2.1 - The Particle Zoo

Question 1

What happens when a cosmic ray enters the earths atmosphere

Answer 1

They create new short lived particles and antiparticles as well as photons

Question 2

Process of how cosmic rays create new short lived particles

Answer 2

Cosmic rays are fast moving protons or small nuclei. When they collide with gas atoms in the atmosphere they create showers of particles and antiparticles that can be detected at ground level by cloud chambers

Question 3

What new types of short lived particles and anti particles were discovered using the cloud chamber

Answer 3

The muon - (heavy electron)
The pion
The kaon

Question 4

Facts about the muon

Answer 4

Heavy electron
Symbol (u)
Negatively charged particle with a rest mass of over 200 times the electron

Question 5

Facts about the pion or pi meson

Answer 5

Can be negative, positive or neutral
Has a rest mass greater than a muon but less than a proton

Question 6

Facts about the kaon

Answer 6

K meson
Can be positive negative or neutral
Has a rest mass greater than a pion but less than a proton

Question 7

how are kaons produced

Answer 7

In twos through strong interaction

-when protons moving at high speeds crash into nuclei and they each travel far beyond the nucleus which they originate from before they decay.

Question 8

Why must kaons decay via the weak interaction

Answer 8

the decay of kaons took longer than expected and includes pions as the product

this is why kaons are called strange particle

Question 9

How can all the new particles be created

Answer 9

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

Question 10

What happens to the protons when they collide

Answer 10

the kinetic energy of the protons is converted into mass in the creation of these new particles

so these new particles can be studied under controlled conditions

Question 11

Kaon decay mode

Answer 11

A kaon can decay into Pions, or a muon and an antineutrino or an antimuon and a neutrino

Question 12

Charged pion decay mode

Answer 12

A charged pion can decay into a muon and an antineutrino or an antimuon and a neutrino

Question 13

A pi 0 meson decays into

Answer 13

high energy photons

Question 14

Muon decay mode

Answer 14

A muon decays into an electron and an antineutrino

Question 15

An antimuon decays into

Answer 15

A positron and a neutrino

Question 16

what must decays always obey

Answer 16

the conservation rules for energy, momentum and charge

Question 17

what is a tv tube in a traditional tv

Answer 17

an accelerator because it accelerates electrons inside it through a potential difference of about 5000V

Question 18

how is the image produced on a traditional tv

Answer 18

the electrons form a beam that hits the inside of the tv screen
magnetic fields produced by electromagnets deflect the beam so it scans the screen to create an image

Question 19

what is the longest accelerator in the world

Answer 19

stanford linear accelerator in California
distance of3km and pd of 50000million volts = 50Gev

Question 20

what is the biggest acellorator in the world

Answer 20

large hadron collider at CERN near Geneva
accelerates particles to energies of more than 7000 GeV
27km circumference

Question 21

what did Hideki Yukawa predict before the discovery of muons kaons and pions?

Answer 21

the existence of exchange particles for the strong nuclear force between nucleons
thought they would have a range of no more than 10^-15 and calculated that there mass would be between the electron and the proton
Called them mesons because they were inbetween

Question 22

what did Carl Anderson obtain a photo of in his cloud chamber

Answer 22

could have been produced by a meson but it had a track length of 40mm so lasted longer than a strongly interacting particle should
proved to be heavy electron later called muon
decays through weak interaction

Question 23

when was Yukawa’s meson discovered

Answer 23

years later by British Physicist Cecil Powell from tiny microscopic tracks found in photographic emulsion exposed to cosmic rays atvs high altitude
Powell called them Pi mesons /pions