Würzburg 2018 – wissenschaftliches Programm
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T: Fachverband Teilchenphysik
T 74: Higgs: Erweiterte Modelle II / Suchen
T 74.2: Vortrag
Donnerstag, 22. März 2018, 16:45–17:00, Philo-HS2
Monte Carlo studies on the estimation of ZZ → ℓℓνν background using Zγ → ℓℓγ events — •Mangesh Sonawane1, Beate Heinemann2, Pieter Everaerts2, Sarah Heim2, and Jorge Sabater Iglesias2 — 1IISER Pune, Indien — 2DESY Hamburg, Deutschland
In the search for Dark Matter (DM) at the LHC, SM particles are produced in association with DM particles, which are invisible as they don*t interact with the detector. Thus, events with large imbalance in transverse momentum are of interest. One such signature is ℓℓ +ETmiss.
The dominant background contributing to the search for DM in the ℓℓ +ETmisschannel is ZZ → ℓℓνν. Currently, this background is determined using Monte Carlo simulation, with an uncertainty of about 10%. The goal of this study is to establish a data driven method to estimate this background, and reduce the uncertainty. Using Zγ → ℓℓγ, a process with low backgrounds and a high BR×σ, it is possible to estimate the ZZ → ℓℓνν contribution. In regions where pT(γ) ≫ MZ, the two processes are kinematically similar. They have the same production mechanisms, but differ due to the photon and Z boson couplings to the quarks being different, as well as the difference in mass (photons are massless, while Z bosons are massive). Introducing a transfer factor R as the ratio σ(ZZ)/σ(Zγ) which is determined from simulation, the contribution of ZZ → ℓℓνν to the background can be estimated from Zγ → ℓℓγ data. The uncertainty on the prediction of R due to theoretical aspects is estimated in this work.