school of arts & sciences dean’s coffee presentation suny institute of technology, february 4,...

School of Arts & Sciences Dean’s Coffee Presentation SUNY Institute of Technology, February 4, 2005

High Energy Physics: An Overview of Objectives, Challenges

and Outlooks

Amir FariborzAmir Fariborz

Dept. of Math./ScienceDept. of Math./Science

SUNY Institute of TechnologySUNY Institute of Technology

Utica, New YorkUtica, New York

OutlineIntroductionIntroduction

Objectives:Objectives: ElementaryElementary ParticlesParticles FundamentalFundamental ForcesForces

UnificationUnification

Means and Techniques:Means and Techniques: ExperimentalExperimental

Theoretical Theoretical

Strong InteractionStrong Interaction Hadrons, and their Strong InteractionHadrons, and their Strong Interaction

Models for the Physics of Hadrons Models for the Physics of Hadrons

Future OutlooksFuture Outlooks

Introduction:

What is an elementary particle?What is an elementary particle?

Introduction:

What is an elementary Particle?What is an elementary Particle? A pA particle that is not consist of other particles article that is not consist of other particles

Introduction:


Ex. Water molecule is NOT elementaryEx. Water molecule is NOT elementary

OH

H

Introduction:


Ex. Water molecule is NOT elementaryEx. Water molecule is NOT elementary

Atoms and molecules are not elementary.Atoms and molecules are not elementary.

OH

H

General structure of atoms:

Electron

Electron

Nucleus


Electron

Electron

Nucleus

P

N

N

P


Electron

Electron

Nucleus

P

N

N

P

Quarks


Electron

Electron

Nucleus

P

N

N

P

Quarks

Photon

Quarks (S=1/2)

Elementary Particles: Leptons (s=1/2) Gauge Bosons (S=1)

Quarks (S=1/2)

Elementary Particles: Leptons (s=1/2) Gauge Bosons (S=1) Quarks:Quarks: Flavor Charge (e) Mass (MeV/CFlavor Charge (e) Mass (MeV/C22))

u 2/3 < 10 200 - 400 u 2/3 < 10 200 - 400 d -1/3 < 15 200 - 400 d -1/3 < 15 200 - 400 s -1/3 100-300 200 - 400 s -1/3 100-300 200 - 400 c 2/3 ~ 1,500 c 2/3 ~ 1,500 b -1/3 ~ 5,200b -1/3 ~ 5,200 t 2/3 ~ 180,000t 2/3 ~ 180,000

Quarks:Quarks: Flavor Charge (e) Mass (MeV/CFlavor Charge (e) Mass (MeV/C22))

u 2/3 < 10 200 - 400 u 2/3 < 10 200 - 400 d -1/3 < 15 200 - 400 d -1/3 < 15 200 - 400 s -1/3 100-300 200 - 400 s -1/3 100-300 200 - 400 c 2/3 ~ 1,500 c 2/3 ~ 1,500 b -1/3 ~ 5,200b -1/3 ~ 5,200 t 2/3 ~ 180,000t 2/3 ~ 180,000

u u d

u* d

Quarks (S=1/2)

Elementary Particles: Leptons (s=1/2) Gauge Bosons (S=1) Leptons:Leptons:

Charge (e) Mass (MeV/CCharge (e) Mass (MeV/C22))

e -1 0.5e -1 0.5

ee 0 ? 0 ?

-1 ~105-1 ~105

00 ??

-1 ~ 1,700-1 ~ 1,700

0 ?0 ?

Quarks (S=1/2)

Elementary Particles: Leptons (s=1/2) Gauge Bosons (S=1)

Gauge Bosons:Gauge Bosons:

Charge (e) Mass (MeV/CCharge (e) Mass (MeV/C22))

Photons 0 0Photons 0 0

WW+(-)+(-) +1 (-1) 80,000 +1 (-1) 80,000

Z 0 91,000Z 0 91,000

Gluons 0 0 Gluons 0 0

Gravitational (10 Gravitational (10 –39–39))

Electromagnetic (1) Electromagnetic (1)

FundamentalFundamental ForcesForces::

Weak (10 Weak (10 –11–11))

NuclearNuclear

Strong (10Strong (10 3 3))

Objectives of HEP:

Identify and classify the elementary particlesIdentify and classify the elementary particles

Understand the fundamental forces among the Understand the fundamental forces among the elementary particleselementary particles

Unify the fundamental forces into a single theory:Unify the fundamental forces into a single theory:

““Theory of Everything”Theory of Everything”

GravitationalGravitational

ElectromagneticElectromagnetic

WeakWeak

NuclearNuclear

StrongStrong



WeakWeak

NuclearNuclear

StrongStrong

Electricity + Magnetism

Maxwell (1865)



WeakWeak

NuclearNuclear

StrongStrong


Maxwell (1865)

Glashow,Salam,Weinberg Nobel prize (1979)

Electroweak



WeakWeak

NuclearNuclear

StrongStrong


Maxwell (1865)


GUTs

Electroweak



WeakWeak

NuclearNuclear


Maxwell (1865)


GUTs TOE

Electroweak

Means and Techniques of HEP:

Experimental:Experimental: Particles are accelerated and collided at high Particles are accelerated and collided at high

speeds (comparable to the speed of light) speeds (comparable to the speed of light)

?

Detector: Approx. 10 m high

Several thousands of tones

Approx. 5.3 mi

Other facts about CERN

“WWW invented at CERN”

Initial accelerator LEP e- e+ Next (2005) LHC p p (~14 TeV) for 10-15 yrs

Involves Approx. 6,000 physicists from around the world

Main goals: Z, W+/-, Higgs, SUSY particles

LHC material cost: approx. $2 BillionAnnual cost: approx. $600 M

LHC detectors: ATLAS and CMS ($300 M each)

StrongStrong

10-3

10 10 10 10 10 10 100 3 6 9 12 15 18

Energy (GeV)

GUTs

String

Planck Mass

Electroweak

10-3

10 10 10 10 10 10 100 3 6 9 12 15 18

Energy (GeV)

GUTs

String

Planck Mass

Electroweak

LHCTevatron Fermi Lab

10-3

10 10 10 10 10 10 100 3 6 9 12 15 18

Energy (GeV)

GUTs

String

Planck Mass

Electroweak

LHCTevatron Fermi Lab

Higgs ?

SUSY ?

Large Extra Dimensions ?

Means and Techniques of HEP:

Theoretical:Theoretical: What is going on here What is going on here

?

C lass ica l Q u an tum Rela tivis t ic S ta tis t ica l

P h ys ics


P h ys ics

Relativistic Quantum Mechanics


P h ys ics

Relativistic Quantum Mechanics Creation and Annihilation+


P h ys ics

Relativistic Quantum Mechanics Creation and Annihilation+

Quantum Field Theory

Strong Interaction:

Bounds protons and neutrons inside the Bounds protons and neutrons inside the nucleusnucleus

Strong Interaction:

Bounds protons and neutrons inside the Bounds protons and neutrons inside the nucleusnucleus

Protons and neutrons Protons and neutrons Hadrons Hadrons

Baryons (s = ½ , …) Baryons (s = ½ , …) Hadrons Hadrons

Mesons (s=0,1,…)Mesons (s=0,1,…)

Simplest internal structure of hadrons in terms of quarks: BaryonsBaryons: : QQQ QQQ


p : uud p : uud

charge = 2(2/3e ) + (-1/3e) = e charge = 2(2/3e ) + (-1/3e) = e

n : uddn : udd

charge = (2/3e) + 2 (-1/3e) = 0 charge = (2/3e) + 2 (-1/3e) = 0


p : uud p : uud charge = 2(2/3e ) + (-1/3e) = e charge = 2(2/3e ) + (-1/3e) = e n : uddn : udd charge = (2/3e) + 2 (-1/3e) = 0 charge = (2/3e) + 2 (-1/3e) = 0

MesonsMesons: QQ*: QQ*


p : uud p : uud charge = 2(2/3e ) + (-1/3e) = e charge = 2(2/3e ) + (-1/3e) = e n : uddn : udd charge = (2/3e) + 2 (-1/3e) = 0 charge = (2/3e) + 2 (-1/3e) = 0

MesonsMesons: QQ*: QQ* ++ : u d* : u d* charge = (2/3e) + (1/3 e) = echarge = (2/3e) + (1/3 e) = e

Exotic structure of hadrons:

BaryonsBaryons: QQQQQ* : QQQQQ*

(Physics Today, Feb. 2004) (Physics Today, Feb. 2004)

Exotic structure of hadrons:

BaryonsBaryons: QQQQQ* : QQQQQ*

(Physics Today, Feb. 2004) (Physics Today, Feb. 2004)

MesonsMesons: QQQ*Q*: QQQ*Q*

Hybrid: …QQ* …QQQ*Q* … GHybrid: …QQ* …QQQ*Q* … G [A.F., Int.J.Mod.Phys. A [A.F., Int.J.Mod.Phys. A 1919,2095 (2004)],2095 (2004)] [A.F., Int.J.Mod.Phys. A [A.F., Int.J.Mod.Phys. A 1919,5417 (2004)],5417 (2004)]

Basic Properties of the Strong Interaction:

ConfinementConfinement: Quarks are bounded : Quarks are bounded inside the hadrons (no free quarks)inside the hadrons (no free quarks)

Asymptotic FreedomAsymptotic Freedom: The strength of : The strength of the interaction decreases with energythe interaction decreases with energy

Coulomb’s Force: |F| = 1/(4|F| = 1/(4) qQ/r) qQ/r22

Q qr

r

F

Coulomb’s Force:

|F| = 1/(4|F| = 1/(4) qQ/r) qQ/r22

Q q

F

energy

Strong Interaction:

Strength of interactionStrength of interaction

energyenergy

Theoretical Explanation

Physics Nobel Prize (2004)Gross, Politzer & Wilczek

Experimental ObservationPhysics Nobel Prize (1990)Friedman, Kendall & Taylor

Why are there two different types of mass for light quarks?

Low energy processes:

High energy processes:

The computational difficulty:

A simple description:A simple description:

F(F(aa) = F(0) + F’(0) ) = F(0) + F’(0) aa + ½ F’’(0) + ½ F’’(0) aa2 2 + … + …

The computational difficulty:A simple description:A simple description:

F(F(aa) = F(0) + F’(0) ) = F(0) + F’(0) aa + ½ F’’(0) + ½ F’’(0) aa2 2 + … + …

Strength of interactionStrength of interaction

energy energy

a

Theory of Strong Interactions:

energyQCD is a non abelian gauge field theory based on the color quantum number of quarks

?

Effective theories: Models that are formulated in terms of hadrons

Chiral perturbation theory (< 500 MeV)

Chiral Lagrangians (< 2 GeV)

…

Lattice QCD: Computes physical quantities by directly working with the quark fields

QCD Sum-rules: Provides a bridge between QCD and the physics of hadrons

J=0 J=0,1,2 …

Chiral Lagrangian probe of intermediate states:

+ + …

Symmetries of the low energy strong

interaction

Lagrangian

Future Outlook:

A number of important experiments will be A number of important experiments will be performed within the next 10-15 yearsperformed within the next 10-15 years

Exciting directions for research in HEP, such as Exciting directions for research in HEP, such as neutrino physics, CP violation, beyond the SM, neutrino physics, CP violation, beyond the SM, SUSY, Higgs physics, …SUSY, Higgs physics, …

Students can participate at different levels, from Students can participate at different levels, from undergraduate projects to Ph.D. thesesundergraduate projects to Ph.D. theses

Why should quarks have color?

Why should quarks have color?

Experiment:Experiment:

++ ++ : :

Spin = 3/2 Spin = 3/2

Charge = +2e Charge = +2e

++ ++ : U U U : U U U

Theory of Strong Interactions:

energy

?

energy

?

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