High Energy Physics: The Next Two Decades

Tao HanTao HanUniversity of Wisconsin --- MadisonUniversity of Wisconsin --- Madison

Syracuse UniversitySyracuse University October 21October 21, 2010, 2010

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OutlineOutline

Elementary Particle Physics (HEP): Elementary Particle Physics (HEP): A historical accountA historical account

Tera-scale Physics: Tera-scale Physics: What and Why?What and Why?

Concluding RemarksConcluding Remarks

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Prelude: LHC has started its mission!

On March 29, 2010, CERN LHC successfully collides proton-proton beams at 3,500 GeV + 3,500 GeV.

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Large Hadron Collider (LHC)

At CERN, Geneva:At CERN, Geneva: proton-proton collider:proton-proton collider: 27 km27 km circumference;circumference; 17461746 magnetic dipoles magnetic dipoles at at 8-9 T8-9 T and and 1.9 K1.9 K 7,000 GeV 7,000 GeV energyenergy (14 TeV(14 TeV energy energy when full when full ))

7 mph7 mph slower than the slower than the speed of lightspeed of light

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Largest scientific project ever !Largest scientific project ever ! Stored Energy of Beams unprecedented :

EEbeambeam=1.5=1.5 Giga Joule (N m) Giga Joule (N m)

same kinetic energy as aircraft carrier at same kinetic energy as aircraft carrier at 15 knots ≈ 30 km/h !15 knots ≈ 30 km/h !

Highest energy, probing smallest objects at at 1010-17-17 cm (10 cm (10-10-10 nm ) nm ) !

Compare with Tevatron: 7 times7 times more energetic100 times100 times brighter

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Elementary Particle Physics:Elementary Particle Physics: A Historical Account A Historical Account

The “elementary particles” change with time:The “elementary particles” change with time:

toFrom

Ancient Chinese: Metal, Wood, Water, Fire, Earth Ancient Greeks: Elements, AtomsE. Rutherford: Atom <= Nucleus + Electrons Nucleus <= p+ + n0

M. Gell-Mann: Nucleons (p, n) <= Quarks: u, d, …

So now, all matter around us:p(uud), n(udd), e- plus ,

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The first inspiring unified field theory:The first inspiring unified field theory: Maxwell unified Electricity and Magnetism Maxwell unified Electricity and Magnetism

with his famous equations (1873)with his famous equations (1873)

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(b) The theory L= - F F /4

(a) By introducing the Vector potential A (x) for spin-1,

and the field strength: F= A - A

Maxwell’s equations can be made manifestly Lorentz invariant.

is invariant under the “gauge” transformation:

A (x) A(x) - (x)

A mass term for the field m2 AA

violates “gauge invariance”, a new symmetry! So we understand why photon is massless.

Remarkable Features:

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Dirac introduced relativistic quantum Dirac introduced relativistic quantum theory of electron (1928) theory of electron (1928)

Quantum Electro-DynamicsQuantum Electro-Dynamics

Feynman, Schwinger, Tomonaga, (Dyson) Feynman, Schwinger, Tomonaga, (Dyson)

Theory of electrons and photons with Theory of electrons and photons with precise predictive power precise predictive power (“renormalization”):(“renormalization”):

Anomalous magnetic moment:Anomalous magnetic moment:g/2 ≈ 1 + O(0.001)g/2 ≈ 1 + O(0.001)

Feynman Diagram Approach:

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The weak force:The weak force: Matter spontaneously emits penetrating radiation:Matter spontaneously emits penetrating radiation:

Uranium emissions (Becquerel, 1896) andUranium emissions (Becquerel, 1896) and

Radium emissions (the Curies, 1898)Radium emissions (the Curies, 1898)

beta EnergySpectrum:

A missing neutral particle (1930):(1st particle dark matter!)

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The weak force: Fermi’s TheoryThe weak force: Fermi’s Theory

Fermi formulated the first theory (1934)Fermi formulated the first theory (1934)

of the weak force: of the weak force: “the neutrino”“the neutrino”

n n p e p e-- ee

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Left - Right Left - Right notnot symmetric ! symmetric ! ““Parity” Violated 100% Parity” Violated 100% in the weak force (1957).in the weak force (1957).

This established the basic structure This established the basic structure

of the of the “Standard Model.”“Standard Model.”

The weak interaction is “chiral”The weak interaction is “chiral”(Lee and Yang, 1956)(Lee and Yang, 1956)

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Speculation on Speculation on heavy mediating particleheavy mediating particle

below unitarity boundbelow unitarity bound E < 300 GeV! E < 300 GeV!

The weak theory is “sick” The weak theory is “sick” (Lee and Yang, 1960)(Lee and Yang, 1960)

Theory Theory fails at high energyfails at high energy, , violates the “unitarity limit”violates the “unitarity limit”(or probability conservation)(or probability conservation)

But no theoretical guidance But no theoretical guidance

on what to expect ...on what to expect ...

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The idea …The idea …

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Electroweak Unification: A Successful Model

Glashow, Salam, Weinberg realized that Glashow, Salam, Weinberg realized that

the field responsible for the electromagnetic the field responsible for the electromagnetic force (force (the photonthe photon))

And the fields responsible for the Weak force And the fields responsible for the Weak force (the then undiscovered (the then undiscovered WW++ and W and W-- ) )

Along with a then undiscovered heavy neutral Along with a then undiscovered heavy neutral boson (boson (ZZ) ) a single theory a single theory

Plus a scalar sector,for symmetry breaking (masses).

W/Z Discovery in 1982:W/Z Discovery in 1982:

Rubbia andvan de Meer(1984)

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There is “strong force” tooThere is “strong force” tooAmong Quarks and GluonsAmong Quarks and Gluons

(Analogous to QED)

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Remarkable feature:Remarkable feature:

““Asymptotic freedom”Asymptotic freedom” Predictivity ! Predictivity !

“ “Higher” energy physics, unification; Higher” energy physics, unification;

The Early Universe …The Early Universe …

Interaction strength changes fast with energy/distance scale:Interaction strength changes fast with energy/distance scale:

D. Gross,F. Wilczek,D. Politzer (2004)

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Quarks and Leptons

Discovery of top quarkDiscovery of top quark B meson decays violate B meson decays violate

Charge conj. + Parity (CPv)Charge conj. + Parity (CPv)

Kobayashi,Maskawa, 2008

Neutrino masses and flavor Neutrino masses and flavor oscillations discovered.oscillations discovered.

Necessary condition formatter – antimatter asymmetry: Our existence !

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Simple matter content;Simple matter content; Gauge principle to govern Gauge principle to govern

dynamics;dynamics; Count for all HEP dataCount for all HEP data

True triumph for physics True triumph for physics and science !and science !

The elegant Standard ModelThe elegant Standard Model

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(Tevatron)

Why the photon is so different from W/Z ?

Mt=173 GeV

The Need for Tera-scale new Physics:The Need for Tera-scale new Physics:

Why the top quark is as heavy as a gold atom, while neutrinos are nearly massless ?

(A). Mass Quest:M = 0 !MW ≈ 80 GeVMZ ≈ 90 GeV

m < 1 eV

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(Peter Higgs)

The theory (the Lagrangian) is symmetric, but the vacuum background (the state) is NOT.

Y. Nambu, 2008

A shifted vacuum,New ground state

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Masses determined by interactions with vacuum:

Masses of elementary particlesMasses of elementary particles

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because:

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(B). Is a “lonely” Higgs Enough? (Is EW Scale Natural?)

Weak GUT Planck

Tevatron/LHC Energies

1019 GeV1016100 GeV

Quantum corrections drag weak scale to Planck scale

22PlH MM ≈δ

To keep the Higgs boson naturally light, something else must set in below TeV.

Unnatural cancellation?Unnatural cancellation?

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Natural EW theory predicts TeV scale new physics!Natural EW theory predicts TeV scale new physics!

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(C). The Cosmic Quests

What is Dark Matter?What is Dark Matter? No good candidate in the No good candidate in the Standard ModelStandard Model

What is Dark Energy?What is Dark Energy? SM can’t explain this eitherSM can’t explain this either

New sources of CP violation New sources of CP violation

Natural DM candidates: WIMPs

(Weakly Interacting Massive Particles)

Terascale (neutral stable) particles!

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High Energy Probes Early UniverseHigh Energy Probes Early Universe

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What is the Terascale?What is the Terascale?

1 TeV = 1000 GeV = 1000 x (proton mass)1 TeV = 1000 GeV = 1000 x (proton mass)

1/(101/(10-17-17 cm) cm)

It is where the Higgs mass bound is;It is where the Higgs mass bound is;

It is where the unitarity bound is;It is where the unitarity bound is;

It is where the SUSY/new physics sets in;It is where the SUSY/new physics sets in;

It is where the particle dark matter should be;It is where the particle dark matter should be;

It is the next high energy frontier …It is the next high energy frontier …

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Experimental Opportunities Particle physicists employ two sets of tools:Particle physicists employ two sets of tools: Accelerators: high energy and high luminosity Cosmic rays: higher energy, (unknown) luminosity

We are entering a data-rich era: Low energy experiments:Low energy experiments: Neutrino oscillation expts: Neutrino oscillation expts: SuperK, SNO, KamLand, MINOs, Daya Bay…SuperK, SNO, KamLand, MINOs, Daya Bay… ee, g-2:, g-2: muon anomalous magnetic moment muon anomalous magnetic moment n, en, e-- electric dipole moments: electric dipole moments: New CP violation New CP violation… … … …

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We have had colliders:We have had colliders:

LEP I, II at CERN: LEP I, II at CERN: EW physicsEW physics

HERA at DESY: HERA at DESY: ep collisionsep collisions

BEPC: BEPC: ee++ee-- collisions as a collisions as a /charm factory/charm factory

B-factories at SLAC,KEK:B-factories at SLAC,KEK: B, CP violation B, CP violation

RHIC: RHIC: Gold-on-gold heavy ion collisions for QCDGold-on-gold heavy ion collisions for QCD

And,And,

Astroparticle expts: Astroparticle expts: Auger, Fermi/GLAST, Auger, Fermi/GLAST, IceCube, SDSS, LSST …IceCube, SDSS, LSST …

Cosmological observations … … Cosmological observations … …

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High energy frontier:

TevatronTevatron at FNAL at FNAL(more than 20 yrs now,(more than 20 yrs now,

still running strong!)still running strong!)

LHC at CERNLHC at CERN(Large Hadron Collider)(Large Hadron Collider)

ILC ILC (International Linear Collider)(International Linear Collider)

(muon collider?(muon collider?

VLHC? …) VLHC? …)

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The LHC Era has begun:The LHC Era has begun:Detectors are performing well !Detectors are performing well !(ATLAS, CMS, LHCb, ALICE)(ATLAS, CMS, LHCb, ALICE)

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Experiments at Unprecedented Scale

• Two large multi-purpose detectors

• CMS is 12,000 tons (2 x’s ATLAS)

• ATLAS 8 times the volume of CMS

• LHCb (beauty):

Syracuse U is in.

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Physics Program at the LHC

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LHC will discover LHC will discover SM Higgs boson if it SM Higgs boson if it existsexists

Sensitive to mSensitive to mhh from from 100-1000 GeV100-1000 GeV

Higgs signal in just a Higgs signal in just a few channelsfew channels

Answer to (A):The Higgs

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If there, discovery of SUSYIf there, discovery of SUSY

signal is not TOO hard.signal is not TOO hard. Most of the theoretical modelsMost of the theoretical models

can be discovered and can be discovered and studied.studied.

The challenge is to untangle The challenge is to untangle

the complex signals forthe complex signals for

parameters and to figure out parameters and to figure out the fundamental mechanisms.the fundamental mechanisms.

Answer to (B):TeV scale new particles

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Answer to (C):Answer to (C):Production of particleProduction of particle dark matterdark matter

The DM relic density is closely related to the production

Leading to large “ missing energy ”

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Answer to (C):Answer to (C):

We’d like to detect dark matter in the lab,We’d like to detect dark matter in the lab,to show they’re in the galactic halo …to show they’re in the galactic halo …

The Indirect Detection of Dark The Indirect Detection of Dark MatterMatter

Dan Hooper - Indirect Searches For Particle Dark Matter

1. WIMP Annihilation to SM particles

W+

W-

The Indirect Detection of Dark The Indirect Detection of Dark MatterMatter

Dan Hooper - Indirect Searches For Particle Dark Matter

1. WIMP Annihilation to SM particles2.Decay and/or fragment into electrons, protons, neutrinos, gammas

W+

W-

e+

q

q

p

0

The Indirect Detection of Dark The Indirect Detection of Dark MatterMatter

1. WIMP Annihilation to SM particles

2. Decay and/or fragment into electrons, protons, neutrinos, gammas

3. Relativistic electrons up-scatter starlight/CMB to MeV-GeV energies, and emit synchrotron photons via interactions with magnetic fields

W+

W-

e+

q

q

p

0

e+

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High Precision Inferring new physics effects from high energy scales

through precision measurements at low energies

Combining both stategies gives much more complete understanding than either one alone

Two Paths to Discovery High Energy ThresholdHigh Energy Threshold

Operating at the energy frontierDirect discovery of new particles: Tevatron and LHC

Higgs; SUSY; Strong dynamics; Extra-dimesion; New gauge bosons and fermions; String states; Black holes …

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Linear Collider is the place to measure Higgs couplings!

Answer to (A) Answer to (A) Does the Higgs Generate Mass?

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Threshold behavior measures spin

[20 fb-1 /point]

Linear collider can change initial state energy to do energy scans

Measuring the spin of the Higgs

Very hard to do at the LHC

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Answer to (C) Answer to (C) If LSP is dark matter, LHC and LC If LSP is dark matter, LHC and LC

will complement the direct DM searches:will complement the direct DM searches:

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HEP in an exciting time:HEP in an exciting time:Major Discoveries Ahead!Major Discoveries Ahead!

In HEP, with the upcoming rich data from LHC/cosmology:The Tera-scale physics will dominate the next two decades.

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HERA• Electromagnetic/Neutral current and Charged current unify at the scale of 100 GeV

Unification as expected:

• Experimental evidence for the unification of the weak and electromagnetic forces

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Model highly successful!

“Renormalizable” Theory that works better than 1%!

t’Hooft Veltman

(1999)

EW precision data: A light Higgs indeed?EW precision data: A light Higgs indeed?

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The Roadmap from here:The “EPP2010” CommitteeNational Academies convened this committee inNational Academies convened this committee inresponse to an informal request from NSF and DOEresponse to an informal request from NSF and DOE

1.1. Exploit the opportunities offered by the Exploit the opportunities offered by the LHCLHC

2.2. Plan and initiate a comprehensive program to participate in the global Plan and initiate a comprehensive program to participate in the global effort to complete the necessary R&D to design and plan an effort to complete the necessary R&D to design and plan an international linear colliderinternational linear collider

3.3. … … … … 4.4. Seize the opportunities at the Seize the opportunities at the intersectionintersection of particle physics, of particle physics,

astrophysics, and cosmology by coordinating and expanding domestic astrophysics, and cosmology by coordinating and expanding domestic effortsefforts

5.5. Pursue an internationally coordinated, staged program in the physics of Pursue an internationally coordinated, staged program in the physics of neutrinos and proton decay neutrinos and proton decay … …… …

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Tevatron --> LHC LHC Upgrade ILC

Current – 2011? 2010 2013?

Collider Timeline:

+10?

LHC experimentsLHC experiments

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Current values of electron (g-2)/2Current values of electron (g-2)/2

theory: theory:

0.5 (0.5 (//) - 0.32848 () - 0.32848 (//))22 + 1.19 ( + 1.19 (//))33+.. +.. = (115965230 = (115965230 10) x 1010) x 10-11-11

exp’ment = (115965218.7 exp’ment = (115965218.7 0.4)x100.4)x10-11-11

QED continuedQED continued

Example: magnetic dipole of the electron: Example: magnetic dipole of the electron:

= g = g (eh/2mc) S(eh/2mc) S

Dirac’s theory: Dirac’s theory: g = 2, g = 2,

and thus and thus (g - 2)(g - 2) is the “anomalous magnetic moment” is the “anomalous magnetic moment”

We can calculate!

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A Decade of Discovery

Discovery of top quarkDiscovery of top quark B meson decays violate B meson decays violate

Charge conj.+ParityCharge conj.+Parity

Kobayashi,Maskawa, 2008

Electroweak theory and experimentsElectroweak theory and experiments Neutrino masses and flavor Neutrino masses and flavor oscillationsoscillations --- Three separate neutrino species--- Three separate neutrino species Quantitative understanding of QCDQuantitative understanding of QCD Quarks and leptons structureless Quarks and leptons structureless at at 1010-17-17 cm (TeV scale) cm (TeV scale)

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New York Times:New York Times:

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The international accelerator community The international accelerator community believes that a TeV-scale linear collider believes that a TeV-scale linear collider can be successfully builtcan be successfully built

TESLA Superconducting Cavity

GDE Report publicized in IHEP, Beijing, Feb. 2007

American LC Workshop:Mid. Oct., 2007, FNAL

Revealing the Hidden Nature of Space and Time

Final Report of the Committee on Final Report of the Committee on Elementary Particle Physics in (the Elementary Particle Physics in (the First Decades of) the 21st CenturyFirst Decades of) the 21st Century

May 5, 2006May 5, 2006

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Running of the coupling constants needs a Running of the coupling constants needs a Terascale threshold to unify.Terascale threshold to unify.

(C). Einstein’s Dream of Unification(C). Einstein’s Dream of Unification

SUSY ModelSM

threshold

Gravity may be on the way …

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Answer to (B) and (C)Answer to (B) and (C)Consistency check for GUTsConsistency check for GUTs

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Is this a Higgs or

something else?Relationships to:

mass for W,Z?mass for W,Z?mass for fermions?mass for fermions?Higgs its own mass?Higgs its own mass?

More to ask:

The Nov. Revolution, 1974The Nov. Revolution, 1974

Burton RichterSamuel C. C. Ting

But, the unobservable particle But, the unobservable particle is observed !is observed !

Direct detection of the neutrinosopened up the “neutrino physics”

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High Energy Physics and Society

No physics research, no modern science;No physics research, no modern science;No high-energy physics, no first-class physics.No high-energy physics, no first-class physics.

Human being’s pursuing for knowledge drives science advancement. In return, science serves the society.

In the US, >30% of the GDP is the result of modern physics:Semiconductors; superconductors;Laser, nuclear technology;MRI, NMR;Low temperature technology;Fast electronics, computers, information industry; … …

This colloquium recordThis colloquium record

1: Technion1: Technion

… …… …

March,08: UC IrvineMarch,08: UC Irvine

11/13/08: TTU11/13/08: TTU

July 09/09: N.W. U, Xi’AnnJuly 09/09: N.W. U, Xi’Ann