The ATLAS Detector at the LHC

Transcription

1 The ATLAS Detector at the LHC Results from the New Energy Frontier Cristina Oropeza Barrera Experimental Particle Physics University of Glasgow

2 Somewhere near the Swiss Alps...

3 A Toroidal LHC ApparatuS ATLAS is the largest particle detector ever built! Integrated by four main components:

4 A Toroidal LHC ApparatuS Inner Detector measure momentum of charged particles and reconstruct trajectories and vertices. Transition Radiation Tracker SemiConductor Tracker Pixel detector University of Glasgow involved in its construction

5 A Toroidal LHC ApparatuS Calorimeters measure the energy of neutral and charged particles. LAr electromagnetic calorimeters Tile calorimeters

6 A Toroidal LHC ApparatuS Muon Spectrometer identify and measure the momentum of muons. Muon chambers

7 A Toroidal LHC ApparatuS Magnet System bend charged particles to measure momentum. Solenoid magnet Toroid magnets

8 A Toroidal LHC ApparatuS ATLAS is a general-purpose detector. Physics goals: Re-discover the Standard Model: Minimum Bias Underlying Event W/Z production Top quark Discoveries: Higgs Boson Physics Beyond the SM Heavy Ion Collisions The successful operation of such a complex detector and the careful analysis of the data, can only be done in a Collaboration: University of Glasgow University of Edinburgh ~ 3,000 scientists (1,000 students) ~ 170 institutes ~ 40 countries

9 First Collisions December 2009 ATLAS registers its first collisions with all sub-systems fully operational: 900 GeV proton-proton collision

10 First Collisions December 2009 ATLAS registers its first collisions with all sub-systems fully operational: Happy times!

11 First Collisions Since then, the LHC has delivered much more: 2.36 TeV proton-proton Collision

12 First Collisions Since then, the LHC has delivered much more: 7 TeV proton-proton Collision

13 First Collisions Since then, the LHC has delivered much more: Lead-Lead Collision

14 First Collisions Since then, the LHC has delivered much more: Lead-Lead Collision

15 First Results In little over a year of data-taking: 15 papers published based on 20 collision data (many more coming in the next few weeks!) Over 0 approved results for conferences (many more coming in the next few weeks!) Will discuss only a few selected results. Complete list: Universities of Glasgow and Edinburgh involved...

16 Minimum Bias & Underlying Event arxiv:12.54 The description of low-pt interactions requires phenomenological models. Motivation: evaluate detector performance, characterise biases on high-pt processes, tune models. -2 [ GeV T N ch /d dp 2 ) d T 1/(2 p 1/N ev Ratio ] n ch 2, p > 0 MeV, < 2.5 T ATLAS s = 7 TeV Data 20 PYTHIA ATLAS AMBT1 PYTHIA ATLAS MC09 PYTHIA DW PYTHIA 8 PHOJET Data Uncertainties MC / Data 1 p T [GeV] Underlying event are all those processes accompanying the hard interaction in protonproton collisions. N ch /d d > 2 <d MC/Data arxiv: Transverse Region p > 0.1 GeV and < 2.5 T Data 20 PYTHIA ATLAS MC09 HERWIG+JIMMY ATLAS MC09 ATLAS s = 7 TeV PYTHIA DW PYTHIA Perugia0 PHOJET lead p [GeV] T

17 W/Z Boson Production The W/Z bosons are fundamental milestones for the re-discovery of the Standard Model in the LHC. The Z leptonic decay is an excellent way to calibrate the detector to high precision. W/Z boson decays constitute the dominant backgrounds to new physics searches. Production cross-sections in very good agreement with theoretical predictions. arxiv:.2130

18 Top Quark The top quark was discovered at Fermilab 15 years ago. The LHC is a top-quark factory so its properties can be studied in great detail. Invariant mass of the highest-pt 3jet combination. Agrees with top hypothesis! Pair production cross-section in perfect agreement with theory. It s the most precise measurement at 7 TeV. arxiv:

19 Higgs searches ATLAS-PUB Projecting into the future -1 Integrated Luminosity, fb Median 95% CL limit 1 s=7 TeV s=8 TeV -1 ATLAS Preliminary (Simulation) m H [GeV] -1 Integrated Luminosity, fb 12 ATLAS Preliminary (Simulation) 5 s=7 TeV 5 s=8 TeV 3 s=7 TeV 3 s=8 TeV 95% CL s=7 TeV 95% CL s=8 TeV m H [GeV] With 1 fb -1 of data, ATLAS will be able to provide a 95% C.L. exclusion over the range 130 GeV < MH < 460 GeV. ATLAS excludes at 95% C.L. a SM-like Higgs boson with a production cross-section 1.2σSM a value of MH = 160 GeV in the channel: 95% CL Limit on / SM 3 2 ATLAS Preliminary Observed PCL Expected PCL ± Ldt = 35 pb s = 7 TeV Observed CLs Expected CLs ATLAS-CONF Tevatron <L> = 5.9 fb Observed CLs Expected CLs Tevatron Exclusion m H [GeV]

20 Heavy Ions The heavy ion run at the end of 20 collided Pb-Pb nuclei at a centre-of-mass energy of 2.76 TeV. Collisions of heavy ions at ultra-relativistic energies are expected to produce quark gluon plasma which can produce Jet Quenching. First observation of an enhancement of events with large di-jet asymmetries. arxiv:

21 Summary Excellent performance of the ATLAS Detector in this first year of data-taking. Many interesting physics results already published (only a handful shown here today). Many more results soon to come! LHC has re-started after the winter shutdown. Next couple of years will be dedicated to Higgs-hunting! 2011 will be an exciting year!