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Marcel Vreeswijk (Nikhef/UvA-IoP) First Results of ATLAS at the LHC -- The rediscovery of the Standard Model-- Contents: Intro: The Standard Model Elementairy particles. Status LHC and ATLAS Physics results 2010
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The Standard Model So, what have we been doing in 2010? Measuring ‘backgrounds’! Higgs mechanisme to generate mass! Higgs boson mass > 114 GeV Ultimate goal: detect the Higgs particle (not yet;need more data!)
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Marcel Vreeswijk (Nikhef/UvA-IoP) CERN site LHC P+P at 7TeV 27km 60 ton He at 2K 4 big experiments this talk: ATLAS First year of running. (7TeV) high quality data 2010: ~35pb-1 In 2011: run at 7TeV or higher? >>10-fold luminosity? The LUMINOSITY represents the delivered number of proton collisions In addition: Pb+Pb collisions (not in this talk) atlas Large Hadron Collider (LHC)
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Marcel Vreeswijk (Nikhef/UvA-IoP) LHC physics reach Production Cross-section of top quarks and W, Z bosons are measurable with 2010 data! Top, W,Z signals are important: 1.Standard candles for calibration 2.Background to new physics & Higgs searches 1000 1 1 M 5 T # events in 2010 Higgs Top quarks W,Z bosons Proton-Proton In reach in 2010 Higgs W, Z Promising final states: H W + W - 2 leptons + EtMiss H ZZ 4 leptons Also H 2 photons 7TeV in 2010 jargon: lepton=electron or muon N = L. N = # collisions L = Luminosity = cross-section
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Marcel Vreeswijk (Nikhef/UvA-IoP) Inner detector (charged particle tracks) Calorimeter (energy all particles, but muons) Muon ‘Chambers’ ATLAS p Data rec. 93.5% #working channels >99%
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Marcel Vreeswijk (Nikhef/UvA-IoP) Performance Inner Tracker 1 m Inner Tracker KsKs Kaon discovery: 1947 Pixel detector (80M channels) Silicon strips (6M channels) TRT (350k channels) Operational for 97.5% Momentum measurement in magnetic field of 2T Resolution σ(pT)/pT = 0.05%pT ⊕ 1%
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Marcel Vreeswijk (Nikhef/UvA-IoP) Performance Calorimeter electromagnetic: Liquid Argon sampling calorimeter. Resolution ~10%/sqrt(E) Granularity: eta x phi=0.025 x 0.025 since 1950 Rediscovery of the 0 8m
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Marcel Vreeswijk (Nikhef/UvA-IoP) Di-jet physics
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Marcel Vreeswijk (Nikhef/UvA-IoP) Di-jet invariant mass New energy domain. Highest Pt jet: 1.12 TeV Highest mass: 3.7 TeV Searches for new physics ongoing ATLAS published 3 papers on jet measurements pp jet
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Marcel Vreeswijk (Nikhef/UvA-IoP) Performance Muons Physics signals show up! Muon system: 1200 Muon chamber 350k drift tubes (air core toroidal field 0.5T) Designed for TeV muons (not yet) Z boson ‘rediscovered’ Originally: 1983 at CERN Mass: 91.19 GeV
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Marcel Vreeswijk (Nikhef/UvA-IoP) Muon resonances ATLAS 2010 ? mass Published 2010 Z cross-section in new energy domain=7TeV 1960 1963 1977 1974 1983
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Marcel Vreeswijk (Nikhef/UvA-IoP) Missing Transverse energy W boson ‘rediscovered’ Originally: 1983 at CERN Mass: 80.4 GeV
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Marcel Vreeswijk (Nikhef/UvA-IoP) W boson production W decays to muon + (unseen) neutrino. Missing transverse energy. W q q’ g Transverse W mass:
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Marcel Vreeswijk (Nikhef/UvA-IoP) Top pair (ttbar) production complicated events: 1.Many jets with 2 b-jets (can be ‘tagged’) 2.Electron or Muon 3.EtMiss Standard candle New physics may show up p p t t ttbar has two measurable decays modes: single-lepton di-lepton (mode is set by W decay) ttbar single-lepton Datum Basic prper. Europ. Topds! Last heaviest known particle Last before new
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Marcel Vreeswijk (Nikhef/UvA-IoP) di-leptonic ttbar 2 b-tagged jets
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Marcel Vreeswijk (Nikhef/UvA-IoP) ttbar More info on poster by Ido & Hegoi N. from Nikhef Van Tera naar 100evts selectie Speld hooi
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Marcel Vreeswijk (Nikhef/UvA-IoP) ttbar: theory & experiment
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Marcel Vreeswijk (Nikhef/UvA-IoP) Higgs in 2011 ? We have measured the ‘backgrounds’, now we are ready for the signal ! Conclusion The LHC and the ATLAS detector have demonstrated to be ready for the Standard Model Higgs or new physics See next talk by Paul de Jong!
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Marcel Vreeswijk (Nikhef/UvA-IoP) BACKUP “We know everything about the Higgs boson except its mass” Λ (GeV) Higgs mass (GeV) Triviality Vacuum stability Limits on m h from theory Limits on m h from exper.
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Marcel Vreeswijk (Nikhef/UvA-IoP) W boson cross section
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Marcel Vreeswijk (Nikhef/UvA-IoP) Photon production (QCD compton) photons of hundreds of GeVs ! (Xray 0.0001 GeV)
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Marcel Vreeswijk (Nikhef/UvA-IoP)
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The Standard Model Ultimate goal: detect the Higgs particle (not yet…need more data!) So, what have we been doing in 2010? Measuring ‘backgrounds’! + Higgs boson to generate mass! Promising decay modes H 2 photons H W+W- 2 leptons + EtMiss H ZZ 4 leptons and much more….
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Marcel Vreeswijk (Nikhef/UvA-IoP) The Standard Model Production Cross-section of top quarks and W, Z bosons are measurable with 2010 data! Top, W,Z signals are important: 1.Standard candles for calibration 2.Background to new physics & Higgs searches 1000 1 1 M 5 T # events in 2010 Higgs Top quarks W,Z bosons Proton-Proton In reach in 2010 Note: a proton=many quarks+gluons Higgs W, Z Promising final states: H W + W - 2 leptons + EtMiss H ZZ 4 leptons Also H 2 photons 7TeV in 2010 jargon: lepton=electron or muon
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Marcel Vreeswijk (Nikhef/UvA-IoP) CERN site LHC P+P at 7TeV 27km 60 ton He at 2K 4 big experiments this talk: ATLAS First year of running. (7TeV) high quality data 2010: ~35pb-1 This year (2011): run at 7TeV or higher? >>10-fold luminosity? The LUMINOSITY represents the delivered number of proton collisions 3.2T botsingen 655k hi Pb=Pb
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Marcel Vreeswijk (Nikhef/UvA-IoP) Z boson production Do we understand Z production and its backgrounds? First measurement ever at 7 TeV. Ook in e+e- Diagrammen Lin schaal? Datum Z massa 2Gev wordt 90GeV
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