Fishing for New Physics with Massive Neutral Dibosons: Measurements of ZZ Production Cross Section and the Search for Invisible Higgs Boson Decays Beyond the Standard Model with the CMS Detector at the !HC by Matthew Ervin Chasco #S# in Physics and $%%lied Mathematics& University of (isconsin-Milwau*ee M.S# in Physics, Northeastern University $ dissertation submitted to The Faculty of the College of Science of Northeastern University in %artial ful,llment of the requirements for the degree of Doctor of Philoso%hy December ./& 0/.1 Dissertation directed by Darien (ood Professor of Physics Acknowledgements I would ,rst li*e to than* my advisor& Professor Darien (ood& for his su%%ort and all that I have learned from him over the %ast few years# The content of this thesis would not have been %ossible without his thoughtful in%ut and guidance. I would li*e to ex%ress my gratitude to the other members of my Thesis Committee, Professor George Alverson& Professor Emanuela Barberis, and Professor Pran Nath# It has been a %rivilege wor*ing with and learning from all of them# I would also li*e to than* my collaborators from Northeastern University and CMS# In %articular, I4d li*e to than* Doctor Tim Co2& Doctor Daniele +rocino, 5en)Jie (ang, Professor +oyoko 7rimoto& Rafael de !ima& Doctor Andrew Kubi* and en Kna%%# S%ecial than*s go to Doctor Darin Baumgartel& Doctor 3regory Peim& Doctor Jin9hong Zhang& Doctor Sujeet $*ula& and David Nash for being such good friends as well as collaborators during our time together in Boston# I would also li*e to than* Professor !uis Anchordoqui for his great lectures and encouragement in undergrad# I am grateful to my family for sha%ing me into who I am& and fostering an in) terest in science, especially my %arents Robin Chasco and Corinne Heltemes and my grand%arents Joanne and "rvin Heltemes. I would also li*e to than* my cousin Joseph Heltemes for ,rst telling me about the Higgs boson when we were kids. Finally& I would li*e to than* my %artner and best friend Amy Greenwood for her endless su%%ort, en- couragement and ability to ma*e me laugh and see the bright side of life. ii Abstract of Dissertation The Standard Model of %article %hysics is a theory describing the fundamental inter) actions and %ro%erties of subatomic %articles. $ *ey feature is its ability to ex%lain %article mass through the Higgs mechanism& and a by)%roduct of this mechanism is the Higgs boson# +he discovery of the Higgs boson& in 0/.0 at CERN, com%leted the Standard Model %article zoo& but observed %henomena& li*e dark matter& remain unex%lained# The analyses %resented ex%lore %roton)%roton collison events resulting in a Z boson %lus missing transverse energy ;ME+<# The motivation for this is to investigate two %rocesses: Standard Model ;SM) ZZ %roduction& and beyond Standard Model ; SM) + + ZH %roduction& in %articular the ZZ � �−ν=ν and ZH � �− > H channels. The → → inv %lace-holder Hinv is for all Higgs boson decay modes resulting in undetected “invisible” %articles, which may branch to new %hysics& li*e dar* matter %articles# +he data used are from 5un . ;0/..A0/.0< of CMS& where %roton)%roton collisions at B +eV and D +eV were delivered by the LHC# The Com%act Muon Solenoid (CMS< is a general) %ur%ose detector located along the Large Hadron Collider ;!HC)& which is a %article accelerator at CERN in Geneva, Switzerland# +o extract these signals containing real MET from bac*ground containing fa*e mismeasured MET, a new “reduced MET@ variable is constructed and optimized# This assists in the measurement of the ZZ %roduction cross section# The results of the + +82 +81 exclusive ZZ � �−ν=ν cross section measurement are 0/. 69 fb and 0E1 64 fb from → − − iii the B and D +eC %ortions of Run . data, res%ectively# Bayesian unfolding is used to +68 measure a cross section of 001 70 fb from the D +eV data. +hese results both agree − with next)to-leading order %redictions from the Standard Model# The diFerential cross section as a function of transverse momentum of the Z boson is also measured from unfolding& for the %urpose of %roviding a way to com%are data to new theories. + + +o distinguish ZH � �−>H from ZZ � �−ν=ν a machine learning algorithm is → inv → used with %hysical variables as the in%ut# $ shape analysis is %erformed on the resulting distribution& and an up%er limit is %laced at GHI C#!# on the invisible branching fraction of the Higgs boson# For a Higgs boson with a Standard Model cross section and mass of .0H GeV, the observed limit on the branching fraction is H0I and the ex%ected is 1GI# Considering a mass spectrum of ..H)0// GeV, a fully invisible Higgs is excluded for masses below .EJ 3eV. iv Table of Contents Acknowledgements ii Abstract of Dissertation iii Table of contents v List of figures viii List of tables xii 1 Theory 1 .#. +heStandardModel # # # # # # # # # # # # # # # # ############. .#.#. Particles and Interactions # # # # # # # # # # # # # # # ######. .#.#0 Fields and !agrangians # # # # # # # # # # # # # # # # #######H .#.#J Kuantum Electrodynamics # # # # # # # # # # # # # # # # # ####B .#.#1 Kuantum Chromodynamics # # # # # # # # # # # # # # # # # # # # ./ .#.#H Electrowea* Theory # # # # # # # # # # # # # # # # # # # # # # # # # .. .#.#E The Higgs Mechanism # # # # # # # # # # # # # # # # # # # # # # # .1 .#0 eyond the Standard Model # # # # # # # # # # # # # # # ######### 00 .#0#. Anomalous +ri%le Gauge Cou%lings # # # # # # # # # # # # # # # # 0J .#0#0 Invisible Higgs oson Decays # # # # # # # # # # # # # # # # # # # 01 .#J Massive Neutral Diboson Production # # # # # # # # # # # # # # # # # # # 0B .#J#. Corrections # # # # # # # # # # # # # # # # # ############ 0G 2 Ex erimental Apparatus 32 0#. !arge Hadron Collider # # # # # # # # # # # # # # # # ########### J0 0#.#. !uminosity Parameters # # # # # # # # # # # # # # # # # # # # # # # JE 0#0 Com%act Muon Solenoid Introduction # # # # # # # # # # # # # # # # # # # JD 0#J Su%erconductingSolenoid # # # # # # # # # # # # # # # # ######### 1. 0#1 Inner+rac*er ################# ############### 10 0#H "lectromagnetic Calorimeter # # # # # # # # # # # # # # # # # # # # # # # # 11 0#H#. Barrel 5egion # # # # # # # # # # # # # # # # ############ 1E 0#H#0 Endcap 5egion # # # # # # # # # # # # # # # # ########### 1E 0#H#J Preshower # # # # # # # # # # # # # # # # # ############# 1B 0#E Hadronic Calorimeter # # # # # # # # # # # # # # # # # ########### 1D 0#E#. Barrel 5egion # # # # # # # # # # # # # # # # ############ 1G 0#E#0 EndCap 5egion # # # # # # # # # # # # # # # # # ########## H0 v 0#E#J +ail Catcher # # # # # # # # # # # # # # # # # ############ H0 0#E#1 Forward Calorimeter # # # # # # # # # # # # # # # # # # # # # # # # H1 0#B Muon System # # # # # # # # # # # # # # # # ################ HH 0#B#. Drift +ubes # # # # # # # # # # # # # # # # ############# HE 0#B#0 Cathode Stri% Chambers # # # # # # # # # # # # # # # # # # # # # # HG 0#B#J 5esistive Plate Chambers # # # # # # # # # # # # # # # # # # # # # E1 0#B#1 7%to)mechanical System # # # # # # # # # # # # # # # # # # # # # # EE 0#D +rigger # # # # # # # # # # # # # # # # # # ################## EE ! Event Reconstruction #$ J#. +rac* 5econstruction # # # # # # # # # # # # # # # # # ########### B/ J#0 Primary Certex Reconstruction # # # # # # # # # # # # # # # # # # # # # # B0 J#J Muon 5econstruction # # # # # # # # # # # # # # # # # ########### BJ J#J#. 5ecHits and Segments # # # # # # # # # # # # # # # # # # # # # # # BJ J#J#0 Standalone Muons # # # # # # # # # # # # # # # # ######### BE J#J#J Global Muons # # # # # # # # # # # # # # # # # ########### BB J#J#1 Classi,cation # # # # # # # # # # # # # # # # ############ BD J#J#H CSC Calidation # # # # # # # # # # # # # # # # # ########## BG J#1 "lectron 5econstruction # # # # # # # # # # # # # # # # ########## D0 J#1#. +rac*s and Su%erclusters # # # # # # # # # # # # # # # # # # # # # # D0 J#1#0 Classi,cation # # # # # # # # # # # # # # # # ############ D1 J#H Photon Reconstruction # # # # # # # # # # # # # # # # # ########## DE J#E Particle Flow # # # # # # # # # # # # # # # # ################ DE J#E#. +rac*ingandClustering # # # # # # # # # # # # # # # # # # # # # # DB J#E#0 !in*ing ################ ############### DD J#E#J Particles # # # # # # # # # # # # # # # # # ############## DD J#B Missing +ransverse Energy 5econstruction # # # # # # # # # # # # # # # # G/ J#D Jet 5econstruction # # # # # # # # # # # # # # # # ############# G. J#G Simulated Event 3eneration # # # # # # # # # # # # # # # # # # # # # # # # G1 % Analysis &' (( $# 1#. Motivation################## ################ GE 1#0 Simulation################## ################ GD 1#J 7bject Selection # # # # # # # # # # # # # # # # # ############## GD 1#J#. +rigger # # # # # # # # # # # # # # # # # # ############## GG 1#J#0 Primary Certe2 Selection # # # # # # # # # # # # # # # # # # # # # # GG 1#J#J Muon Identification and Isolation # # # # # # # # # # # # # # # # # .// 1#J#1 Electron Identi,cation and Isolation # # # # # # # # # # # # # # # # ./0 1#J#H Z Candidate Selection # # # # # # # # # # # # # # # # # # # # # # # ./J 1#J#E !oose !e%ton Selection # # # # # # # # # # # # # # # # # # # # # # # ./H 1#J#B Jet Identi,cation& Corrections and -tagging # # # # # # # # # # # ./E 1#J#D Final Signal Selection # # # # # # # # # # # # # # # # # # # # # # # # ../ 1#1 alance and Alignment # # # # # # # # # # # # # # # # # # # # # # # # # # # ... 1#H 5educed Missing +ransverse Energy # # # # # # # # # # # # # # # # # # # # ..J vi 1#H#. 5educed E/ T Definition################### # # # # ..E