CMS pixel module qualification and Monte-Carlo study of H→ τ⁺τ⁻→ l⁺l⁻Eτ

Abstract

The first part of this work reports on the development of test and calibration algorithms for the qualification of the barrel modules of the CMS pixel detector. Several algorithms to test the hardware functionality and performance have been developed and implemented into an object-oriented software framework. Examples are the pixel readout test, the bump bonding test or the noise measurement. The qualification procedure also includes calibration routines. For instance the gain of each pixel or the temperature sensors of the readout chips have to be calibrated. Furthermore, an algorithm to unify the thresholds of all pixels was developed. According to specific quality criteria, each module is graded into one of three categories. Out of 981 tested modules, 806 were qualified for the usage in the detector. The second part of this work deals with a Monte-Carlo study of the Higgs decay channel $H\to \tau^{+}\tau^{-} \to l^{+}l^{-}Et$ with a jet balancing the large transverse momentum of the Higgs boson. In contrast to many other studies, the analysis concentrates not on the vector boson fusion but on the gluon fusion production mechanism. The backgrounds are mainly suppressed by requiring a large invariant mass of the Higgs boson and the balancing jet. The discovery potential is limited by the resolution of the reconstructed missing transverse energy. To improve the resolution, a method to calibrate the missing transverse energy with the help of $Z^{0}/\gamma^{*} \to l^{+}l^{-}$ events was developed. Combining all lepton channels, a signal significance of 2.4$\sigma$ significance is expected for a Higgs boson of 120 GeV mass and an integrated luminosity of 30 $fb^{−1}$