研究多向量玻色子「火球」特徵訊號與參與 CMS 畫素偵測器第一期升級計畫

Abstract

The thesis includes the study of the signature of heavy quarks and the record of the CERN / Taiwan / Finland module production in CMS barrel pixel detector (BPIX) phase 1 upgrade. For the first part, in order to solve the known problem of a matter-dominant universe, new CP violation source beyond the standard model of particle physics is needed. Adding new heavy quarks, such as sequential 4th generation quarks or vector-like quarks, to the model is a promising candidate solution. When the mass of the new quark is very heavy and hence their associated Yukawa coupling can be very large, a new fireball-like signature may appear if their strong couplings lead to annihilation in a thermal way. The emitted particles from the annihilation could be mainly longitudinal vector bosons, and the multiplicity is exceptionally high. We present the study of such a fireball experimental signature with the fast simulated samples produced by the Madgraph5 generator. The detector effect is modelded by the Delphes package assuming a simplified CMS detector model. If the signal is discovered with a data set corresponding to an integrated luminosity of 100 $fb^{-1}$ collected at the LHC 13 TeV pp collisions, a statistical significance of $5sigma$ can be reached if the mass of the new heavy quark is below 1 TeV/$c^2$. If no excess above the background from other standard model processes is seen, a limit on the new heavy quark mass can be set to 1.35 TeV/$c^2$ at 95\% confidence level. For the second part, the CMS BPIX phase 1 upgrade has been being on going since 2011 with the provision for the progress of the LHC upgrade plans (high-luminosity LHC) and the expectation of even larger instant luminosity ($sim 2 imes 10^{34} cm^{-2}s^{-1}$) and pile-up effect in near future. One of the important tasks is barrel pixel module production which is in charge of five different consortia in Europe. CERN / Taiwan / Finland is the consortium responsible to 176 barrel pixel modules which are one-half the quota required for the Layer-3 BPIX. The module production progressing in CERN, including the module assembly procedure as well as the qualification tests, are recorded. As the writer participated in the x-ray qualification tests, both the procedure and analysis result in x-ray tests would be particularly detailed out. In the end of our module production in August 2016, there are 207 barrel pixel modules contributed to the Layer-3 BPIX, and additional 3 pixel modules to the backup modules for the Layer-4 BPIX.