Mississippi studentsat CERN

Cosmic Ray Lecture-Demo

The Particle Journey

• Greeks and others believe the earth and heavens werelinked by four elements of nature earth, air, water and fire.• Much of science was utilitarian, alchemy, astrology !• Advances came by invention, discovery, accident.

• All the objects in the universe are composed of very small, indestructible building blocks. • In the late fifth century B.C. Democritus and Leucippus taught that the hidden substance in all physical objects consists of different arrangements of 1) atoms and 2) void.

Atomism or not!

• Aristotle asserted that the elements of fire, air, earth, and water were not made of atoms, but were continuous. 330 B.C.

Greek stamp honoring Democritus and his modern significance.

• Assyrians first realized that glass spheres could be used as magnifying devices circa B.C./A.D. • Probably invented anonymously and developed over a period of time- Vikings, Italians, Germans, etc. • Allowed one to see things in more detail!

Spectacles - 13th century

Italy circa 1352

Telescope

• The telescope was unveiled in the Netherlandsin October 1608! • Galileo made the instrument famous. He constructed a 20-powered telescope in 1609 which was able to see Jupiter's moons - an event of major enlightenment!

Johannes Hevelius observing with one of his telescopes.

"O telescope, instrument of much knowledge, more precious than any sceptre! Is not he who hold thee in his hand made king and lord of the works of God?" - Johannes Kepler

Microscope - 1662

• In 1662 Robert Hooke was named Curator of Experimentsof the newly formed Royal Society of London. • Hooke devised the compound microscope and illumination system and used it in his demonstrations at the Royal Society's meetings. • He displayed plant cells! in a slice of cork (below).

Microscope -1668

• The father of microscopy, Anton van Leeuwenhoek of Holland, started as an apprentice in a dry goods store where magnifying glasses were used to count the threads in cloth. • He was the first to see and describe bacteria, yeast plants, the teeming life in a drop of water, and the circulation of blood corpuscles in capillaries.

" I have thought it my duty to put down my discovery on paper, so that all ingenious people might be informed thereof' .

Modern Electricity• Benjamin Franklin and others conducted extensiveresearch on electricity in the 18th century.• Alessandro Volta perfected a chemical battery. • Two types of charges exist positive(+) and negative (-).Like charges repel, Unlike charges attract !

+ + + + + + + + + + +

- - - - - - - - - - - -

Franklin

Volta

Volta's ChemicalBattery

+++

- - -

Periodic Table of the Elements•IN 1869 Russian chemist Dmitri Mendeleev organized the known elements in to a table to illustrate recurring ("periodic") properties- Z = charge, A = Atomic Weight

AXZ1.0079H1

12.0112C64.0026He2

Electron Tubes - Particle Accelerator• 1850's experimenters began passing electricity through

evacuated and gas filled tubes from negative to positive electrode.

• James Crookes developed a series of tubes and observed cathode (-) rays!

• 1897, JJ Thompson measured the mass of the rays to be very small compared to an atom -> electrons!

- +Thompson's 2nd experiment

Crooke's Tube

Rutherford Atom• In 1911 Rutherford experimented with alpha particles and goldfoil and discovers that atoms have a small positive nucleusmade of protons and outer negative cloud - electrons.

Building an Hydrogen Atomp+

e-

H atomE <12.6 eV

e-

E >13.6 eV

p+ p+

e-

Electro-magnetic Force

= photon or gamma rayforce carrier

scattering

Rutherford Scattering revisited

•By scattering experiments one can study the physical properties of the scattering particles and the internal forces. -Properties: mass, charge, intrinsic magnetism

4He2

E~5MeV

197Au79

4He2

197Au79

Electro-magnetic Force

Discovery of the Neutron

• In 1932 James Chadwick discovered a heavy neutralparticle, the neutron.

4Be2

209Po84

1n0

212X86

Nuclear Binding Force •If the nucleus is made of protons, why do the positivecharges stick together?

+p +p

Does not bind!

= nuclear binding forcegluon

+p

+pn

n

Helium

4H2

+p n

n

Tritium

3H1

+p n

Deuterium

2H1

+p

1H1

Hydrogen

force carrier

The Weak Force and the Neutrino

np e-

Never observed!

•In radioactive beta decay neutrons transmute to protons with the emission of an electron. •In 1930 W. Pauli proposed that a 3rd invisible particle called the neutrino was emitted, consistent with experiment.

n

pe-

Pauli's solution, the neutrino.

1n01p1

0e-1W-

Today's picture

Anti Matter •In 1928 Paul Dirac proposed that every particle should have an associated anti-particle with reversed electric charge.•In 1936, at age 31, Carl Anderson became the second youngest Nobel laureate for his discovery of antimatter when he observed positrons in a cloud chamber.

Quarks • Scattering experiments in the 50's and 60's gave evidence that protons and neutrons were made of fractionally charges particles called quarks.

•Today we believe there are 6 quarks. up charm top q=+2/3e

down strange bottom q=-1/3e

•A proton is then two ups and a down.

u(+2/3)u(+2/3)d(-1/3)

proton

Todays Particle Picture E&M

Gravity

Wea

k

Strong

n p

e-W-

Weak Force

p+ p+

e-

Electromagnetic Force

e-

p

n

g

Strong Force

n gluonphoton

W and Z bosons

m m

m

g

Gravitional Force

m graviton

p

STANDARD MODEL

The Higgs Boson • Why do particles have mass? • In the 1960's Peter Higgs proposed a particle named the the higgs boson which gives mass to all particles.

h t

hhh

h

h

hhh h

hhh

h h

h

h

h

h

h

hh

h

h h

h

hh

h

h hh h

hh

photon

photon

toploop

H

H

gluon

gluon

proton

proton

(1) Higgs to Gamma Gamma

t

t

t

t

(2) Higgs to 4 Leptons

H

gluon

gluon

proton

proton

Z

Z

l+

l-

l+

l-

H l+ l- l+ l

top

top

(3) Higgs to 2 Leptons + 2 jets

H

gluon

gluon

proton

proton

Z

Z

l+

l-

q-jet

q-jet

H l+ l- j j

top

top

(4) Higgs to 2 Leptons + 2 jets

H

gluon

gluon

proton

proton

Z

Z

q-jet

q-jet

H j j j j

top

top

q-jet

q-jet

BH

gluon

gluon

proton

proton

BH l l

l l l

l

l

l

(5) Black Hole to 4 leptons

CMS DETECTOR

CMS SLICE