2.4- QUARKS AND ANTIQUARKS

Question 1

What were kaons called when they were first discovered?

Answer 1

called V particles

Question 2

Why were kaons called V particles when they were first discovered?

Answer 2

cloud chamber photographs often showed V-shaped tracks

Question 3

What did investigation show about V particles?

Answer 3

showed that the V tracks decay into pions only, or into pions and protons

Question 4

What kind of particles were V particles called after the investigation that the V tracks decay into pions only, or into pions and protons?

Answer 4

strange particles

Question 5

What do all strange particles decay through?

Answer 5

weak interaction

Question 6

What strange particles were referred to as kaons?

Answer 6

those that decay into pions

Question 7

Although strange particles all decay through the weak interaction what were sigma particles found to .. ? (2)

Answer 7

have different rest masses which were always greater than the proton’s rest mass

decay either in sequence or directly into protons and pions

Question 8

In what numbers are strange particles created?

Answer 8

strange particles created in twos

Question 9

Is strangeness always conserved in strong interactions?

Answer 9

yes

Question 10

Is strangeness always conserved in weak interactions?

Answer 10

no- strangeness can change by 0, +1, or -1 in weak interactions

Question 11

Examples of properties of hadrons? (3)

Answer 11

charge
strangeness
rest mass

Question 12

How can the properties of hadrons be explained?

Answer 12

by assuming they’re composed of smaller particles known as quarks and antiquarks

Question 13

What are the 3 types of quarks and antiquarks I need to know for hadrons?

Answer 13

up, down and strange

Question 14

How are up, down and strange quarks denoted?

Answer 14

u, d, s

Question 15

Are mesons hadrons?

Answer 15

yes

Question 16

What do mesons consist of?

Answer 16

a quark and an antiquark

Question 17

What combination is a π^0 meson?

Answer 17

– or –

uu dd

Question 18

Why’re combinations that include - not called pions?

ss

Answer 18

they decay much faster than pions

Question 19

How many uncharged kaons are there?

Answer 19

two

Question 20

What are the uncharged kaons?

Answer 20

K^0 meson and -^0 meson

K

Question 21

What is the antiparticle of any meson?

Answer 21

quark-antiquark pair

Question 22

What is the antiparticles of a meson as it’s made up of a quark-antiquark pair?

Answer 22

meson

Question 23

What are baryons and antibaryons?

Answer 23

hadrons that consist of three quarks for a baryon or three antiquarks for an antibaryon

Question 24

What is the quark combination for a proton?

Answer 24

uud

Question 25

What is the quark combination for a neutron?

Answer 25

udd

Question 26

What is the quark combination for an antiproton?

Answer 26

uud

Question 27

What is the Σ particle?

Answer 27

baryon containing a strange quark

Question 28

What is the only stable baryon?

Answer 28

proton

Question 29

What does a free neutron decay into?

Answer 29

proton

Question 30

What does a free neutron release when it decays a proton?

Answer 30

releases an electron and an electron antineutrino, as in β− decay

Question 31

What happens in β− decay?

Answer 31

neutron in a neutron-rich nucleus change into a proton, releasing an electron + electron antineutrino

Question 32

In quark terms what happens in β− decay?

Answer 32

down quark changes to an up quark

Question 33

What happens in β+ decay?

Answer 33

proton in proton-rich nucleus changes into a neutron, releasing a positron + electron neutrino

Question 34

In quark terms what happens β+ decay?

Answer 34

up quark changes to a down quark