New Physics Scenarios Jay Wacker SLAC SLAC Summer Institute August 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 predictions Best motivation Parameters are “Unnatural” Well defined and have good theoretical motivation Reduce/Explain the multitude of parameters Typically has limited success, frequently untestable To know what is possible Let’s us know what we can look for in experiments Limited only by creativity and taste

The Plan Beyond 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 principles used in a half dozen paradigms that 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 Supersymmetry Extra Dimensions Strong Dynamics

Standard Model: a story of economy 5 Particles3 Couplings symmetryunification 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 FieldColorWeakHypercharge

Motivations for Physics Beyond the Standard Model The Hierarchy Problem Dark Matter Exploration

The Hierarchy Problem The SM suffers from a stability crisis Higgs vev determined by effective mass, not bare mass Many contributions that must add up to -(100 GeV) 2 =

A recasting of the problem: Why is gravity so weak? Explain how to make G F large (i.e. v small) Explain why G N is so small (i.e. M Pl large)

1998: Large Extra Dimensions (Arkani-Hamed, Dimopoulos, Dvali) High scale is a “mirage” Gravity is strong at the weak scale Need 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 composite Resolve substructure at small distances Why hadrons are lighter than Planck Scale

A New Symmetry Scalar Fermion Supersymmetry Scalar Mass related to Fermion Mass 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 special UV 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 matter Electrically & Color Neutral Cold/Slow Relatively 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” Increasing

Boltzmann Equation Solves for Frozen out when

We want to see what’s there! Muon, Strange particles, Tau lepton not predicted before discovery Serendipity favors the prepared! Exploration

Chirality Anomaly CancellationFlavor SymmetriesGauge Coupling Unification Effective Field Theory Organizing Principles for 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 Breaking Breaking 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 as an “Effective Theory” that describes the dynamics Shouldn’t be constrained by renormalizability One way of looking for new physics is by looking 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) U(1) SU(3) It works, but is a big constraint!

Gauge coupling unification: Our Microscope (GeV) Counts charged matter Weak scale measurement High scale particle content

Grand Unification Gauge 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 cancellation restricts new charged particles Making sure that there is no new sources of 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

Supersymmetry Doubles Standard Model particles Dirac pair of Higgsinos Gauginos Sfermions 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 running Gauge 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, but SUSY breaking effects can be parameterized in the Lagrangian

Problem with Parameterized SUSY Breaking There are over 100 parameters once Supersymmetry no longer constrains interactions Most of these are new flavor violation parameters or CP violating phases Horribly excluded Susy breaking is not generic!

Soft Susy Breaking i.e. Super-GIM mechanism Universality of soft terms Need to be Flavor Universal Couplings Scalar Masses Trilinear A-Terms Approximate degeneracy of scalars

Proton Stability New particles ⇒ new ways to mediate proton decay Lightest Supersymmetric Particle is stable Dangerous couplings Must be neutral and colorless -- Dark Matter Proton Pion Supersymmetric couplings that violate SM symmetries A new symmetry forbids these couplings:

Mediation of Susy Breaking MSSM Primoridal Susy Breaking Mediation Susy breaking doesn’t occur inside the MSSM Felt through interactions of intermediate particles Studied to reduce the number of parameters Gauge Mediation Universal “Gravity” Mediation Anomaly Mediation Usually only 4 or 5 parameters... but for phenomenology, these are too restrictive

The Phenomenological MSSM The set of parameters that are: Not strongly constrained Easily 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 Total Parameters

Charginos & Neutralinos The 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 NeutralinosCharginosSleptonsSquarksGluinos Mass

Collider signatures Trileptons+MET: If sleptons are available Neutralinos Charginos Sleptons Mass 3 Leptons + MET

Collider signatures Trileptons+MET Without sleptons in the decay chain Neutralinos Charginos Sleptons Mass 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 log Fine 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 mSUGRA are still being explored A lot of the qualitative signatures of Susy appear in other models

Extra Dimensions TaxonomyLarge TeV Small FlatCurved UEDs RS ModelsGUT ModelsADD Models

Kaluza-Klein Modes The general method to analyze higher dimensional theories Equations of Motion One 5D field = tower of 4D fields

Large Extra Dimensions Gravity SM nL km 21 mm 310nm nm 5100fm 61fm Integrate out extra dimension Set

Large Extra Dimension Signatures Monophoton+MET

Large Extra Dimension Signatures Black Holes at the LHC for BHs decay thermally, violating all global conservation laws High multiplicity events with lots of energy

Universal Extra Dimensions +Gravity SM Standard Model has KK modes All fields go in the bulk Mass Impose Dirichlet Boundary Conditions

UED KK Spectra Levels 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 odd SM and even-leveled KK modes are even Looks like a degenerate Supersymmetry spectrum until you can see 2nd KK level LKP is stable! Usually KK partner of Hypercharge Gauge boson

Typical UED Event Pair 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 get scrunched, high dimension operators get enlarged! Motivated putting SM fields in bulk except for the Higgs UV BraneIR 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 breaking breaks electroweak symmetry Technicolor is a scaled-up version of QCD RS Models are the modern versions of Technicolor

In Technicolor theories Not necessarily a Higgs boson Technirhos usually first resonance Mediate contributions to with 90 GeV 800 GeV etc Need to be lighter than 1 TeV 90 GeV 3 TeV etc Can push off the Technirhos usually a scalar resonance becomes narrow 600 GeV starts playing the role of the Higgs Requires assumptions about technicolor dynamics Would like to get scalars light without dynamical assumptions

Higgs as a Goldstone boson Higgs boson is a technipion Pions are light because the are Goldstone bosons of approximate symmetries f set by Technicolor scale Goldstone bosons only have periodic potentials

Little Higgs Theories Special 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 theories have something to do with the weak scale

References S. P. Martin hep-ph/ C. Csaki et al “Supersymmetry Primer” “TASI lectures on electroweak symmetry breaking from extra dimensions” hep-ph/ M. Schmaltz, D. Tucker-Smith “Little Higgs Review” hep-ph/ I. Rothstein hep-ph/ “TASI Lectures on Effective Field Theory” G. Kribs “TASI 2004 Lectures on the pheomenology of extra dimensions” hep-ph/ J. Wells hep-ph/ “TASI Lecture Notes: Introduction to Precision Electroweak Analysis” R. Sundrum “TASI 2004: To the Fifth Dimension and Back” hep-ph/

New Gauge Symmetries New Abelian Gauge Sectors New Non-Abelian Gauge Sectors