Abstract
A search for dark matter (DM) particles is performed using events with a Higgs boson candidate and large missing transverse momentum. The analysis is based on proton- proton collision data at a center-of-mass energy of 13 TeV collected by the CMS experiment at the LHC in 2016, corresponding to an integrated luminosity of 35.9 fb−1. The search is performed in five Higgs boson decay channels: mathrm{h}to mathrm{b}overline{mathrm{b}} , γγ, τ+τ−, W+W−, and ZZ. The results from the individual channels are combined to maximize the sensitivity of the analysis. No significant excess over the expected standard model background is observed in any of the five channels or in their combination. Limits are set on DM production in the context of two simplified models. The results are also interpreted in terms of a spin-independent DM-nucleon scattering cross section and compared to those from direct-detection DM experiments. This is the first search for DM particles produced in association with a Higgs boson decaying to a pair of W or Z bosons, and the first statistical combination based on five Higgs boson decay channels.
Highlights
Background estimationSince full kinematic reconstruction of the Higgs boson mass and pT is impossible in this decay channel because of the presence of undetected neutrinos and dark matter (DM) particles, to maximize the sensitivity of the search, a boosted decision tree (BDT) multivariate classifier has been trained for each of the two signal models
The results are interpreted in terms of a spin-independent DM-nucleon scattering cross section and compared to those from directdetection DM experiments. This is the first search for DM particles produced in association with a Higgs boson decaying to a pair of W or Z bosons, and the first statistical combination based on five Higgs boson decay channels
For the Z 2HDM, the signal is normalized to the cross section calculated for mass values of Z and A bosons of 1200 and 300 GeV, respectively, and for g = 0.8, tan β = 1
Summary
The central feature of the CMS apparatus is a superconducting solenoid of 6 m internal diameter, providing a magnetic field of 3.8 T. 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. (η) coverage provided by the barrel and endcap detectors. Events of interest are selected using a two-tiered trigger system [43]. 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 in a time 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 around 1 kHz before data storage. The integrated luminosity of the data sample used in all the analyses described in this paper corresponds to 35.9 fb−1, after imposing data quality requirements
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