2.4 - Quarks and Antiquarks

Question 1

what do k-mesons decay into

Answer 1

π-mesons

Question 2

what do Σ particles decay into

Answer 2

π-mesons & protons

Question 3

when is strangeness always conserved

Answer 3

in the strong interaction

Question 4

describe the 3 quark model of hadrons

• how does this explain their properties

Answer 4

baryons = made up of 3 quarks

mesons = made up of a quark and an antiquark pair

quark compositions explained the rest masses, overall charges, and strangeness properties of hardons

Question 5

name all the quarks (6)

• give their charge, baryon no, and strangeness

Answer 5

C S

U +2/3 0

U -2/3 0

D -1/3 0

D +1/3 0

S -1/3 -1

S +1/3 +1

(all quarks have an B no. = 1/3)

Question 6

meson diogram

Answer 6

Question 7

describe the π⁰ - meson

• gove all its possible quark combinations

Answer 7

they are made of a quark and corresponding anti-quark

UU

DD

SS

Question 8

is there such a thing as an anti-meson

-why

Answer 8

no

• since all mesons are made of a quark - antiquark, thus there’s so anti-mesons just another meson

Question 9

what’s the diff between a baryon and antibaryon

Answer 9

baryon = 3 quarks

antibaryon = 3 antiquarks

Question 10

give the B- and B+ decay in therm of quarks

Answer 10

B- ; D –> U + e- + Ve

B+ ; U –> D + e+ + Ve

Proton = UUD => U

Neutron = UDD => D

Question 11

describe quark confinement

Answer 11

it states that you cannot get a quark to exist by itself

-the energy required to remove a quark from a hardon creates a quark-antiquark pair and the quark trying to be removed remains in the hardon

Question 12

what can weak interaction do to quarks

• give an example

Answer 12

change the quarks character

• eg) in B- decay; a D quark from a neutron changes to a U quar forming the proton from the weak interaction