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Register a new userA model for the LHC diboson excess
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The first run of the LHC showed hints of a new resonance with mass near $1.9$ TeV decaying into electroweak gauge boson pairs as well as into dijets. While Run 2 has neither confirmed nor ruled out such a resonance, it has yielded new constraints on models attempting to explain these decays. Additionally in $W$ models where this new resonance is a charged vector boson that is a weak isospin singlet there is the potential for conflict with the electroweak precision $T$ parameter. We construct variants of a $W$ resonance model that provide an excellent fit to both Run 1 and Run 2 data, as well as electroweak precision measurements. The model also predicts a neutral vector boson, a $Z$, with mass close to $3$ TeV. This $Z$ is compatible with the intriguing Run 2 observation of a dielectron pair with invariant mass of $2.9$ TeV at CMS.
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The ATLAS collaboration has recently reported a 2.6 sigma excess in the search for a heavy resonance decaying into a pair of weak gauge bosons. Only fully hadronic final states are being looked for in the analysis. If the observed excess really originates from the gauge bosons decays, other decay modes of the gauge bosons would inevitably leave a trace on other exotic searches. In this paper, we propose the use of the Z boson decay into a pair of neutrinos to test the excess. This decay leads to a very large missing energy and can be probed with conventional dark matter searches at the LHC. We discuss the current constraints from the dark matter searches and the prospects. We find that optimizing these searches may give a very robust probe of the resonance, even with the currently available data of the 8 TeV LHC.
We use the current CMS and ATLAS data for the leptonic $pp to WW, WZ$ channels to show that diboson production is, for a broad class of flavour models, already competitive with LEP-1 measurements for setting bounds on the dimension six operators parametrising the anomalous couplings between the quarks and the electroweak gauge bosons, at least under the assumption that any new particle is heavier than a few TeV. We also make an estimate of the HL-LHC reach with $3$ ab$^{-1}$. We comment on possible BSM interpretations of the bounds, and show the interplay with other searches for a simplified model with vector triplets. We further study the effect of modified $Z$-quark-quark couplings on the anomalous triple gauge coupling bounds. We find that their impact is already significant and that it could modify the constraints on $delta g_{1z}$ and $delta kappa_gamma$ by as much as a factor two at the end of HL-LHC ($lambda_gamma$ is only marginally affected), requiring a global fit to extract robust bounds. We stress the role of flavour assumptions and study explicitly flavour universal and minimal flavour violation scenarios, illustrating the differences with results obtained for universal theories.
We provide an interpretation of the recent ATLAS diboson excess in terms of a class of supersymmetric models in which the scale of supersymmetry (SUSY) breaking is in the few TeV range. The particle responsible for the excess is the scalar superpartner of the Goldstone fermion associated with SUSY breaking, the sgoldstino. This scalar couples strongly to the Standard Model vector bosons and weakly to the fermions, with all coupling strengths determined by ratios of soft SUSY breaking parameters over the SUSY breaking scale. Explaining the ATLAS excess selects particular relations and ranges for the gaugino masses, while imposing no constraints on the other superpartner masses. Moreover, this signal hypothesis predicts a rate in the $Zgamma$ final state that is expected to be observable at the LHC Run II already with a few fb$^{-1}$ of integrated luminosity.
We propose novel collider searches which can significantly improve the LHC reach to new gauge bosons $Z$ with mixed anomalies with the electroweak (EW) gauge group. Such a $Z$ necessarily acquires a Chern-Simons coupling to the EW gauge bosons and these couplings can drive both exotic $Z$ decays into $Zgamma$ if the new gauge boson is sufficiently light, as well as $Z$ decays into EW gauge bosons.While the exotic decay rate of the heavy $Z$ into $Zgamma$ is too small to be observed at the LHC, for a light $Z$, we show the potential of a lepton jet search in association with a photon to probe the rare decay $Z to Z gamma$.
We investigate a possibility for explaining the recently announced 750,GeV diphoton excess by the ATLAS and the CMS experiments at the CERN LHC in a model with multiple doubly charged particles, which was originally suggested for explaining tiny neutrino masses through a three-loop effect in a natural way. The enhanced radiatively generated effective coupling of a new singlet scalar $S$ with diphoton with multiple charged particles in the loop enlarges the production rate of $S$ in $ppto S+X$ via photon fusion process and also the decay width $Gamma(Sto gammagamma)$ even without assuming a tree level production mechanism. We provide detailed analysis on the cases with or without allowing the mixing between $S$ and the standard model Higgs doublet.
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