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# Why New Physics the Terascale - PowerPoint PPT Presentation

Non-SUSY Physics Beyond the Standard Model. J. Hewett, Pre-SUSY 2010. Why New Physics @ the Terascale?. Electroweak Symmetry breaks at energies ~ 1 TeV (SM Higgs or ???) WW Scattering unitarized at energies ~ 1 TeV (SM Higgs or ???)

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the Standard Model

J. Hewett, Pre-SUSY 2010

• Electroweak Symmetry breaks at

energies ~ 1 TeV (SM Higgs or ???)

• WW Scattering unitarized at energies ~ 1 TeV (SM Higgs or ???)

• Gauge Hierarchy: Nature is fine-tuned or Higgs mass must be stabilized by

New Physics ~ 1 TeV

• Dark Matter: Weakly Interacting Massive Particle must have mass ~ 1 TeV to reproduce observed DM density

All things point to the Terascale!

Brief review of features which guide & restrict BSM physics

SGauge =  d4x FY FY + F F + Fa Fa

SFermions =  d4x   fDf

SHiggs =  d4x (DH)†(DH) – m2|H|2 + |H|4

SYukawa =  d4x YuQucH + YdQdcH† + YeLecH†

( SGravity =  d4x g [MPl2 R + CC4] )

Generations

f = Q,u,d,

L,e

SM predictions @ 2+ loop level

Jet production rates @

Tevatron agree with QCD

Standard Model predictions well described by data!

Pull

Q1

u1

d1

L1

e1

.

. 2

.

. 3

Rotate 45 fermions into each other

U(45)

SM matter secretly has a large symmetry:

Explicitly broken by gauging 3x2x1

Rotate among generations

U(3)Q x U(3)u x U(3)d x U(3)L x U(3)e

Explicitly broken by quark Yukawas + CKM

Explicitly broken by charged lepton Yukawas

U(1)e x U(1) x U(1)

Explicitly broken by neutrino masses

U(1)B

Baryon Number

Lepton Number

U(1)L (Dirac)

(or nothing) (Majorana)

1 + i2

3 + i4

Four real degrees of freedom

Higgs Doublet:

Secretly transforms as a

1

2

3

4

4 of SO(4)

Decomposes into

subgroups

(2,2) SU(2) x SU(2)

SU(2)L of EW

Left-over Global Symmetry

1 + i2

3 + i4

Four real degrees of freedom

Higgs Doublet:

Secretly transforms as a

Gauging U(1)Y explicitly breaks

Size of this breaking given by Hypercharge coupling g’

1

2

3

4

SU(2)Global Nothing

4 of SO(4)

Decomposes into

subgroups

MW2 g2

=  1 as g’0

MZ2 g2 + (g’)2

(2,2) SU(2) x SU(2)

New Physics may excessively break SU(2)Global

SU(2)L of EW

Remaining Global Symmetry

Custodial Symmetry

-

Fermions cannot simply ‘pair up’ to form mass terms

i.e., mfLfR is forbidden Try it!

(Quc) 1 2 -1/2

(Qdc) 1 2 +1/2

(QL) 3 1 -1/3

(Qe) 3 2 +7/6

(ucdc) 3x3 1 -1/3

(ucL) 3 2 -7/6

(uce) 3 1 +1/3

(dcL) 3 2 -5/6

(dce) 3 1 +4/3

(Le) 1 2 +1/2

SU(3)C SU(2)L U(1)Y

Fermion masses must be generated by Dimension-4 (Higgs) or higher operators to respect SM gauge invariance!

-

-

-

-

-

-

Anomaly Cancellation

Quantum violation of current conservation

SU(3)

SU(3)

SU(2)L

SU(2)L

U(1)Y

U(1)Y

g

g

3[ 2‧(1/6) – (2/3) + (1/3)] = 0

Q uc dc

U(1)Y

U(1)Y

U(1)Y

U(1)Y

3[3‧(1/6) – (1/2)] = 0

Q L

3[ 6‧(1/6)3 + 3‧(-2/3)3 + 3‧(1/3)3

+ 2‧(-1/2)3 + 13] = 0

3[(1/6) – (2/3) + (1/3) – (1/2) +1]

= 0

Q uc dc L e

Can’t add any new fermion  must be chiral or vector-like!

SU(3)C x SU(2)L x U(1)Y

Exact

Broken to U(1)QED

• Gauge Symmetry

• Flavor Symmetry

• Custodial Symmetry

• Chiral Fermions

• Gauge Anomalies

U(3)5 U(1)B x U(1)L (?)

Explicitly broken by Yukawas

SU(2)Custodial of Higgs sector

Broken by hypercharge so  = 1

Need Higgs or Higher order operators

Restrict quantum numbers of new fermions

SU(3)C x SU(2)L x U(1)Y

Exact

Broken to U(1)QED

• Gauge Symmetry

• Flavor Symmetry

• Custodial Symmetry

• Chiral Fermions

• Gauge Anomalies

U(3)5 U(1)B x U(1)L (?)

Explicitly broken by Yukawas

SU(2)Custodial of Higgs sector

Broken by hypercharge so  = 1

Need Higgs or Higher order operators

Restrict quantum numbers of new fermions

Any model with New Physics must respect these symmetries

An effective field theory has a finite range of applicability in energy:

, Cutoff scale

Energy

SM is valid

Particle masses

All interactions consistent with gauge symmetries are permitted, including higher dimensional operators whose mass dimension is compensated by powers of 

Precision Electroweak

Generic Operators

Flavor Violation

CP Violation

Baryon Number Violation

Contact Operators

Constraints on Higher Dimensional Operators

Λ≳ 1016 GeV

Λ≳ 1015 GeV

Λ≳ 106 GeV

Λ≳ 106 GeV

Λ≳ 103 GeV

Λ≳ 103 GeV

Λ≳ 3x102 GeV

• What sets the cutoff scale  ?

• What is the theory above the cutoff?

New Physics, Beyond the Standard Model!

• SM parameters are unnatural

• New physics introduced to “Naturalize”

• SM gauge/matter content complicated

• New physics introduced to simplify

• Deviation from SM observed in experiment

 New physics introduced to explain

Technically Natural

• Fermion masses

(Yukawa Couplings)

• Gauge couplings

• CKM

Logarithmically

sensitive to the cutoff

scale

• Technically Unnatural

• Higgs mass

• Cosmological constant

• QCD vacuum angle

• Power-law sensitivity to the cutoff scale

The naturalness problem that has had the greatest impact on collider physics is:

The Higgs (mass)2 problem

or

The hierarchy problem

The Hierarchy collider physics is:

Energy (GeV)

1019

Planck

1016

GUT

desert

Future Collider Energies

103

Weak

All of known physics

Solar System

Gravity

10-18

The Hierarchy Problem collider physics is:

Energy (GeV)

1019

Planck

Quantum Corrections:

Virtual Effects drag

Weak Scale to MPl

1016

GUT

desert

Future Collider Energies

mH2 ~

~ MPl2

103

Weak

All of known physics

Solar System

Gravity

10-18

A Cellar of New Ideas collider physics is:

a classic!

aged to perfection

better drink now

mature, balanced, well

developed - the Wino’s choice

’67 The Standard Model

’77 Vin de Technicolor

’70’s Supersymmetry: MSSM

’90’s SUSY Beyond MSSM

’90’s CP Violating Higgs

’98 Extra Dimensions

’02 Little Higgs

’03 Fat Higgs

’03 Higgsless

’04 Split Supersymmetry

’05 Twin Higgs

svinters blend

all upfront, no finish

lacks symmetry

bold, peppery, spicy

uncertain terrior

complex structure

young, still tannic

needs to develop

sleeper of the vintage

what a surprise!

finely-tuned

double the taste

J. Hewett

Last Minute Model Building collider physics is:

Anything Goes!

• Non-Communtative Geometries

• Return of the 4th Generation

• Hidden Valleys

• Quirks – Macroscopic Strings

• Lee-Wick Field Theories

• Unparticle Physics

• …..

(We stilll have a bit more time)

New Physics @ LHC7 collider physics is:

Most cases controlled by

Parton flux

Supermodel Discovery Criteria:

• Large σLHC giving ≥ 10 events at ℒ = 10 pb-1

• Small σTevatron giving ≤ 10 events with ℒ = 10 fb-1

• Large BF to easy to detect final state

• Consistency with other bounds

Solid: 7 TeV vs Tevatron

Dashed: 10 TeV vs Tevatron

Bauer etal 0909.5213

New Physics @ LHC7 collider physics is:

Most cases controlled by

Parton flux

Supermodel Discovery Criteria:

• Large σLHC giving ≥ 10 events at ℒ = 10 pb-1

• Small σTevatron giving ≤ 10 events with ℒ = 10 fb-1

• Large BF to easy to detect final state

• Consistency with other bounds

Naive, but a reasonable guide

Solid: 7 TeV vs Tevatron

Dashed: 10 TeV vs Tevatron

Bauer etal 0909.5213

QCD Pair Production Reach @ LHC7 collider physics is:

-

-

• gg,qq → QQ

• Assumes 100% reconstruction efficiencies

• No background

Current Tevatron bound

On 4th generation T’ quark:

~ 335 GeV (4.6 fb-1)

Tevatron

exclusion

LHC7 should cover entire

4th generation expected

region!

Bauer etal 0909.5213

High Mass Resonances collider physics is:

Z’ Resonance: GUT Models collider physics is:

LRM

E6 GUTS

LHC7

Tevatron Bounds

Rizzo

Small collider physics is:

Large

TeV

Extra Dimensions Taxonomy

Flat

Curved

GUT Models

UEDs

RS Models

Extra dimensions can be difficult to visualize collider physics is:

• One picture: shadows of higher dimensional

• objects

2-dimensional shadow of a rotating cube

3-dimensional shadow of a rotating hypercube

Extra dimensions can be difficult to visualize collider physics is:

• Another picture:extra dimensions are too small

for us to observe  they are

‘curled up’ and compact

The tightrope walker only sees one dimension: back & forth.

The ants see two dimensions: back & forth and around the circle

Every point in spacetime has curled up extra dimensions associated with it

One extra dimensionis a circle

Two extra dimensions can be represented by a sphere

Six extra dimensions can be represented by a Calabi-Yau space

The Braneworld Scenario associated with it

• Yet another picture

• We are trapped on a

• 3-dimensional spatial

• membrane and cannot move

• in the extra dimensions

• moves in the extra space

• The extra dimensions can

• be either very small or

• very large

Are Extra Dimensions Compact? associated with it

• QM tells us that the momentum of a particle traveling along an infinite dimension takes a continuous set of eigenvalues. So, if ED are infinite, SM fields must be confined to 4D OTHERWISE we would observe states with a continuum of mass values.

• If ED are compact (of finite size L), then QM tells us that p5 takes on quantized values (n/L). Collider experiments tell us that SM particles can only live in ED if 1/L > a few 100 GeV.

Kaluza-Klein tower of particles associated with it

E2 = (pxc)2 + (pyc)2 + (pzc)2 + (pextrac)2 + (mc2)2

In 4 dimensions, looks like a mass!

Recall pextra = n/R

Tower of massive particles

Kaluza-Klein tower of particles associated with it

E2 = (pxc)2 + (pyc)2 + (pzc)2 + (pextrac)2 + (mc2)2

In 4 dimensions, looks like a mass!

Recall pextra = n/R

Tower of massive particles

Large radius gives finely separated Kaluza-Klein particles

Small radius gives well separated Kaluza-Klein particles

Action Approach: associated with itConsider a real, massless scalarin flat 5-d

Time-like or Space-like Extra Dimensions ? associated with it

Consider a massless particle, p2 =0, moving in flat 5-d

Then p2 = 0 = pμpμ± p52

If the + sign is chosen, the extra dimension is time-like,

then in 4-d we would interpret p52 as a tachyonic mass

term, leading to violations of causality

Thus extra dimensions are usually considered to be

space-like

Higher Dimensional Field Decomposition associated with it

• As we saw, 5d scalar becomes a 4d tower of scalars

• Recall: Lorentz (4d) ↔ Rotations (3d)

scalar scalar

4-vector Aμ A, Φ

tensor Fμν E, B

• 5d: 5d ↔ 4d

scalar (scalar)n

vector AM (Aμ, A5)n

tensor hMN (hμν, hμ5, h55)n

KK towers

Higher Dimensional Field Decomposition associated with it

• As we saw, 5d scalar becomes a 4d tower of scalars

• Recall: Lorentz (4d) ↔ Rotations (3d)

scalar scalar

4-vector Aμ A, Φ

tensor Fμν E, B

• (4+δ)d: (4+δ)d ↔ 4d (i=1…δ)

scalar (δ scalars)n

vector AM (Aμ, Ai)ni

tensor hMN (hμν, hμi, hij)n

KK towers

1 tensor, δ 4-vectors, ½ δ(δ+1) scalars

• Experimental observation of KK states: associated with it

Signals evidence of extra dimensions

• Properties of KK states:

Determined by geometry of extra dimensions

 Measured by experiment!

The physics of extra dimensions is the physics of the KK excitations

What are extra dimensions good for? associated with it

• Can unify the forces

• Can explain why gravity is weak (solve hierarchy problem)

• Can break the electroweak force

• Contain Dark Matter Candidates

• Can generate neutrino masses

……

Extra dimensions can do everything SUSY can do!

If observed: Things we will want to know associated with it

• How many extra dimensions are there?

• How big are they?

• What is their shape?

• What particles feel their presence?

• Do we live on a membrane?

If observed: Things we will want to know associated with it

• How many extra dimensions are there?

• How big are they?

• What is their shape?

• What particles feel their presence?

• Do we live on a membrane?

• Can we park in extra dimensions?

• When doing laundry, is that where all the socks go?

Searches for extra dimensions associated with it

Three ways we hope to see extra dimensions:

• Modifications of gravity at short distances

• Effects of Kaluza-Klein particles on astrophysical/cosmological processes

• Observation of Kaluza-Klein particles in high energy accelerators

The Hierarchy Problem: associated with itExtra Dimensions

Energy (GeV)

1019

Planck

Simplest Model:

Large Extra Dimensions

1016

GUT

desert

Future Collider Energies

103

Weak – Quantum Gravity

= Fundamental scale in

4 +  dimensions

MPl2 = (Volume) MD2+

Gravity propagates in

D = 3+1 +  dimensions

All of known physics

Solar System

Gravity

10-18

Large Extra Dimensions associated with it

Arkani-Hamed, Dimopoulos, Dvali, SLAC-PUB-7801

Motivation: solve the hierarchy problem by removing it!

SM fields confined to 3-brane

Gravity becomes strong in the bulk

Gauss’ Law: MPl2 = V MD2+ , V = Rc 

MD = Fundamental scale in the bulk

~ TeV

Bulk Metric: associated with itLinearized Quantum Gravity

• Perform Graviton KK reduction

• Expand hAB into KK tower

• SM on 3-brane

• Set T = AB (ya)

• Pick a gauge

• Integrate over dy

• Interactions of Graviton KK states with SM fields on 3-brane

Feyman Rules: Graviton KK Tower associated with it

Massless 0-mode + KK states have indentical coupling to matter

Han, Lykken, Zhang; Giudice, Rattazzi, Wells

Collider Tests associated with it

Graviton Tower Exchange: associated with itXX  Gn  YY

Giudice, Rattazzi, Wells

JLH

Search for 1) Deviations in SM processes

2) New processes! (gg  ℓℓ)

Angular distributions reveal spin-2 exchange

M

Gn are densely packed!

(s Rc) states are exchanged! (~1030 for =2 and s = 1 TeV)

Forward-Backward Asymmetry associated with it

Drell-Yan Spectrum @ LHC

MD = 2.5 TeV

4.0

JLH

Graviton Exchange

Graviton Exchange @ 7 TeV LHC associated with it

Graviton Tower Emission associated with it

Giudice, Ratazzi,Wells

Mirabelli,Perelstein,Peskin

-

• e+e- /Z + Gn Gn appears as missing energy

• qq  g + Gn Model independent – Probes MD

directly

• Z  ff + Gn Sensitive to 

Parameterized by density of states:

-

Discovery reach for MD (TeV):

Graviton Emission @ LHC associated with it

Detailed LHC/ATLAS MC Study associated with it

The 14 TeV LHC is seen

to have considerable search

reach for KK Graviton

production

Hinchliffe, Vacavant

BEWARE! associated with it

• There is a subtlety in this calculation

• When integrating over the kinematics, we enter a region where the collision energies EXCEED the 4+n-dimensional Planck scale

• This region requires Quantum Gravity or a UV completion to the ADD model

• There are ways to handle this, which result in minor modifications to the spectrum at large ET that may be observable

The Hierarchy Problem: associated with itExtra Dimensions

Energy (GeV)

1019

Planck

Model II:

Warped Extra Dimensions

1016

GUT

strong curvature

desert

Future Collider Energies

103

Weak

wk = MPl e-kr

All of known physics

Solar System

Gravity

10-18

Non-Factorizable Curved Geometry: Warped Space associated with it

Area of each grid is equal

faster with more volume

 Drop to bottom brane

Gravity appears weak on top brane!

Localized Gravity: Warped Extra Dimensions associated with it

Randall, Sundrum

5 = -24M53k2

k = curvature scale

Hierarchy is generated by exponential!

Naturally stablized via Goldberger-Wise

4-d Effective Theory associated with it

Davoudiasl, JLH, Rizzo

Phenomenology governed by two parameters:

 ~ TeV

k/MPl≲ 0.1

5-d curvature:

|R5| = 20k2 < M52

Interactions associated with it

Recall  = MPlekr ~ TeV

Randall-Sundrum Graviton KK spectrum associated with it

Davoudiasl, JLH, Rizzo

Unequal spacing signals curved space

e+e- →μ+μ-

e+e-+-

LHC

pp → l+l-

Different curves for k/MPl =0.01 – 1.0

Summary of Theory & Experimental Constraints associated with it

LHC can cover entire allowed parameter space!!

Problem with Higher Dimensional Operators associated with it

• Recall the higher dimensional operators that mediate proton decay & FCNC

• These are supposed to be suppressed by some high mass scale

• But all high mass scales present in any RS Lagrangian are warped down to the TeV scale.

• ⇒ There is no mechanism to suppress these dangerous operators!

• Could employ discrete symmetries ala SUSY – but there is a more elegant solution….

Peeling the Standard Model off the Brane associated with it

• Model building scenarios require SM bulk fields

• Gauge coupling unification

• Supersymmetry breaking

•  mass generation

• Fermion mass hierarchy

• Suppression of higher dimensional operators

• Gauge boson KK towers have coupling gKK = 8.4gSM

• Precision EW Data Constrains: m1A > 25 TeV   > 100 TeV!

• SM gauge fields alone in the bulk violate custodial symmetry

Davoudiasl, JLH, Rizzo

Pomarol

Schematic of Wavefunctions associated with it

Can reproduce

Fermion mass

hierarchy

Planck brane

TeV brane

Fermions in the Bulk associated with it

• Zero-mode fermions couple weaker to gauge KK states than brane fermions

towards Planck brane

towards TeV brane

Precision EW Constraints

Collider Signals are more difficult associated with it

KK states must couple to gauge fields or top-quark to

be produced at observable rates

-

gg  Gn  ZZ

gg  gn  tt

Agashe, Davoudiasl, Perez, Soni hep-ph/0701186

Lillie, Randall, Wang, hep-ph/0701164

Black Hole Production @ LHC: associated with it

Dimopoulos, Landsberg

Giddings, Thomas

Black Holes produced when s > MD

Classical Approximation: [space curvature << E]

E/2

b < Rs(E)  BH forms

b

E/2

^

MBH ~ s

Geometric Considerations:

Naïve = FnRs2(E), details show this holds up to a

factor of a few

Blackhole Formation Factor associated with it

Potential Corrections to Classical Approximation associated with it

RS2/(2Rc)2

n = 2 - 20

• Distortions from

finite Rc as Rs Rc

2. Quantum Gravity Effects

Higher curvature term

corrections

Critical point for

instabilities for n=5:

(Rs/Rc)2 ~ 0.1 @ LHC

n = 2 - 20

Gauss-Bonnet term

n2≤ 1 in string models

Production rate is enormous! associated with it

Naïve ~ n for large n

1 per sec at LHC!

MD = 1.5 TeV

JLH, Lillie, Rizzo

Black Hole Decay associated with it

• Balding phase: loses ‘hair’ and multiple moments by gravitational radiation

• Spin-down phase: loses angular momentum by Hawking radiation

• Schwarzschild phase: loses mass by Hawking radiation – radiates all SM particles

• Planck phase: final decay or stable remnant determined by quantum gravity

Decay Properties of Black Holes (after Balding): associated with it

Decay proceeds by thermal emission of Hawking radiation

Not very sensitive to BH rotation for n > 1

At fixed MBH, higher dimensional BH’s are hotter:

N ~ 1/T

 higher dimensional BH’s emit fewer quanta, with each quanta having higher energy

Multiplicity for n = 2 to n = 6

Harris etal hep-ph/0411022

Grey-body Factors associated with it

Particle multiplicity in decay:

 = grey-body factor

Contain energy & anglular emission information

p associated with itT distributions of Black Hole decays

Provide good discriminating power for value of n

Generated using modified CHARYBDIS linked to PYTHIA

with M* = 1 TeV

Cosmic Ray Sensitivity to Black Hole Production associated with it

No suppression

Ringwald, Tu

Anchordoqui etal

Summary of Exp’t Constraints on M associated with itD

Anchordoqui, Feng

Goldberg, Shapere

Summary of Physics Beyond the Standard Model associated with it

• There are many ideas for scenarios with new physics! Most of our thinking has been guided by the hierarchy problem

• They must obey the symmetries of the SM

• They are testable at the LHC

• We are as ready for the LHC as we will ever be

• The most likely scenario to be discovered at the LHC is the one we haven’t thought of yet.

Exciting times are about to begin.

Be prepared for the unexpected!!

Fine-tuning does occur in nature associated with it

2001 solar eclipse as viewed from Africa

H. Murayama associated with it

Most Likely Scenario @ LHC: