Performance Of The Cms Missing Transverse Momentum Reconstruction In Pp Data At Sqrt S
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Performance of the CMS Missing Transverse Momentum Reconstruction in Pp Data at $\sqrt{s}$
The performance of missing transverse energy reconstruction algorithms is presented by our team using√s=8 TeV proton-proton (pp) data collected with the CMS detector. Events with anomalous missing transverse energy are studied, and the performance of algorithms used to identify and remove these events is presented. The scale and resolution for missing transverse energy, including the effects of multiple pp interactions (pileup), are measured using events with an identified Z boson or isolated photon, and are found to be well described by the simulation. Novel missing transverse energy reconstruction algorithms developed specifically to mitigate the effects of large numbers of pileup interactions on the missing transverse energy resolution are presented. These algorithms significantly reduce the dependence of the missing transverse energy resolution on pileup interactions. Furthermore, an algorithm that provides an estimate of the significance of the missing transverse energy is presented, which is used to estimate the compatibility of the reconstructed missing transverse energy with a zero nominal value.
Heavy Neutral Particle Decays to Tau Pairs
Author: Michail Bachtis
language: en
Publisher: Springer Science & Business Media
Release Date: 2013-12-13
The work presented in this thesis spans a wide range of experimental particle physics subjects, starting from level-1 trigger electronics to the final results of the search for Higgs boson decay and to tau lepton pairs. The thesis describes an innovative reconstruction algorithm for tau decays and details how it was instrumental in providing a measurement of Z decay to tau lepton pairs. The reliability of the analysis is fully established by this measurement before the Higgs boson decay to tau lepton pairs is considered. The work described here continues to serve as a model for analysing CMS Higgs to tau leptons measurements.
Measurement of the Top Quark Mass in the Dileptonic Decay Channel at CMS
This dissertation presents a measurement of the top quark mass (Mt) in the dileptonic decay channel using data from proton-proton collisions at sqrt(s) = 8 TeV recorded by the CMS experiment at the LHC, corresponding to an integrated luminosity of 19.7 ± 0.5 fb-1. The analysis is based on three observables whose distributions are sensitive to the value of Mt. The Mbl invariant mass and MT2 'stransverse mass' observables are employed in a simultaneous fit to determine the value of Mt and an overall jet energy scale factor (JSF). In a complementary approach, the MT2-assisted on-shell reconstruction technique is used to construct an Mblv invariant mass observable that is combined with MT2 to measure Mt. The shapes of the observables, along with their evolutions in Mt and JSF, are modeled by a non-parametric Gaussian process regression technique. The sensitivity of the observables to the value of Mt is investigated using a Fisher information density function. The top quark mass is measured to be 172.22 ± 0.18 (stat) ± 0.91 (syst) GeV. This dissertation also presents a missing transverse momentum (MET) significance variable, which is used to estimate the compatibility of the reconstructed MET with a zero nominal value. This variable may be used to discriminate between events containing real MET due to undetected particles and spurious MET due to object misreconstruction, finite detector resolution, or detector noise. The MET significance variable is tuned using data-driven techniques, and its performance is evaluated using the CMS Run 1 and Run 2 datasets. ...