[Paper Review] LHC 750 GeV diphoton resonance explained as a heavy scalar in top-seesaw model

Archil Kobakhidze, Fei Wang+3 more|arXiv (Cornell University)|Dec 17, 2015

Particle physics theoretical and experimental studies64 citations

TL;DR

This paper proposes that the LHC 750 GeV diphoton resonance can be explained by a heavy scalar singlet in a top-seesaw model, where the resonance is produced via gluon fusion and decays to diphotons through loops of vector-like top/bottom partners. The model also enhances the total width via additional right-handed neutrinos and predicts strong correlations among $S \to \gamma\gamma$, $S \to Z\gamma$, and $S \to ZZ$ decays, offering testable signatures for future LHC runs.

ABSTRACT

In this letter, we explain the recent LHC-13 TeV diphoton resonance excess at $\sim 750$ GeV in a top-seesaw model, in which a heavy singlet scalar is produced in gluon fusion and decays into two photons through vector-like top/bottom partner loop. The total width of the resonance can be enhanced by introducing extra right-handed neutrino. We show that our model can accommodate the observed signal and is consistent with the current LHC data. Besides, our model predicts a strong correlation between $S o \gamma\gamma$, $S o Z \gamma$ and $S o ZZ$ decays. This behavior may help to test the diphoton excess in our model in future LHC experiments.

Motivation & Objective

• To explain the observed 750 GeV diphoton resonance excess at the LHC in the context of a top-seesaw model.
• To address the theoretical viability of the resonance by ensuring consistency with current LHC data.
• To explore mechanisms that enhance the total width of the resonance, particularly through the inclusion of right-handed neutrinos.
• To predict observable correlations between $S \to \gamma\gamma$, $S \to Z\gamma$, and $S \to ZZ$ decay modes for future experimental testing.

Proposed method

• Introduce a heavy singlet scalar field as a candidate for the 750 GeV resonance in a top-seesaw framework.
• Implement vector-like top and bottom partners that mediate the $S \to \gamma\gamma$ decay via loop diagrams.
• Use gluon fusion as the dominant production mode for the resonance at the LHC.
• Introduce additional right-handed neutrinos to enhance the total decay width of the scalar resonance.
• Calculate branching ratios and decay correlations among $S \to \gamma\gamma$, $S \to Z\gamma$, and $S \to ZZ$ using effective field theory techniques.
• Assess model consistency with existing LHC data on resonance production and decay rates.

Experimental results

Research questions

• RQ1 Can the 750 GeV diphoton resonance be consistently explained within a top-seesaw model with a heavy scalar singlet?
• RQ2 How do vector-like top and bottom partners contribute to the diphoton decay of the resonance?
• RQ3 What role do right-handed neutrinos play in enhancing the total width of the resonance to match experimental constraints?
• RQ4 Are there observable correlations between $S \to \gamma\gamma$, $S \to Z\gamma$, and $S \to ZZ$ decay modes in this model?
• RQ5 Can this model be tested in future LHC data through these predicted decay correlations?

Key findings

• The model successfully explains the observed 750 GeV diphoton resonance excess through a heavy scalar singlet produced in gluon fusion and decaying into two photons via loops of vector-like top and bottom partners.
• The inclusion of right-handed neutrinos significantly enhances the total width of the resonance, bringing it into alignment with experimental limits.
• The model predicts strong correlations between the decay rates of $S \to \gamma\gamma$, $S \to Z\gamma$, and $S \to ZZ$, which could serve as a distinctive signature for future LHC searches.
• The model remains consistent with current LHC data on resonance production and decay, supporting its viability as a phenomenological framework.
• The predicted decay correlations offer a clear, testable signal for confirming or ruling out the model in upcoming LHC runs.