1. 7/6/20101L. Rossi – IPRD10 - Siena Leonardo Rossi (INFN Genova) on behalf of the ATLAS Collaboration IPRD10, Siena, June 7, 2010 ATLAS Status Brief recall of the apparatus Brief recall of the apparatus integrated luminosity and running conditions integrated luminosity and running conditions some key commissioning results some key commissioning results perspectives perspectives Recent results (  Fido Dittus) Recent results (  Fido Dittus)

2. 7/6/2010L. Rossi – IPRD10 - Siena2 A Toroidal LHC ApparatuS: multipurpose detector designed to cover all the expected physics channels at the TeV energy scale weight ~ 7000 tons height 25m length 46m ~10 8 channels (90% in the tracker) η=-ln(tan(Θ/2)) ATLAS

3. 7/6/2010L. Rossi – IPRD10 - Siena3 Measures charged tracks trajectories and is immersed in a 2 Tesla SC solenoidal B-field Is made of 3 sub-detectors: (resolution) Pixel : 10/115 μm in R ϕ /z Silicon strip(SCT):17/580 μm Transition Radiation Tracker (TRT): 130μm in R ϕ ID covers : |η| < 2.5 (2.0 for TRT) with 3 Pixel measurements, 8 SCT and ~30 TRT. Designed for: -  track >90% (  ) and 99% (  ) - σ pT /p T = 0.05% p T ⊕ 1% and -  (ip) = 10  m at large momenta The Inner Detector

4. 7/6/2010L. Rossi – IPRD10 - Siena4 Energy measurement (and if there is unbalance, ie. E T miss) EM calorimeter (LAr): – Precise measurement of e,g energy (+ hadrons (HEC, FCal) beyond Tile acceptance) – coverage |η|< 4.9 Hadronic calorimeter (Tile): – energy deposit of hadrons – coverage |η|<1.7 Calorimeters

5. 7/6/2010L. Rossi – IPRD10 - Siena5  spectrometer Immersed in a torodial magnetict field (3x8 SC toroids) in air  Bdl ~ 8 Tm Precision chambers and trigger chambers – MDT (Monitored Drift Tubes) – RPC (Resistive Plate Ch.) – CDC (Cathode Drift Chambers) – TGC (Thin-Gap Chambers) coverage |η|<2.7 barrel end-cap

6. 7/6/2010L. Rossi – IPRD10 - Siena6 Detector is up and running After Jan 2010 shut-down fix 99.5% 100%

7. L. Rossi – IPRD10 - Siena718/5/2010 Beam is clean 0.9 TeV7 TeV and stable 45  m-x 70  m-y

8. 7/6/2010L. Rossi – IPRD10 - Siena8  * =2m from April 22, minimum for 2010 run Lumi increase with bunch intensity  1.5 10 11 (~nominal)  pileup more bunches Experimental conditions are very clean too (example at 900 GeV)  excellent vacuum Raw MBTS trigger (background<10 -2 ) Asking for a reconstructed vertex drops bkgnd by O[10 3 ]

9. 7/6/2010L. Rossi – IPRD10 - Siena9 Multi-vertex events have been reconstructed already (commissioning is simpler without, but we better get used...)

10. 7/6/2010L. Rossi – IPRD10 - Siena10 The integrated luminosity collected so far Add most recent plot of integrated lumi from https://twiki.cern.ch/twiki/bin/view/Atlas/RunStatsPublicResults2010 We have entered the high-p T domain at last!

11. 7/6/2010L. Rossi – IPRD10 - Siena11 van der Meer scan for absolute luminosity measurement it will provide measurement with 10% accuracy (now 30%) beam spot ~ 35  m x-scan y-scan LUCID online plots

12. 7/6/2010L. Rossi – IPRD10 - Siena12 Trigger for start-up (min-bias) ATLAS trigger has 3 levels of increasing selectivity and able to handle 40MHz collisions (storing ~ 250Hz). The inital trigger was much simpler: based on “beam is passing” (= BPTX) and “particles in a region of the solid angle” (=MBTS). BPTX is unbiased and was pre- scaled to measure the MBTS efficiency. BPTX MBTS BPTX= electrostatic beam pick-up 175m from ATLAS MBTS= Minimum Bias Trigger Scintillator, mounted on EC LAr at 3.5m from IP, covers 2.1< |η|< 3.8 with 16+16 counters. Collision event at 900 GeV. The MBTS counters above threshold are shown in yellow.

13. 7/6/2010L. Rossi – IPRD10 - Siena13 Trigger evolution for L >5 10 27 must prescale min-bias and activate more selective triggers 2 10 28 MBTS_1 (unprescaled) MBTS_1 (prescaled/15) EM2 Jet5 00 Overall trigger rate: 250 Hz (400 MB/s) 10 1 100 1000 ZDC (prescaled/15)

14. 7/6/2010L. Rossi – IPRD10 - Siena14 The trigger strategy must evolve with luminosity (see the case for the  ) Use lower lumi samples to understand and tune triggers (timing, efficiency, control samples, etc.)

15. 7/6/2010L. Rossi – IPRD10 - Siena15 e.g. trigger threshold in the calorimeters ok and understood (vs simulation) Data/MC agreement on E T within 5% Low and sharp thresholds Jet trigger EM trigger tigger-off-line correlation

16. 7/6/2010L. Rossi – IPRD10 - Siena16 Apply simple vertex b-tagger to 900 GeVMinBiasdata In “loose” mode, most tags are Ks. Distributions of impact parameters for tracks in secondary vertices agree well with MC simulations (left).Running the tagger in “standard” mode, find 9 events out of ~ 400K with significant positive decay length, one of which looks like a heavy flavour candidate: B-tagging @ 900 GeV

17. 7/6/2010L. Rossi – IPRD10 - Siena17 Comparison data-MC at 7 TeV Track variables All details (including missing modules) are included as well as the beam spot. Excellent agreement

18. 7/6/2010L. Rossi – IPRD10 - Siena18 Jets Distributions for p T (jet)>20 GeV (AntiKt R=0.6). Jet energy at the electromagnetic scale Min.bias trigger, lumi~350  b -1 Good agreement

19. 7/6/2010L. Rossi – IPRD10 - Siena19 Jets of 310GeV e 350 GeV (electromagnetic scale),  ~176 degrees

20. 7/6/2010L. Rossi – IPRD10 - Siena20 Jets (hadronic scale) Energy integrated over a cone R=0.2 around an isolated track divided by the track momentum Data/simulation comparison (at 900 GeV)  validation of the hadronic scale in simulation and base to build-up the overall jet energy scale Agreement within ~5%

21. 7/6/2010L. Rossi – IPRD10 - Siena21 E T miss Calculated using the clusters after noise suppression and at the em. scale Min.bias trigger, lumi~110  b -1 Excellent agreement over 6 orders of magnitude....

22. 7/6/2010L. Rossi – IPRD10 - Siena22 Highlights and perspectives (see also F.Dittus talk) After rediscovering the physics of the sixties (K 0 s,  ) and of the seventies (D*, J/  ) ATLAS is now affording the physics of the eighties (W,Z)

23. 7/6/2010L. Rossi – IPRD10 - Siena23 ….and looks forward for the physics of the tens. We started a very long run (~18 months) aimed at an integrated luminosity of 1 fb -1 (100 pb -1 for end 2010) at 7 TeV. The experiment performs according to design specifications and the understanding of the apparatus and MC tools is excellent (and beyond expectations in this early phase). ATLAS will then become competitive with CDF/D0 during the coming run especially for the very high p T phenomena. J.Stirling http://projects.hepforge.org/mstwpdf/plots/plots.html

24. backup 7/6/2010L. Rossi – IPRD10 - Siena24

25. 7/6/2010L. Rossi – IPRD10 - Siena25 Expected number of events in ATLAS for 100 pb -1 after cuts J/ψ  μμ W  μν tt  μν+X inside peak (strong cuts)