Institut für Kern- und Teilchenphysik, Professur für experimentelle Teilchenphysik Analysis of the Process pp -> at the ATLAS Detector and Preparation of a Discovery of Vector Boson Scattering Felix Socher supervised by: Anja Vest, Michael Kobel Dresden, 6.3.213
σ total [pb] Motivation 1 1 5 4 35 pb 35 pb ATLAS Preliminary LHC pp Theory s = 7 TeV Data (L =.35-4.6 fb ) 1 3 5.8 fb LHC pp s = 8 TeV Theory Data (L = 5.8 fb ) 1 2 1. fb 5.8 fb 1 1. fb 4.6 fb 4.6 fb 2.1 fb 4.6 fb 5.8 fb 1 tt t t haps://twiki.cern.ch/twiki/bin/view/atlaspublic/combinedsummaryplots Standard Model predic/ons extensively tested at LHC no cross- sec/on measurement of at 8 TeV 2
production rela/vely clean signature due to 3 leptons in the final state inclusive cross- sec/on measurement is already systema/cs dominated is a probe for triple gauge couplings 3
Event Topology 4
Backgrounds Main Backgrounds: g g, taken from MC +jets, es/mated from data Other Backgrounds: γ top produc/on, es/mated from data +gamma, taken from MC 5
Object and Event Selection Object Selec/on Baseline: Loose uality leptons, p T > 15 GeV, η < 2.47 candidates: added isola/on and medium uality criteria candidates: /ghter isola/on and /ght uality criteria Event Selec/on Event Trigger with one of the selected leptons matching it Primary Vertex: at least 3 good associated tracks Remove Overlaps (done on baseline leptons) veto: reject events with more than 3 baseline leptons candidate: m ll m < 1 GeV MET > 25 GeV M T () > 2 GeV 6
Event Selection 35 3 25 2 15 1 5 data /+ γ +jet +jet tt ATLAS Preliminary Internal s = 8 TeV, L dt = 13. fb 6 7 8 9 1 11 12 Events / 1 GeV 22 2 18 16 14 12 1 8 data invariant mass of best candidates /+γ best candidate is the +jet pair yielding +jet the mass closest to the mass candidates are ATLAS opposite Internal sign, same flavor lepton s = pairs 8 TeV, L dt = 13 fb 6 4 2 5 1 15 2 25 tt 12 1 /+γ transverse mass of reconstructed +jet 8 cut at 2 GeV already applied 6 4 2 data M ll +jet tt ATLAS Internal s = 8 TeV, L dt = 13 fb [GeV] Ref: ATLAS- COM- CONF- 213-16 2 4 6 8 1 12 14 16 Events / 2 GeV Events / 5 GeV 12 1 18 data 16 14 12 1 8 6 8 6 4 2 p T /+γ +jet +jet tt s = 8 TeV, [GeV] data /+γ +jet +jet tt ATLAS Preliminary Internal ATLAS Internal s = 8 TeV, L dt = 13 fb L dt = 13 fb 4 2 2 4 6 8 1 12 14 16 M T (l,met) [GeV] 1 2 3 4 5 6 7 8 Events / 2 GeV 7 18 16 14 12 1 8 6 4 2
Results MC yields are scaled to 12.8 d - 1 top contribu/ons for eee and eeµ channel are absorbed into /+jets background Final State eee eeµ eµµ µµµ Combined Observed 192 27 298 334 194 1.5±.2±.7 15.±.3±.8 13.±.2±.7 19.±.2±1. 57.5±.5±1.6 /+jets 36.6±2.9±1.8 32.6±3.9±1.2 56.7±3.7±11.2 46.8±4.8±14.3 188.±7.9±26.5 Top 6.3±.5±3.4 9.1±.7±4.9 / + 13.6±3.±.8 1.3±.7±.1 17.5±3.3±1. 32.4±4.5±1.3 Bkg (total) 61±4±11 55±4±1 87±5±11 75±5±14 278±9±25 Expected signal 146±3±13 22±3±16 23±3±16 28±3±21 831±6±34 Reconstruction.144.188.199.276 Acceptance Factor ATLAS Preliminary Ref: ATLAS- COM- CONF- 213-16 8
σ total [pb] Results ATLAS Preliminary 1 ) NLO QCD (MCFM, CT1, 66<m <116 GeV) (pp (pp) ll 1 LHC Data 212 ( s=8 TeV) ATLAS lνll (66<m <116 GeV) L=13 fb LHC Data 211 ( s=7 TeV) ATLAS lνll (66<m <116 GeV) L=4.6 fb Tevatron ( s=1.96 TeV) D lνll (6<m <12 GeV) L=8.6 fb CDF lνll L=7.1 fb ll ll ll 2 4 6 8 1 12 14 s [TeV] domina/ng systema/cs are: uncertain/es on data driven methods, luminosity uncertainty Ref: ATLAS- COM- CONF- 213-16 9
Vector Boson Scattering Vector Boson ScaAering (VBS) contains triple gauge boson ver/ces uar/c gauge boson ver/ces interac/ons of the Higgs boson with the weak massive gauge bosons 1
Vector Boson Scattering not in Vector Boson ScaAering (VBS) contains triple gauge boson ver/ces uar/c gauge boson ver/ces interac/ons of the Higgs boson with the weak massive gauge bosons 11
Outlook +JJ QCD examples g g g g +JJ E examples () ( ) 12
Outlook aier cross- sec/on measurement: studies of the >2 jet bins, interpreta/on w.r.t. VBS less sta/s/cs background es/ma/on has to be redone examina/on of jet systema/cs Events 6 5 4 3 ATLAS ATLASwork in progress L dt = 13.3 fb, lllν s = 8 TeV +jets bb+jets ttbar(+v) γ,γ jj-qcd jj-e +Jets Signal -QCD Signal -E Data 212 SM (stat) Events / 4 GeV 14 +jets 12 1 8 6 ATLAS ATLASwork in in progress L dt = 13.3 fb, lllν s = 8 TeV bb+jets ttbar(+v) γ,γ jj-qcd jj-e +Jets Signal -QCD Signal -E Data 212 SM (stat) 2 4 1 2 Data MC 1.8 2 1.6 1.4 1.2.8 1.6.4.2 1 2 3 4 5 6 7 8 9 n(j) 1 2 3 4 5 6 7 8 9 n(jet) n(j) Data MC 1.8 2 1.6 1.4 1.2.8 1.6.4.2 2 4 6 8 1 12 14 16 18 2 pt(jet) p (j) [GeV] [GeV] T 13
Outlook Events / 2. GeV 25 2 15 ATLASwork in progress ATLAS work in progress L dt = 2.3 fb lllν, s = 8 TeV +jets bb+jets ttbar(+v) γ,γ jj-qcd jj-e +Jets invariant mass of the tagging jets (highest pt jets) is sensi/ve variable QCD contribu/on shows steeper slope than E contribu/on 1 5 Signal -QCD Signal -E analysis of the high invariant mass regime is in the making 5 1 15 2 25 3 m(j,j) long term goals: disentangling QCD and E contribu/ons to VBS of further interest: sejng limits on aqgcs - > T3.7 14
Outlook Events / 2. GeV 6 ATLAS work in progress in progress +jets 5 4 3 2 1 L dt = 2.3 fb lllν, s = 8 TeV bb+jets ttbar(+v) γ,γ jj-qcd jj-e +Jets Signal -QCD Signal -E invariant mass of the tagging jets (highest pt jets) is sensi/ve variable QCD contribu/on shows steeper slope than E contribu/on analysis of the high invariant mass regime is in the making 1 15 2 25 3 m(j,j) long term goals: disentangling QCD and E contribu/ons to VBS of further interest: sejng limits on aqgcs - > T3.7 15
Thank you for your aaen/on! 16
References A Measurement of Produc3on in Proton- Proton Collisions at srt(s)=8tev with the ATLAS Detector ATLAS- COM- CONF- 213-16 Measurement of the total produc3on cross sec3on in proton- proton collisions at s = 8 TeV in 2 H 1 with the ATLAS detector ATLAS- COM- CONF- 213-2 17