Search for resonant diboson production in the $$\mathrm {\ell \ell }q\bar{q}$$ ℓ ℓ q q ¯ final state in $$pp$$ p p collisions at $$\sqrt{s} = 8$$ s = 8  TeV with the ATLAS detector

Abstract

This paper reports on a search for narrow resonances in diboson production in the final state using collision data corresponding to an integrated luminosity of fb collected at TeV with the ATLAS detector at the Large Hadron Collider. No significant excess of data events over the Standard Model expectation is observed. Upper limits at the 95 % confidence level are set on the production cross section times branching ratio for Kaluza–Klein gravitons predicted by the Randall–Sundrum model and for Extended Gauge Model bosons. These results lead to the exclusion of mass values below 740 and 1590 GeV for the graviton and boson respectively.

Angular observables for spin discrimination in boosted diboson final states

“…In addition, for the νqq analysis, the cos θ l distribution is asymmetric because the charge of the lepton distinguishes leptons from the anti-lepton, in constrast to the 4q case. We begin again by summarizing the semi-leptonic analyses by ATLAS and CMS [11,13,14,17,19,20] and then present the corresponding angular distributions.…”

“…In addition, all leptons must pass a track isolation (calorimeter isolation) requirement (see ref. [13] for details). The lepton pair must have 66 GeV< m < 116 GeV and p T > 400 GeV.…”

“…Observing the excess in these decays is also critical, though, because the exclusive rates for the semi-leptonic and fully leptonic modes will help diagnose the underlying W + W − vs. W ± Z vs. ZZ nature of the purported resonance, which is difficult to disentangle using only hadronic diboson decays. Currently, ATLAS has searches for electroweak diboson resonances with 8 TeV data in the ν channel [12], jj channel [13], and the νjj channel [14], which have been combined with the fully hadronic search in ref. [15].…”

“…CMS and ATLAS also search in the νjj channel [11,19], respectively, and ATLAS also has performed analyses in the jj channel [20] as well as the ννjj channel [21]. Although the integrated luminosity at 13 TeV is only 3.2 fb −1 for ATLAS and 2.6 fb −1 for CMS, in comparison to the 20 fb −1 datasets for each experiment at 8 TeV, naive parton luminosity rescaling from 8 TeV to 13 TeV for the simplest new physics explanations of the 2 TeV excess point to ATLAS and CMS being at the edge of NP exclusion sensitivity (see figure 8 of [10], figure 4 of [19], figure 4 of [21], and figures 9 and 10 of [11]). …”

Search for ZZ resonances in the 2ℓ2ν final state in proton-proton collisions at 13 TeV

“…For values ofk < 1, the width of the KK bulk graviton relative to its mass is less than ≈6% for m G as large as 2 TeV, and therefore a narrow resonance is expected. Previous direct searches at ATLAS and CMS have set limits on the cross section for the production of G bulk as a function of m G [22][23][24][25][26][27] using LHC data taken at center-of-mass energies of 7, 8, and 13 TeV.…”