Presentation on Quark Particles

QUARK A quark is an elementary particle and a

fundamental constituent of matter. Quarks combine to form

composite particles called hadrons, the most stable of which are protons and neutrons, the components of atomic nuclei.

Quarks are never found in isolation.

Composition: Elementary particle

Statistical behavior: Fermion

Generation: 1st, 2nd, 3rd

Interaction:Electromagnetism, Gravitation, Strong, Weak

Symbol(s): q

Antiparticle: Antiquark (q)

Discovered: (~1968)

Electric charge: +2⁄3 e, −1⁄3 e

Color charge: Yes

Spin: 1⁄2

A proton composed of two up quarks and one down quark

Quarks•Since 1969, many other experiments have been conducted to determinethe underlying structure of protons/neutrons.

All the experiments come to the same conclusion. Protons and neutrons are composed of smaller constituents.

These quarks are the same ones predicted by Gell-Mann & Zweig in 1964.

(1.6 x 10-15 m)

1x 10-18 m(at most)

Protons 2 “up” quarks 1 “down” quark

Neutrons 1 “up” quark 2 “down” quarks

HISTORY

.

The quark model was independently proposed by physicists Murray Gell-Mann and George Zweig in 1964

• At the time of the quark theory's inception, the "particle zoo " included, amongst other particles, a multitude of hadrons . Murray

Gell-Mann

GeorgeZweig

TYPES OF QUARK PARTICLES

There are six type of Quark

The 6 Quarks, when & where…

Quark Date WhereMass

[GeV/c2]Comment

up, down

- -~0.005, ~0.010

Constituents of hadrons, most prominently, proton

and neutrons.

strange 1947 - ~0.2 discovered in cosmic rays

charm 1974SLAC/

BNL~1.5

Discovered simultaneously in both pp and e+e- collisions.

bottom 1977Fermi-

lab~4.5

Discovered in collisions of protons on nuclei

top 1995Fermi-

lab~175 Discovered in pp collisions

SLAC = Stanford Linear AcceleratorBNL = Brookhaven National Lab

Generation Of QuarksGenerations

I II III

Charge =

-1/3d

(down)

s(strange)

b (bottom)

Charge =

+2/3u

(up)c (charm)

t(top)

Increasing mass

Also, each quark has a corresponding antiquark.The antiquarks have opposite charg to the quarks

Six of the particles in the Standard Model are quarks (shown in purple).

The Standard Model is the theoretical framework describing all the currently known elementary particles, as well as the unobserved Higgs boson.

This model contains six flavors of quarks (q), named up(u), down (d), charm (c), strange (s), top (t), and bottom (b).

Antiparticles of quarks are called antiquarks and are denoted by a bar over the symbol for the corresponding quark, such as u for an up antiquark.

PROPERTIES OF QUARK

QUARK POSSESS FIVE PROPERTIES

ELECTRIC CHARGESPINWEAK INTERACTIONSTRONG INTERACTION & COLOR CHARGEMASS

ELETRIC CHARGEQuarks have fractional electric charge values

either −1⁄3 or +2⁄3 times the elementary charge depending on flavor. Up, charm, and top quarks (collectively referred to as up-type quarks) have a charge of +2⁄3, while down, strange, and bottom quarks (down-type quarks) have −1⁄3.

Antiquarks have the opposite charge to their corresponding quarks; up-type antiquarks have charges of −2⁄3 and down-type antiquarks have charges of +1⁄3

spinSpin is an intrinsic property of elementary

particles, and its direction is an important degree of freedom.

The spin value of up quark is +1/2 & -1/2 for down quark.

Spin can be represented by a vector whose length is measured in units of the reduced Planck constant ħ (pronounced "h bar").

For quarks, a measurement of the spin vector component along any axis can only yield the values +ħ/2 or −ħ/2

Weak InteractionA quark of one flavor can transform into a quark

of another flavor only through the weak interaction.

By absorbing or emitting a W boson, any up-type quark (up, charm, and top quarks) can change into any down-type quark (down, strange, and bottom quarks) and vice versa.

. This flavor transformation mechanism causes the radioactive process of beta decay in which a neutron (n) "splits" into a proton (p), an electron (e−) and an electron antineutrino(νe) .

n→ p + e− + νe (Beta decay, hadron notation)

Strong interaction and colour charge

•Quarks possess a property called color charge.

• There are three types of color charge, arbitrarily labeled blue, green, and red.

•Each of them is complemented by an anticolor—antiblue, antigreen, and antired. Every quark carries a color, while every antiquark carries an anticolor.

massTwo terms are used in referring to a quark's

mass: current quark mass refers to the mass of a quark by itself, while constituent quark mass refers to the current quark mass plus the mass of the gluon particle field surrounding the quark.

These masses typically have very different value.

ADVANTAGEQuarks, gluons, neutrinos and all sorts of other things much smaller than protons and electrons.

Gluons only exist to hold quarks together, so we can't do anything with them.

REFERENCES:-

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