1. ITEP Physics Winter School, Moscow, 13-20/02/2010 1 D. Froidevaux, CERN Honorabilis et amplissimus rector, laudati conlegae Experimental prospects at the LHC

2. ITEP Physics Winter School, Moscow, 13-20/02/2010 2 D. Froidevaux, CERN Particle detection and reconstruction at the LHC (and Tevatron) Lecture 1 + Introduction to ATLAS/CMS experiments at the LHC: historical perspective and physics goals + Experimental environment and main design choices Lecture 2 + Expected performances of ATLAS and CMS detectors Lecture 3 + Experience collected with cosmics (2008-2009), first data with collisions (end 2009) and expectations for early physics

3. ITEP Physics Winter School, Moscow, 13-20/02/2010 3 D. Froidevaux, CERN 33 ALICE: first events (no magnetic field)  ~ 16:41

4. ITEP Physics Winter School, Moscow, 13-20/02/2010 4 D. Froidevaux, CERN 44  TPC track  TRD track  HMPID  Cherenkov Ring  Muon Spectrometer  ITS  TPC, TRD, TOF, HMPID  On 6 th December, ‘stable beams’  were declared & we could switch on  all ALICE detectors for the first time.. ALICE: first events (full detector on)

5. ITEP Physics Winter School, Moscow, 13-20/02/2010 5 D. Froidevaux, CERN 55  15/2/2006 LHCC Status Report J. Schukraft  Total events collected: > 1 M  ‘Good pp interactions’: 500 k  - 100 k : B = 0 (alignment)  - 10 k : B reversed (systematics)  - 30 k : √s = 2.36 TeV  TPC  No vertex cut !  ALICE special: Particle Identification  (very important for heavy ion physics later in 2010) ALICE: first events (full detector on)  ITS  TRD  Electrons  Pions  Velocity v/c  TOF  Protons  Kaons  Pions  all plots:  preliminary calibration & alignment !

6. ITEP Physics Winter School, Moscow, 13-20/02/2010 6 D. Froidevaux, CERN 66  PDG: 1115.7 MeV  p  PDG: 497.6 MeV  K 0 s   PDG: 1115.7 MeV  p  … National Geographic was sort of correct..      PDG: 1019.5 MeV ALICE: first events (full detector on)

7. ITEP Physics Winter School, Moscow, 13-20/02/2010 7 D. Froidevaux, CERN 77    e + e - e + e -  TPC Rods  SSD  TPC Vessel 1  TPC Vessel 2  SDD  SPD  -ray image of ALICE  photon conversion vertices     1 < p t < 1.5 GeV  PHOS (9 m 2 )  p  ALICE: first events (full detector on)

8. ITEP Physics Winter School, Moscow, 13-20/02/2010 8 D. Froidevaux, CERN 88  Sunday 6 December: machine  protection system commissioned  stable (safe) beams for first time  full tracker at nominal voltage  whole ATLAS operational  ATLAS: first events (full detector on)

9. ITEP Physics Winter School, Moscow, 13-20/02/2010 9 D. Froidevaux, CERN 99  Jet1: E T (EM scale)~ 16 GeV, η= -2.1  Jet2: E T (EM scale) ~ 6 GeV, η= 1.4  8, 14, 16 December: collisions at √s = 2.36 TeV (few hours total)  ATLAS records ~ 34000 events at flat-top  ATLAS: first events (full detector on)

10. ITEP Physics Winter School, Moscow, 13-20/02/2010 10 D. Froidevaux, CERN  10

11. ITEP Physics Winter School, Moscow, 13-20/02/2010 11 D. Froidevaux, CERN  11  γ  e + e - conversions e+e+ e-e-  γ conversion point  R ~ 30 cm (1 st SCT layer)  p T (e + ) = 1.75 GeV, 11 TRT high-threshold hits  p T (e - ) = 0.79 GeV, 3 TRT high-threshold hits  ATLAS: first events (full detector on)

12. ITEP Physics Winter School, Moscow, 13-20/02/2010 12 D. Froidevaux, CERN  12  π 0  γγ ■ 2 photon candidates with E T ( γ ) > 300 MeV ■ E T ( γγ ) > 900 MeV ■ Shower shapes compatible with photons ■ No corrections for upstream material  Data and MC normalised  to the same area  Note: soft photons are  challenging because of  material in front of  EM calorimeter  (cryostat, coil):  ~ 2.5 X 0 at η =0  ATLAS: first events (full detector on)

13. ITEP Physics Winter School, Moscow, 13-20/02/2010 13 D. Froidevaux, CERN  13  Jets  √s=2.36 TeV  √s=900 GeV  ATLAS: first events (full detector on)

14. ITEP Physics Winter School, Moscow, 13-20/02/2010 14 D. Froidevaux, CERN  14  Uncalibrated EM scale  Monte Carlo normalized to number of jets or events in data  events with  2 jets p T > 7 GeV  ATLAS: first events (full detector on)

15. ITEP Physics Winter School, Moscow, 13-20/02/2010 15 D. Froidevaux, CERN  15  Missing transverse energy ■ Sensitive to calorimeter performance (noise, coherent noise, dead cells, mis-calibrations,  cracks, etc.) and backgrounds from cosmics, beams, … ■ Measurement over full calorimeter coverage (360 0 in φ, |η| < 5, ~ 200000 cells)  METy  METx / METy indicate x/y  components of missing E T vector  METx  ATLAS: first events (full detector on)

16. ITEP Physics Winter School, Moscow, 13-20/02/2010 16 D. Froidevaux, CERN  Data: N(  )/N(  0 ) = 0.020 ± 0.003  MC: N(  )/N(  0 ) = 0.021 ± 0.003  Data: N(  )/N(  0 ) = 0.020 ± 0.003  MC: N(  )/N(  0 ) = 0.021 ± 0.003  Dec09 LHC2- CMS    CMS 2009 Preliminary Uncorrected    CMS 2009 Preliminary  CMS: first events (full detector on)

17. ITEP Physics Winter School, Moscow, 13-20/02/2010 17 D. Froidevaux, CERN  Dec09 LHC2- CMS  CMS: first events (full detector on)

18. ITEP Physics Winter School, Moscow, 13-20/02/2010 18 D. Froidevaux, CERN Muons: A Dimuon Event at 2.36 TeV  p T (  1 ) = 3.6 GeV, p T (  2 ) = 2.6 GeV, m(  )= 3.03 GeV  CMS: first events (full detector on)

19. ITEP Physics Winter School, Moscow, 13-20/02/2010 19 D. Froidevaux, CERN LHC Tevatron 10 events with 100 pb -1 However, early data analysis will focus mostly on SM processes with two goals: 1.understand performance of complex detector 2.measure basic SM processes and compare to theory and various MC tools First physics with early data: a few examples … Main point is that this is going to be unchartered territory! This is far more important than superseding e.g. Tevatron Higgs-boson limits, in the cases where they are not at the level of the expected rates for a SM Higgs boson

20. ITEP Physics Winter School, Moscow, 13-20/02/2010 20 D. Froidevaux, CERN Jets are going to be everywhere… Look for the unexpected!

21. ITEP Physics Winter School, Moscow, 13-20/02/2010 21 D. Froidevaux, CERN Low-p T physics triggers for 10 times larger electron statistics Crucial for early understanding of detector and trigger Direct J/  Direct  b,c  e DY  ee (m ee <80GeV) W  e Z  ee Z’(1TeV) Electrons pairs in ATLAS at low luminosity Threshold for ee Threshold for single e L=10 31 cm -2 s -1, 100 pb -1 L=10 33 cm -2 s -1, 100 pb -1 J/  ~250k  ~45k b,c  e 10 7 W  e ~10 6 Z  ee ~50k

22. ITEP Physics Winter School, Moscow, 13-20/02/2010 22 D. Froidevaux, CERN 10 pb -1 After all cuts: ~ 4200 (800) J/  (Y)   evts per day at L = 10 31 (for 30% machine x detector data taking efficiency) Muon spectrometer alignment, ECAL uniformity, energy/momentum scale of full detector, lepton trigger and reconstruction efficiency, … Same with muons … After all cuts: ~ 160 Z   evts per day at L = 10 31 Note:  Z (LHC)/  Z (Tevatron) ~ 10 Tracker momentum scale, trigger performance, detector efficiency, … Precision on  (Z  with 100 pb -1 : < 2% (exp. error), ~10% (luminosity error) Beware background from heavy flavours and  /K decays

23. ITEP Physics Winter School, Moscow, 13-20/02/2010 23 D. Froidevaux, CERN Z decays to leptons: a tool for precise understanding of the detector

24. ITEP Physics Winter School, Moscow, 13-20/02/2010 24 D. Froidevaux, CERN First top quarks seen outside Fermilab: top-pair cross-section through semileptonic channel

25. ITEP Physics Winter School, Moscow, 13-20/02/2010 25 D. Froidevaux, CERN 1 fb -1 With 100 pb -1 large enough signal for discovery up to m > 1 TeV Signal is (narrow) mass peak on top of small Drell-Yan background Ultimate calorimeter performance not needed Ultimate ATLAS reach (300 fb -1 ): ~ 5 TeV Tevatron reach (5 , 7 fb -1 ): ~ 1 TeV Obvious candidates for first searches: heavy resonances decaying to leptons (e.g. Z’ SSM ) Mass Expected events for 1 fb -1 Integrated luminosity needed for discovery (after all analysis cuts) (corresponds to 10 observed events) 1 TeV ~ 160 ~ 70 pb -1 1.5 TeV ~ 30 ~ 300 pb -1 2 TeV ~ 7 ~ 1500 pb -1

26. ITEP Physics Winter School, Moscow, 13-20/02/2010 26 D. Froidevaux, CERN Jets + E T miss 100 pb -1 m ~ 1 TeV m ~ 700 GeV At the LHC, for m squark,gluino ~ 1 TeV, expect 10 events/day at L=10 32 If it is at the TeV scale, it should be found “quickly” …. Large (strong) cross-section for Spectacular signatures (many jets, leptons, missing E T )  Ldt Discovery of well understood data (95% C.L. exclusion) 0.1-1 fb -1 (2009) ~1.1 TeV (1.5 TeV)  1 fb -1 (2009-2010) ~1.7 TeV (2.2 TeV) 300 fb -1 (ultimate) up to ~ 3 TeV LHC reach for gluino mass Hints with only 100 pb -1 up to m ~ 1 TeV, but precise understanding of backgrounds will require ~1 fb -1 Tevatron 95% C.L. reach: up to ~400 GeV Obvious candidates for first searches: R-parity conserving SUSY

27. ITEP Physics Winter School, Moscow, 13-20/02/2010 27 D. Froidevaux, CERN Opportunities for discoveries of new physics are numerous and detectors have been optimised using benchmarks from many models But some things might be beyond reach of LHC (and even SLHC!): Higgs-boson self-coupling Charginos and neutralinos in most scenarii Excited quarks q*   q: up to m  6 TeV Leptoquarks: up to m  1.5 TeV Monopoles pp   pp: up to m  20 TeV Compositeness: up to   40 TeV Z’  ll, jj: up to m  5 TeV W’  l : up to m  6 TeV etc.... etc…. Eventual discovery reach of the LHC LHC discovery potential versus time L=10 35