In the earliest stages of evaluating new collider data, especially if a small excess may be present, it would be useful to have a method for comparing the data with entire classes of models, to get ...an immediate sense of which classes could conceivably be relevant. In this paper, we propose a method that applies when the new physics invoked to explain the excess corresponds to the production and decay of a single, relatively narrow, \(s\)-channel resonance. A simplifed model of the resonance allows us to convert an estimated signal cross section into model-independent bounds on the product of the branching ratios corresponding to production and decay. This quickly reveals whether a given class of models could possibly produce a signal of the required size at the LHC. Our work sets up a general framework, outlines how it operates for resonances with different numbers of production and decay modes, and analyzes cases of current experimental interest, including resonances decaying to dibosons, diphotons, dileptons, or dijets. If the LHC experiments were to report their searches for new resonances beyond the standard model in the simplified limits variable \(\zeta\) defined in this paper, that would make it far easier to avoid blind alleys and home in on the most likely candidate models to explain any observed excesses.
The renormalizable coloron model, which has previously been shown in the literature to be consistent with a wide array of theoretical and precision electroweak constraints, includes a pair of ...spinless bosons (one scalar, one pseudoscalar). We show that either of them, or both together if they are degenerate, could be responsible for the diphoton resonance signal for which both CMS and ATLAS have seen evidence. Because either of these bosons would be produced and decay through loops of spectator fermions, the absence of signals in dijet, \(t\bar{t}\), and electroweak boson pair channels is not a surprise.
A narrow resonance decaying to dijets could be discovered at the 14 TeV run of the LHC. To quickly identify its color structure in a model-independent manner, we introduced a method based on a color ...discriminant variable, determined from the measurements of the resonance's production cross section, mass and width. This talk introduces a more transparent theoretical formulation of the color discriminant variable that highlights its relationship to the branching ratios of the resonance into incoming and outgoing partons and to the properties of those partons. The formulation makes it easier to predict the value of the variable for a given class of resonance. We show that this method applies well to color-triplet and color-sextet scalar diquarks, distinguishing them clearly from other candidate resonances.
The LHC is actively searching for narrow dijet resonances corresponding to physics beyond the Standard Model. Among the many resonances that have been postulated (e.g., colored vectors, scalars, and ...fermions) one that would have a particularly large production rate at the LHC would be a scalar diquark produced in the s-channel via fusion of two valence quarks. In previous work, we introduced a color discriminant variable that distinguishes among various dijet resonances, drawing on measurements of the dijet resonance mass, total decay width and production cross-section. Here, we show that this model-independent method applies well to color-triplet and color-sextet scalar diquarks, distinguishing them clearly from other candidate resonances. We also introduce a more transparent theoretical formulation of the color discriminant variable that highlights its relationship to the branching ratios of the resonance into incoming and outgoing partons and to the properties of those partons. While the original description of the color discriminant variable remains convenient for phenomenological use upon discovery of a new resonance, the new formulation makes it easier to predict the value of the variable for a given class of resonance.
While the recent discovery of a Higgs-like boson at the LHC is an extremely important and encouraging step towards the discovery of the {\it complete} standard model(SM), the current information on ...this state does not rule out possibility of beyond standard model (BSM) physics. In fact the current data can still accommodate reasonable values of the branching fractions of the Higgs into a channel with `invisible' decay products, such a channel being also well motivated theoretically. In this study we revisit the possibility of detecting the Higgs in this invisible channel for both choices of the LHC energies, 8 and 14 TeV, for two production channels; vector boson fusion(VBF) and associated production(\(ZH\)). In the latter case we consider decays of the \(Z\) boson into a pair of leptons as well as a \(b \bar b\) pair. For the VBF channel the sensitivity is found to be more than \(5 \sigma\) at both the energies up to an invisible branching ratio \({\cal B}r_{invis} \sim 0.80\), with luminosities \(\sim 20/30 {\rm fb}^{-1}\). The sensitivity is further extended to values of \({\cal B}r_{invis} \sim 0.25\) for \(300 {\rm fb}^{-1}\) at 14 TeV. However the reach is found to be more modest for the \(ZH\) mode with leptonic final state; with about \(3.5 \sigma\) for the planned luminosity at 8 TeV, reaching \(8 \sigma\) only for 14 TeV for \(50 {\rm fb}^{-1}\). In spite of the much larger branching ratio of the \(Z\) into a \(b \bar b\) channel compared to the dilepton case, the former channel, can provide useful reach upto \({\cal B}r_{invis} \gsim 0.75\), only for the higher luminosity (\(300{\rm fb}^{-1}\)) option using jet-substructure and jet clustering methods for \(b\)-jet identification.
We consider ZH and WH production at the Large Hadron Collider, where the Higgs decays to a bb pair. We use jet substructure techniques to reconstruct the Higgs boson and construct angular observables ...involving leptonic decay products of the vector bosons. These efficiently discriminate between the tensor structure of the HVV vertex expected in the Standard Model and that arising from possible new physics, as quantified by higher dimensional operators. This can then be used to examine the CP nature of the Higgs as well as CP mixing effects in the HZZ and HWW vertices separately.
We examine the `diboson' excess at \(\sim 2\) TeV seen by the LHC experiments in various channels. We provide a comparison of the excess significances as a function of the mass of the tentative ...resonance and give the signal cross sections needed to explain the excesses. We also present a survey of available theoretical explanations of the resonance, classified in three main approaches. Beyond that, we discuss methods to verify the anomaly, determining the major properties of the various surpluses and exploring how different models can be discriminated. Finally, we give a tabular summary of the numerous explanations, presenting their main phenomenological features.
