• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 1
  • Tagged with
  • 1
  • 1
  • 1
  • 1
  • 1
  • 1
  • 1
  • 1
  • 1
  • 1
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

The first observation of ϓ(1S) pair production and Hadron calorimetry upgrade at CMS

Haytmyradov, Maksat 01 May 2017 (has links)
This dissertation dicusses two topics; the cross section measurement of ϓ(1S) meson pair production [1] and simulation studies of High Granularity Calorimetry (HGCal). The first part of the dissertation is dedicated for the analysis of ϓ(1S) meson pair production and measurement of its cross section. The data for this analysis were collected by the CMS experiment at Large Hadron Collider (LHC) at a center-of-mass energy of 8 TeV and correspond to an integrated luminosity of 20.7 fb −1 . Simultaneous production of two ϓ(1S) mesons is observed for the first time with 38 events, corresponding to a local significance exceeding five standard deviations from the expected combinatorial background b-quark decays. Both ϓ(1S) candidates are fully reconstructed via their decays to μ + μ − . The fiducial acceptance of the detector is measured from the simulation and is defined by an absolute Υ(1S) rapidity smaller than 2.0. To minimize the model-dependence, the acceptance and efficiency corrections are calculated on an event-by-event basis using measured ϓ meson and muon momenta. The fiducial cross section of ϓ(1S) meson production, assuming both ϓ(1S) mesons decay isotropically, is measured to be 68.8 ± 12.7 (stat) ± 7.4 (syst) ± 2.8 (B) pb, where the third uncertainty comes from the uncertainty in the branching fraction of ϓ(1S) decays to μ + μ − . Different assumptions about ϓ productions imply modifications to the cross section ranging from −38% to +36%. Cross section measurement of ϓ pair production will provide better understanding of the parton vstructure of proton and enhance precision of existing particle production models. LHC is planning to increase luminosity and energy of colliding protons. Due to accumulated radiation damage and to improve detector performance CMS experiment is expected to undergo upgrade plans. Hadron calorimeter is among them, and it is planned to be replaced with better performance high granularity calorimetry (HGCal). HGCal needs to be integrated with existing components of CMS and its smooth functioning is essential. The second part of the dissertation describes simulation studies performed to validate readiness of HGCal for the Phase II upgrade.

Page generated in 0.46 seconds