Measurement of Total and Differential Charm Cross Sections at 7 TeV with the CMS Detector

This thesis presents the total charm cross section measurement in the full kinematic phase space of pp collisions at the LHC. It was performed using open data (2010) from the CMS experiment at a center-of-mass energy of 7 TeV due to its special low p$_{T}$ tracking. The integrated luminosity is determined in a data-driven way using unprescaled triggers as a basis and information from the luminosity database of the CMS collaboration to be 3.00 nb$^{-1}$. This is the first and so far only measurement of charm at 7 TeV in CMS. The charm reconstruction was done through the D*$^{\pm}$ $\rightarrow$ K$^{\mp}$ $\pi$$^{\pm}$ $\pi$$^{\pm}$ final state. Since this analysis is statistically limited, one of the main strategies of this analysis is to use pileup vertices from muon and electron datasets as a physics resource. The D*$^{\pm}$ measured cross section is 1096 $\pm$ 133 (stat.) $\mu$b in the phase space of 0 < |y| < 2 and p$_{T}$ > 1 GeV, and also 2 < |y| < 2.5 and p$_{T}$ > 8 GeV, in which the double-differentially measured cross sections were integrated. This analysis has covered the largest possible kinematic phase space at the LHC from a single experiment with p$_{T}$ down to 1 GeV. This includes three new phase space regions where no D* cross section measurement has been done before at the LHC for p$_{T}$ below 3.5 GeV. The total charm cross section is then extracted from this analysis. By combining with the LHCb measurements, which covered most of the region outside the CMS detector coverage, and some extrapolation from PYTHIA and FONLL, the total charm cross section for the full kinematic phase space is measured to be 9.40 $\pm$ 0.45 (statistical )$_{-0.95}^{+2.50}$ (FONLL/PYTHIA) mb with an extrapolation factor of 1.4 throughout all phase space. This is the smallest extrapolation achieved for the total charm cross section at the LHC so far. Apart from the main result of this thesis, the validation of CMS Open Data with the Higgs to four leptons example at 7 (2011) and 8 (2012) TeV is also shown. This validation reproduces approximately part of the CMS Higgs discovery publication at 7 and 8 TeV with partial datasets in CMS Open Data. The purpose of the validation is to give an example of using CMS Open Data for educational purposes and show its potential for research applications.The Higgs peak is extracted at a significance of two standard deviations, compared to the original publication, which is 3.2 standard deviations in this channel alone. The corresponding example code was publicly released together with the CMS primary dataset for 2012. It has been used as reference by many ever since.