Recent ATLAS Higgs Results and KoRIA
2nd AKPA Physics Symposium
January 20, 2012
Dr. Jaehoon Yu
Outline
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What is High Energy Physics?
Where are we at present with Higgs?
What have we seen in Higgs at the LHC?
What can we do with KoRIA?
Conclusions
High Energy Physics
• Definition: A field of physics that pursues understanding
the fundamental constituents of matter and basic
principles of interactions between them.
• Known interactions (forces):
– Gravitational
– Electro-Weak
– Strong
• Current theory: The Standard Model of Particle Physics
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Unified Weak and Electromagnetic: SU(2)xU(1)
Strong Interaction: SU(3)
Currently:SU(3)xSU(2)xU(1)
Meaning: 8+4 mediators for forces
Jan. 20, 2012
ATLAS Higgs, HEP and KoRIA Dr.
Jaehoon Yu
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The Standard Model of Particle Physics
• Prescribes the following fundamental structure:
Discovered
in 1995,
~175mp
~0.1mp
Directly
observed in
2000
Family
• Three families of leptons and quarks together with
12 force mediators  Simple and elegant!!!
• Jan.Tested
to a precision
ofHEP1andpart
million!
20, 2012
ATLAS Higgs,
KoRIA per
Dr.
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Jaehoon Yu
Good, but still lots we don’t know…
• Why are there three families of quarks and leptons?
• Why is the mass range so large (0.1mp – 175 mp)?
• How do matters acquire mass?
– Higgs mechanism but where is the Higgs, the God particle?
• Why is the matter in the universe made only of particles?
– What happened to anti-particles? Or anti-matters?
• Why are there only three apparent forces?
• Is the picture we present the real thing?
– What makes up the 96% of the universe?
– How about extra-dimensions?
• How is the universe created?
• Are there any other theories that describe the universe better?
– Does the super-symmetry exist?
Jan. 20, 2012
ATLAS Higgs, HEP and KoRIA Dr.
Jaehoon Yu
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Fermilab Tevatron and
LHC
at
CERN
• World’s Highest Energy p-p collider
World’s Highest Energy proton-anti-proton collider
– 27km circumference, 100m underground
– Design Ecm=14 TeV (=44x10-7J/p 362M
Joules on the area smaller than 10-4m2)
 Equivalent to the kinetic energy of a B727
(80tons) at the speed 193mi/hr  312km/hr
– 4km circumference
– Ecm=1.96 TeV (=6.3x10-7J/p 13M Joules on the
area smaller than 10-4m2)
– Equivalent to the kinetic energy of a 20t truck at the
speed 81mi/hr 130km/hr
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~100,000 times the energy density at the ground 0 of the
Hiroshima atom bomb
– Was shut down at 2pm CDT, Sept. 30, 2011
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Other parts of the complex is still running!!
Chicago
CDF
p
Tevatron
Jan. 20, 2012

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~3M times the energy density at the ground 0 of the
Hiroshima atom bomb
First 7TeV collisions on 3/30/10  The highest energy
humans ever achieved!!
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First collisions in 2012 in mid March, 2012
DØ
p
ATLAS Higgs, HEP and KoRIA Dr.
Jaehoon Yu
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ATLAS Detector
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Weighs 7000 tons and 10 story tall
Can inspect 1,000,000,000 collisions/second
Records 200 – 400 collisions/second
Records approximately 350,000,000 bytes/second
Record 2x1015 (2,000,000,000,000,000) bytes each year (2
PetaByte).  200*Printed material of the US Lib. of Congress
Jan. 20, 2012
ATLAS Higgs, HEP and KoRIA Dr.
Jaehoon Yu
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ATLAS Integrated Luminosity in 2011
LHC delivered 2010 - 2011: 5615 pb-1
ATLAS recorded 2010 - 2011: 5252pb-1
ATLAS data taking ε: 94%
About 160 times the data taken in 2010!!
1700pb-1 in one month!!  2012 expects close
to 10,000pb-1
Jan. 20, 2012
ATLAS Higgs, HEP and KoRIA Dr.
Jaehoon Yu
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Step one: Understanding the ATLAS Detector
Cables
C-fiber
shell
Cooling
pipe
Pixel module
Data
Simulation
Allows detailed understanding of the detector material
via location of interactions.
Jan. 20, 2012
ATLAS Higgs, HEP and KoRIA Dr.
Jaehoon Yu
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Step two: Verify SM  Weak Bosons
• Important first steps are the verification of the Standard Model physics at √s = 7 TeV
• W/Z weak vector boson are powerful tools to constrain PDF’s and to understand detector
Jan. 20, 2012
ATLAS Higgs, HEP and KoRIA Dr.
Jaehoon Yu
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Of course, we see Z  ee and μμ!!
Z  μμ candidate
Z  ee candidate
Total efficiency : ~ 30%
Main background: QCD
S/B ~ 100
Jan. 20, 2012
ATLAS Higgs, HEP and KoRIA Dr.
Jaehoon Yu
Total efficiency: ~ 40%
Main background: tt, Z ττ
S/B ~ 400
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Step 3: Understanding SM background to Higgs!!
W+Njet x-sec
W x-sec vs CMS Energy
Validation of theoretical predictions!!
Jan. 20, 2012
ATLAS Higgs, HEP and KoRIA Dr.
Jaehoon Yu
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130GeV
Higgs x-sec and Branching Ratio
Jan. 20, 2012
ATLAS Higgs, HEP and KoRIA Dr.
Jaehoon Yu
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ATLAS Higgs Search Strategy
• Use gg  H production
– MH<130GeV
• H  bb dominant decay
– High QCD background
• H   cleanest but low BR
• H  t t  with leptonic decays of t Small branching ratio
– 130GeV<MH<2MZ: H  WW * , H  ZZ *
– MH>2MZ: H  WW , H  ZZ , H  tt
• Use multi-lepton final state from decays of bosons
• tt final state dominated by QCD production of top.
• Use WH or ZH production at low mass (MH<120GeV)
– Use leptonic decay of bosons with two b-jets.
Jan. 20, 2012
ATLAS Higgs, HEP and KoRIA Dr.
Jaehoon Yu
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What do we know on Higgs before LHC?
 
M W ~ M t2  ln M H2
LEPJan.
EWWG:http://www.cern.ch/LEPEWWG
20, 2012
ATLAS Higgs, HEP and KoRIA
Jaehoon Yu
Dr.
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114<MH<300+700-186 GeV
Golden Channels in Higgs Searches
• Higgs boson is a ramification of the mass generation mechanism  Highest
priority in HEP and the last standing mystery
• Higgs decays in to various final states
– H  ZZ*  4e, 2e2 and 2e2
– Very clean signal w/ modest background
– Narrow mass peak
e+ (μ+)
– High PT electron identification key
e- (μ-)
e+
e-
Jan. 20, 2012
ATLAS Higgs, HEP and KoRIA Dr.
Jaehoon Yu
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After all selections: kinematic cuts, γ identification and isolation
 22489 events with 100 < mγγ < 160 GeV observed in the data
 expected signal efficiency: ~ 35% for mH=125 GeV
mγγ spectrum fit with exponential function for
background plus Crystal Ball + Gaussian for sign
 background determined directly from data
Systematic uncertainties on
signal expectation
Main systematic uncertainties
Expected signal yield : ~ 20%
H γγ mass resolution : ~ 14%
H γγ
p modeling
: ~ 8%
16 T20, 2012
Jan.
ATLAS Higgs, HEP and KoRIA Dr.
Background modeling : ±0.1-5.6 events
Jaehoon Yu
Excluded (95% CL):
114 ≤ mH ≤ 115 GeV, 135 ≤ mH≤ 136 GeV
Consistency of the data with the
background-only expectation
Maximum deviation from background-only
expectation observed for mH~126 GeV:
 local p0-value: 0.27% or 2.8σ
 expected from SM Higgs: ~ 1.4σ local
 global p0-value: includes probability for
such an excess to appear anywhere in
the investigated mass range 110-150 GeV
(“Look-Elsewhere-Effect”): ~7% (1.5σ)
Expected from SM
Higgs at given mH
Where are we with Higgs searches?
LEP
ATLAS+CMS
Combination
Higgs could be discovered this year!!
ATLAS
today
Jan. 20, 2012
ATLAS Higgs, HEP and KoRIA Dr.
Jaehoon Yu
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ATLAS Higgs in 2012??
We could find the Higgs
particle at the LHC this
year!!
Once found, the precision
measurement of the Higgs
becomes very important!!
Jan. 20, 2012
ATLAS Higgs, HEP and KoRIA Dr.
Jaehoon Yu
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A Future Linear Collider
• An electron-positron collider on a straight line for precision
measurements
• CMS Energy: 0.5 – 1 TeV
• 10~15 years from now (Japanese PM announced that they would bid
for a LC in Japan)
• Takes 10 years to build the accelerator and the detector
L~31km
Circumference ~6.6km
~300 soccer fields
Jan. 20, 2012
ATLAS Higgs, HEP and KoRIA Dr.
Jaehoon Yu
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Gas Electron Multipliers (GEM)
GEM foil etching
140μm
70μm
GEM field and
multiplication
Gains
Jan. CERN-open-2000-344,
20, 2012
Higgs, HEP and KoRIA Dr.
From
A.ATLAS
Sharma
Jaehoon Yu
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100cmx100cm GEM Planes!!
CERN GDD Workshop delivered the
first 5 of 33cmx100cm GEM foils in
2010  Qualification completed!!
Each of the GEM 100cmx100cm
planes will consist of three
33cmx100cm unit chambers
Sept. 29, 2011
GEM DHCAL, J. Yu
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GEM Application Potential
FAST X-RAY IMAGING
Using the lower GEM signal, the
readout can be self-triggered with
energy discrimination:
9 keV absorption
radiography of a small
mammal (image size ~
60 x 30 mm2)
A. Bressan et al,
Nucl. Instr. and Meth. A 425(1999)254
F. Sauli, Nucl. Instr. and Meth.A 461(2001)47
Jan. 20, 2012
ATLAS Higgs, HEP and KoRIA Dr.
Jaehoon Yu
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Radioactive Source Run with Internal Trigger
Noisy channels masked out!
Can you see what the object is?
Jan. 20, 2012
ATLAS Higgs, HEP and KoRIA Dr.
Jaehoon Yu
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And in not too distant future, we could do …
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KoRIA, A World-class Accelerator Facility
• Future high priority high energy physics topics will require
even higher energy and higher flux
– Searching and precisely measuring the properties of SUSY
particles, dark matter, dark Energy and extra dimensions
– Massive detailed studies of quark-gluon plasma!
– Creating and accumulating anti-matters in mass!!
• KoRIA is a great starting point for establishing a versatile
world-class accelerator facility in Korea
• Attract large number of scientists and promote advancement
of accelerator related technologies
• Advance significantly the understanding the origin of the
universe and help the whole human race in the long run
Jan. 20, 2012
ATLAS Higgs, HEP
and KoRIA Dr.
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So how can KORIA get there?
• The current KoRIA must be solidly established and carry out
its mission successfully
• A clear vision for the long-term future of KoRIA must be
established from the get-go
• Phased plan must be established to shape the future of
KoRIA even as the current KoRIA is being constructed
• Build up manpower through the strong collaboration with
existing labs, such as Fermilab and CERN
– Train domestically to increase technical manpower
• A stage for a historic future is set!
• Need to get organized now to make it happen in 30yrs!
Jan. 20, 2012
ATLAS Higgs, HEP
and KoRIA Dr.
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Conclusions
• The LHC opened up a whole new kinematic regime
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The LHC performed extremely well this year
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1fb-1 expected but obtained over 5fb-1
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Latest results on Higgs show some hints of its existence
We expect over 10fb-1 additional data expected 2012
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We could find the Higgs particle this year or disprove its existence
In 2013 – 2014, an 18 month work on the accelerator toward the designed 14TeV
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Linear collider and advanced detectors are being developed for future
precision measurements of Higgs and other newly discovered particles
• Outcome and the bi-product of HEP research impacts our daily lives
– WWW came from HEP
– GEM will make a large screen low dosage X-ray imaging possible
• KoRIA is a fruit of aspiration for excellence in basic sciences
– Need to plan now to shape KoRIA to its long term future and to realize the dream
• Strong US-Korea collaboration will help this happen
Jan. 20, 2012
ATLAS Higgs, HEP and KoRIA Dr.
Jaehoon Yu
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KoRIA in 30 years?
15 kilometers
Booster complex
Jan. 20, 2012
ATLAS Higgs, HEP
and KoRIA Dr.
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