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.
Highlights
We were able to construct a heteroticstring model in which the desired symmetry is anomaly free [24]
Plausible candidates include the SO(10) neutral singlet in the 27 of E6, and E6 singlets that arise in the string models, with the production and decay being produced via one-loop couplings to heavy vector-like matter states
The Z model under consideration here was obtained in the class of Pati–Salam heterotic-string models, which are generated by a set of 13 boundary condition basis vectors B = {v1, v2, . . . , v13}
Summary
We were able to construct a heteroticstring model in which the desired symmetry is anomaly free [24]. Plausible candidates include the SO(10) neutral singlet in the 27 of E6, and E6 singlets that arise in the string models, with the production and decay being produced via one-loop couplings to heavy vector-like matter states Such vector-like matter states are precisely those required from anomaly cancellation of the extra Z gauge symmetry. Heterotic-string models give rise to states that do not satisfy the E6 quantisation of the Z charges Such states arise in string models due to the breaking of the E6 symmetry by Wilson lines and can produce viable dark matter candidates. This would be the case if the Z symmetry is broken by a state that carries standard E6 charge. If their exotic Z charges can be determined experimentally, they provide a distinct signatures of the heterotic-string models that utilise discrete Wilson lines to break the E6 symmetry
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