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Hunting for New Particles
&Forces
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Example: Two particles produced
• Animations:• QPJava-22.html
u
u
d
u
d
u
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Example: Dark Matter Particle produced
• Animations:• QPJava23.html
u
u
d
u
d
u
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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
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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.
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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
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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
)
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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
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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
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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
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SM Higgs: Event SignaturesmH<135 GeV
mH>135 GeV
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Status of Direct Search for Higgs boson
• 2010: 8 fb-1
– Exclude115 < mH < 125 GeV and 150 <mH < 180 GeV
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The Next Energy Frontier
The Large Hadron Collider
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SM Higgs boson production• Gluon fusion
• Vector Boson Fusion
• W, Z associated production
• tt, bb associated production
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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
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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
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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?
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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!
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Unification of the Forces
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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
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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
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-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.
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Adding super-partners
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104 108 1012 1016 1020
Q [GeV]
60
40
20
0
-1
-1
-1
-1
With SUSY
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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.
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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
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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
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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 ?
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New Particles?
• Solution to the dark matter problem?
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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!!
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Physics Beyond Borders
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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
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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.
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What is the story they may tell…
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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