Boosted searches for WW/WZ resonances in the lνj final state BILLIE LUBIS COLUMBIA UNIVERSITY REU 2016
CERN Founded in 1954 by 12 Western European countries Now 22 member countries Aims to conduct cutting-edge particle physics research and foster collaboration Scientific accomplishments include development of WWW, creation of anti-hydrogen atoms, discovery of Higgs boson Home to LHC as well as many other accelerators 3 August 2016 BILLIE ELIZABETH LUBIS 2
Large Hadron Collider - LHC Built from 1998 2008 Largest and most powerful particle collider in the world 27 km ring, 175 m below ground Numerous detectors including ATLAS, CMS, ALICE, and LHCb 3 August 2016 BILLIE ELIZABETH LUBIS 3
ATLAS A Toroidal LHC ApparatuS General purpose detector at LHC Studies collisions of high energy protons Over 3000 physicists from 138 countries 3 August 2016 BILLIE ELIZABETH LUBIS 4
ATLAS Detector 46 meters long, 25 meters in diameter 7000 tons Components Inner Detector Electromagnetic calorimeters Hadronic calorimeter Muon detectors Magnets 3 August 2016 BILLIE ELIZABETH LUBIS 5
Standard Model Leptons ½ integer spin Electron, muon, tau interact electromagnetically Neutrinos interact via weak force Quarks ½ integer spin Have color charge Interact via strong force Combine to form hadrons (baryons, mesons) 3 August 2016 BILLIE ELIZABETH LUBIS 6
Standard Model Bosons Integer spin Force carriers for the different types of interactions 3 August 2016 BILLIE ELIZABETH LUBIS 7
Particle Identification 3 August 2016 BILLIE ELIZABETH LUBIS 8
VV Resonances Searching for VV resonances in semileptonic decay mode Specifically VV lνqq WW or WZ resonances W decays leptonically to lν pair Reconstruct W boson from lepton and neutrino vectors W/Z decays hadronically to quark and anti-quark Reconstruct in a large-r jet using anti-kt algorithm Calculate VV mass of event Signals used are Heavy vector triplet (HVT) or graviton (RS G*) 3 August 2016 BILLIE ELIZABETH LUBIS 9
Objects Selection Leptons We require a final state with one lepton Veto events with more than one loose lepton while keeping signal candidate events with one tight lepton Tight and loose based on preselection cuts 3 August 2016 BILLIE ELIZABETH LUBIS 10
Objects Selection Triggers Applied missing transverse energy trigger to muon channel Applied electron trigger to electron channel 3 August 2016 BILLIE ELIZABETH LUBIS 11
Objects Selection Small-R jets ΔR > 1 between small-r and large-r jets Classified as b-jet if b-tagging variable MV2C10 > 0.1758 3 August 2016 BILLIE ELIZABETH LUBIS 12
Objects Selection Large-R jets ΔR > 1 between large-r jet and lepton (removed overlap) η < 2.0 m J > 50 GeV p T > 200 GeV Use mass cut and substructure cut to identify jets from hadronic W/Z decays Mass cut: ~65 120 GeV Substructure cut (based on the D2 variable): Differentiate W/Z from QCD jets 3 August 2016 BILLIE ELIZABETH LUBIS 13
Description of Background/Data Data is from 2015 and 2016 Luminosity = 13.2 fb -1 and center of mass energy = 13 TeV Background composed of W+ jets, tt, ҧ Z+ jets, and SM dibosons QCD is negligible Generators V+ jets: Sherpa v22 & N jets correction applied tt: ҧ Powheg-Pythia SM db: Sherpa HVT/Gravitons: MadGraph+Pythia8, with a mass width of ~6% Signal is normalized Backgrounds scaled to cross sections 3 August 2016 BILLIE ELIZABETH LUBIS 14
Control and Signal Regions High purity regions pass substructure cut Low purity regions fail substructure cut 3 August 2016 BILLIE ELIZABETH LUBIS 15
Control and Signal Regions 3 August 2016 BILLIE ELIZABETH LUBIS 16
High purity WCR plots 3 August 2016 BILLIE ELIZABETH LUBIS 17
High purity WCR plots 3 August 2016 BILLIE ELIZABETH LUBIS 18
High purity TCR plots 3 August 2016 BILLIE ELIZABETH LUBIS 19
High purity TCR plots 3 August 2016 BILLIE ELIZABETH LUBIS 20
High purity SR plots 3 August 2016 BILLIE ELIZABETH LUBIS 21
High purity SR plots 3 August 2016 BILLIE ELIZABETH LUBIS 22
Low purity WCR plots 3 August 2016 BILLIE ELIZABETH LUBIS 23
Low purity WCR plots 3 August 2016 BILLIE ELIZABETH LUBIS 24
Low purity TCR plots 3 August 2016 BILLIE ELIZABETH LUBIS 25
Low purity TCR plots 3 August 2016 BILLIE ELIZABETH LUBIS 26
Low purity SR plots 3 August 2016 BILLIE ELIZABETH LUBIS 27
Low purity SR plots 3 August 2016 BILLIE ELIZABETH LUBIS 28
Data/MC Summary 3 August 2016 BILLIE ELIZABETH LUBIS 29
Conclusions Added low purity region to increase sensitivity Overall normalization problem Background fits shape of data fairly well 3 August 2016 BILLIE ELIZABETH LUBIS 30
Acknowledgements Thank you to John Parsons for this REU opportunity Poppy Iordanidou for her help and encouragement, and immense knowledge of ROOT The Columbia ATLAS group for their support Questions? 3 August 2016 BILLIE ELIZABETH LUBIS 31