Fundamental particles Flashcards
What are anti-particles?
Simply put, an anti-particle has the opposite charge to the original particle, but the same mass.
proton p+ anti-proton p-
electron e- anti-electron(positron) e+
More generally, an antiparticle is signified by a short line drawn above it.
What are the two types of fundamental particles?
Leptons and quarks.
What are the three lepton families?
The electron, e
The muon, μ
The tau, τ
What are the relative heaviness of the lepton families compared to each other?
The electron and muon are very light particles but the tau is about 1800 times heavier than an electron.
What is pair production?
Pair production is the creation of a particle and its anti-particle when a gamma ray photon passes close to a nucleus.
What is pair annihilation?
Pair annihilation is when a particle and its anti-particle collide. The result is energy in the form of gamma ray photons and/or other particles being produced.
What is the antiparticle of an electron?
A positron.
What are neutrinos?
There are three types, one for each charged lepton.
They’re very hard to detect and yet come from vast numbers from all directions in space.
They pass through the Earth virtually undiminished in intensity and interact so rarely that they need to pass through lead many light years thick to halve their intensity.
What are the three neutrinos?
Electron neutrino, muon neutrino, and tau neutrino.
How were neutrinos discovered?
In 1930 it was observed that the energy spectrum of electrons (the beta particle) emitted in nuclear beta-decay was continuous. This observation could not be explained at the time. The particle emitted in beta decay is actually an antineutrino.
What are the six types of quarks?
up (u) …………………….down (d)
charm (c) ………………..strange (s)
top (t) …………………….bottom (b
Can quarks exist on their own?
No- they exist in hadrons formed from various quark combinations.
What charges can a quark carry?
+2/3e or -1/3e where e is 1.60 x 10-19C.
What ‘generations’ are the quarks split up into?
First generation- up and down quarks.
Second generation- strange and charm quarks.
Third generation- top and bottom quarks.
What was the strangeness property initially defined to explain?
The behaviour of massive particles such as kaons and hyperons.
These strange particles are created in pairs in collisions and have a longer than expected lifetime.
This property of strangeness is conserved during their creation, but not when they subsequently decay.
What is the lepton number and charge of electrons, muons and taus?
+1 and -1
What is the lepton number and charge of anti-electrons, anti-muons and anti-taus?
-1 and +1
What is the lepton number and charge of electron neutrinos, muon neutrinos and tau neutrinos?
+1 and 0
What is the lepton number and charge of electron anti-neutrinos, muon anti-neutrinos and tau anti-neutrinos?
-1 and 0
What are the 12 leptons?
Electron Muon Tau Anti-electron Anti-muon Anti-tau Electron neutrino Muon neutrino Tau Electron anti-neutrino Muon anti-neutrino Tau anti-neutrino
What quarks are in a proton?
u u d …… charge totals ( +2/3 +2/3 -1/3 = +1 )
What quarks are in a neutron?
u d d …….charge totals ( +2/3 -1/3 -1/3 = 0 )
What quarks are in a anti-proton?
uud. ….. charge totals ( -2/3 -2/3 +1/3 = -1 )
What quarks are in a anti-neutron?
udd…… charge totals ( -2/3 +1/3 +1/3 = 0 )
How many fundamental particles and antiparticles are there in the standard model?
12 particles and 12 antiparticles.
What is the charge on a strange anti-quark?
+1/3
What is the baryon number on a strange antiquark?
-1/3
What quarks have a charge of -1/3?
Down, strange and bottom.
What quarks have a charge of +2/3?
Up, charm and top.
What is the order of increasing mass of the quarks?
Up + down
Charm + strange
Top + bottom
What are hadrons?
Hadrons are not fundamental particles. Hadrons are exclusively composed of quarks. Further, hadrons are affected by both the ‘strong’ and the ‘weak’ nuclear forces.
Hadrons fall into 2 groups called baryons and mesons.
What are baryons?
Baryons are composed of 3 quarks. There are only two baryons with quarks in stable configurations. These are the proton(uud) and the neutron(udd).
What are mesons?
Mesons are composed of 2 quarks (a quark and an anti-quark). Note, the quarks and anti-quarks can be of different flavours.
Mesons fall into two families called pions and kaons. Each family(including anti-particles) has 6 members
What are the two types of hadrons?
Baryons and mesons
Particles that can feel the strong nuclear force are called…?
Hadrons.
Are hadrons fundamental particles and why?
No because they are made of smaller particles called quarks.
Name two particles that are baryons.
Protons and neutrons
Why do baryons want to turn into protons?
Because all baryons are unstable except from the proton
What is the baryon number of a proton and a neutron?
+1
What is the baryon number of a antiproton and antineutron?
-1
What is the baryon number of an electron?
0
Which interaction causes beta decay?
Weak interaction
Mesons interact with baryons through what force?
The strong force.
What happens when a proton and a negative pion interact?
The proton turns into a neutron
Name two types of Mesons?
Pions and kaons
Kaons are ___ unstable then pions
More
Kaons are ____ than pions
Heavier
neutron → β (electron) +
proton + anti neutrino
State the combination of quarks that makes up a neutron.
d + d + u
Whats the strangeness of particles that contain a strange quark?
-1
The K0 meson has a strangeness of +1 so contains what?
A strange antiquark.
Particles made from three strange quarks would have a strangeness of what?
-3
What happens with the strangeness when a strange particle decays through a weak interaction?
Strangeness is not conserved. For example, strangeness is not conserved when a strange quark decays into an up quark.
When is strangeness conserved?
When there is a strong interaction (one in which the strong force is involved).
What leptons have a lepton number of +1?
electron electron neutrino muon muon neutrino tau tau neutrino
What leptons have a lepton number of -1?
anti electron electron anti neutrino anti muon muon anti neutrino anti tau tau anti neutrino
What is the charge, baryon number and strangeness of the up quark?
+2/3 e
+ 1/3
0
What is the charge, baryon number and strangeness of the d quark?
-1/3 e
+1/3
0
What is the charge, baryon number and strangeness of the s quark?
-1/3 e
+1/3
-1
What is the symbol for the electron and its antiparticle?
e- and e+
What is the symbol for the electron neutrino and its antiparticle?
νe and νe (with a minus above it)
What is the symbol for the muon and its antiparticle?
μ- and μ+
What is the symbol for the muon neutrino and its antiparticle?
νμ and νμ (with a minus above it)
What is the symbol for the tau and its antiparticle?
τ- and τ+
What is the symbol for the tau neutrino and its antiparticle?
ντ and ντ (with a minus above it)(with a minus above it)
What is the quark structure for K^0?
One down quark & one anti-strange quark.
What is the quark structure for a π+ (positive pion)?
ud
-
What are the four forces exchange particles?
Gravity – gravitons
Electromagnetic force – virtual photons
Strong nuclear force – gluons
Weak nuclear force – W+, W- bosons
What fundamental force is responsible for electron capture?
The weak interaction.
Show that when a proton collides with a negative pion it can produce a neutron and an uncharged pion.
p + π- -> n + π0
Charge conservation: +1 - 1 -> 0 + 0 ✓
Baryon number: +1 + 0 -> +1 + 0 ✓
Lepton number: 0 + 0 -> 0 + 0 ✓
What happens to the quarks sequence when a neutron decays into a proton?
udd -> uud
Explain why there is a minimum amount of energy required for pair production to occur?
E = mc^2
Minimum energy is equivalent to (combined) mass of both particles
By analogy with the beta decay of a free neutron, suggest the decay products of a
free antineutron.
Antiproton, positron
Antielectron neutrino
Electron neutrino
Name the classification of particles that has this type of structure
Meson
