https://doi.org/10.1140/epjc/s10052-016-4404-2
Regular Article - Theoretical Physics
LHC di-photon excess and gauge coupling unification in extra 
heterotic-string derived models
1
Department of Mathematical Sciences, University of Liverpool, Liverpool, L69 7ZL, UK
2
School of Physics and Astronomy, University of Southampton, Southampton, SO17 1BJ, UK
3
Department of Particle Physics, Rutherford Appleton Laboratory, Chilton, Didcot, OX11 0QX, UK
4
Dipartimento di Matematica e Fisica “Ennio De Giorgi”, Università del Salento and INFN-Lecce, Via Arnesano, 73100, Lecce, Italy
* e-mail: alon.faraggi@liv.ac.uk
Received:
15
June
2016
Accepted:
26
September
2016
Published online:
22
October
2016
A di-photon excess at the LHC can be explained as a Standard Model singlet that is produced and decays by heavy vector-like colour triplets and electroweak doublets in one-loop diagrams. The characteristics of the required spectrum are well motivated in heterotic-string constructions that allow for a light . Anomaly cancellation of the 
symmetry requires the existence of the Standard Model singlet and vector-like states in the vicinity of the breaking scale. In this paper we show that the agreement with the gauge coupling data at one-loop is identical to the case of the Minimal Supersymmetric Standard Model, owing to cancellations between the additional states. We further show that effects arising from heavy thresholds may push the supersymmetric spectrum beyond the reach of the LHC, while maintaining the agreement with the gauge coupling data. We show that the string-inspired model can indeed produce an observable signal and discuss the feasibility of obtaining viable scalar mass spectrum.
© The Author(s), 2016
