Abstract
A search for a narrow, high-mass resonance decaying into Z and Higgs (H) bosons is presented. The final state studied consists of a merged jet pair and a τ pair resulting from the decays of Z and H bosons, respectively. The analysis is based on a data sample of proton–proton collisions at a center-of-mass energy of 8 TeV, collected with the CMS experiment in 2012, and corresponding to an integrated luminosity of 19.7 fb−1. In the resonance mass range of interest, which extends from 0.8 to 2.5 TeV, the Z and H bosons are produced with large momenta, which implies that the final products of the two quarks or the two τ leptons must be detected within a small angular interval. From a combination of all possible decay modes of the τ leptons, production cross sections in a range between 0.9 and 27.8 fb are excluded at 95% confidence level, depending on the resonance mass.
Highlights
Very recently, the validity of the standard model (SM) of particle physics has been confirmed by the discovery of a Higgs boson with mass near 125 GeV by the ATLAS and CMS experiments [1,2]
The nuisance parameters are described with log-normal prior probability distribution functions, except for those related to the extrapolation from sideband events, which are expected to follow a distribution [61]
In the all-leptonic and semileptonic channels, the numbers of signal and background events are calculated for a region corresponding to ±2.5 times the expected resolution around each mass point in mZH, while in the all-hadronic channel we consider the number of expected background, signal and observed events in mZH > 800 GeV for each mass point
Summary
The validity of the standard model (SM) of particle physics has been confirmed by the discovery of a Higgs boson with mass near 125 GeV by the ATLAS and CMS experiments [1,2]. In this model a heavy SU(2)L vector triplet (HVT) containing neutral (Z ) and charged (W ,±) spin-1 states is introduced This scenario is well-motivated in cases where the new physics sector is either weakly coupled [26], or strongly coupled, e.g., in the minimal composite model [27]. In the high-mass case under study, the directions of the particles stemming from Z and H boson decays are separated by a small angle This feature is referred to as the “boosted” regime. The experimental strategy is to reconstruct and identify the two bosons and to combine their information into a variable that can discriminate between signal and background and on which a statistical study can be performed This variable is the estimated mass of the Z after applying dedicated reconstruction techniques to the boosted qq and τ τ pairs (mZH). The mZH distribution would show an excess of events at the assumed Z mass if a signal were present
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