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On the verge of pivotal discoveries at the new energy frontier

On the verge of pivotal discoveries at the new energy frontier. Andrey Korytov. Next 45 minutes. Palace of the Standard Model of elementary particles Cracks in the Palace Higgs boson to hold it all together... Where is the Higgs boson? The answer is just around the corner...

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On the verge of pivotal discoveries at the new energy frontier

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  1. On the verge of pivotal discoveries at the new energy frontier Andrey Korytov Andrey Korytov, UF Physics Colloquium

  2. Next 45 minutes... • Palace of the Standard Model of elementary particles • Cracks in the Palace • Higgs boson to hold it all together... • Where is the Higgs boson? • The answer is just around the corner... • How do we get there? Andrey Korytov, UF Physics Colloquium

  3. ne nt nm e- t- m- u u u u u u c u t d d d d d d d s b Caveat: quarks come in three different “colors” and exist only in bound “colorless” states, e.g.: u u u d d d d proton neutron pion and many more... u SM: Three Generations of Fermions (s=1/2) muon Andrey Korytov, UF Physics Colloquium

  4. e- e- p p proton proton u u d u u d n e- proton neutron d u u u d d u d time SM: Three Fundamental Forces • ELECTROMAGNETIC: photon (g) • couples to electrically charged particles • no self-interaction, massless • STRONG: 8 gluons (g) • couple to color-charged quarks • change color charge of quarks • self-interacting, massless • WEAK: W and Z0 bosons • couple to all fermions • W transforms particles • self-interacting, MASSIVE Andrey Korytov, UF Physics Colloquium

  5. Beautiful Palace of Standard Model • Origin of beauty—symmetries: • all three forces can be related to local gauge invariance... • local gauge invariance is a highly sought after symmetry... Andrey Korytov, UF Physics Colloquium

  6. Standard Model: EM Force (1) • EM fields can be described by one 4-vector field Andrey Korytov, UF Physics Colloquium

  7. Standard Model: EM Force (2) • 1919:Weyl points out that is not uniquely defined gauge transformation does not change physical fields, Andrey Korytov, UF Physics Colloquium

  8. Standard Model: EM Force (3) • Late 1920s:Relativistic Quantum Mechanics • Wave function f(x) • Relativistic equations for spin=0 particle • Lagrangian: • with potential energy density: Andrey Korytov, UF Physics Colloquium

  9. Standard Model: EM Force (4) • Phase Invariance? • rotate f(x) by an arbitrary phase • probabilities of locating particle at x, |f(x)|2, do not change... • one may expect that the new wave function would also be a solution... • BUT Lagrangian is NOT invariant! Andrey Korytov, UF Physics Colloquium

  10. g g2 Standard Model: EM Force (5) • Solution: add EM field and make Am and f interact • Building Full Lagrangian • Full Lagrangian is now invariant w.r.t. • all terms popping up from field derivatives • can be absorbed in • However, EM field must remain massless... Otherwise, the term in the form would break the Lagrangian invariance Andrey Korytov, UF Physics Colloquium

  11. strong force coupling Standard Model: EM Force (6) • 1930s: Relativistic Quantum Mechanics is stalled... • only leading order perturbation is calculable • higher order loop corrections diverge! • 1940s: Way out—Renormalization procedure • absorb all divergences into definition of coupling constants (sweeping the problem under the rug) • remnant of the procedure: charge, mass, magnetic moment become energy-dependent • it all works to astonishing precision: ~10-10 • 1970s: Gauge-invariant theories are renormalizable Andrey Korytov, UF Physics Colloquium

  12. Standard Model: Strong Force • Building Strong Force • U(x) = 3x3 unitary matrix • 8 independent phases  8 gauge fields (gluons) • self-interacting • all massless Andrey Korytov, UF Physics Colloquium

  13. Standard Model: Weak Force • Building Weak Force • U(x) = 2x2 unitary matrix • 3 independent phases  3 gauge fields: W+, W-, Z0 • self-interacting • all massless Predicted theoretically! Was found later... Oops... Andrey Korytov, UF Physics Colloquium

  14. Cracks in the Palace • Gauge bosons W & Z have masses • This is why the weak force is weak... • Putting them in by hand breaks the gauge invariance, the very same symmetry that their existence is derived from Fermions have masses • Parity violation in weak interactions can be accommodated without breaking the gauge invariance only if fermion masses are zeros Andrey Korytov, UF Physics Colloquium

  15. Cracks in the Palace • Why worry? Let it be broken... • theory is not renormalizable, needs new physics at some scale L; this new physics must take care of the divergences somehow... • for some processes this scale had better be below 1 TeV Andrey Korytov, UF Physics Colloquium

  16. Higgs Boson field • 1964: Peter Higgs – one can give mass to • vector field without breaking gauge invariance! • potential of conventional complex scalar field (s=0) • consider complex field with weird potential • the lowest energy state for f is not f=0 • field has non-zero vacuum expectation value • vacuum is going to be filled with non-zero field— New Age Ether! Andrey Korytov, UF Physics Colloquium

  17. Higgs Boson trick • Require local gauge invariance for f • Expand f around local minimum: • Re-write L in terms real h(x) and a(x)... • Behold! EM field appears to have mass: Mass is proportional to vacuum expectation value v0 and coupling g Andrey Korytov, UF Physics Colloquium

  18. Standard Model Masses • Apply the trick to the Weak Force • get masses for W and Z (effectively, they acquire masses by interacting with all penetrating Higgs field, the Ether of 21 century) • How about fermions? • start from massless fermions • force Higgs field interact with fermions, with different hand-picked couplings; hmm... • expand f around its vacuum expectation value... now fermions appear to have masses, too; their masses proportional to the picked couplings Andrey Korytov, UF Physics Colloquium

  19. So, what is all this trickery, after all? • Free Lunch?.. • Hocus-Pocus?.. • Intelligent Design?.. • Can it be tested? Andrey Korytov, UF Physics Colloquium

  20. Higgs Boson Mass • If you have field, • you can make splashes... • waves = particles, Higgs particles... • What is the Higgs boson mass? • l is the only free parameter in theory • all other parameters are fixed by observed couplings and masses • Can the Higgs mass be anything? Andrey Korytov, UF Physics Colloquium

  21. 0.001% tuning 0.1% tuning non-perturbative New Physics Energy Scale L (GeV) 103 106 109 1012 1015 1018 unstable vacuum 10% tuning 0 200 400 600 Higgs mass MH (GeV) Can Higgs Boson mass be anything? (theory) • No, unless there is new physics at some scale energyL... • Given mass MH, as measured at 100-1000 GeV energy scale, we know coupling at this energy scale • Renormalization makescoupling l “run” with energy • MH cannot be too light:l flips sign at some scale (and vacuum breaks loose—potential does not have minimum) • MH cannot be too heavy:l gets large and theory becomes non-perturbative (and all theorists can retire) • Whatever MH might be, corrections to it diverge ~L2 fine tuning of seemingly unrelated parameters is required at the level of ~(200/L)2~10% at 1 TeV, 0.1% at 10 TeV Andrey Korytov, UF Physics Colloquium

  22. e- H gluon gluon top-quark loop Z H Z e+ Z b H H Z b MH=200 GeV MH=100 GeV How can we see Higgs experimentally? • Particle Masses proportional to Particle-Higgs couplings... • to give birth to Higgs boson, one needs to produce a heavy particle first • Higgs boson will decay to the heaviest pair of particles accessible to it by kinematics: m < MH/2 Mtop=170 GeV MZ=90 GeV Andrey Korytov, UF Physics Colloquium

  23. } jet (b-tagged) MJJ=MH =? e- jet (b-tagged) b b H LEP Energy 209 GeV } q Z0 jet Z0 e+ q MJJ=MZ=91 GeV CERN, near Geneva e+e- collisions energy 209 GeV 4 Experiments Operated 1989-2000 jet Higgs Boson mass: experimental limits (1) • If Higgs mass were small, we would’ve seen it directly at Large Electron-Positron Collider, but we have not seen it:MH>114 GeV • If Higgs was lighter that 209-91=118 GeV, • LEP would have enough energy and intensity to produce it... Andrey Korytov, UF Physics Colloquium

  24. W W H Higgs Boson mass: experimental limits (2) • If Higgs boson were too light or too heavy, its presence in virtual loops would alter various SM parameters: • masses, • couplings, • decay branching ratios, • scattering asymmetries... New Global Fit of Precision Data MH = 117+65-45 GeV MH < 250 GeV (95% CL) Andrey Korytov, UF Physics Colloquium

  25. D0 CDF TEVATRON, near Chicago proton-antiproton collisions Energy 2,000 GeV 2 Experiments: CDF and D0 Will operate till 2009 UF is a member of CDF Can we find Higgs at Tevatron? Andrey Korytov, UF Physics Colloquium

  26. proton Proton – Proton Cross Section Center of Mass Energy, TeV Can we find Higgs at Tevatron? Tevatron Signal—a few events over 10 yrs Signal : Background = 1 : 1014 Maybe, by 2009, if MH<120 GeV... • Large Hadron Collider • larger x-section by 1000 • larger intensity by 100 • Signal—lots of events • Signal : Background = 1 : 1011 • Odds look better... Andrey Korytov, UF Physics Colloquium

  27. France 6 miles Geneva airport Switzerland Large Hadron Collider (LHC) • LHC is Proton-Proton Collider at CERN • tunnel 27 km in circumference, 100 m underground • 1,300 14-m long 8-T field magnets to keep protons on orbit • start of operation 2007 Andrey Korytov, UF Physics Colloquium

  28. Proton-Proton Collision at LHC • Collision Energy: 14,000 GeV (7 times Tevatron) • Particles per Collision: ~100 (similar to Tevatron) • Collision Rate: 109 Hz (100 times Tevatron) proton proton Andrey Korytov, UF Physics Colloquium

  29. LHC Experiments: ATLAS, CMS, LHC-b, ALICE Andrey Korytov, UF Physics Colloquium

  30. Collaboration 38 countries 168 institutions 2220 physicists UF role in CMS Muon System (GM) Endcap muon detectors (AK) Endcap muon trigger (DA) Computing (PA) Physics with CMS (ALL) Compact Muon Solenoid Trivia Solenoid: 4 T field, 8 m diameter, 16 m length, 3109 J Overall size: 12,500 ton weight, 15 m diameter, 22 m long Electronics channels: 50 million Compact Muon Solenoid Experiment Andrey Korytov, UF Physics Colloquium

  31. Why Muons? • When in 1940s it became clear that the newly discovered particle (muon) was not a long sought after Yukawa particle (pion), but rather it behaved more like a very heavy electron, • Rabi exclaimed “Who ordered that?!” • Experimentalists! Andrey Korytov, UF Physics Colloquium

  32. Why Muons? HZZ+-+- • Higgs decay into 4 muons is called“golden” channel,since muons can be easily filtered from background particles by placing material on their way • Muons will be similarly effective in many • - new physics searches and • - Standard Model precision • measurements Andrey Korytov, UF Physics Colloquium

  33. Muon Detectors for CMS • Requirements: • high precision (100 mm), fast (5 ns), ... • huge sensitive area: 6,000 m2 (football field) • Does such technology exist? The answer for the first point is Yes, Cathode Strip Chambers invented by Charpak in 1979, but never attempted at scale over few m2 as it did not appear to be feasible... Andrey Korytov, UF Physics Colloquium

  34. ? Muon Detectors for CMS  2 • UF made this happen Andrey Korytov, UF Physics Colloquium

  35. First Full Scale Muon Detector We need 500 of these! Andrey Korytov, UF Physics Colloquium

  36. Muon Detectors at UF • UF developed comprehensive program of chamber testing • 6 Sites world-wide commissioned 500 chambers using these tests • Half of the US-made chambers were commissioned at UF UF HEE Lab Andrey Korytov, UF Physics Colloquium

  37. Muon Detectors: all finished Andrey Korytov, UF Physics Colloquium

  38. Golden Channel What’s next? • Get Ready to Run the Experiment • Get Ready to Discover Higgs Andrey Korytov, UF Physics Colloquium

  39. jet q g jet Z q Z q g jet q jet How we will sort out Higgs from Background SIGNAL BACKGROUND MH=200 GeV t H most of the time • looks nearly identical • happens 1011 times more often Andrey Korytov, UF Physics Colloquium

  40. n m- jet n W- m+ 10% m+ g g b t c Z m- n m+ Z 10% m- g g c t b m- W+ jet m+ n How we will sort out Higgs from Background SIGNAL BACKGROUND MH=200 GeV 10% t 3% H 3% 10% We keep 1 event out of 1000 H Only ~100 events in 3 years Top quarks are now BACKGROUND! ~20,000 events in 3 years Kill by requiring no muons in jets Andrey Korytov, UF Physics Colloquium

  41. m+ m+ g Z Z q m- m- m+ m+ Z g q Z m- m- How we will sort out Higgs from Background SIGNAL BACKGROUND MH=200 GeV t 3% H 3% We keep 1 event out of 1000 H Only ~100 events in 3 years Looks very much the same as Higgs But 4 muons do not come from one particle! Andrey Korytov, UF Physics Colloquium

  42. Higgs = Peak in 4-muon invariant mass Higgs Signal Various Bkgd’s Andrey Korytov, UF Physics Colloquium

  43. Finding Golden Needles in Haystack • Start from Signal : Background = 1 : 1011 • Look for 4 muons: 1 : 200 • Put haystack in water, collect sunk needles! And... • most of sunk needles are made of iron, but we need golden ones... • None of muons inside particle jets: 1 : 10 • Use magnet to sort out iron needles, collect non-magnetic ones. And... • most of non-magnetic needles are copper, but we need gold... • Look at invariant mass of 4 muons: 10:1 (we got it!) • Sort out remaining needles by weight. And... • the golden needles group around the same weight! Andrey Korytov, UF Physics Colloquium

  44. CMS Higgs Boson Discovery Reach By 2010 • Assuming LHC startup in 2007 and nominal operation • Standard Model Higgs • whatever mass it has • and if it exists at all • will be discovered by • 2010 or earlier... discovery threshold of 5s significance Andrey Korytov, UF Physics Colloquium

  45. Is the Higgs Boson the End of Journey? • If we DO find Higgs, • What keeps its mass small? Expect new physics at 1 TeV scale... • Why does it couple so differently to different particles? • How shall we deal with so “thick” vacuum energy density? (1054 times more than what we see in the Universe) • If we do NOT find Higgs, • Expect new exotic physics at 1 TeV scale... • Why do we have three nearly identical generations? • Pattern of masses clearly signifies something... • Pattern of mixing angles is a telltale sign of something... • Do three forces unite at some high energy scale? • New physics at 1 TeV scale is needed to make it happen... Andrey Korytov, UF Physics Colloquium

  46. Higgs boson hypothesis has been around for 40 years... And now we seem to see light at the end of tunnel... Summary LHC tunnel • The Standard Model of elementary particles and fundamental forces, however beautiful it may be, is incomplete and breaks at 1 TeV scale • Higgs Boson is the most elegant hypothesis known so far that would give particle masses • Higgs Boson comes with its own bag of problems, more new physics is just around the corner at 1 TeV scale • Higgs Boson AND/OR more “new physics” will be discovered at LHC Andrey Korytov, UF Physics Colloquium

  47. ALEPH Collaboration data - 2000 Points—data Dashed line—expected background (no-Higgs processes) Tight Cuts small excess? MH (GeV/c2) Higgs boson: have we seen it at LEP? After taking more data and combining results of all 4 experiments, the final word from LEP: No discovery... Consistency with background: ~1.7s Limit on Higgs mass: MH > 114.4 GeV @95% CL Formally, it looked like 4s effect! If it was Higgs, they saw too many... Other 3 experiments did not see it... LEP was let run longer to get more data Phys. Lett. B565 (2003) 61 Andrey Korytov, UF Physics Colloquium

  48. D0 CDF excluded at LEP TEVATRON, near Chicago proton-antiproton collisions Energy 2,000 GeV 2 Experiments: CDF and D0 Will operate till 2009 expected integrated luminosity by 2009 L = 4 – 8 fb-1 current integrated luminosity (2001-2005) L = 1 fb-1 UF is a member of CDF Higgs boson: can we discover it at Tevatron? • only if MH<125 GeV • only 3s-evidence, hard to claim discovery... • with some luck we may see more events... Andrey Korytov, UF Physics Colloquium

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