section 1. Particles Flashcards
1
Q
What are isotopes?
A
Atoms with a different number of neutrons, but the same number of protons
2
Q
What is a radioisotope?
A
An isotope that is radioactive
3
Q
What is carbon 14 used in?
A
Carbon dating
4
Q
What is the specific charge of a nucleus or ion?
A
Its charge per unit mass
5
Q
What is specific charge used in?
A
Mass spectrometry to identify nuclei
6
Q
How to calculate specific charge?
A
specific charger= Charge / mass
7
Q
Units for specific charge?
A
Ckg⁻¹
8
Q
What is each type of nucleus called?
A
A nuclide
9
Q
What is the range of the strong force?
A
3 fm (small)
10
Q
What is 1 fm in m?
A
10⁻¹⁵ m
11
Q
What does the strong force act between?
A
Nucleons (e.g. protons and neutrons)
12
Q
Is the strong force attractive or repulsive?
A
Both
13
Q
Why is the strong force both attractive and repulsive?
A
Otherwise the nucleus would collapse or explode
14
Q
When is the strong force attractive?
A
> 0.5 fm
15
Q
When is the strong force repulsive?
A
< 0.5 fm
16
Q
For light nuclei, what is the ratio of neutrons to protons?
A
Proton number = neutron number → the two particles must exist together
17
Q
For heavy nuclei, what is the ratio of neutrons to protons?
A
More neutrons than protons (and very large nuclei and radioactive)
18
Q
What is equilibrium separation?
A
A point when the resultant force is zero and the attractive and repulsive forces balance
19
Q
What is the decay of americium-241 used for?
A
Smoke alarms
20
Q
What is the decay of polonium-210 used for?
A
Ionisers
21
Q
What force is responsible for beta decay?
A
The weak force
22
Q
How strong is the weak force?
A
1 millionth the value of the strong force
23
Q
How does the range of the weak force compare to that of the strong force?
A
It has a smaller range
24
Q
What does the weak force act on?
A
Leptons and hadrons
25
What are the types of beta decay?
β+ and β-
26
When does beta decay occur?
When the nucleus emits an electron or a positron
27
What does a free neutron decay into in beta decay?
A proton, an electron and an anti-neutrino
28
What does a free proton decay into in beta decay?
A neutron, a positron and a neutrino
29
What type of beta decay is it when a free neutron decays into a proton?
β-
30
What type of beta decay is it when a free proton decays into a neutron?
β+
31
Why it called β- decay when a neutron decays into a proton?
An electron is produced
32
Why is it called β+ decay when a proton decays into a neutron?
A positron is produced
33
What are the energies of the particles emitted in beta and alpha decay?
* beta decay - beta particles emitted have a range of energies
* alpha decay - monoenergetic
34
What happens to the unaccounted-for energy in beta decay?
It is carried away by the neutrinos
35
What happens if the nucleus is still unstable after emitting alpha or beta radiation?
It is in an excited state, and gives off gamma radiation
36
What type of wave is gamma?
Electromagnetic
37
What is the mass and charge of gamma?
Has no mass or charge
38
What does the strong force overcome?
The electrostatic forces of repulsion between protons in the nucleus
39
Why was the existence of the neutrino hypothesised?
To account for conservation of energy in beta decay
40
What type of particle are neutrinos?
Leptons
41
What does an electromagnetic wave consist of?
An electric wave and a magnetic wave which travel together in phase
42
When are electromagnetic waves emitted?
When a charged particle loses energy
43
When can a charged particle lose energy (and an electromagnetic wave emitted as a result)?
* when a fast moving electron is stopped, slows down or changes direction
* when electrons move to a lower energy shell
44
In what form is electromagnetic radiation emitted?
Photons - bursts or packets of energy
45
How do photons travel?
In one direction only in a straight line
46
What happens to an atom's energy when it emits a photon?
Its energy changes by an amount equal to the photon energy
47
What is the amount of energy contained in each quantum proportional to?
The frequency of the radiation
48
the equation for energy of a photon is found on the data sheet what do the symbols stand for?
E=hf=hc/λ
E=hf=hc/λ
E= energy in joules
h= planc constant (found on data sheet)
f= frequency (hz)
c=speed of light (3x10^8)
λ= wavelength (m)
49
What is the Planck constant measured in?
joule-seconds, Js
50
What is photon energy usually given in?
Electron-volts (eV)
51
What is one electron volt defined as?
The energy transferred when an electron is moved through a p.d. of 1V
52
What is the value of 1 eV?
1.6 x 10⁻¹⁹ J
53
What was Dirac's theory about particles and antiparticles?
For every type of particle, there is a corresponding antiparticle that:
* annihilates the particle and itself if they meet, converting total mass to photons
* has same rest mass and opposite charge
54
When does annihilation occur?
When a particle and its corresponding antiparticle meet and their mass is converted into radiation energy
55
What can the rest energy of an antiparticle be calculated from?
By using the rest mass of the colliding particles and E=mc²
E= energy (joules)
m= mass (kg)
c= speed of light (ms)
56
What is pair production?
When a photon (**γ**) with enough energy can change into a particle antiparticle pair
57
What is minimum energy required by the photon in pair production?
The rest energy of the particle pair
58
What are the four fundamental interactions?
* strong
* electromagnetic
* weak
* graviational
59
What is the exchange particle for strong interaction? what particles does the strong interaction affect?
* gluon (for quarks)
* pion (for nucleons)
hadrons feel the strong force only
60
what's the mass of a w gauge boson?
the mass of a w boson is around 100 times that of a proton and hence it has a tiny range.
61
What is the exchange particle for electromagnetic interaction? what particles are affected?
* A virtual Photon **γ. has zero rest mass + infinite range**
* **only charged particles are affected**
62
What is the exchange particle for weak interaction? what does it affect?
The weak interaction exchange particle is the W boson.
The weak force affects all particle types.
63
What is the exchange particle for gravitational interaction?
Graviton
64
Generally, what happens when two particles interact?
They exert equal and opposite forces on each other
65
What happens if two protons approach each other?
They repel and move away
66
Why do protons repel when they approach each other?
Due to the electromagnetic interaction and the exchange of a virtual photon
67
What would happen if we tried to intercept virtual photons?
We would stop the exchange from happening
68
What is the interaction model of repulsive forces?
Two people on skateboards facing each other - throwing a ball between them causes them to move away from each other
69
What is the interaction model of attractive forces?
Two people on skateboards - throw a boomerang and momentum causes them to move towards each other
70
In interaction diagrams, what do the straight and wavy lines represent?
* the lines do NOT represent the paths of the particles
* the wavy line shows the exchange particle and w bosons carry charge from one side of the diagram to the other.
71
What must be conserved in interaction diagrams?
Charge, lepton and baryon number
72
Describe the interaction diagram between two protons.
* lines show protons approaching
* wavy line shows virtual photon as the exchange particle
* then shows that protons move away
73
Describe the interaction diagram between a neutron and a neutrino.
* lines show neutron and neutrino approaching
* wavy line shows W⁻ boson as the exchange particle
* then shows that a proton and an electron move away
74
Describe the interaction diagram between a proton and an anti-neutrino.
* lines show proton approaching an anti-neutrino
* wavy line shows W⁺ boson as the exchange particle
* then shows that a neutron and a positron move away
75
Describe the interaction diagram for electron capture.
* lines show a proton and electron approaching each other
* wavy line shows W⁺ boson as the exchange particle
* then shows that a neutron and a neutrino move away
76
Describe the interaction diagram for β- decay.
* line shows neutron
* wavy line shows W⁻ boson as the exchange particle
* then shows that a proton, electron and anti-neutrino move away
77
Describe the interaction diagram for β+ decay.
* line shows proton
* wavy line shows W⁺ boson as the exchange particle
* then shows that a neutron, positron and neutrino move away
78
What is the process of electron capture?
When a proton in a proton-rich nucleus turns into a neutron, as a result of interacting with an inner shell electron from outside the nucleus
79
Why can't strong or electromagnetic interaction be responsible for beta decay?
* strong force holds neutrons and protons in a nucleus together, but doesn't cause neutron to change into proton
* electromagnetic force only when a charged particle loses energy → neutron not charged
80
What do leptons exist as?
Particles on their own
81
What do quarks exist as?
Only exist bound together
82
Examples of leptons?
* electron
* electron neutrino
* muon
* tau
83
Which leptons are constituents of ordinary matter (1st family)?
* electons
* electron neutrinos
84
Which leptons are only found in cosmic rays and particle accelerators?
* muon
* muon neutrino
* tau
* tau neutrino
85
Charge on an electron neutrino?
0
86
Which quarks are part of the 1st family?
* up
* down
87
Which quarks are part of the 2nd family?
* charm
* strange
88
Which quarks are part of the 3rd family?
* top
* bottom
89
Which quarks are protons made up of?
Two up quarks and one down quark
90
Which quarks are neutrons made up of?
One up quark and two down quarks
91
Which quarks are antiprotons made up of?
Two antiup quarks and one antidown quark
92
What is a muon?
A heavier relative of the electron
93
What is the charge on a muon?
-1
94
What is a tau?
A heavier relative of the electron and muon
95
What is a strange particle?
A heavier relative of the down quark
96
What are hadrons?
Particles that feel the strong force
97
How do hadrons decay?
Weak interaction
98
What groups are hadrons split into?
* baryons - 3 quarks
* mesons - 2 quarks
99
Are protons and neutrons fundamental? Why is this?
No, they are made up of quarks
100
Are protons and neutrons mesons or baryons? Why is this?
Baryons - they are made up of three quarks
101
What is the only stable baryon?
Protons
102
What is the pion?
The exchange particle of the strong nuclear force
103
What do strange particles contain?
A strange quark
104
How are strange particles produced?
Strong interaction
105
How do strange particles decay?
Weak interaction
106
When is strangeness conserved?
Only in strong interactions
107
What do Kaons decay into?
Pions
108
Do leptons feel the strong force?
No
109
What force are leptons affected by?
Weak interaction
110
What do muons decay into?
Electrons
111
What can leptons and antileptons interact to produce?
Hadrons
112
How fast do neutrinos travel?
Almost as fast as light
113
How can leptons change into other leptons?
Weak interaction
114
What do mesons consist of?
A quark and an antiquark
115
What do pions consist of?
Up and down quarks
116
What do kaons consist of?
A strange quark and either an up or down quark
117
What charge can pions have?
Zero charge, or positively/negatively charged
118
What are the kaon combinations?
* strange-antiup (-1)
* strange-antidown (0)
* antistrange-up (1)
* antistrange-down (0)
119
When does beta decay occur?
When the nucleus emits an electron or a positron
120
What is conserved in beta decay?
Charge, spin, baryon number and lepton number
121
What else needs to be conserved (along with charge, spin, baryon and lepton no.) in particle reactions?
Energy and momentum
122
what are the two types of hadrons?
hadrons are made of baryons and mesons
123
what are the mesons quark compositions?
124
Describe the nuclear model of an atom.
• Central nucleus containing protons and neutrons • Electrons orbit the nucleus
125
What are nucleons?
Protons and neutrons
126
What is the collective name for protons and neutrons?
Nucleons
127
How the charge and mass of protons, neutrons and electrons usually given?
• It can be given and coulombs and kilograms, but the numbers are very small (e.g. +1.60 x 10^-19 coulombs) • Therefore, the RELATIVE charges and masses are used instead sometimes (e.g. +1)
128
Do you need to learn the charges and masses of protons, electrons and neutrons?
No, they are given to you in the exam. However, you need to know the RELATIVE charges and masses.
129
What is the unit for charge of particles?
Coulombs (C)
130
What is the unit for the mass of a particle?
Kilograms (kg)
131
What is the charge of protons, neutrons and electrons?
• Protons = + 1.60 x 10^-19 C • Neutrons = 0 C • Electrons = - 1.60 x 10^-19 C
132
What is the mass of protons, neutrons and electrons?
• Protons = 1.67 x 10^-27 kg • Neutrons = 1.67 x 10^-27 kg • Electrons = 9.11 x 10^-31 kg
133
What is the relative charge of protons, neutrons and electrons?
• Protons = +1 • Neutrons = 0 • Electrons = -1
134
What is the relative mass of protons, neutrons and electrons?
• Protons = 1 • Neutrons = 1 • Electrons = 0.0005
135
What is the symbol for proton number?
Z
136
What is the symbol Z?
The proton number
137
What does the proton number determine?
Which element the atom is of.
138
What does the electron number determine?
The chemical behaviour and reactions.
139
What is another name for the mass number?
The nucleon number.
140
What is the nucleon number?
The number of protons and neutrons.
141
What is an atom's relative atomic mass equal to?
The nucleon number (the number of protons and neutrons).
142
What are isotopes?
Atoms with the same number of protons but different number of neutrons.
143
How does changing the number of neutrons in atom affect it?
• Doesn't affect the chemical properties • Affects the stability of the nucleus -\> May cause decay
144
How can isotopes be used to find out how old a sample is?
The amount of radioactive carbon-14 left in a sample can be used to calculate the approximate age (if the object is made of organic matter).
145
Why can carbon-14 be used to find out how old stuff is?
• All living things contain the same percentage of carbon-14 taken in from the atmosphere • After they die, the amount of carbon-14 decreases with time as it decays • Looking at a sample, the amount of carbon-14 tells you how old it is
146
What is specific charge?
The ratio of the charge of a particle to its mass.
147
What is the unit for specific charge?
Coulombs per kilogram (C/kg)
148
What is the equation for specific charge?
Specific charge = Charge / Mass
149
What would happen in the nucleus if the strong attraction didn't exist?
Electrostatic repulsion would overcome gravity and the particles would fly apart.
150
What does the strong nuclear force do?
Binds nucleons together in the nucleus.
151
What are the properties of the strong nuclear force?
• Stronger than the electrostatic force • Very short range - only a few femtometres (the size of a nucleus) • Works equally between all nucleons (i.e. The force is the same between proton-proton, neutron-neutron, neutron-proton) • At very short separations, it is repulsive. At larger separations, it is attractive.
152
Describe how the strong nuclear force changes with separation.
• At very small separations (below 0.5fm), it is repulsive • At the "equilibrium distance" (about 0.5fm), no force is exerted • At larger separations (over 0.5fm), it is attractive. It reaches a maximum attractive value and then falls rapidly. It is almost zero past 3fm.
153
Why must the strong nuclear force be repulsive at very small separations?
Otherwise it would crush the nucleus to a point.
154
In what nuclei does alpha emission happen and why?
• Very big nuclei, like uranium and radium. • The nuclei are too massive for the strong nuclear force to keep them stable.
155
What happens to proton number and nucleon number when alpha decay happens?
• Proton number decreases by 2 • Nucleon number decreases by 4
156
Compare when alpha and beta emission happen.
• Alpha emission -\> In very large nuclei • Beta emission -\> In neutron-rich nuclei
157
What is the range of alpha particles and how can this be observed?
• Very short • By looking at tracks left by alpha particles in a cloud chamber or by using a Geiger counter to observe how count rate drops with distance
158
What is beta-minus decay?
The changing of a neutron into a proton, while emitting an electron and antineutrino from the nucleus.
159
In what nuclei does beta-minus decay happen and why?
• Neutron-rich nuclei • Having many more neutrons than protons in the nucleus makes it unstable
160
What happens to proton number and nucleon number when beta-minus decay happens?
• Proton number increases by 1 • Nucleon number stays the same
161
What is the range of beta particles?
Much greater than alpha particles.
162
What does the antineutrino in beta decay do?
Carries away some energy and momentum.
163
Describe how the first hypothesis about neutrinos was created.
• Scientists at first thought only electrons were emitted during beta decay. • However, it was observed that the energy after beta decay was less than before beta decay. • This led to the idea that another particle was emitted too, which carried the missing energy. • It would have to have no charge and almost zero mass. • This was later found to be the neutrino.
164
Remember to revise the graph of the strong nuclear force.
Pg 4 of the revision guide.
165
What is the order of the EM spectrum by increasing frequency?
• Radio waves • Microwaves • Infrared • Visible light • UV • X-rays • Gamma rays
166
What equation links frequency and wavelength of EM waves?
Frequency = Speed of Light in Vacuum / Wavelength f = c / lambda (NOTE: This is a variation of the "v = f x lambda" equation)
167
What is the speed of light in a vacuum?
3.00 x 10^8 m/s
168
What are photons?
Packets of electromagnetic radiation.
169
When are EM waves emitted?
When a charged particle loses energy. This can be when: • A fast-moving electron is stopped • An electron in a shell moves to a shell of lower energy
170
Describe the structure of an EM wave.
A magnetic wave and an electric wave at 90\* to each other and to the direction of travel. They are in phase. (See diagram pg 8 of textbook)
171
What is the equation for the energy of a photon?
Energy (J) = Planck's constant (Js) x Frequency (Hz) E = h x f
172
What is the wavelength of visible light?
400-700nm
173
What is Planck's constant?
6.63 x 10^-34 Js
174
What is the equation for the power of a laser?
Power = No. of photons passing a point per second x Photon energy P = n x E = n x h x f
175
What units may be used to give the energy of a photon?
Joules (J) or Mega electronvolts (MeV)
176
How many joules is one MeV?
1.60 x 10^-13 J
177
What equation can be used to calculate the rest energy of a particle?
E = m x c^2
178
What is an electronvolt?
The energy that one electron would gain when accelerated through a potential difference of 1 volt.
179
How do you convert from joules to MeV?
Divide by 1.6 x 10^-13.
180
What is an antiparticle?
A corresponding particle to a particle with the same mass and rest energy, but opposite charge.
181
What is the general unit for rest energy?
MeV
182
Describe simply the idea of energy and mass equivalence.
Energy can turn into mass and mass can turn into energy.
183
What is the rest energy of a particle?
The "energy equivalent" of the particle's mass.
184
What happens in terms of mass production when energy is converted into mass?
Equal amounts of matter and antimatter are produced.
185
What is the antiparticle of the proton?
Antiproton
186
What is the antiparticle of the neutron?
Antineutron
187
What is the antiparticle of the electron?
Positron
188
What is the antiparticle of the neutrino?
Antineutrino
189
What is beta-plus decay?
* When a proton turns into a neutron, and a positron and neutrino are emitted.
* It is not a natural form of decay and it only happens in experiments.
190
What is pair production?
When a photon turns into a particle and antiparticle.
191
When can pair production happen?
When the photon has enough energy to produce the mass of the particle and antiparticle.
192
Which photons have enough energy to produce mass through pair production?
Gamma ray photons.
193
Where does pair production usually happen and why?
Near the nucleus, which helps conserve momentum.
194
What are the most common particles produced by pair production and why?
Electron-positron pairs because they have low mass.
195
The minimum energy of a photon in pair production is equal to...
...the total rest energy of the particles produced.
196
What is the symbol for rest energy?
E0
197
What is the equation for the minimum energy of a photon during pair production?
Minimum energy of photon = 2 x Rest energy of each particle produced Emin = 2E0 or h x fmin = 2E0
198
What happens when a particle and antiparticle meet?
• Annihilation • All of the mass of the particles is converted back to energy.
199
The total minimum energy of both photons produced in annihilation is equal to...
... the total of the minimum energies of the particle and antiparticle.
200
What is the energy for the minimum energy of a photon produced in annihilation?
Total minimum energy of both photons = Total minimum energy of particle and antiparticle 2Emin = 2E0 ...and so... Emin = E0
201
Is the interaction between two distant objects instantaneous?
No - this is explained by the need for exchange particles, which cause forces.
202
What is the collective name for exchange particles?
Gauge bosons
203
What are the four fundamental forces?
• Weak nuclear force • Strong nuclear force • Electromagnetic force • Gravity
204
What is the exchange particle of electromagnetic force?
Virtual photon (gamma symbol)
205
What particles are affected by the electromagnetic force?
Charged particles
206
What is the exchange particle of the weak nuclear force?
W+, W- and Z0 bosons
207
What particles are affected by the weak nuclear force?
All types
208
What is the exchange particle of the strong nuclear force?
• Gluons exchanged between quarks • Pions exchanged between nucleons
209
What particles are affected by the strong nuclear force?
Hadrons only
210
What is the exchange particle of gravity?
Graviton
211
What particles are affected by gravity?
All types
212
Is particle physics concerned with gravity?
Not really - it is usually ignored because it is very feeble unless large masses are involved.
213
What is the mass of a W boson?
About 100 times that of a proton.
214
Compare and explain the ranges of a W boson and a photon.
• W boson - Very short range because it has a large mass. This means it requires a lot of energy to create and can't travel very far. • Photon - Infinite range because it has zero mass.
215
What are the different types of line on a Feynman diagram used to represent?
• Gauge bosons (exchange particles) - wiggly lines • Other particles - straight lines
216
What are the rules for drawing Feynman diagrams?
• Incoming particles start at the bottom and move upwards • Baryons and leptons can't cross from one side to the other • Make sure charges on both sides balance • A W- particle going to the left has the same effect as a W+ parcial going to the right
217
What exchange particle is involved in two electrons repelling each other?
Virtual (gamma) photon
218
What are electron capture and electron-proton collisions?
• Electron capture is when a proton and electron are attracted by the electromagnetic interaction and a W+ boson goes from the proton to the electron, causing a neutron and neutrino to be formed. • Electron collision is when the proton and electron collide. The same products are formed but a W- boson travels from the electron to the proton instead.
219
What is the difference between electron capture and electron-proton collision?
• In electron capture, a W+ boson travels from the proton to the electron. • In electron-proton collisions, a W- travels from the electron to the proton.
220
What is the particle equation for beta-minus decay?
Neutron -\> Proton + Electron + Antineutrino
221
What is the particle equation for beta-plus decay?
Proton -\> Neutron + Positron + Neutrino
222
Why is an antineutrino produced in beta-minus decay, while a neutrino is produced in beta-plus decay?
To conserve lepton number.
223
What is a virtual particle?
Particles which exist for only a very short time and cannot be detected.
224
Remember to learn specific Feynman diagrams.
Pg 9
225
Practice drawing our a spider diagram of the different types of particles.
Do it!
226
What are hadrons?
Particles that feel the strong nuclear force. They are not fundamental.
227
What are hadrons made of?
Quarks
228
Are hadrons fundamental particles?
No, they are made of quarks.
229
What are the two types of hadrons?
• Baryons • Mesons
230
What is the difference between baryons and mesons?
• Baryons - Made of 3 quarks and decay into a proton directly or indirectly • Mesons - Made of a quark and antiquark and do not decay into a proton
231
Name some baryons.
• Protons • Neutrons • Other particles (e.g. Sigmas)
232
What is the only stable baryon?
Proton - this means all baryons will decay in sequence and eventually form a proton.
233
Are antibaryons found in ordinary matter?
No, because they annihilate with baryons.
234
What values are particles given in baryon number conservation?
• Baryons = +1 • Antibaryons = -1 • Other particles = 0
235
What are some examples of antibaryons?
• Antiprotons • Antineutrons
236
Why does beta decay happen?
Neutrons are not stable baryons, but protons are, so a neutron will decay into a proton.
237
Are mesons stable?
No
238
What are the different types of meson?
Pions and kaons
239
What is another name for a pion?
Pi-meson
240
What is another name for a kaon?
K-meson
241
What is the difference between pions and kaons?
• Pions - Lighter, less unstable, not strange • Kaons - Heavier, more unstable, strange
242
What happens to kaons?
They decay into pions.
243
How were pions and kaons discovered?
In cosmic rays.
244
How do mesons interact with baryons?
Through the strong force.
245
What are the general rules for determining the type of interaction in a reaction?
• If any leptons involved at all -\> Weak interaction • If strangeness isn't conserved -\> Weak interaction • All others -\> Strong interaction
246
What are leptons?
Particles that do not feel the strong interaction. They are fundamental.
247
What are the different leptons?
• Electrons • Muons • Neutrinos • Tau
248
What happens to muons?
The eventually decay into electrons. This is because muons are unstable.
249
What can muons be described as?
Heavy electrons.
250
What is the mass and charge of neutrinos?
• Mass - Almost zero • Charge - Zero
251
How does lepton conservation work?
• There are 3 generations of lepton number - electron, muon and tau • Each lepton number must be conserved separately • Each normal lepton and its respective neutrino is given a lepton number of +1 • Each anti-lepton and its respective antineutrino is given a lepton number of -1
252
What are the symbols for each lepton number?
• Electron lepton number = Le • Muon lepton number = Lmuon • Tau lepton number = Lt
253
What are antiparticles of hadrons made from?
Antiquarks
254
How do strange particles (e.g. kaons) interact?
• Created by the strong interaction • Decay via the weak interaction
255
Strange particles are always produced in pairs (e.g. K+ and K-). Why?
The strangeness cancels out to become 0, so that strangeness is conserved. Therefore, the reaction is a strong interaction.
256
What are the types of quark?
•Up • Down • Strange
257
What is the charge of an up quark?
+2/3
258
What is the charge of a down quark?
-1/3
259
What is the charge of a strange quark?
-1/3
260
What is the charge of an anti-up antiquark?
-2/3
261
What is the charge of an anti-down antiquark?
+1/3
262
What is the charge of an anti-strange antiquark?
+1/3
263
What is the strangeness of a strange quark?
-1
264
What is the strangeness of an anti-strange antiquark?
+1
265
What is unusual about strangeness?
• It is not ALWAYS conserved • Strange quarks are given a strangeness of -1 and anti-strange antiquarks are given a strangeness of +1
266
What quarks make up a proton?
uud
267
What quarks make up an antiproton?
anti-u, anti-u, anti-d
268
What quarks make up a neutron?
udd
269
What quarks make up an antineutron?
anti-u, anti-d, anti-d
270
What are baryons made of?
3 quarks
271
What are mesons made of?
A quark and an antiquark
272
What is the antiparticle of a pi-plus meson?
A pi-minus meson.
273
What is a weak interaction in terms of quarks?
A weak interaction is something that changes the quark type (e.g. A neutron (udd) turning into a proton (uud))
274
What properties are conserved in an interaction?
• Charge • Baryon number • Strangeness (only in strong interactions) • Lepton number (all 3 generations separately)
275
Can a quark exist on its own?
No.
276
What is quark confinement?
The idea that quarks cannot exist not their own.
277
Through which interaction do hadrons tend to decay?
Weak
278
Describe the mass, range and charge of a W boson.
• Non-zero rest mass • 0.001fm range • Can be positively or negatively charged
279
What are the quarks in a K0 meson?
• Anti-s • d
280
What are the quarks in an anti-K0 meson?
• s • Anti-d
