Hunting for New Particles

&Forces

Example: Two particles produced

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Example: Dark Matter Particle produced

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Physics at the Tevatron

mb -

b -

nb -

pb -

fb -

100 120 140 160 180 200- - - -

Higgs Mass [GeV/c2]

Total Inelastic

bb

WZ

tt-

-

WZ

Tevatron

3 x 1014

2 x 1011

6 x 107

2 x 107

28,00016,000, 12,000

HiggsWH,ZH 4000 ~ 400

400 ~ 40

jets (qq, qg, gg)

Single Top

obse

rved

Tevatron Cross Sections

The Higgs cross section is10-11 orders of magnitudes lower than the total inelastic cross section.

Recent evidence of single top quark production is an important milestone towards the Higgs boson.

Light quarks are ubiquitous.

Plenty of W and Z bosons → calibration.

Total inelastic cross section.

W

W

top

bottom

Higgs

Tevatron: Improve Higgs Mass Pred. via Quantum Corrections

Mtop (GeV)

MW

(GeV

)

150 175 200

80.5

80.4

80.3

1 GeV = 1 GeV / c2 ~ proton mass

M higgs

= 1

00 G

eV20

0 GeV

300

GeV

500

GeV

1000

GeV

W

top

bottom

Z

top

topW, Z

Higgs

Tevatron: Higgs Mass Prediction via Quantum Corrections

Clues to the Higgs ?

MH = 92+45-32 GeV;

MH < 186 @ 95% CLMtop (GeV)

Tevatron Run II

MW

(GeV

)

Tevatron: Higgs Mass Prediction via Quantum Corrections

Clues to the Higgs ?

MH = 76+33-24 GeV; 114 < MH < 182 @ 95% CL

Winter 2007Winter 2007

2tW mm 2ln HW mm

Higgs boson production @ Tevatron

• Associated Production• mH < 135 GeV

– (W,Z+H) ¼ 0.15 pb H bb H WW

• Gluon fusion• mH > 135 GeV

– (H) ¼ 0.45 pb

Higgs boson decays• H ff, WW, ZZ

– couples to mass;– heaviest final state

dominates

• mH < 135 GeV– H bb

• mH > 135 GeV– H WW

Tevatron can explore bb and WW(ℓ+ℓ-) decay modes

SM Higgs: Event SignaturesmH<135 GeV

mH>135 GeV

Status of Direct Search for Higgs boson

• 2010: 8 fb-1

– Exclude115 < mH < 125 GeV and 150 <mH < 180 GeV

The Next Energy Frontier

The Large Hadron Collider

SM Higgs boson production• Gluon fusion

• Vector Boson Fusion

• W, Z associated production

• tt, bb associated production

Tevatron: Improve Higgs Mass Pred. via Quantum Corrections

Mtop (GeV)

MW

(GeV

)

LHC: Designed to discover Higgs with Mhiggs = 100 ~ 800 GeV

M (GeV)

130 GeV HiggsL = 100 fb-1

# of

eve

nts

/ 0.

5 G

eV

Tevatron LHC

MHiggs (GeV)

5 D

isco

very

Lum

inos

ity (

fb-1)

Tevatron: Improve Higgs Mass Pred. via Quantum Corrections

Mtop (GeV)

MW

(GeV

)

LHC: Designed to discover Higgs with Mhiggs = 100 ~ 800 GeV

Tevatron LHC

Mtop (GeV)

MW

(GeV

)

MHiggs (GeV)

5 D

isco

very

Lum

inos

ity (

fb-1)

Tevatron: Improve Higgs Mass Pred. via Quantum CorrectionsLHC: Designed to discover Higgs with Mhiggs = 100 ~ 800 GeV

Tevatron LHC

easy

hard

Will the Tevatron’s prediction agree with what LHC sees?

tan

MA (GeV)

LHC

Mtop (GeV)

MSSM

MW

(GeV

)

TevatronLHC

Tevatron LHC

Higgs in Minimal Supersymmetric Extension of Standard Model

LHC will be the best place to discover Higgs particles!

Unification of the Forces

Unification

We want to believe that there was just one force after the Big Bang.

As the universe cooled down, the single force split into the four that we know today.

1TeV = 103GeV(1016K)10-11 s

1016GeV(1029 K)10-38 s

1019GeV(1032K)10-41 s

2.3 x 10-13 GeV(2.7K)

12x109 y

EnergyTempTime

Unification of electromagnetic & weak forces

(electroweak theory)

Long term goal since 60’sWe are getting there.

Beautifully demonstratedat HERA ep Collider at DESY

The main missing link is Higgs boson

HERA

Q2 [GeV2]

Electromagnetic ForceWeak Force

f

HERA:H1 +ZEUS

-1

-1

-1

104 108 1012 1016 1020

Q [GeV]

60

40

20

0

-1

13 orders of magnitude higher energy

The Standard Model fails to unify the strong and electroweak forces.

Adding super-partners

104 108 1012 1016 1020

Q [GeV]

60

40

20

0

-1

-1

-1

-1

With SUSY

With SUSYUnifying gravity with the other 3 is accomplished by string theory.

String theory predicts extra hidden dimensions in spacebeyond the three we sense daily.

Other models predict large extra dimensions:large enough to observe up to multi TeV scale.

Extra Dimensions?• Attempts to unify gravity with other forces predicts extra dimensions.• Explains why gravity appears weak.• These extra dimensions could be very small, which is why we don't see

them. – To a tightrope walker, the tightrope is one-dimensional: he can only move

forward or backward

– But to an ant, the rope has an extra dimension: the ant can travel around the rope as well

Large Extra Dimensions of Space

LHC can discover partner towers up to a given energy scale.

qq,gg GN e+e-,+-

Mee, [GeV]

LHC

Mee [GeV]

DZero

Tevatron

GNq

q

e+

e-

Tevatron Sensitivity2.4 TeV @95% CL

Mee [GeV]

Eve

nts

/ 50

GeV

/ 1

00 f

b-1

102

10

1

10-1

10-2

LHC

New forces of nature new gauge boson

LHC has great discovery potential for multi TeV Z’.

Mee [GeV] M [GeV]

Tevatron LHC 104

103

102

10

1

10-1

Events/2GeV

qq Z’ e+e-

Tevatron sensitivity~1 TeV

CDF Preliminary

Little Higgs Models ? New strong Dynamics ?

New Particles?

• Solution to the dark matter problem?

We are hoping in the next ~5 years we will discover Higgs. This will open windows for discovering new laws of nature.

Discovering “laws of nature” is exciting!!

Physics Beyond Borders

Why high energy?

E= hc

(courtesy Louis de Broglie)

Visible light 10-6 mElectron microscope 10-10 mRutherford's a-particles 10-14 m1 TeV protons 10-18 m

Smallest length scale probed

Particles Tell Stories!

The discovery of a new particle is often the opening chapter revealing unexpected features of our universe.

Particles are messengers telling a profound story

about nature and laws of nature in microscopic world.

The role of physicists is to find the particles and to listen to their stories.

What is the story they may tell…

Entire new particle spectrum?Super Symmetry

– Attempting to unify gravity with the other fundamental forces leads to a startling prediction:

• every fundamental matter particle should have a massive "shadow" force carrier particle, and every force carrier should have a massive "shadow" matter particle. ….

http://www.particleadventure.org