2.1- THE PARTICLE ZOO

Question 1

What are cosmic rays?

Answer 1

high-energy particles that travel through space from the stars, including the Sun

Question 2

What happens when cosmic rays enter the Earth’s atmosphere?

Answer 2

create new short-lived particles and antiparticles, and photons

Question 3

What did most physicists think about cosmic rays?

Answer 3

they were formed from terrestrial radioactive substances

Question 4

How was the theory of cosmic rays being formed from terrestrial radioactive substances disproved?

Answer 4

when physicist + amateur balloonist Victor Hess, found ionising effects of the rays was significantly greater at 5000m than at ground level

Question 5

What did further investigations into cosmic rays show?

Answer 5

cosmic rays were fast-moving protons or small nuclei

Question 6

What do the fast-moving protons/ small nuclei in cosmic rays do?

Answer 6

collide with gas atoms in atmosphere, creating showers of particles and antiparticles that can be detected at ground level

Question 7

What was used to discover new types of short-lived particles and antiparticles?

Answer 7

using cloud chambers and other detectors

Question 8

What particles were discovered using the cloud chambers and other detectors?

Answer 8

the muon, pion and kaon

Question 9

What is a muon?

Answer 9

a muon, or heavy electron is a negatively charged particle

Question 10

What is the symbol for muon?

Answer 10

μ

Question 11

What is the rest mass of a muon in comparison to an electron?

Answer 11

rest mass over 200 times the rest mass of the electron

Question 12

What is the symbol of the pion?

Answer 12

π

Question 13

What charge can a pion have?

Answer 13

positive, negative or neutral

Question 14

What is the rest mass of a pion like?

Answer 14

rest mass greater then a muon but less than a proton

Question 15

What is the kaon also known as?

Answer 15

K meson

Question 16

What charge can a kaon have?

Answer 16

positive, negative or neutral

Question 17

What is the rest mass of a kaon like?

Answer 17

rest mass greater than a pion but still less than a proton

Question 18

How were kaons discovered?

Answer 18

when photographs from cloud chambers revealed existence of short-lived particles

Question 19

In what numbers a kaon produced?

Answer 19

kaons are produced in twos

Question 20

Through what interaction are kaons produced?

Answer 20

strong interaction

Question 21

How are kaons produced?

Answer 21

When protons moving at high speed crash into nuclei and they each travel far beyond nucleus in which they originate before they decay

Question 22

How long did kaons take to decay?

Answer 22

decay of kaons took longer than expected

Question 23

What is one of the products of kaon decay?

Answer 23

pions

Question 24

As kaons took longer than expected to decay + one product is pions, what does this mean?

Answer 24

kaons must decay via the weak interaction

Question 25

What did the properties of kaons lead them to being called?

Answer 25

strange particles

Question 26

How can these particles be produced?

Answer 26

using accelerators in which protons collide head-on with other protons at high speed

Question 27

What is the kinetic energy of protons converted into?

Answer 27

mass in the creation of these new particles

Question 28

What does a kaon decay into?

Answer 28

into pions, or a muon and an antineutrino, or an antimuon and a neutrino

Question 29

What can a charged pion decay into?

Answer 29

into a muon and an antineutrino, or an antimuon and a neutrino

Question 30

What does a π^0 decay into?

Answer 30

into high-energy photons

Question 31

What does a muon decay into?

Answer 31

an electron and an antineutrino

Question 32

What does an antimuon decay into?

Answer 32

a positron and a neutrino

Question 33

What do decays always obey?

Answer 33

the conservation rules of energy, momentum and charge