Search for WZ resonances in the fully leptonic channel using pp collisions ats=8TeVwith the ATLAS detector

Abstract

Search for WZ resonances in the fully leptonic channel using pp collisions at √ s = 8 TeV with the ATLAS detector .ATLAS Collaboration a r t i c l e i n f o a b s t r a c t A search for resonant WZ production in the ν ( , = e, μ) decay channel using 20.3 fb −1 of √ s = 8 TeV pp collision data collected by the ATLAS experiment at LHC is presented. No significant deviation from the Standard Model prediction is observed and upper limits on the production cross sections of WZ resonances from an extended gauge model W and from a simplified model of heavy vector triplets are derived. A corresponding observed (expected) lower mass limit of 1.52 (1.49) TeV is derived for the W at the 95% confidence level.

Interference effect on resonance studies in searches of heavy particles

“…1(a) of [74], where the branching fractions of W/Z decays have been taken into consideration. The background simulations follow Refs [23,[76][77][78][79], for which we implement only the basic event selection cuts. It should be aware that in the high mass region all these channels might suffer from large systematic and/or statistical uncertainties, depending on the future high en- ergy data.…”

“…We reduce the rescaled JJ background in the hadronic channel from the 8 TeV data by a factor of two, assuming for more events at LHC Run II more jet techniques are used and a more aggressive cut is made. For simplicity we implement only the simple cuts as did in [76] and [23]. The quark jet smearing is performed as stated above, while for the charged leptons we assume naïvely the energy uncertainty ∆E/E 1% [80].…”

Angular observables for spin discrimination in boosted diboson final states

“…The ATLAS 13 TeV analysis [10] uses energy correlation functions [112][113][114] to characterize the number of hard subjets in their set of trimmed jets. The relevant 1-point, 2-point and 3-point energy correlation functions are 12) where the sums are performed over jet constituents and β is a parameter weighting the angular separations of constituents against their p T fractions. Since the sums are performed over jet constituents, the energy correlation functions are independent of any jet algorithm.…”

“…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].…”

Scalar Hint from the Diboson Excess?

“…In the semi-leptonic decay channel of the diboson resonances, however, there seems no excess [3,4]. Also, in the fully leptonic decay channel of the W Z resonance, no significant deviation from the Standard Model (SM) prediction is observed [5,6]. Even if the excesses in the fully hadronic decay channels are not just a fluctuation, there is a possibility that a new resonance around 2 TeV contributes to some of the channels, while others are populated by misidentification of the boson-tagged jet: for instance, one may have a neutral resonance that only couples to the W W and ZZ channels, so that the excess in the other W Z channel is just a contamination owing to uncertainties of the tagging selections.…”