and anomaly cancellation.

Findings

Heterotic-string models can produce Z' and scalar states explaining LHC excesses.

Extra vector-like states are crucial for the observed width of diphoton events.

Future experiments can distinguish high-scale from low-scale string models.

Abstract

The ATLAS and CMS collaborations recently recorded possible di-photon excess at 750 GeV and a less significant di-boson excess around 1.9 TeV. Such excesses may be produced in heterotic-string derived Z' models, where the di-photon excess may be connected with the Standard Model singlet scalar responsible for the Z' symmetry breaking, whereas the di-boson excess arises from production of the extra vector boson. Additional vector-like states in the string Z' model are instrumental to explain the relatively large width of the di-photon events and mandated by anomaly cancellation to be in the vicinity of the Z' breaking scale. Wilson line breaking of the non-Abelian gauge symmetries in the string models naturally gives rise to dark matter candidates. Future collider experiments will discriminate between the high-scale heterotic-string models, which preserve the perturbative unification paradigm indicated by the Standard Model data, versus the low scale string models. We also discuss the possibility for the production of the di-photon events with high scale $U(1)_{Z^\prime}$ breaking.