Energy Frontier High Energy Physics The LHC Project February 18, 2009 Takahiko Kondo KEK, Professor Emeritus First International Winter School of the Global COE on the Quest of Fundamental Principle in Universe, Nagoya University, at Kintetsu Aqua Villa Ise-Shima 1 Original file at : http://atlas.kek.jp/sub/OHP/2009/20090218KondoNagoya.pdf http://atlas.kek.jp/sub/OHP/2009/20090218KondoNagoya.pptx V2 (2009.3.1)
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Energy Frontier High Energy Physics The LHC Project
V2 (2009.3.1). Energy Frontier High Energy Physics The LHC Project. February 18, 2009 Takahiko Kondo KEK, Professor Emeritus First International Winter School of the Global COE on the Quest of Fundamental Principle in Universe, Nagoya University, at Kintetsu Aqua Villa Ise-Shima. - PowerPoint PPT Presentation
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Energy Frontier High Energy Physics
The LHC ProjectFebruary 18, 2009
Takahiko KondoKEK, Professor Emeritus
First International Winter School of the Global COE on the Quest of Fundamental Principle in Universe,
Nagoya University,at Kintetsu Aqua Villa Ise-Shima
1Original file at : http://atlas.kek.jp/sub/OHP/2009/20090218KondoNagoya.pdf
Standard Model(based on gauge-invariant Quantum Field Theory)
All forces are generated by the exchange of gauge bosons Gauge boson
5
Fundamental problems
[1] How to avoid infinity in calculations?Infinite number of higher orderterms must be summed andusually you get !
[2] Why bare quarks never come out ?My first experiment in graduate course (~1967) was to search for 1/3e particles in cosmic rays. No bare quarks found so far. But nucleons are made out of three quarks. proton neutron
[3] Why W,Z bosons and quarks/leptons have mass?Gauge-invariance (with parity violation) prohibits mass of particles. However, mW~81 GeV, mZ~91GeV, mt~172 GeV, me=0.55 MeV. (Note:Without gauge-invariance, infinity problem (1) cannot be solved.)
Nobel prizes were awarded to the solvers of each problem !
6
7
Solution for [1] : Quantum Electro Dynamics ( QED)
Tomonaga Feynmann Schwingers
In 1940s , a renormalization method (くりこみ法) was developed successfully to avoid the infinities, making high precision predictions possible.e.g. anomalous magnetic moment
Renormalization is possible because QED is gauge invariant.
Theory must be local gauge invariant .
(theory) 88700011596521.0
exp.)(80850011596521.02
2
gae
"for their fundamental work in quantum electrodynamics, with deep-ploughing consequences for the physics of elementary particles”
1965
xh
(x1 y1 z1)x
hx
h
(x2 y2 z2)(x3 y3 z3)
Local gauge invariance
Theory is invariant under arbitrary rotations of internal coordinates.
)()( )( xex xiq
Solution for [2] : Quantum Chromo Dynamics (QCD)
D. Gross H.D. Politzer F. Wilczek
• Quarks have 3 color charges. • Gluons of 8 colors carry force.
• Particles (π,p, n….) have no color.
• Asymptotic freedom: Force is like rubber band. Smaller as closer, stronger as farther.
"for the discovery of asymptotic freedom in the theory of the strong interaction"2004
If one tries to separate two quarks by force, quark pairs (e.g. d, dbar) is created from vacuum since it is energetically smaller. Thus bare quarks never come out.
8
Solution for [3] : Glashow-Weinberg-Salam Model
• Electroweak symmetry SU(2)L and weak-hypercharge symmetry U(1)Y exists at higher energies.
• They are spontaneously broken by a Higgs field. 3 gauge bosons become massive by eating 3 Higgs fields.
• At least one Higgs particle must exist.
• Quarks/leptons can be massive.
S. Glashow S. Weinberg A. Salam"for their contributions to the
theory of the unified weak and electromagnetic interaction between elementary particles, including, inter alia, the prediction of the weak neutral current"
• In 1971, ‘t Hooft proved GWS model is renormalizable.
• Discovery of neutral current in 1973 at CERN.
• ep scattering experiment at SLAC proved the GWS model in 197
"for elucidating the quantum structure of electroweak interactions in physics"
1999
D ‘t Hooft M. Veltman
R. Brout F. Englert P. Higgs
Why it is called Higgs particle ?
In 1964, several theorists independently pointed that mass-less gauge bosons become massive when the symmetry breaks down spontaneously in the presence of self-coupling scalar field, mathematically. Weinberg and Salam applied their findings in the electroweak theory.
Standard Model predicts all the processes from ~ 1eV through 100,000,000,000 eV level with very high precisions. No phenomenon against Standard Model is found so far (except DM).
Total hadronic cross section of the e-e+ annihilation process
Standard model
0gluonm
0 m
GeV 91GeV 80
Z
W
mm
Higgs particles is the only missing element to be discovered. All other elements were discovered in 20th Century.
Standard Model : SU(3)C×SU(2)L×U(1)Y
13
• Higgs mass mH is a free parameter. Most likely 100 ~ 1000 GeV.
• Search at LEP mH > 114.4 GeV
• Search at Tevatron mH ≠ 170 GeV
• Indirect measurements via quantum corrections
mH < 144 GeV
• The main goal of the LHC project is to discover the Higgs particles. 14
Properties of SM Higgs Particles
Higgs simulation at LHC: pp → H → Z Z → μ+μ-μ+μ- (yellow tracks).
(yellow) excluded by direct search.(blue) probability via SM radiative quantum corrections.
15
CERN
GenevaCERN
CERN
Founded in1954, 20 member countries, 2500 staffs, 9000 users annual budget 1,000 MCHF
Invention of WWW in 1990.
16
Circumference26.6 km
major experiments
ATLASCMS
ALICELHCb
Approved in 1994
Completed in 2008
Cost : 10B$
LHC (Large Hadron Collider)
17ATLAS
C M S
ALICE
tunnel 26.6 km
pp energy 7+7 TeVluminosity 1034 cm-2s-1 dipole magnets 8.33T, 1232
1232 dipole superconducting dipole magnet bends the beam.
2 beam in 1 magnetCool down to 1.9KMagnetic field 8.33
Tesla 19
20
ATLAS Experiment• A general purpose detector for pp collision to search for Higgs and new.• International collaboration of 2,200 scientists, from 37 countries (incl.
Japan).• Height 25m, length 44m, eight 7000 t .• Construction cost : about 550 MCHF. Construction took 14 years.• > 80,000,000 signal channels.• 15 Japanese institutes (incl. Nagoya) contributes in
Muon trigger
Silicon detector
Superconducting solenoid
Major contributionby Japan
21ATLAS detector under construction at November 2005
22
ATLAS : example of contribution by Japan Endcap Muon trigger system (Japan, Israel and
China)
Cosmic-ray test at Kobe Univ.
1200 chamber production at KEK
(2000-2004)
Assembly at CERN (2005-2007)
Installation at underground hall (2006-2008 )
320K channels of electronics at
KEK Nagoya U. N group
Construction of ATLAS (ATLAS_construction.wmv)
23
Proton beam of 450 GeV successfully went around the LHC ring in 50 min. with live broadcasting to the whole world.
First beam in the LHC 10 Sep. 2008
24
25
Beam successfully went 1 turn clock-wise within 50 min. of injection start.
ATLAS observed many muons created upstream by the proton beam.
The beam orbit is measured on-line by position monitors with instant feedback actions.
Next day, the beam was synchronously captured by RF cavity resulting several undred turns.
26
• 9 days after, a large He leak occurred during power test of sector 34, the last sector that should have been tested before 10 Sept.
• One (out of >10,000) connection btwn two magnets melted down, causing He leak of 6 tons. Evaporated He gas damaged and moved many magnets.
• After investigation, 53 magnets were removed to surface for repair.
• Much better safety measures are being taken to prevent similar incidents.
• The beam test will resume in Sept. 2009. 5+5 TeV physics runs will start in Oct. 2009 and continue till the 2010 fall.
27
He leak incident on 19 Sept. 2008
A cable connection melted down causing large He leak.
Some magnets moved due to He gas pressure.
28
Reconstruction of H→
Higgs discovery at LHC
2010 (?)
2011(?)
2012(?)
• s(production) and decay branchin rations are well predicted as a function of mH .
• Main decay modes for discovery:
• Data taking will start in Oct. 2009 (hopefully) at ECMS = 10 TeV.
(red) 5s discovery line(blue) 95% excllusion line
,
HjjWWH
ZZHH
Hierarchy (fine tuning, naturalness ) problem
• Higgs particles get large quantum mass corrections (because it is scalar)
mH = 200 GeVdmH = 1,000,000,000,000,000,000 GeVif next new physics were at ~1019 GeV (Planck scale). This is very unnatural.
Solution 1 : SUSYIf SUSY particles exist, the quadratic mass correction term exactly cancel out.
Solution 2 : Extra DimensionsThe next new physics exists at 1~10 TeV.
29
...../ln6216 cutoff
22cutoff2
22 ee
eH mm
ym
d
Quantum corrections on mH
...../ln42 16
~ cutoff2~
2cutoff2
~ 2 eee
H mmym
d
H H
H H
LR e~,e~
Re
Le
Quantum corrections by SUSY particles
30
SUSY (Super Symmetry)
Symmetry between fermions (half spin) and bosons (integer spin)
No SUSY particles are found so far SUSY must be broken softly.
q
+
31
• Coupling constants varies as a function of energy (distance).
QED : shielding (stronger as E↑ )
QCD : anti-shielding (weaker as E↑ )
due to gluon self-coupling
•
quark
quark
EM
EMEM qn
qN
q 2
2
20
02 3N ,
ln3
)(1
)()(
0
Shielding by vacuum polarization in QED
Running coupling constants
20
2203
2032
3
ln33212
)(1
)()(
qn
q
f
-+- +
- +-+
-+
-+ - +
-+
Anti-shielding by vacuum polarization in QCD if nq < 33/2
clouds of gluons & quarks
quark
gluo
n
32
GUT (Grand Unification Theory)
11
21
31
Three forces may be unified at 2x1016 GeV if SUSY particles exist at 1 TeV. note: based on RGE equations given by U. Amaldi et al., Phys. Lett. B260(1991)447. data for 1/1 are scaled from 1/EM by 3/5*cos2W
33
colliding galaxy cluster
Dark Matter (DM)
dark matter map using gravity
lens
3K microwave background
rotation of galaxy
motion of galactic cluster
Standard Model explains only 4%
of our Universe ! !
SUS
Y (M
SSM
)
34
to be discovered
Dark Matter
candidate:Neutralino
s
within reach of LHC !!
Thermodynamics in expanding universe with cold DM scenario
Sta
ndar
d M
odel
223 EQnnvAHn
dtdn s
1.02 hDM
pb 1 ~ v TeV, 1~1.0~ sm
35
• SUSY particles carry R-parity = -1:
• Because of R-parity, LSP (lightest supersymmetric particle) is neutral, stable and be intact with matter, a good DM candidate!
• LSP escapes from the detector leaving large missing Et.
SLBR 231 0
1~ (LSP)
g~
g~
u
uq
qg
p
p
SUSY particle production at LHC.
dete
ctor
Detection of DM at LHC
Simulated SUSY event in CMS detector
Large Extra Dimension New approach to solve the hierarchy problem
Interaction energy
3 forces
gravity in 4+2 extra dimensions
Electro-weak scale Planck scale1016
Newton gravity F ~ 1/r2
Gravity extends to large bulk, while SM stays on 4-dim brane.
36
LHC will reach back to 10-12 sec after the Big Bang.
Rest Energy KE of Highest energy CM Energy Nuclear Binding Atomic of Flea Sprinter Cosmic rays of LHC Energy Binding Energy
QUANTUM END OF END OF MATTER ● Formation GRAVITY GRAND ELECTROWEAK DOMINATION of Atoms ● Supergravity? UNIFICATION UNIFICATION ● Formation of ● Decoupling of -● Ex Dim? ● Origin of Matter- ● End of SUSY? Quark Hadron Structure begins Matter and ● Supersymmetry? Antimatter Symmetry Transition Big Bang ● Superstrings? ● Monploles Nucleosynthesis
● Inflation
History of Universefrom E. Kolb and M. Turner p.73
Rest Energy KE of Highest energy CM Energy Nuclear Binding Atomic of Flea Sprinter Cosmic rays of LHC Energy Binding Energy
QUANTUM END OF END OF MATTER ● Formation GRAVITY GRAND ELECTROWEAK DOMINATION of Atoms ● Supergravity? UNIFICATION UNIFICATION ● Formation of ● Decoupling of -● Ex Dim? ● Origin of Matter- ● End of SUSY? Quark Hadron Structure begins Matter and ● Supersymmetry? Antimatter Symmetry Transition Big Bang ● Superstrings? ● Monploles Nucleosynthesis
● Inflation
History of Universefrom E. Kolb and M. Turner p.73
B I
G
B
A
N
G
Leptons &
Quarks
GaugeBosons
Photons
..... Y,X, Z,W
GLUONS
bt
sc
duee
pn
e
,
eLiHeHeDH
,,,,,
7
4
3
LiHeHeDH
7
4
3
,,,,
R(matter/radiation)=5x10-10
3K CMB
2K bkgd
1 103 106 109 Years
LHC could elucidate this region
40
• Standard Model describes all the phenomena with high accuracy .
• Spontaneous Symmetry Breaking must exist to explain the masses of W, Z and quarks/leptons. Higgs particle must exist.
• LHC accelerator and detectors ATLAS and CMS has just completed aiming at Higgs discovery.
• Higgs will be discovered in a few years of LHC operation.
• If LHC discover SUSY, hierarchy problem be solved, Grand Unification may become likely and dark matter may be explained.
• New results from LHC may extend our understandings on fundamental principles from 100 GeV to1 possibly 1016 GeV, corresponding to 10-11 to 10- 38sec after the Big Bang.
Summary
Some useful introduction references with more details:
1) Lecture at the 2008 summer school for young students ( 日本語 ) http://atlas.kek.jp/sub/OHP/2008/20080820Kondo.ppt http://atlas.kek.jp/sub/OHP/2008/20080820Kondo.pdf
2) Introduction to physics calculations and histrogramming ( 日本語 ) http://atlas.kek.jp/seminar