ATLAS diboson excess could be an $R$-parity violating dismuon excess

We propose a new possible explanation of the ATLAS diboson excess: that it is due to heavy resonant slepton production, followed by decay into dismuons. The smuon has a mass not too far from the $W$ and $Z$ masses, and so it is easily confused with $W$ or $Z$ bosons after its subsequent decay into dijets, through a supersymmetry violating and $R$-parity violating interaction. Such a scenario is not currently excluded by other constraints and remains to be definitively tested in Run II of the LHC. Such light smuons can easily simultaneously explain the discrepancy between the measurement of the anomalous magnetic moment of the muon and the Standard Model prediction.

Figure 1

Slepton resonance mimicking the ATLAS diboson excess. The resonant charged slepton/sneutrino has a mass of around 1.9 TeV, and the smuons must be in the mass regime 80–105 GeV, such that they would be mistaken for $W$ or $Z$’s after their boosted hadronic decay.

Figure 2

95% C.L. exclusion region (red shaded) derived from LEP II data for dismuon production cross sections, followed by smuon decay into dijets, as a function of the smuon mass. For comparison, we also show the pair production cross sections for ${\tilde{\mu }}_L$ (blue solid), ${\tilde{\mu }}_R$ (green dashed) and ${\tilde{\nu }}_{\mu }$ (brown dotted) at $\sqrt{s}=209\mathrm{GeV}$.

Figure 3

Branching ratios of slepton decays to diquarks and dismuons through RPV couplings given by Eqs. (1) and (2), respectively.

Figure 4

The RPV parameter space favored by the ATLAS diboson excess in 8 TeV LHC data (blue shaded region). The 8 TeV exclusion regions from CMS dijet (solid orange) and diboson (green) as well as the 13 TeV exclusion from CMS dijet (dashed orange) searches are also shown. The magenta dashed vertical line shows the upper limit for the $j=1$ case on $|{\lambda }_{111}^{\prime }|$ due to null results from a recent $0\nu \beta \beta$ search, assuming the lightest neutralino mass of 1 TeV. The light red region in the top half of the plot is nonperturbative as estimated by Eq. (24), and the region outside of the solid brown line has a resonance width larger than 100 GeV. The horizontal pink dashed line is the suggestive upper bound for $|A_{j22}|$ obtained from Eq. (25) beyond which one might develop a charge-breaking minimum.