THE COMING REVOLUTIONS IN PARTICLE PHYSICSlutece.fnal.gov/Talks/PrairieRevolutions.pdfare welcome to...

2nd ANNUAL MEETING of the PRAIRIE SECTION of the AMERICAN PHYSICAL SOCIETYheld in conjunction with the Chicago Section of the American Association of Physics Teachers (CSAAPT)

Thursday, November 18, 7:00 p.m.Wishnick Hall AuditoriumIIT Main Campus, Chicago, IL

Students, faculty, alumni, IIT Community are welcome to this free public lecture.

The Large Hadron Collider provides the greatest leap in capability of any instrument in the history of particle physics. We do not know what it will find, but the discoveries we make and the new puzzles we encounter are certain to change the face of particle physics and to echo through neighboring sciences.

Join us as we welcome Chris Quigg, the highly respected physicist at the forefront of today’s revolutions in particle physics. His work ranges over many topics, from electroweak symmetry breaking and supercollider physics to heavy quarks and the strong interaction among them to ultrahigh-energy neutrino interactions.

THE COMING REVOLUTIONS IN PARTICLE PHYSICS

RSVP: Professor Christopher White | whitec@iit.edu

Theoretical Physics Department, Fermilab2011 J. J. Sakurai Prize for Theoretical Particle Physics Recipient

CHRIS QUIGG1

The Coming Revolutions in Particle Physics

Chris Quigg

2

Atoms became real in the 20th century

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To explain a complicated visible by a simple invisible

Eric

Wee

ks, E

mor

y U

.

Jean Perrin

4

5

6

All things are made of atoms–little particles that move around in perpetual motion, attracting each other when they are

a little distance apart, but repelling upon being squeezed

into one another.

—Richard Feynman, Six Easy Pieces

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Quantum Mechanics

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Great Lesson of XXth Century Science

The human scale of space & time is not privileged for understanding Nature . . .

and may even be disadvantaged

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The world’s most powerful microscopes

Tevatron collider at Fermilabprotons on antiprotons at 1+1 TeV

speed of light: c ≈ 109 km/h (30 cm/nanosecond)speed of proton: c – 495 km/h

Protons pass my window 45,000 times / second>10 million collisions per second

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D0

CDFCQ

www.fnal.gov

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CDF Experiment

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CDF two-jet event (70% of energy ⊥ beam direction)

quark + antiquark → jet + jet

The World’s Most Powerful Microscopesnanonanophysics

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Walk of Ideas, Altes Museum Berlin (2006)

Lien

hard

Sch

ulz

(Wik

iped

ia)0

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D0 top quark + antiquark

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Accelerators as time machines …

15

Pointlike (r ≤ 10−18 m) quarks and leptons

Our Picture of Matter (the revolution just past)

uRdR

cRsR

tRbR

eR

R

R

uLdL

cLsL

tLbL

eLL

L12

3

1

2

3

d u

u

Gravitation, electromagnetism, radioactivity, strong interaction

16

New Law of Nature #1

Quantum chromodynamics (QCD): color symmetry among quarksred· green· blue gluons

d u

u

D. Leinweber

uRdR

cRsR

tRbR

uLdL

cLsL

tLbL

17

M78· SDSS

Lattice QCD: quark confinement origin of nucleon masshas explained nearly all visible mass in the Universe

18

New Law of Nature #2

uLdL

cLsL

tLbL

eLL

Le

Electroweak theory:family symmetryu ↔ d ; ν ↔ e ; …

weak bosons (W+, W–, Z0) + photon

19

Weak interactions, electromagnetism seem so different …

Weak Electromagnetic

range: 1% proton size infinite range

W: 90 × proton mass massless photon

How can they share a common origin (symmetry)?

20

Symmetry of laws �⇒ symmetry of outcomes

Stud

ies

amon

g th

e Sn

ow C

ryst

als

... by

Wils

on B

entle

y, vi

a N

OA

A P

hoto

Lib

rary

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Meissner Effecthidden EM symmetry

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Superconductivity suggestsa field that permeates all of spacecould hide electroweak symmetry

Peter Higgs+ R. Brout, F. Englert, G. Guralnik, R. Hagen, T. Kibble

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Higgs boson: massive particle with spin zerohides electroweak symmetry

gives mass to W and Zgives mass to electron, quarks, etc.

Not yet observed!

Theory does not predict Higgs-boson mass

“Standard” Electroweak Theory

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Gedankenexperiment

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100 150 200 250 300

!! 2

0

2

4

6

8

10

12

LEP

excl

usio

n at

95%

CL

Teva

tron

exc

lusi

on a

t 95%

CL

Theory uncertainty

Fit including theory errors

Fit excluding theory errors

MH (GeV)

3!

2!

1!

G fitter SM

March 2009

Where the (standard) Higgs boson might be

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Large Hadron Collider· CERN

proton-proton collisions at 3.5 → 7 TeV/beam

LHCb

ATLASALICE

CMS

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CMS

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CMS

30

30

CMS

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32

ATLAS

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Das LHC Projekt S.Bethke Max-Planck-Institut für Physik 3320

ATLAS

33

ATLAS

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Fabiola Gianotti (ATLAS) : If we do not find the Higgs boson,that means that the theory is just wrong!

35

• New kind of force? (Higgs boson)

• New force from a new symmetry?

• Residual force from strong dynamics?

• Echo of extra spacetime dimensions?

Which path has nature taken?

What hides the electroweak symmetry?

36

Why will it matter?

Understanding the everyday …

Why atoms? Why chemistry? Why stable structures?

37

Without a Higgs mechanism …

Electron and quarks would have no massQCD would confine quarks into protons, etc. Proton mass little changedSurprise: QCD would hide EW symmetry, give tiny masses to W, ZMassless electron: atoms lose integrity No atoms means no chemistry, no stable composite structures like liquids, solids, …

… character of the physical worldwould be profoundly changed

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Much more to learn …

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Revolution: the meaning of identity

• What makes a top quark a top quark and an electron an electron?

• What sets masses of quarks & leptons?

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!"#$

!"#%

!"#&

!"#'

!"#(

!"#!

!""

)*++,-.*/01*2.

13*45.6 2.789:+

;7 <;*4/+

69=: <;*4/+

.

;6

1

+

8

>

!

"

Higgs boson knows something we don’t know!41

KATRIN aims at 0.2 eV

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Strings?

1018

Planck scale

Quantum gravity?

[A PUZZLE RAISED BY THE HIGGS]

Unexplained gap

Limit of LHC

Strong-electro

weak

uni!cation sc

ale?

Electroweak scale

Electron

Neutrino masses

Muon

Top

Bottom

Tau

Charm

Proton

Neutron

10–6

10–3

100

103

106

109

1012

1015

10–9

HiggsUp Down

Strange ZW

H

Energy Scale (GeV)

An electroweak puzzle:Does MH < 1 TeV make sense?The peril of quantum corrections

Scientific American

43

How to separate electroweak, higher scales?

Extend electroweak theory on the 1-TeV scale …

composite Higgs boson

technicolor / topcolor

supersymmetry

…

Ask instead why gravity is so weak

44

MPlanckM*1/R(1 mm)�–1

1 TeV

Stre

ngth

of F

orce

s3-2-1

LED

Conventional Gravity

Suppose at scale R … gravity propagates in 4+n dimensions

1/r 2

1/r 2+n

MPlanck would be a mirage!45

Range !G (meters)

Lamoreaux

Irvine

Eöt-Wash

Boulder

10–6 10–5 10–4 10–3 10–2

108

104

100

10–4

Rel

ativ

e S

tren

gth "

G

Stanford

Gravity follows Newtonian force law down to ≲ 1 mm

1 0.110E (meV)A

nom

alou

s C

oupl

ing

46

Another “minor” problem

• Higgs field fills all of space with energy density 1028 g/liter

• But empty space weighs next to nothing: < 10-26 g/liter

• New evidence that vacuum energy is present (accelerating universe)

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New physics in the LHC range?More

If dark matter interacts weakly …

… its likely mass is 0.1 to 1 TeV

COSMOS

48

Dark matter relics of the big bang?

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Revolution:Unity of Quarks & Leptons

•What do quarks and leptons have in common?

•Why are atoms neutral?

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Conjectured Law of Nature?

eLL

Le

uLdL

cLsL

tLbL

A symmetry among quarks and leptons …… would have to be a hidden symmetry

eLL

Le

uLdL

cLsL

tLbL

Extended quark–lepton families: proton decay!

51

SU(3)c

SU(2)L

U(1)Y

log10

�E

1 GeV

�

1/α

60

40

20

0 5 10 15

Unification of Forces?

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Connections …

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ALICE Experiment: Pb-Pb Collisions at 287 TeV

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?55

“It was as if, suddenly, we had broken into a walled orchard, where protected trees had flourished and all kinds of exotic fruits had ripened in great profusion.”

— Cecil Powell1950 Nobel Prize

56

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Thanks to …

Eric Weeks for the film of Brownian motion www.physics.emory.edu/~weeks

J. D. Jackson for the photo of Peter Higgs

58