Physics at the TeV scale: ATLAS

1. Physics at the TeV scale: ATLAS • Programme: 2005-2010 • Group composition: • 16 staff, 8 postdoc, 24 PhD. • Publications: • 18 theses • 296 publications • University partner: UvA, RUN • Investment in experiment: • 11.911 kE (2.7% ATLAS) Stan Bentvelsen 20-sept-2011 Stan Bentvelsen

2. ATLAS group • Exploitation phase ATLAS • Permanent staff ~ constant • Decrease technical staff • Increase of PhD student and postdocs • D∅ activity is closed down • After period with activity in top-quarks and SM Higgs. • In-kind contribution:production of Monte Carlo samples • Reached goal: excellent preparations for LHC 20-sept-2011 Stan Bentvelsen

3. Mission and research questions Mission: To find and study the Higgs particle(s) responsible for the generation of mass. To search for physics beyond the Standard Model, such as supersymmetry, large extra space-time dimensions, or unexpected phenomena. • Our current research topics • Top quark physics • Top-quark production and properties • Observation of single top • Supersymmetry • Inclusive searches with missing energy • Flavour tagging in supersymmetry • Higgs particle • H→ZZ→4 leptons • H→WW→2l±+2ν 20-sept-2011 Stan Bentvelsen

4. Semi Conducting Tracker Installation End-cap Trigger/DAQ Muon Read Out System/Drivers Top quark physics Supersymmetry Higgs physics Muon tracking ID tracking Combined Tracking Muon precision chambers 96 MDT BOL chambers End-cap toroids In-kind contribution Atlas program - Stan Bentvelsen - SAC April 17, 2008 Groesbeek April 22 7 4

5. Highlights … • Leadership roles • in period 2005-2011 • Awarded funding • Conferences organised • 2nd Trigger workshop in Amsterdam (2010) • Particle Physics Symposium: experiment meets theory (2011) 20-sept-2011 Stan Bentvelsen

6. Tracking in ATLAS Point at 2.36 TeV by Kayl (cum laude) Nikhef reconstruction • First collisions in 2010-2011 • Track density determination • Drell-Yan with muons • Status SCT/MDT detectors • Excellent performance • both in efficiency, noise, and reliability • Plans: • Complete muon softwarereconstruction, including taggers 20-sept-2011 Stan Bentvelsen 6

7. Top quark physics W Verkerke, P Ferrari, S Bentvelsen • Top anti-top quark pairs • Why? • Precision tests Standard Model • Searches for New Physics • Background to supersymmetry • Production cross section • Single lepton final state • Nikhef contributions to paper editor,fake lepton estimates and W+jets from data • Mass of top-anti-top quarks • Ongoing and plans: • New physics searches in top; tau leptons in top-events • Observe and study single top production • Search for W-t channel, close collaboration with Nikhef theory After >1 year data approaches Tevatron precision; more top quarks collected 20-sept-2011 Stan Bentvelsen

8. Search for supersymmetry P de Jong • Cascade decay of SUSY particles • Signatures with large missing energy from LSP • Searches at Nikhef with zero, one or two leptons • Sweep phase space withincoming data • No ‘easy’ supersymmetry observed • Plans • Study more difficult regions of supersymmetry • with less missing energy and focus on 3rd generation:top, sbottom, stau • Benefit from 14 TeV runs 2010→2011 20-sept-2011 Stan Bentvelsen

9. Higgs searches • Effort in two decay channels • H→WW*→lνlν • The most sensitive process for 130 < mH < 200 GeV • Challenging: reconstruction invariant mass of this system not possible • Nikhef in ‘cut and count’ method, and multivariate analysis • H→ZZ*→llll • Very clean, but small rates • Nikhef contributes in muon reconstruction calibration, efficiency optimisation, baseline analyses 20-sept-2011 Stan Bentvelsen

10. Higgs combined limits Standard Model Higgs boson mass excluded at 95% CL: 146 < mH < 232 GeV 256 < mH < 282 GeV 296 < mH < 466 GeV Verkerke • Combined ATLAS results • Combination ofmany Higgs decaychannels • RooFit package • Implements combination s/w,statistical analysis • Used throughout ATLAS, CMS, LHCb and others • Plans • Observe or exclude SM Higgs in WW and ZZ final states 20-sept-2011 Stan Bentvelsen

11. Upgrade plans: physics Need ~ 3000 fb-1 First make full use of 14 TeV run • Clarify the Electro-Weak symmetry breaking • What happens if there is no light Higgs... • Some mechanismto prevent WW scatteringto violate unitarity • Exploration at Nikhef started • Check properties of Higgs (in case it exists) • Higgs “self couplings”, branching fractions to various decay modes • Search for new physics at the TeV scale • Explore all reachable regions of supersymmetry 20-sept-2011 Stan Bentvelsen

12. Upgrade plans: technical case services • Shutdown 2013-1014 • Increase cm energy to 14 TeV run • Install “b-layer” in existing pixel detector • Development front end chips & readout • CO2 cooling • Shutdown 2018 • Luminosity tot 2.2 1034 cm-2s-1 • Upgrade muon system • Muon read-out system • Fast track trigger & track finder • Shutdown 2021-2022 • Luminosity levelling to 5 1034 cm-2s-2 • Installation entire new Inner Detector • Inner tracker layout and mechanics • Possible with GOSSIP detector? 20-sept-2011 Stan Bentvelsen

13. Points of attention & remarks • Nikhef in ATLAS • One of the larger institutes • Hardware responsibilities, leading roles in muon performance, top quarks, Susy, Tier-1 • Big group with many responsibilities • Continue to keep group focused to coherent set of activities • Upgrade plans • Further away, and maybe less concretethan other LHC experiments • Make sure that Nikhef resources will remain to be available for ATLAS • For individuals difficult to stand out in large collaboration • At CERN supervision for PhD students • Make sure postdoc positions remain available 20-sept-2011 Stan Bentvelsen

14. Conclusion and schedule physics 2 fb-1 down; 2998 fb-1 to go! • Thanks to the LHC for delivering so well and so fast • Eagerly waiting the 14 TeV runs • Higgs hunting approaches the moment of truth • Closing on Higgs masses - moderate excess • Measurement of quantum numbers and couplings of the Higgs further away • Unfortunately, New Physics was not “around the corner” • Experimental challenges as we enter further the Multi-TeV world. • Funding for FOM ATLAS program ends January 1st, 2016 • Research program continues beyond 20-sept-2011 Stan Bentvelsen

15. Output 2010 • The scientific output of ATLAS • 21 ATLAS paperssubmitted • 3042 authors • 9 papers withvisible Nikhefcontribution • 99 conference notes • 432 internal notes 20-sept-2011 Stan Bentvelsen

16. Highlights • The Dutch know about LHC • Appeal to the imagination! • General public • Numerous outreach presentations • Higgs movie, Newspapers • Annual open days • ... • Starting collisions 20-sept-2011 Stan Bentvelsen

17. Construction of 96 large ‘muon chambers’ • Construction of 96 large ‘muon chambers’ P SAC April 2006

18. Semi Conducting Tracker • Responsible one endcap • Construction SI modules • Mounting all modules • Assembly endcap • Installation in ATLAS • 4 space-points on track 20-sept-2011 Stan Bentvelsen

19. Top quarks Event display of a top pair e-μ dilepton candidate with two b-tagged jets. The electron is shown by the green track. The two b-tagged jets are shown by the purple cones. 20-sept-2011 Stan Bentvelsen

20. 20-sept-2011 Stan Bentvelsen