2. Backup slides

3. Z 0 Z 0 production Once  s > 2M Z ~ 182.4 GeV ÞPair production of Z 0 Z 0 via t-channel electron exchange. e+e+ e-e- e Z0Z0 Z0Z0 Other signatures in detector: e.g. 4 electrons (2e +,2e - )

4. WW  qql (2 constraints fit) –Missing neutrino WW  qqqq (5 constraints fit) –Ambiguity due to jet assignment (3 choices) W-mass measurement Reconstruct the W mass directly in each WW event: Form jets using particle 4- vectors –iterative clustering to 2- or 4-jets Constrain total (E,p) to (  s,0) –4 constraints –obtain E beam from LEP Constrain two W’s to have equal mass W+W+ W-W-

5. Higgs search results OPAL 183-189 GeV data of last summer Plot of the Higgs mass for Higgs candidates Large contribution Z 0 Z 0 events

6. Trigger detector trash save PIPELINE NO YES trigger 10 9 evts/s Much more difficult than at LEP Interaction rate: ~ 10 9 events/second Can record ~ 100 events/second (event size 1 MB) Trigger decision  ms  larger than interaction rate of 25 ns Store massive amount of data in pipelines while trigger performs calculations Trigger organized in three levels T rigger rejection ~ 10 7 10 2 evts/s

7. High mass Higgs H  ZZ  + –  jet jet –Need higher Branching fraction (also  for the highest masses ~ 800 GeV/c 2 ) –At the limit of statistics

8. -- SM Higgs boson can be discovered at  5  with 10 fb -1 / experiment (nominally one year at 10 33 cm -2 s -1 ) for m H  130 GeV -- Discovery faster for larger masses -- Whole mass range can be excluded at 95% CL after ~1 month of running at 10 33 cm -2 s -1. However, it will take time to operate, understand, calibrate ATLAS and CMS

9. SM Higgs: properties (II) Relative couplings Higgs to fermions/bosons –Well predicted in Standard Model –Biggest uncertainty(5-10%): Luminosity Relative couplings statistically limited

10. SM Higgs: properties (III) Self-coupling –From HH production –Cross sections are low Relevant for M H <200 GeV Need (unrealistically) high statistics, i.e. luminosities for example, with 10x the statistics: measures to 20-25% Very hard at LHC  Linear e+e- TeV collider fb

11. Summary Symmetry Breaking in the SM (and beyond!) still not really understood –Higgs missing; perhaps Tevatron, LHC designed to find it Physics at the LHC will be extremely rich –SM Higgs (if there) in the pocket Turning to measurements of properties (couplings, etc.) –Supersymmetry (if there) ditto Can perform numerous accurate measurements –Large com energy: new thresholds TeV-scale gravity? Large extra dimensions? Black Hole production? The end of small-distance physics? And of course, compositeness, new bosons, excited quarks… There might be a few physics channels that could benefit from more luminosity… LHC++? We just need to build the machine and the experiments

13. Contents Introduction –Question: why LHC? Standard Model –Matter and forces –EW symmetry breaking –Higgs particle –Theoretical limits Current status of Higgs searches –LEP collider –LEP2 searches –Higgs limits pp interactions –Experimental techniques –Kinematics –Minimum bias The LHC machine –Parameters –Construction The ATLAS detector –Construction –NIKHEF participation What about Tevatron? –Running status –First physics results What with LHC if Tevatron finds the Higgs? –Break— SM Higgs At LHC & Tevatron –Low mass region –Intermediate+high mass The year 2007 Beyond the Higgs The future

14. All experiments Combination of OPAL data with other three experiments; same c.m. energies: No Higgs left

15. B-tagging Neural net tag: Info from lifetime, Jet kinematics, Lepton tag (from b  cl  )