LHC State of the Art and News

Transcription

1 LHC State of the Art and News ATL-GEN-SLIDE June 2010 Arno Straessner TU Dresden on behalf of the ATLAS Collaboration FSP 101 ATLAS Vulcano Workshop 2010 Frontier Objects in Astrophysics and Particle Physics May 24-29, 2010

2 Outline Introduction Status of the Large Hadron Collider and the LHC Experiments First LHC Measurements Physics Prospects until 2011 Conclusion mainly ATLAS results are shown here results of other experiments very similar LHC State of the Art and News - Arno Straessner 2

3 The Large Hadron Collider LHC design values: LHCb ATLAS pp collisions at 14 TeV centre-ofmass energy 1232 super-conducting dipole magnets with 8.3 T field CMS ALICE instantaneous luminosity of L = cm -2 s ns bunch spacing 2808 bunches per beam 1.15 x protons per bunch stored energy of 350 MJ/beam LHC State of the Art and News - Arno Straessner 3

4 The LHC Detectors ATLAS CMS Standard Model, Higgs Bosons, SUSY, and more LHCb ALICE CP physics Heavy Ion Collisions LHC State of the Art and News - Arno Straessner 4

5 A Long Way Towards Regular LHC Running repair work after disastrous magnet incident in 2008 new quench protection system for magnets sensitive to small resistance increases (nω) full repair will be carried out in LHC shutdown 2011/12 LHC ready for pp collisions in Nov+Dec 2009: at 2 x 450 GeV injection energy integrated luminosity μb 1 (ATLAS+CMS) recorded with stable beams: μb 1 (±30% syst. uncertainty) 538,000 collision candidates in ATLAS during stable conditions collision candidates at 2.36 TeV: 34,000 first LHC results on 0.9 TeV and 2.36 TeV collisions are now published LHC State of the Art and News - Arno Straessner 5

6 World Record pp Collision Energy of 7 TeV LHC reached 7 TeV centre-of-mass energy with 1 st collision events on March 30, 2010 very good luminosity lifetime longest physics fill: 30 hours peak luminosity continuously improved: L max = 8x10 28 cm -2 s -1 2 and 3 colliding bunches collimator and beam dump tests very important: machine studies for safe high intensity operation reached p per bunch goals for 2010/2011 run 7 TeV max. energy 768 colliding bunches total luminosity of 1 fb 1 beyond 2013: go for TeV ultimate energy fb 1 until fb 1 until 2030 LHC State of the Art and News - β* squeezed to 2m x10 improvement Arno Straessner higher beam intensity 6

7 Integrated Luminosity data taking efficiency ~ 95% very similar for CMS, LHCb, and ALICE (>80%) LHC State of the Art and News - Arno Straessner 7

8 7 TeV Collisions in ATLAS largest physics cross-section at LHC: inelastic pp collisions (minimum bias) LHC State of the Art and News - Arno Straessner 8

9 7 TeV Collisions With Pile-Up CMS no. of pile-up events increases with intensity per bunch at nominal LHC luminosity and energy: ~25 pile-up events (in-time) LHC State of the Art and News - Arno Straessner 9

10 ATLAS Detector Performance η <3.0 η <4.9 4 Tesla 2 Tesla η <2.5 LHC State of the Art and News - Arno Straessner 10

11 ATLAS Status Page on 1 st Day of 7 TeV Run high operational fraction of all detector components: Pixel 97.5% of 80 M channels SCT 99.8% of 6 M channels TRT 98% of 370 k channels calorimeter channels > 97.3 % (LAr, Tile) muon spectrometer > 99% (MDT, CSC) muon trigger chambers > 99% (RPC, TGC) LHC State of the Art and News - Arno Straessner 11

12 The ATLAS Trigger System 40 MHz Collision Rate Hardware ACTIVE 75 khz L1 Trigger Software MONITORING MODE 3 khz L2 Trigger 200 Hz EF Trigger ~1.5 MB/ev storage Minimum Bias Trigger Scintillator primary trigger in trigger commissioning phase: minimum bias trigger scintillators MBTS hit on either of the detector sides >99.8 % efficient time difference between hits on both sides is used to estimate beam background in collision events other triggers run in parallel to compare their performance to offline analysis LHC State of the Art and News - Arno Straessner 12

13 The ATLAS Trigger System 40 MHz Collision Rate Hardware ACTIVE 75 khz L1 Trigger Software MONITORING MODE 3 khz L2 Trigger 200 Hz EF Trigger ~1.5 MB/ev storage Minimum Bias Trigger Scintillator primary trigger in trigger commissioning phase: minimum bias trigger scintillators MBTS hit on either of the detector sides >99.8 % efficient time difference between hits on both sides is used to estimate beam background in collision events after offline vertex identification other triggers run in parallel to compare their performance to offline analysis LHC State of the Art and News - Arno Straessner 13

14 The ATLAS Trigger System example: turn-on curves of trigger efficiencies measured at 900 GeV L1 jet trigger L1 e/γ trigger these triggers are ready to be used ATLAS is prepared for higher luminosities same holds for CMS, LHCb, and ALICE LHC State of the Art and News - Arno Straessner 14

15 Performance of the Inner Detector hits on reconstructed particle tracks: TRT SCT overlay of many events from one run Pixel RMS dominated by vertex resolution of 75 μm intrinsic accuracy: pixel 10 μm (rφ) 115 μm (z) SCT 17 μm (rφ) 580 μm (z) TRT 130 μm LHC State of the Art and News - Arno Straessner 15

16 Reconstruction of Kaons and Lambdas PDG: m K0 =497.6 MeV reconstructed mass peaks in good agreement with PDG values well described by MC simulation very good understanding of detector PDG: m Λ = MeV LHC State of the Art and News - Arno Straessner 16

17 Tagging of b-jets important for top physics measurements, since BR(t Wb)=100% essential for particle searches, e.g. b-associated production of SUSY-Higgs-Bosons secondary vertex with 4 tracks LHC State of the Art and News - Arno Straessner 17

18 Calorimeter Performance e.m. shower profiles well described example: energy of photon candidates in 2 nd LAr calorimeter layer π 0 γγ reconstruction of π 0 γγ mass peak very good understanding of calorimetry LHC State of the Art and News - Arno Straessner 18

19 Missing Transverse Energy and Jet p T missing transverse energy agrees well with MC predictions over 6 orders of magnitude missing E T resolution as expected from MC important ingredient for searches for SUSY look for LSP signatures highest jet p T of 350 GeV observed in 7 TeV collisions LHC State of the Art and News - Arno Straessner 19

20 ATLAS Muon Spectrometer muon system with large η coverage for momentum measurement and trigger s=7 TeV Ldt=320 μb -1 J/ψ μμ signal observed muon tracks reconstructed in muon spectrometer and inner detector gaussian-mean mass: 3.06±0.02 GeV resolution: 0.08±0.02 GeV N signal = 49±12 N background = 28±4 (computed in a mass range 3σ around the peak) LHC State of the Art and News - Arno Straessner 20

21 Ready For Some Physics An Overview inelastic pp scattering dominates minimum bias QCD processes have large crosssections 2-jet events, 3-jet events,... with and w/o b-jets many events with W and Z bosons LHC is a top quark factory new particles searches for: Higgs (SM and supersymmetric), SUSY,.. 13 orders of magnitude LHC State of the Art and News - Arno Straessner 21

22 Measurement of Hadron Production model independent measurement of primary charged particle multiplicity distributions from inelastic events kinematic range η <2.5 and p T > 500 MeV, N ch 1 in this phase space use MBTS single-arm scintillator trigger for high efficiency in phase space no removal of Single Diffractive (SD) component. correct reconstructed-track distributions back to hadron level trigger and vertex corrections are measured in data main systematics is from track reconstruction efficiency (4% on dn ch /dη) 1 st ATLAS pp physics paper Phys Lett B 688 (2010) 21 LHC State of the Art and News - Arno Straessner 22

23 More Hadronic Activity Then Predicted rate higher than modeled by PYTHIA and PHOJET tunes, both at 0.9 TeV and 7 TeV similar observation by CMS LHC State of the Art and News - Arno Straessner 23

24 Parton Luminosities And Event Rates examples of dominating partonic processes at the LHC: q (') q W/Z g g t t t H g g t t g g t t t Process (no selection cuts) Evts (7 TeV) in 100 pb -1 Ratio 7 TeV/14 TeV QCD, p T >100 GeV 32 M 0.2 Z inclusive (NLO) 3 M (3% Z ll) 0.4 W inclusive (NLO) 10 M (11% W lv) 0.5 top pairs (NLO+NNLL) H (m H =150 GeV, NNLO) several W μv, W ev and Z ee candidates observed at 7 TeV using ~8 nb -1 of data LHC State of the Art and News - Arno Straessner 24

25 W μv Candidate LHC State of the Art and News - Arno Straessner 25

26 Z ee Candidate LHC State of the Art and News - Arno Straessner 26

27 Expectations For The 2010/2011 Run the goal is to collect 1 fb -1 of data per experiment at s=7 TeV (ATLAS, CMS) we expect 2.5 M selected events in the channels W ev and W μv each 5 times more than Tevatron today measurement of W boson mass possible, but systematics are challenging: lepton energy scale, missing p T calibration, PDF's, W p T, backgrounds, pile-up,... top physics will be very interesting: Top Pair Yields cross-section measurements of top pairs at 7 TeV centre-of-mass energy top quark mass measurement aim for m top by ATLAS and CMS by the end of 2010 systematics: jet energy scale, background, pile-up,... we will overtake Tevatron with ~150 pb -1 LHC State of the Art and News - Arno Straessner 27

28 Standard Model Higgs Searches LEP and Tevatron today: m H <114.4 GeV and 162 GeV<m H <166 GeV excluded (95% C.L.) gg H WW is the most sensitive channels in the relevant mass range 7 TeV with two experiments and 1 fb -1 at s=7 TeV: if no signal found: 95% CL exclusion between 140 GeV and 200 GeV possible evidence/discovery with 3-5 sigma for m H = GeV LHC State of the Art and News - Arno Straessner 28

29 SUSY Searches msugra no mass degeneracy of particles and sparticles breaking of super-symmetry gravity mediated SUSY breaking msugra model R-parity is conserved in msugra: SUSY production in pairs lightest stable SUSY particle (LSP) is the neutralino typical SUSY signatures: multi-jets, multi-leptons, missing E T... understanding the SM background is essential p X g q LSP escapes detection missing E T p ql 0 2 q q R 0 1 LHC State of the Art and News - Arno Straessner 29

30 SUSY Discovery Reach CMS expectation in all-hadronic channels: ATLAS estimate for lepton + jets + missing-e T channel: quickly beyond Tevatron reach with 100 pb -1 squarks and gluinos with masses above 500 GeV can be discovered with 1fb -1 at 7 TeV 200 pb -1 higher energies in 2013 will push the search window wide open LHC State of the Art and News - Arno Straessner 30

31 Conclusion LHC had a very good start in 2010 at 7 TeV record centre-of-mass energy continuous machine development in parallel to data taking ATLAS, CMS, LHCb, and ALICE detectors are in good shape work ongoing to further improve performance first measurements of charged particle production at 0.9 TeV 7 TeV Standard Model physics is about to take off new physics signatures are in close reach stay tuned: LHC State of the Art and News - Arno Straessner 31