Search For Heavy Majorana Neutrinos In Mu Superscript More Or Less Mu Superscript More Or Less Jets E Superscript More Or Less E Superscript More Or Less Jets Events In Pp Collisions At Square Root Of S

In this study, a search is performed for heavy Majorana neutrinos (N) decaying into a W boson and a lepton using the CMS detector at the Large Hadron Collider. A signature of two jets and either two same sign electrons or a same sign electron-muon pair is searched for using 19.7 inverse femtobarns of data collected during 2012 in proton-proton collisions at a centre-of-mass energy of 8 TeV. The data are found to be consistent with the expected standard model (SM) background and, in the context of a Type-1 seesaw mechanism, upper limits are set on the cross section times branching fraction for production of heavy Majorana neutrinos in the mass range between 40 and 500 GeV. The results are additionally interpreted as limits on the mixing between the heavy Majorana neutrinos and the SM neutrinos. In the mass range considered, the upper limits range between 0.00015 - 0.72 for

A search is performed for heavy Majorana neutrinos (N) using an event signature defined by two muons of the same charge and two jets ($\mu^\pm \mu^\pm \mathrm{j j}$). The data correspond to an integrated luminosity of 19.7 fb$^{-1}$ of proton-proton collisions at a center-of-mass energy of 8 TeV, collected with the CMS detector at the CERN LHC. No excess of events is observed beyond the expected standard model background and upper limits are set on $

The discovery of neutrino oscillations provides evidence that the Standard Model neutrinos have mass. Many models generate the mass for the light neutrinos by postulating the existence of heavy neutrinos. This thesis presents the search for a heavy Majorana neutrino decaying into a W boson and a muon that was performed using the ATLAS detector at the LHC. The search is performed using final states with two same-sign muons, two or more high momentum jets and low missing transverse energy. The events are required to pass the ATLAS muon trigger and the improvements made in the muon trigger algorithms are also presented. The data used in this thesis were collected using pp collisions at sqrt(s) = 7 TeV in 2011 and correspond to an integrated luminosity of 4.7 fb-1. In the search no excess of events above the background prediction is observed and 95% confidence level upper limits are set on the cross section times branching ratio for the production of heavy Majorana neutrinos. Limits are set for heavy Majorana neutrinos with masses ranging from 100 to 300 GeV, in which the observed limits range between 28 to 3.4 fb. These are most stringent direct limits to date for heavy neutrino masses larger than 100 GeV.

A search for heavy Majorana neutrinos in events containing a pair of high-pT leptons of the same charge and high-pT jets is presented. The search uses 20.3 fb-1 of pp collision data collected with the ATLAS detector at the CERN Large Hadron Collider with a centre-of-mass energy of [arrow]" = 8 TeV. The data are found to be consistent with the background-only hypothesis based on the Standard Model expectation. In the context of a Type-I seesaw mechanism, limits are set on the production cross-section times branching ratio for production of heavy Majorana neutrinos in the mass range between 100 and 500 GeV. The limits are subsequently interpreted as limits on the mixing between the heavy Majorana neutrinos and the Standard Model neutrinos. In the context of a left-right symmetric model, limits on the production cross-section times branching ratio are set with respect to the masses of heavy Majorana neutrinos and heavy gauge bosons WR and Z'.

The fourth edition includes new developments, in particular a new section on the double beta decay including a discussion of the possibility of a neutrinoless decay and its implications for the standard model.

This book covers a very broad spectrum of experimental and theoretical activity in particle physics, from the searches for the Higgs boson and physics beyond the Standard Model, to detailed studies of Quantum Chromodynamics, the B-physics sectors and the properties of hadronic matter at high energy density as realised in heavy-ion collisions. Starting with a basic introduction to the Standard Model and its most likely extensions, the opening section of the book presents an overview of the theoretical and phenomenological framework of hadron collisions and current theoretical models of frontier physics. In part II, discussion of the theory is supplemented by chapters on the detector capabilities and search strategies, as well as an overview of the main detector components, the initial calibration procedures and physics samples and early LHC results. Part III completes the volume with a description of the physics behind Monte Carlo event generators and a broad introduction to the main statistical methods used in high energy physics. LHC Phenomenology covers all of these topics at a pedagogical level, with the aim of providing young particle physicists with the basic tools required for future work on the various LHC experiments. It will also serve as a useful reference text for those working in the field.

This 2006 book uses the standard model as a vehicle for introducing quantum field theory.