INVASIONS IN PARTICLE PHYSICS Compton Lectures Autumn 2001 Lecture 8 Dec

2 LECTURE 9 The power and glory of the Standard Model HIGGS SUSY

3 Local Gauge Invariance –Symmetries Generate Interactions Spontaneous Symmetry Breaking –Gives mass to force carriers –Predicts a Higgs Non-Abelian –The force carriers can have charge Add in the matter fields of the quarks and leptons and some extra parameters –Correctly predict the results of every high energy physics experiment for the last 30 years. INGREDIENTS OF THE STANDARD MODEL

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10 Electromagnetism infinite range acts between charged objects Weak Force short range can act between neutral objects (neutrinos with quarks) and can change the nature of particles SU(2) x U(1) with , W + W - Z 0 Unification Because of the masses of the Ws and the Z Because of the Higgs (electroweak symmetry breaking mechanism)

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13 A symmetric system may have a symmetric solution which is stable Or else the system would end up in an asymmetric solution If a field has a stable symmetric solution then the world it describes is symmetric If a field has a stable asymmetric solution then the phenomena in this world will also show the asymmetry.

14 Mexican-hat potential Breaking Rotational Symmetry

15 Mexican-hat potential Breaking Rotational Symmetry

16 And THIS is the Higgs degree of freedom Mexican-hat potential Breaking Rotational Symmetry

17 T<T c T>T c  Order parameter  Free energy Order parameter  Free energy Similarly in superconductivity there is a symmetry breaking mechanism Meissner Effect: The EM fields disturb condensate of Cooper pairs mass of Ws and Z: The weak bosons (W,Z) react with the Higgs and get mass

18 The Standard Model contains about 20 numbers for which we don’t know why they have the values they have. And which we cannot calculate from first principles. Given these numbers we can (in principle) calculate any other physical phenomenon It works! It works extremely well. To tremendous accuracy. (Precision EWK measurements, the race for the Higgs)

19 Constraining the Higgs from the mass of the top quark and the mass of the W boson Indirect EW fits to SM Higgs imply Tevatron has good hunting Complementary to direct searches, sensitive to other new physics RUN 1 Data Run 2 Projections

20 CONSIDER THIS SETUP A symmetric object could stay in equilibrium for ever

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22 Even Worse : Try an asymmetrical equilibrium

23 (uh)...

24 The Running Couplings Strenght in the Standard Model

25 Extrapolate at higher energies (smaller lenghts)

26 The natural value of the Higgs mass is , the scale of new physics: If the SM describes physics up to the GUT scale an exquisitely precise fine tuning (EWK/M GUT ) 2 is required.

27 Is this possible?

28 SUSY|boson>= |fermion> SUSY|fermion>=boson

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30  Apparently Unifies the three gauge couplings  R=(-1) 3(B-L)+2S +1 (SM particles) -1 SUSY particles  If R-parity is conserved - sparticles are produced in pairs and eventually decay to the Lightes SUSY Particle (LSP) - the LSP is stable and weakly interacting: missing energy signature  LSP is a good candidate for dark matter

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35 Production/Decay Graphs of squarks and gluinos

36 e.g. SUSY Candidate Event at CDF

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39 SUSY signal Standard Model

40 Next: Standard Model issues SUSY and STRINGS EXTRA DIMENSIONS THEORY SPACE COSMIC CONNECTIONS and what have you.