Abstract
A search for heavy resonances decaying to a pair of Z bosons is performed using data collected with the CMS detector at the LHC. Events are selected by requiring two oppositely charged leptons (electrons or muons), consistent with the decay of a Z boson, and large missing transverse momentum, which is interpreted as arising from the decay of a second Z boson to two neutrinos. The analysis uses data from proton-proton collisions at a center-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 35.9 fb−1. The hypothesis of a spin-2 bulk graviton (X) decaying to a pair of Z bosons is examined for 600 ≤ mX ≤ 2500 GeV and upper limits at 95% confidence level are set on the product of the production cross section and branching fraction of X → ZZ ranging from 100 to 4 fb. For bulk graviton models characterized by a curvature scale parameter tilde{k}=0.5 in the extra dimension, the region mX< 800 GeV is excluded, providing the most stringent limit reported to date. Variations of the model considering the possibility of a wide resonance produced exclusively via gluon-gluon fusion or mathrm{q}overline{mathrm{q}} annihilation are also examined.
Highlights
The CMS detectorThe central feature of the CMS detector is a 3.8 T superconducting solenoid with a 6 m internal diameter
With a single compactified extra dimension and a modification to the space-time metric by an exponential “warp” factor
The hypothesis of a spin-2 bulk graviton (X) decaying to a pair of Z bosons is examined for 600 ≤ mX ≤ 2500 GeV and upper limits at 95% confidence level are set on the product of the production cross section and branching fraction of X → ZZ ranging from 100 to 4 fb
Summary
The central feature of the CMS detector is a 3.8 T superconducting solenoid with a 6 m internal diameter. Within the solenoid volume are a silicon pixel and strip tracker, a lead tungstate crystal electromagnetic calorimeter (ECAL), and a brass and scintillator hadron calorimeter (HCAL), each composed of a barrel and two endcap sections. Events of interest are selected using a two-tiered trigger system [28]. The first level, composed of custom hardware processors, uses information from the calorimeters and muon detectors to select events at a rate of around 100 kHz within a time interval of less than 4 μs. The second level, known as the high-level trigger, consists of a farm of processors running a version of the full event reconstruction software optimized for fast processing, and reduces the event rate to less than 1 kHz before data storage. A detailed description of the CMS detector, together with a definition of the coordinate system used and the relevant kinematic variables, can be found in ref. [29]
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