New Physics Scenarios

Jay WackerSLAC

SLAC Summer InstituteAugust 5&6, 2009

Any minute now!When’s the revolution?

An unprecedented moment

What is a “New Physics Scenario”?

“New Physics”:

A structural change to the Standard Model Lagrangian

“Scenario”:

“A sequence of events especially when imagined”

Why New Physics?Four Paradigms

Experiment doesn’t match theoretical predictionsBest motivation

Parameters are “Unnatural”Well defined and have good theoretical motivation

Reduce/Explain the multitude of parametersTypically has limited success, frequently untestable

To know what is possibleLet’s us know what we can look for in experiments

Limited only by creativity and taste

The PlanBeyond the SM Physics is 30+ years old

There is no one leading candidate for new physics

New physics models draw upon all corners of the SM

In 2 hours there will be a sketch some principlesused in a half dozen paradigmsthat created hundreds of models

and spawned thousands of papers

Outline

The Standard Model

Motivation for Physics Beyond the SM

Organizing Principles for New Physics

New Physics Scenarios

SupersymmetryExtra DimensionsStrong Dynamics

Standard Model: a story of economy

5 Particles 3 Couplings

symmetry unification

4 forces, 20 particles, 20 parameters

x 3

Mystery of Generations:

15 Particles, 12 Force carriers 2700 Couplings

The Standard Model... where we stand today

Standard Model Charges

Field Color Weak Hypercharge

Motivations for Physics Beyond the Standard Model

The Hierarchy Problem

Dark Matter

Exploration

The Hierarchy ProblemThe SM suffers from a stability crisis

Higgs vev determined by effective mass, not bare massMany contributions that must add up to -(100 GeV)2

=

A recasting of the problem:

Why is gravity so weak?

Explain how to make GF large (i.e. v small)

Explain why GN is so small (i.e. MPl large)

1998: Large Extra Dimensions (Arkani-Hamed, Dimopoulos, Dvali)

High scale is a “mirage”

Gravity is strong at the weak scaleNeed to explain how gravity is weakened

2001: Universal Extra Dimensions (Appelquist, Cheng, Dobrescu)

1978: Technicolor(Weinberg, Susskind)

1999: Warped Gravity(Randall, Sundrum)

2001: Little Higgs(Arkani-Hamed, Cohen, Georgi)

The Higgs is compositeResolve substructure at small distances

Why hadrons are lighter than Planck Scale

A New Symmetry

Scalar

Fermion

Supersymmetry

Scalar Mass related to Fermion Mass

Scalar

Scalar

Shift Symmetry

Scalar Mass forbidden

1981: Supersymmetric Standard Model(Dimopoulos, Georgi)

2001: Little Higgs(Arkani-Hamed, Cohen, Georgi)

1974: Higgs as Goldstone Boson(Georgi, Pais)

not specialUV dynamics at

Dark Matter

85% of the mass of the Universe is not described by the SM

There must be physics beyond the Standard Model

Cold dark matterElectrically & Color Neutral

Cold/SlowRelatively small self interactions

Interacts very little with SM particles

No SM particle fits the bill

The WIMP Miracle DM was in equilibrium with SM in the Early Universe

DM too dilute to find each other

Reverse process energetically disfavored

Relic density is “frozen in”

Incr

easi

ng

Boltzmann Equation Solves for

Frozen out when

We want to see what’s there!

Muon, Strange particles, Tau leptonnot predicted before discovery

Serendipity favors the prepared!

Exploration

Chirality

Anomaly Cancellation

Flavor Symmetries

Gauge Coupling Unification

Effective Field Theory

Organizing Principlesfor going beyond the SM

Chirality

A symmetry acting a fermions that forbids masses

Vector symmetry

Allows mass

Axial symmetry

Forbids mass

Can do independent phase rotations

The Standard Model is a Gauged Chiral Theory

All masses are forbidden by a gauge symmetry

15 different bilinears all forbidden

etc...

The Standard Model force carriers forbid fermion masses

Electroweak Symmetry BreakingBreaking of Chiral Symmetry

Fermions pick up Dirac Masses

Effective Field Theory

Take a theory with light and heavy particles

If we only can ask questions in the range

with

Dynamics of light fields described by

Only contribute as

known as “irrelevant operators”

Nonrenomalizable!

We have only tested the SM to certain precision

How do we know that there aren’t those effects?

We know the SM isn’t the final theory of nature

We should view any theory we test asan “Effective Theory” that describes the dynamics

Shouldn’t be constrained by renormalizability

One way of looking for new physics is bylooking for these nonrenormalizable operators

Limits on Non-Renormalizable Operators

Baryon Number Violation

Lepton Number Violation

Flavor Violation

CP Violation

Precision Electroweak

Contact Operators

Generic Operators

Flavor Symmetries

Symmetries that interchange fermions

Turn off all the interactions of the SM = Free Theory

45 Total fermions that look the same in the free theory

global symmetry

Gauge interactions destroy most of this symmetry

Yukawa couplings break the rest...but they are the only source of U(3)5 breaking

U(N) symmetry

Prevents Flavor Changing Neutral Currents

Imagine two scalars with two sources of flavor breaking

Higgs doesn’t change flavor, but other scalar field is a disaster

Unless or

Can diagonalize mass matrix with unitary transformations

Anomaly Cancellation

Quantum violation of current conservation

An anomaly leads to a mass for a gauge boson

Anomaly cancellation:

but the Standard Model is chiral

One easy way: only vector-like gauge couplings

SU(3)SU(3)

SU(3)

U(1)U(1)

U(1)

U(1)SU(3)

SU(3)It works, but is a big constraint!

Gauge coupling unification: Our Microscope

(GeV)

30

40

20

10

1

2

3

Counts charged matter

Weak scale measurement

High scale particle content

Grand UnificationGauge coupling unification indicates forces arise from single entity

Standard Model Summary

The Standard Model is chiral gauge theory

It is an effective field theory

It is anomaly free & anomaly cancellationrestricts new charged particles

Making sure that there is no new sourcesof flavor violation ensures that new theories are

not horribly excluded

SM Fermions fit into GUT multiplets,but gauge coupling unification doesn’t quite work

The Scenarios

Supersymmetry

Little Higgs Theories

Extra Dimensions

Technicolor

SupersymmetryDoubles Standard Model particles

Dirac pair of Higgsinos GauginosSfermions

Squarks, Sleptons Gluino, Wino, Bino

Fermions Higgs Gauge

Susy Taxonomy

Needed for anomaly cancellation

Susy Gauge Coupling Unification

Too good!(Two loop beta functions, etc)

But significantly better than SM or any other BSM theory

Only need to add in particles that contribute to the relative runningGauge Bosons, Gauginos, Higgs & Higgsinos

SUSY Interactions

Rule of thumb: take 2 and flip spins

SUSY Breaking

SUSY is not an exact symmetry

We don’t know how SUSY is broken, butSUSY breaking effects can be parameterized in the Lagrangian

Problem with Parameterized SUSY Breaking

There are over 100 parameters onceSupersymmetry no longer constrains interactions

Most of these are new flavor violation parametersor CP violating phases

Horribly excluded

Susy breaking is not generic!

Soft Susy Breaking

i.e. Super-GIM mechanismUniversality of soft terms

Need to be Flavor Universal Couplings

Scalar Masses

Trilinear A-Terms

Approximate degeneracy of scalars

Proton StabilityNew particles ⇒ new ways to mediate proton decay

Lightest Supersymmetric Particle is stable

Dangerous couplings

Must be neutral and colorless -- Dark Matter

Pro

ton

Pion

Supersymmetric couplings that violate SM symmetries

A new symmetry forbids these couplings:

Mediation of Susy Breaking

MSSMPrimoridal

Susy BreakingMediation

Susy breaking doesn’t occur inside the MSSM

Felt through interactions of intermediate particles

Studied to reduce the number of parametersGauge Mediation

Universal “Gravity” Mediation

Anomaly Mediation

Usually only 4 or 5 parameters...but for phenomenology, these are too restrictive

The Phenomenological MSSMThe set of parameters that are:

Not strongly constrainedEasily visible at colliders

First 2 generation sfermions are degenerate

3rd generation sfermions in independent

Gaugino masses are free

Independent A-terms proportional to Yukawas

Higgs Masses are Free

5

5

3

3

4

20 Total Parameters

Charginos & NeutralinosThe Higgsinos, Winos and Binos

After EWSB: 2 Charge +1 Dirac Fermions

4 Charge 0 Majorana Fermions

All mix together, but typically mixture is small

Tend find charginos next to their neutralino brethren

Neutralinos are good DM candidates

Elementary Phenomenology

Neutralinos Charginos Sleptons Squarks Gluinos

Mas

s

Collider signaturesTrileptons+MET: If sleptons are available

Neu

tral

inos

Cha

rgin

os

Sle

pton

s

Mas

s

3 Leptons +

ME

T

Collider signaturesTrileptons+MET

Without sleptons in the decay chain

Neu

tral

inos

Cha

rgin

os

Sle

pton

s

Mas

s

30% leptonic Br of W, 10% leptonic Br of Z

3% Total Branching Rate

Collider signatures

Gluino Pairs: 4j +MET Squark Pairs: 2j +MET Squark-Gluino Pairs: 3j +MET

mSUGRA Search

Away from mSUGRA Gluino Search

The Higgs Mass Problem

Higgs mass gain is only logFine tuning loss is quadratic

Difficult to make the Higgs heavier than 125 GeV in MSSM

Need a susy copy of quartic coupling, only gauge coupling works in MSSM

Susy is the leading candidate for BSM Physics

Dark Matter candidate

Gauge Coupling Unification

Compelling structure

Become the standard lamppost

Basic Susy Signatures away from mSUGRAare still being explored

A lot of the qualitative signatures of Susyappear in other models

Extra Dimensions Taxonomy

Large TeV Small

Flat Curved

UEDs RS Models GUT ModelsADD Models

Kaluza-Klein ModesThe general method to analyze higher dimensional theories

Equations of Motion

One 5D field = tower of 4D fields

Large Extra Dimensions

GravitySM

n L

1 1010 km

2 1 mm

3 10nm

4 10-2nm

5 100fm

6 1fm

Integrate out extra dimension

Set

Large Extra Dimension Signatures

Monophoton+MET

Large Extra Dimension SignaturesBlack Holes at the LHC

for

BHs decaythermally, violating all

global conservation laws

High multiplicity eventswith lots of energy

Universal Extra Dimensions

+GravitySM

Standard Model has KK modes

All fields go in the bulkM

ass

Impose Dirichlet Boundary Conditions

UED KK SpectraLevels are degenerate at tree level

All masses within 30% of each other!(This is a widely spaced example!)

KK Parity

All odd-leveled KK modes are oddSM and even-leveled KK modes are even

Looks like a degenerate Supersymmetry spectrumuntil you can see 2nd KK level

LKP is stable!

Usually KK partner of Hypercharge Gauge boson

Typical UED EventPair produce colored 1st KK level

Each side decays separately

Difficult is in Soft Spectra

Randall Sundrum Models

TeV Scale Curved Extra Dimensions

Warp factor

UV Brane IR Brane

At each point of the 5th dimension,there is a different normalization of 4D lengths

Effects of the Warping

Need to go to canonical normalization

All mass scales on IR brane got crunched by warp factor

Super-heavy IR brane Higgs becomes light!

An IR brane scalar

Can put all fields on IR brane...

but just like low dimension operators getscrunched, high dimension operators get enlarged!

Motivated putting SM fields in bulk except for the Higgs

UV Brane IR Brane

SM Gauge + Fermions

Higgs boson

Now have SM KK modes, but no KK parity

Resonances not evenly spaced either

Get light KK copies of right-handed top

Tonnes of Theory & Pheno and Models for RS Models!

AdS/CFT

Theories in Anti-de Sitter space (RS metric)

Equivalent to 4D theories that are conformal (scale invariant)

5D description is way of mocking up complicated 4D physics!

Warping is Dimensional Transmutation

IR Brane is breaking of conformal symmetry

Technicolor Theories

Imagine there was no Higgs

QCD still gets strong and quarks condense

Condensate has SM gauge quantum numbers

Like the Higgs!

QCD confinement/chiral symmetry breakingbreaks electroweak symmetry

Technicolor is a scaled-up version of QCD

RS Models are the modern versions of Technicolor

In Technicolor theoriesNot necessarily a Higgs boson

Technirhos usually first resonance

Mediate contributions to

with90 GeV

800 GeV

etc

Need to be lighter than 1 TeV

90 GeV

3 TeV

etc

Can push off the Technirhosusually a scalar resonance becomes narrow

600 GeV

starts playing the role of the Higgs

Requires assumptions about technicolor dynamics

Would like to get scalars lightwithout dynamical assumptions

Higgs as a Goldstone boson

Higgs boson is a technipion

Pions are light because the areGoldstone bosons of approximate symmetries

f set by Technicolor scale

Goldstone bosons only have periodic potentials

Little Higgs TheoriesSpecial type of symmetry breaking

Looks like normal “Mexican hat” potential

Lots of group theory to get specific examples

All have some similar features

New gauge sectors

Vector-like copies of the top quarks

There are extended Higgs sectors

SU(2)L singlets, doublets & triplets

Conclusion

Beyond the Standard Model Physics is rich and diverse

Within the diversity there are many similar themes

These lectures were just an entry way into the phenomenology of new physics

We’ll soon know which parts of these theorieshave something to do with the weak scale

References

S. P. Martin

hep-ph/9709356

C. Csaki et al

“Supersymmetry Primer”

“TASI lectures on electroweak symmetry breaking from extra dimensions”hep-ph/0510275

M. Schmaltz, D. Tucker-Smith

“Little Higgs Review”

hep-ph/0502182

I. Rothstein

hep-ph/0308286“TASI Lectures on Effective Field Theory”

G. Kribs

“TASI 2004 Lectures on the pheomenology of extra dimensions”

hep-ph/0605325

J. Wells

hep-ph/0512342

“TASI Lecture Notes: Introduction to Precision Electroweak Analysis”

R. Sundrum“TASI 2004: To the Fifth Dimension and Back”

hep-ph/0508134