Status of LHC experiments and prospects for early physics. Sergio Bertolucci INFN LP07, Daegu, August 18, 2007

Transcription

1 Status of LHC experiments and prospects for early physics Sergio Bertolucci INFN LP07, Daegu, August 18,

2 W + LHCf +TOTEM 2/39

3 How are the experiments doing? Impressive progress from all the experiments Credible schedules, compatible with the machine Endgame performed avoiding dangerous shortcuts Unavoidable problems being solved with a lot of ingenuity (and extra work!) All the experiments are undergoing the delicate transformation from a set of subsystem to a single detector 3

4 Bat 40 CERN Building 40 (ATLAS and CMS building) 4

5 MAGNET (S) ATLAS Air-core toroids + solenoid in inner cavity 4 magnets Calorimeters in field-free region CMS Solenoid Only 1 magnet Calorimeters inside field TRACKER EM CALO Si pixels+ strips TRT particle identification B=2T σ/p T ~ 5x10-4 p T 0.01 Pb-liquid argon σ/e ~ 10%/ E uniform longitudinal segmentation HAD CALO Fe-scint. + Cu-liquid argon (10 λ) σ/e ~ 50%/ E 0.03 Si pixels + strips No particle identification B=4T σ/p T ~ 1.5x10-4 p T PbWO 4 crystals σ/e ~ 2-5%/ E no longitudinal segm. Cu-scint. (> 5.8 λ +catcher) σ/e ~ 100%/ E 0.05 MUON Air σ/p T ~ 7 % at 1 TeV standalone Fe σ/p T ~ 5% at 1 TeV only combining with tracker 5

6 ATLAS October 2005 Barrel toroid system (eight 25m long-100 tons superconducting coils): tested at full field (20 ka current) in November

7 Barrel calorimeter (EM Pb/LAr + Hadron Fe/scintillator) in its final position at Z=0. EM calorimeter is filled with LAr and cold (87 K) November 2005 October

8 One end-cap calorimeter (LAr EM, LAr HAD, LAr Forward inside same cryostat, surrounded by HAD Fe/Scintillator Tilecal) being moved inside the barrel toroid 8

9 Inner tracker 3 sub-systems: Silicon pixels : channels Silicon strips (SCT) : channels Transition Radiation Tracker (TRT) : straw tubes filled with gas, channels SCT TRT Cosmic muon recorded in the barrel TRT (in the assembly surface room) February

10 SCT + TRT in place, May 2007 Inner Detector installation in underground cavern completed Pixels (+ beam pipe) insertion June

11 Installation of barrel muon chambers (~ 700 stations) started in December 2005 and is ~ completed. 11

12 Forward muon spectrometer: 6 out of 8 big wheels installed in the cavern 4 big wheels End-cap toroid End-wall wheels 12

13 The two end-cap toroid magnets installed in June-July

14 First data collected in the underground cavern: cosmic muons Very useful to: run together several sub-detectors with common trigger, data acquisition and monitoring systems. Data analyzed with final software shake-down and debug the detector in its final position fix problems gain global operation experience before collisions start Rate (~100 m below ground): ~ O(10 Hz) Cosmic muon in Muon Spectrometer Cosmic muon in LAr EM calorimeter and Tile calorimeter 14

15 CMS Compact and modular : assembled at the surface and lowered in the cavern slice by slice (11 in total) 15

16 First slices going down end 2006, six out of eleven installed so far 16

17 The central heaviest slice (2000 tons) including the solenoid magnet lowered in the underground cavern in Feb CMS solenoid: Magnetic length 12.5 m Diameter 6 m Magnetic field 4 T Nominal current 20 ka Stored energy 2.7 GJ Tested at full current in Summer

18 Hadron calorimeter completed in 2006 Cosmic muon in HCAL 18

19 CMS Magnet Test and Cosmic Challenge in August-October 2006 Cosmics run of a ~ full detector slice (few percent of CMS coverage) inside 4T field. 200 million cosmic muons collected in the surface hall (rate is khz at surface) ECAL Magnet HCAL Tracker A gold-plated muon traversing all detectors Muon chambers 19

20 CMS Inner tracker: ~ 220 m 2 of Si sensors 10.6 million Si strips 65.9 million Pixels Inner Disks TID Outer Barrel TOB Pixels End-cap TEC Installation in underground cavern in September TIB inserted into TOB (Jan. 2007) Inner Barrel TIB End-cap (TEC) disk 20

21 CMS ECAL BARREL W σ = 1.5% 21/39

22 ECAL endcap planning Logistically most efficient installation window after completion of Dee 2 Dee1 mid Dec Dee2 end Feb Dee3 end May Dee4 June 22

23 Expected performance: muon measurement Muon momentum resolution in CMS ATLAS Muon Spectrometer: E µ ~ 1 TeV Δ~500 µm B~0.5T σ/p σ ~10% δδ~50 µm - alignment accuracy to ~20 µm y L~5m z! 23

24 Electron measurement Electron E-resolution measured in beam tests of ATLAS EM calorimeter (Pb/LAr) Electron E-resolution measured in beam tests of CMS EM calorimeter (crystals) σ / E 9.4% / E 0.1% Mean Resolution (18 crystals): µ + µ - KK resonance in TeV -1 ED M c = 4 TeV 1 TeV e ± (µ ± ): σ (E)/E 0.5% (5%) heavy narrow resonances will likely be discovered in the X ee channel e + e - m(l + l - ) GeV 24

25 LHCb detector ~ 300 mrad p p 10 mrad Forward spectrometer (running in pp collider mode) Inner acceptance 10 mrad from conical beryllium beam pipe 25

26 LHCb detector Vertex locator around the interaction region Silicon strip detector with ~ 30 µm impact-parameter resolution 26

27 LHCb detector Tracking system and dipole magnet to measure angles and momenta Δp/p ~ 0.4 %, mass resolution ~ 14 MeV (for B s D s K) 27

28 LHCb detector Two RICH detectors for charged hadron identification 28

29 LHCb detector e h Calorimeter system to identify electrons, hadrons and neutrals 29

30 LHCb detector µ Muon system 30

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33 Installing ITS SSD + SDD 33

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35 Starting ITS (close the to) installation final position of the ITS detector 35

36 SPD: the beauty of 10 Million pixels 36

37 FMD- part 1 37

38 DAQ ALICE Control Room during TPC test June 07: first operation of TRG, DAQ, HLT, DCS, ECS from the ACR CR1 The left row of racks: TPC LDC s with DDL patch cords. 38

39 and in parallel DAQ TRIGGERS Detector Control Systems Online and Offline software Commissioning Analysis groups 39

40 ~120 computing centers ~ 40 countries The LHC Computing Grid (LCG) relies on grid infrastructure provided by EGEE, OSG, Nordugrid. Enormous progress made in the middleware, data handling, databases, analysis tools, etc.. In depth tests (Data Challenges) have constantly upgraded the level of service. The system has been stress tested for MC production/organized event reconstruction and distribution. It has not yet been tested on the analysis 40

41 ATLAS 2007 computing timeline W Running continuously throughout the year (increasing rates): Simulation production Cosmic ray data-taking (detector commissioning) January to June: Data streaming tests February through May: Intensive Tier-0 tests From February onwards: Data Distribution tests From March onwards: Distributed Analysis (intensive tests) May to July: Calibration Data Challenge June to October: Full Dress Rehearsal November: GO! So far we are on track following this timeline 41/39

42 CMS 2007 computing timeline MC Production 30Mevts/mth Jan Feb 1_2_0 1_2_3 - W HLT Exercise Pre CSA07 50Mevts/mth CSA07 Mar April May June July Aug 1_3_0-1_4_0-1_5_0 - Sep Oct 42/39

43 General General LHC LHC schedule schedule W Engineering run originally foreseen at end 2007 now precluded by delays in installation and equipment commissioning. 450 GeV operation now part of normal setting up procedure for beam commissioning to high-energy General schedule being reassessed, accounting for inner triplet repairs and their impact on sector commissioning All technical systems commissioned to 7 TeV operation, and machine closed April 2008 Beam commissioning starts May 2008 First collisions at 14 TeV c.m. July 2008 Pilot run pushed to 156 bunches for reaching cm -2 s -1 by end 2008 No provision in success-oriented schedule for major mishaps, e.g. additional warm-up/cooldown of sector 43/39

44 General General LHC LHC schedule Schedule W Consolidation. Machine Operation testing of available sectors Beam pipes installed and backed out Checkout Beam Commissioning to 7 TeV Interconnection of the continuous cryostat Leak tests of the last sub-sectors Inner Triplets repairs & interconnections Global pressure test &Consolidation Flushing Cool-down. Warm up Powering Tests 44/39

45 First Month at W ALICE, ATLAS and CMS will collect millions of minimum bias events and huge number of di-jets events With these data experiments will perform first alignment and calibrations and performance studies of the detector. Also first QCD measurements (Jet cross sections, features of the minimum bias events) Tuning Montecarlo for min bias events 45/39

46 From the Tevatron to the LHC High-p T QCD jets g g q q W, Z q W, Z q Higgs m H =150 GeV g g t H q, g pairs, m ~ 1 TeV g g q q q No hope to observe light objects (W, Z, H?) in fully-hadronic final states rely on l, γ Mass resolutions of ~ 1% (10%) needed for l, γ (jets) to extract tiny signals from backgrounds, and excellent particle identification (e.g. e/jet separation) Fully-hadronic final states (e.g. q* qg) can be extracted from backgrounds only with hard O(100 GeV) p T cuts works only for heavy objects S (EW) /B (QCD) larger at Tevatron than at LHC 46

47 With the first physics data in fb -1 (100 pb -1 ) 1 (m)year (1 (m)month) at L= cm -2 s -1 may collect a O(100 pb -1 ) per experiment by end early 2009 Channels (examples ) Events to tape for 100 pb -1 Total statistics from (per expt: ATLAS, CMS) some of previous Colliders W µ ν ~ 10 6 ~ 10 4 LEP, ~ 10 6 Tevatron Z ~ 10 5 ~ 10 6 LEP, ~ 10 5 Tevatron tt W b W b µ ν +X ~ 10 4 ~ 10 4 Tevatron QCD jets p T > 1 TeV > m = 1 TeV ~ g g With these data: Understand and calibrate detectors in situ using well-known physics samples e.g. - Z ee, µµ tracker, ECAL, Muon chambers calibration and alignment, etc. - tt blν bjj jet scale from W jj, b-tag performance, etc. Rediscover and measure SM physics at s = 14 TeV : W, Z, tt, QCD jets (also because omnipresent backgrounds to New Physics) prepare the road to discoveries it will take time 47

48 Jump in a new territory very soon Jet cross section QCD Jet cross-section Explore E T (jet) > 500 GeV after few weeks at cm -2 s -1 Expect >10 3 events with E T (jet) > 1 TeV with 100 pb -1 (by LP09) Going fast beyond the Tevatron reach Early sensitivity to quark compositeness: LHC Λ ~ 5 (8)TeV with 100 (1000) pb -1 Tevatron Compositeness : LHC ultimate sensitivity up to Λ 40 TeV 48

49 Example of initial measurement: understanding detector and physics with top events Can we observe an early top signal with limited detector performance? And use it to understand detector and physics? σ tt 250 pb for tt bw bw blν bjj ATLAS preliminary 4 jets p T > 40 GeV 50 pb -1 2 jets M(jj) ~ M(W) Isolated lepton p T > 20 GeV 3 jets with largest p T W+n jets (Alpgen) + combinatorial background NO b-tag!! E T miss > 20 GeV Top signal observable in early days with no b-tagging and simple analysis (100 ± 20 evts for 50 pb -1 ) measure σ tt to 20%, m to 10 GeV with ~100 pb -1? In addition, excellent sample to: understand detector performance for e, µ, jets, b-jets, missing E T, understand / constrain theory and MC generators using e.g. p T spectra 49

50 An easy case : Z e + e -, mass ~ 1 TeV with SM-like couplings (Z SSM ) Mass Expected events for 1 fb -1 Integrated luminosity needed for discovery (after all analysis cuts) (corresponds to 10 observed evts) 1 TeV ~ 160 ~ 70 pb TeV ~ 30 ~ 300 pb -1 2 TeV ~ 7 ~ 1.5 fb -1 large enough signal for discovery with ~100 pb -1 up to m > 1 TeV small SM background signal is (narrow) mass peak above background 50

51 SUSY searches at LHC Dominant processes : q q, q g, g g production strong production huge cross-section e.g. q q α s α s g ~ q ~ q m( q, g ) ~ 1 TeV e.g. for ~ 100 events produced with 100 pb -1 ~ q, ~ g heavy (present Tevatron limits: m > GeV) cascade decays g q q q spectacular signatures with many jets, leptons + missing E relatively easy to extract SUSY signal from SM backgrounds at LHC (in most cases ) χ 0 2 χ 0 1 Z This particle (lightest neutralino) is stable, neutral and weakly interacting escapes detection (like ν) apparent missing energy in the final state 51

52 Main backgrounds to SUSY searches in jets + E T miss topology (one of the most dirty signatures ) : W/Z + jets with Z νν, W τν ; tt; etc. QCD multijet events with fake E T miss from jet mis-measurements (calorimeter resolution and non-compensation, cracks, ) cosmics, beam-halo, detector problems overlapped with high-p T triggers, Run II V. Shary CALOR04 Understanding E T miss spectrum (and tails from instrumental effects) is one of most crucial and difficult experimental issues for an early SUSY discovery. Estimate backgrounds using as much as possible data (control samples) and MC Background process (examples.) Z ( νν) + jets W ( τν) + jets tt blνbjj QCD multijets Control samples (examples.) Z ( ee, µµ) + jets W ( eν, µν) + jets tt blν blν lower E T sample 52

53 Example : CMS m ( q, g ) ~ 400 GeV LHC discovery reach Needed Ldt / time Reach in gluino mass 100 pb -1 (end 2008?) ~ 1.3 TeV 1 fb -1 (mid 2009?) ~ 1.7 TeV ultimate (300 fb -1 ) up to ~ 3 TeV SUSY can be discovered quickly (in principle with 100 pb -1 ) provided detectors and backgrounds well understood (this will take more time than in the previous/z case) If nothing found at LHC, (low-e) SUSY is likely dead need another explanation for e.g. dark matter 53

54 A difficult case: a light Higgs (m H ~ GeV) Higgs production cross sections at LHC 54

55 H f ~ m f f Remember: light fully-hadronic final states cannot be extracted from QCD background at hadron colliders m H < 130 GeV : H bb, ττ dominate best search channels at the LHC : tth bb l+x, qqh qq ττ H γγ (rare decay mode) This is the most difficult region (S/B <<1)! m H > 130 GeV : H WW (*), ZZ (*) dominate best search channels at the LHC : H ZZ (*) 4l (gold-plated) H WW (*) lν lν Especially in the region m H <130 GeV, excellent detector performance needed to suppress the huge backgrounds: b-tag, l/γ E-resolution, γ/j separation, missing E T resolution, forward jet tag, etc. Higgs searches used as benchmarks for ATLAS and CMS detector design 55

56 H γγ CMS 100 fb -1 H eeµµ Requires excellent EM calorimetry (E-resolution, γ/π 0 separation) Gold-plated channel at LHC (~ background free ) 56

57 Summary of Higgs discovery potential at the LHC Needed Ldt per experiment (fb -1 ) With 1 fb -1 : 95% C.L. exclusion 5 fb -1 : 5σ discovery over full allowed mass range Final word about Higgs mechanism by 2010? Most difficult region ATLAS+CMS If Higgs found, mass can be measured to 0.1%, couplings to ~ 10-20% major insight into electroweak symmetry breaking mechanism 57

58 What about the Tevatron? /exp. CDF+D0 sensitivity Today : ~ 3 fb -1 /experiment 2009: expect 6-7 fb -1 /experiment Tevatron operation in 2010 being discussed With 4 (8) fb -1 : ~no 5σ sensitivity 3σ evidence up to 120 (130) GeV 95% C.L. exclusion up to ~ 130 (180) GeV competition between Tevatron and LHC in 2009 if m H < 130 GeV 58

59 Flavor Physics A specialized detector + ATLAS & CMS At LHCb huge xsection (.5 mb), long decay length (1 cm).but high backgrounds, high performance trigger fundamental. Systematics will be more important than statistics, at the startup at least. Rich program possible, even at modest luminosities A few examples 59

60 Very Rare B Decays: B s µ + µ Very rare loop decay, sensitive to New Physics: BR ~3.5x10 9 in SM, can be strongly enhanced in SUSY Current 90% CL limit from CDF+D0 with 1 fb 1 is ~20 times SM s µ + W? t " b W? µ " Main issue is background rejection With limited MC statistics, indication that main background is b µ, b µ MSSM 60

61 Very Rare B Decays: B s µ + µ Limit at 90% C.L. Integrated (only luminosity bkg is observed) (fb 1 ) BR (x10 9 ) Expected final CDF+D0 Limit Uncertainty in bkg prediction SM prediction BR (x10 9 ) LHCb Sensitivity (signal+bkg is observed) 5σ SM prediction 3σ Integrated Luminosity (fb -1 ) Integrated Luminosity (fb -1 ) 0.05 fb 1 competitive with CDF+D0 0.5 fb 1 exclude BR values down to SM 2 fb 1 3σ evidence of SM signal 10 fb 1 >5σ observation of SM signal 61

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65 And of course there is more Forward Physics QCD studies σ tot.. In particular one should not forget Heavy Ions: even a short run at a very modest luminosity could deliver exciting results! 65

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68 To conclude One year is dividing us from the LHC start-up, but we can clearly see the light at the end of the tunnel. Experiments of unprecedented complexity and power are preparing to exploit the new energy domain, and will be ready at the machine turn-on. Even modest integral luminosities will allow an exciting physics program, where (long awaited) surprises are not excluded. The success of this enterprise is the keystone for the future of the field. 68