http://hep.uchicago.edu/compton 1

INVASIONS IN

PARTICLE PHYSICS

Compton Lectures Autumn 2001Lecture 8

Dec 1 2001

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LECTURE 9 LECTURE 9

The power and glory of the Standard ModelHIGGS SUSY

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• 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 MODELINGREDIENTS OF THE STANDARD MODEL

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Electromagnetisminfinite rangeacts between charged objects

Weak Forceshort rangecan act between neutral objects(neutrinos with quarks) and canchange the nature of particles

SU(2) x U(1) with, W+W- Z0

Unification

Because of themasses of the Ws and the Z

Because of the Higgs (electroweak symmetry breaking mechanism)

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A symmetric systemmay have a symmetricsolution which is stable

Or else the systemwould end up in anasymmetric solution

If a field has a stable symmetric solutionthen the world it describes is symmetric

If a field has a stable asymmetric solutionthen the phenomena in this world will also show the asymmetry.

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Mexican-hat potentialBreaking Rotational Symmetry

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Mexican-hat potentialBreaking Rotational Symmetry

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And THIS is the Higgs degree of freedom

Mexican-hat potentialBreaking Rotational Symmetry

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T<TcT>Tc

Order parameter

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Order parameter

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Similarly in superconductivitythere is a symmetry breaking mechanism

Meissner Effect: The EM fields disturb condensate of Cooper pairsmass of Ws and Z: The weak bosons (W,Z) react with the Higgs and get mass

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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)

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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

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CONSIDER THIS SETUP

A symmetric object could stay in equilibrium for ever

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Even Worse : Try an asymmetrical equilibrium

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(uh)

...

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The Running Couplings Strenght in the Standard Model

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Extrapolate at higher energies (smaller lenghts)

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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/MGUT)2 is required.

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Is this possible?

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

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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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M1M2M3

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01χ~

01χ~

Production/Decay Graphsof squarks and gluinos

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e.g.SUSY Candidate Event at CDF

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SUSY signal

Standard Model

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Next:Standard Model issuesSUSY and STRINGSEXTRA DIMENSIONSTHEORY SPACECOSMIC CONNECTIONSand what have you.