Heavy Flavour: Identification (I) b- and c-hadrons decay weakly towards c- and s-hadrons, with a macroscopic lifetime (1.6 ps for b’s), corresponding to few mm’s at LEP  10 cm  1 cm 3d-vertexing determines secondary and tertiary vertices. High resolution is crucial. Impact parameters of reconstructed tracks allow b quarks to be tagged with very good purity. Mass of secondary vertex tracks is a very powerful discriminator of flavour (b, c, and light quarks):

Heavy Flavour: Identification (II) Vertex Mass for Events With a Secondary Vertex In SLD Vertex Mass (GeV/c 2 ) b (MC) c (MC) uds (MC) Data Vertex detectors (Si  -strips, CCD’s, pixels): At LEP: inner radius 6 cm, good resolution; At LEP: inner radius 6 cm, good resolution; At SLC: inner radius 2.3 cm, superior resolution. At SLC: inner radius 2.3 cm, superior resolution. SLD can do both b- and c-tagging with good purity.

Heavy Flavour:Results Use double-tag method to reduce uncertainties from the simulation, e.g., in bb events: Take  c,  uds, and  b (all small) from simulation. Solve for  b and R b ! With this measurement alone: m top  150  25 GeV/c 2 (dependence on m H,  s, … cancel in the ratio) R b =  bb /  had -

Prediction of M top A top mass of 177 GeV/c 2 was predicted by LEP & SLC with a precision of 10 GeV/c 2 in March One month later, FNAL announced the first 3  evidence of the top. In 2005: Perfect consistency between prediction and direct measurement. Allows a global fit of the SM (with m H ) to be performed. / SLD

Detour - TEVATRON  last discovery of a fundamental particle

# of Physicists for Particle Discovery Tevatron ~ 800 Year Discovered Number of Physicists LHC

The Tevatron Collider –Beam energy =980 GeV –36x36 bunches, 396 ns coll. sep. –Recycler and e-cooling in use –Pbar “stashes” >350e9 in recycler

Tevatron Luminosity Peak luminosity record: 2.2 x10 32 cm -2 s -1 Integrated luminosity – Weekly record: 33 pb -1 /week/expt – Total delivered: 1.7 fb -1 /expt. Total recorded: 1.5 fb -1 /expt Doubling time: ~1 year Future: ~2 fb -1 by 2006, ~4 fb -1 by 2007, ~6-8 fb -1 by 2009 Today’s Presentation: 300 pb -1 ~ 1 fb -1 Peak Luminosity Integ. Lum. (delivered) / Experiment

The CDF Detector

The DØ Detector

Why top physics is interesting? Production cross section can be accurately predicted by QCD calculations BR(t  Wb)≈1 in SM. Measurement of V tb is test standard model Spin of W boson is direct probe of top spin and the only way to measure spin correlations in unbound quarks Are there resonances in the top quark pair spectrum? Measure top quark mass - dominant term in electro-weak radiative loop corrections provide constraint of Higgs boson mass Are there other objects that decay to b quarks and W bosons?

Top Quark Mass Today CDF & D0: The top quark mass measurement has become a precision determination.  crucial for SM tests

Mtop & Mz Mtop & MZ are very precisely known today

Prediction of M W Predict m W in the SM: m W 2 = m Z 2 (1+  )cos 2 W eff Direct Measurements* Precision Measurements m H dependence in the SM through quantum corrections (see later)

W + W -  q 1 q 2 l : Two hadronic jets, Two hadronic jets, One lepton, missing energy. One lepton, missing energy. W mass at LEP 2 W + W -  q 1 q 2 q 3 q 4 : Four well separated jets. Four well separated jets W + W -  l 1 1 l 2 2 : Two leptons, missing energy Two leptons, missing energy  s  2m W 45.6% 43.8% 10.8%

W mass at LEP 2 m W (thresh.) = (80.40  0.22) GeV/c 2 Systematics: Beam energy

W mass at LEP II 5 Constraints: 0 unknowns, 5C fit 3 unknowns, 2C fit Fitted Mass (GeV/c 2 )  GeV  GeV

W mass at LEP II Good consistency between experiments; Good consistency between experiments; Good consistency with hadron colliders Good consistency with hadron colliders Fair consistency with Z data (LEP/SLD). Fair consistency with Z data (LEP/SLD). m W (LEP) =  0.029

Standard Model Fit Knowing m top, most electroweak observables have a sensitivity to m H through 

2direct top 2EW top GeV/ GeV/ cm cm   Standard Model Fit Global fit of m H and m top : EW Higgs GeV/ 85cm    C.L. 95%at GeV/ Higgs cm 

Standard Model Fit Internal Consistency of the Standard Model Largest discrepancy (-2.7  ) well inside statistical expectation;  2 probability ~ 20%. Just fine. A great success but we are still missing one very important ingredient  need to find the Higgs

Precision SM Tests: Summary –The 0.1% precision tests of the theory have taken approximately 20,000 man-years of effort!!! > 2000 physicists working for about 10 years –Its significance cannot be underestimated … the first fundamental force unification since Maxwell unified electricity and magnetism 100 years earlier points the way to greater unification and, perhaps, to a fully unified theory of fundamental interactions … demonstrates the relevance of Yang-Mills Gauge theories for an accurate description of nature at sub-atomic length scales validates the use of quantum field theory to determine higher order corrections to the tree-level processes provides support for the Higgs mechanism and suggests the existence of a light Higgs boson (with mass < 200 GeV)

Direct Higgs Searches at LEP 2  s = m Z Z  Hff -  s  m H +m Z H HHHH He  e  Hqq - -  sensitivity for 200 pb -1 :  s = 192 GeV for m H = 100 GeV/c 2 ;  s = 192 GeV for m H = 100 GeV/c 2 ;  s = 210 GeV for m H = 115 GeV/c 2 ;  s = 210 GeV for m H = 115 GeV/c 2 ;

A few more candidates at 115 GeV 31-Jul-2000 Mass: 112 GeV s/b 115 = Aug-2000 Mass: 110 GeV s/b 115 = Jul-2000 Mass: 114 GeV s/b 115 = 0.4 e + e -  bb _ _ DELPHI L3 14-Oct-2000 Mass: 114 GeV s/b 115 = Jun-2000 Mass: 113 GeV s/b 115 = 0.52 ALEPH

LEP Summary 205 GeV 208+ GeV GeV 220 pb -1 delivered in 2000: starting at GeV starting at GeV (April-May) (April-May) Regularly above 206 GeV Regularly above 206 GeV (from June onwards) (from June onwards) Only above GeV Only above GeV (September to November) (September to November) m H  GeV/c 2 Excluded at 95% C.L. (144 cavities) (176) (240) (272) (288) Notes: 372 cavities: 372 cavities:  E = 220 GeV;  E = 220 GeV; 4 straight sections 4 straight sections  E = 240 GeV.  E = 240 GeV.

SM Higgs - where can it be? In the Standard Model:

LHC : 27 km long 100m underground General Purpose, pp, heavy ions CMS +TOTEM ATLAS Heavy ions, pp ALICE pp, B-Physics, CP Violation Higgs Search at the LHC

The CMS Detector today at point 5 The ATLAS Barrel Toroid. End of November 2005

NLO

v is vev of Higgs field = 246 GeV Right bottom plot includes uncertainties from the quark masses m t, m b, m c and  s (M Z ) tree level couplings SM Higgs Couplings and BR

Important Decay Modes Discovery of the inclusive Higgs boson production with decay modes:Discovery of the inclusive Higgs boson production with decay modes: –H->ZZ->4l –H->  –H->WW->2l

Background: tt, ZZ, ll bb (“Zbb”) Selections : - lepton isolation in tracker and calo - lepton impact parameter, , ee vertex - mass windows M Z(*), M H H->ZZ->ee  H  ZZ*  4l

Signal and background at 5 sigma discovery ee  CMS at 5  sign. CMS H  ZZ*  4l Mh ~140 GeV Mh ~200 GeV

Signal significance: new vs old results; no big change ~ 125 GeV H  ZZ*  4l

H  H  

Discovery potential of H->  SM light h->  in MSSM inclusive search CMS ECAL TDR CMS ECAL TDR CMS PTDR CMS PTDR ATLAS ATLAS NLO NLO count. exp NLO NLO cut based NLO NLOoptimized* TDR (LO) New, NLO Cut based New, NLO likelihood ~ Significance for SM Higgs M H =130 GeV for 30 fb -1 * NN with kinematics and  isolation as input, s/b per event

Stat. error only H  ZZ*  + H   

Luminosity needed for 5  discovery for incl. Higgs boson production

with K factors LHC: Higgs Discovery Potential Bottom line: If the Higgs exists the LHC will find it …

Summary/Conclusions –The Standard Model is one of the great triumphs of 20th century science... –However, there are many unanswered questions which point the way to the need for new physics - and a more complete theory of elementary particles... (see lecture of A. Hocker) –Particle Physics has great relevance to Cosmology and the Early Universe and addresses many fundamental questions of the “what are we?”, “why are we here?” kind … –Plenty remains to be done and the key to the origin of mass and (maybe CP violation) may be just round the corner for the next generation of graduate students !

Without the Higgs (mechanism) … Quarks and Leptons would remain massless

Tevatron SM Higgs Search Updated in 2003 in the low Higgs mass region W(Z)H  l (,ll)bb to include  better detector understanding  optimization of analysis Sensitivity in the mass region above LEP limit starts at ~2 fb -1 Meanwhile  optimizing analysis techniques  understanding detectors better  searching for non-SM Higgs with higher production cross sections or enhanced branching into modes with lower backgrounds LEP Tevatron Ldt (fb -1) Tevatron Outlook: 2007: improve LEP limit of 114 GeV 2009: exclude up to 180 GeV - have 5 Sigma on Mh=115 GeV (2009 less optimistic: exclude up to 140 GeV - have 3 Sigma on Mh=115 GeV)