Classification of particles and forces

Particle Physicslecture 1

Classification of particles

Yazid Delenda

Departement des Sciences de la matiereFaculte des Sciences - UHLB

http://delenda.wordpress.com/teaching/particlephysics/

Batna, 07 September 2014

1/21 Particle Physics - lecture 1

Classification of particles and forcesElementary particles and fundamental forcesLeptons and conservation lawsHadrons (Baryons and Mesons)

Elementary particles and fundamental forcesElementary particles and fundamental forces:

Elementary particles: are point-like particles with zero-dimensionand no spacial extensions or internal structure or excited states.Examples include: the electron, the photon.Note that the proton (p) and neutron (n) are not considered aselementary particles because they have an internal structure (madeof quarks) and dimensions (∼ fm).There are three types of elementary particles:

1 Force carriers: also known as gauge bosons, of spin-0, spin-1or spin-2. For example: the photon is the electromagneticforce carrier.

2 Leptons: are spin-half (fermions) particles, for example theelectron and the electron neutrino.

2/21 Particle Physics - lecture 1

Classification of particles and forcesElementary particles and fundamental forcesLeptons and conservation lawsHadrons (Baryons and Mesons)

Elementary particles and fundamental forcesElementary particles and fundamental forces:

Elementary particles: are point-like particles with zero-dimensionand no spacial extensions or internal structure or excited states.Examples include: the electron, the photon.Note that the proton (p) and neutron (n) are not considered aselementary particles because they have an internal structure (madeof quarks) and dimensions (∼ fm).There are three types of elementary particles:

1 Force carriers: also known as gauge bosons, of spin-0, spin-1or spin-2. For example: the photon is the electromagneticforce carrier.

2 Leptons: are spin-half (fermions) particles, for example theelectron and the electron neutrino.

2/21 Particle Physics - lecture 1

Classification of particles and forcesElementary particles and fundamental forcesLeptons and conservation lawsHadrons (Baryons and Mesons)

Elementary particles and fundamental forcesElementary particles and fundamental forces:

Elementary particles: are point-like particles with zero-dimensionand no spacial extensions or internal structure or excited states.Examples include: the electron, the photon.Note that the proton (p) and neutron (n) are not considered aselementary particles because they have an internal structure (madeof quarks) and dimensions (∼ fm).There are three types of elementary particles:

1 Force carriers: also known as gauge bosons, of spin-0, spin-1or spin-2. For example: the photon is the electromagneticforce carrier.

2 Leptons: are spin-half (fermions) particles, for example theelectron and the electron neutrino.

2/21 Particle Physics - lecture 1

Classification of particles and forcesElementary particles and fundamental forcesLeptons and conservation lawsHadrons (Baryons and Mesons)

Elementary particles and fundamental forcesElementary particles and fundamental forces:

Elementary particles: are point-like particles with zero-dimensionand no spacial extensions or internal structure or excited states.Examples include: the electron, the photon.Note that the proton (p) and neutron (n) are not considered aselementary particles because they have an internal structure (madeof quarks) and dimensions (∼ fm).There are three types of elementary particles:

1 Force carriers: also known as gauge bosons, of spin-0, spin-1or spin-2. For example: the photon is the electromagneticforce carrier.

2 Leptons: are spin-half (fermions) particles, for example theelectron and the electron neutrino.

2/21 Particle Physics - lecture 1

Classification of particles and forcesElementary particles and fundamental forcesLeptons and conservation lawsHadrons (Baryons and Mesons)

Elementary particles and fundamental forcesElementary particles and fundamental forces:

Elementary particles: are point-like particles with zero-dimensionand no spacial extensions or internal structure or excited states.Examples include: the electron, the photon.Note that the proton (p) and neutron (n) are not considered aselementary particles because they have an internal structure (madeof quarks) and dimensions (∼ fm).There are three types of elementary particles:

1 Force carriers: also known as gauge bosons, of spin-0, spin-1or spin-2. For example: the photon is the electromagneticforce carrier.

2 Leptons: are spin-half (fermions) particles, for example theelectron and the electron neutrino.

2/21 Particle Physics - lecture 1

Classification of particles and forcesElementary particles and fundamental forcesLeptons and conservation lawsHadrons (Baryons and Mesons)

Elementary particles and fundamental forcesElementary particles and fundamental forces:

Elementary particles: are point-like particles with zero-dimensionand no spacial extensions or internal structure or excited states.Examples include: the electron, the photon.Note that the proton (p) and neutron (n) are not considered aselementary particles because they have an internal structure (madeof quarks) and dimensions (∼ fm).There are three types of elementary particles:

1 Force carriers: also known as gauge bosons, of spin-0, spin-1or spin-2. For example: the photon is the electromagneticforce carrier.

2 Leptons: are spin-half (fermions) particles, for example theelectron and the electron neutrino.

2/21 Particle Physics - lecture 1

Classification of particles and forcesElementary particles and fundamental forcesLeptons and conservation lawsHadrons (Baryons and Mesons)

Elementary particles and fundamental forcesElementary particles

1 Quarks: are the constituents of (for example) the proton andneutron. They are fermions of fractional electric charge (1/3or 2/3).

Note that quarks cannot be observed as free particles. They areconfined into hadrons (confinement property).Hadrons: are particles composed of quarks. Thus they are notelementary and they have dimensions (of order fm) and excitedstates.Examples of hadrons: the proton (p), the neutron (n) withspin-half, and the pions (π± and π0) with spin-1 or 0, and manyothers.

3/21 Particle Physics - lecture 1

Classification of particles and forcesElementary particles and fundamental forcesLeptons and conservation lawsHadrons (Baryons and Mesons)

Elementary particles and fundamental forcesElementary particles

1 Quarks: are the constituents of (for example) the proton andneutron. They are fermions of fractional electric charge (1/3or 2/3).

Note that quarks cannot be observed as free particles. They areconfined into hadrons (confinement property).Hadrons: are particles composed of quarks. Thus they are notelementary and they have dimensions (of order fm) and excitedstates.Examples of hadrons: the proton (p), the neutron (n) withspin-half, and the pions (π± and π0) with spin-1 or 0, and manyothers.

3/21 Particle Physics - lecture 1

Classification of particles and forcesElementary particles and fundamental forcesLeptons and conservation lawsHadrons (Baryons and Mesons)

Elementary particles and fundamental forcesElementary particles

1 Quarks: are the constituents of (for example) the proton andneutron. They are fermions of fractional electric charge (1/3or 2/3).

Note that quarks cannot be observed as free particles. They areconfined into hadrons (confinement property).Hadrons: are particles composed of quarks. Thus they are notelementary and they have dimensions (of order fm) and excitedstates.Examples of hadrons: the proton (p), the neutron (n) withspin-half, and the pions (π± and π0) with spin-1 or 0, and manyothers.

3/21 Particle Physics - lecture 1

Classification of particles and forcesElementary particles and fundamental forcesLeptons and conservation lawsHadrons (Baryons and Mesons)

Elementary particles and fundamental forcesElementary particles

1 Quarks: are the constituents of (for example) the proton andneutron. They are fermions of fractional electric charge (1/3or 2/3).

Note that quarks cannot be observed as free particles. They areconfined into hadrons (confinement property).Hadrons: are particles composed of quarks. Thus they are notelementary and they have dimensions (of order fm) and excitedstates.Examples of hadrons: the proton (p), the neutron (n) withspin-half, and the pions (π± and π0) with spin-1 or 0, and manyothers.

3/21 Particle Physics - lecture 1

Classification of particles and forcesElementary particles and fundamental forcesLeptons and conservation lawsHadrons (Baryons and Mesons)

Elementary particles and fundamental forcesFundamental forces:

Fundamental Forces There are four fundamental forces of nature:

1 Electromagnetic forces (EM): are responsible for thebinding of electrons and protons in atoms, and they lead tothe process of photon emission from atoms and nuclei.

2 Weak Interactions: are responsible for electron emission andneutrino emission (β-decay) from a nucleus - see nuclearphysics course.

3 Strong interactions: are responsible for the binding ofquarks in hadrons and are also responsible for the binding ofprotons and neutrons into the nuclei.

4 Gravity: is so weak that we ignore it (at microscopic level).

4/21 Particle Physics - lecture 1

Classification of particles and forcesElementary particles and fundamental forcesLeptons and conservation lawsHadrons (Baryons and Mesons)

Elementary particles and fundamental forcesFundamental forces:

Fundamental Forces There are four fundamental forces of nature:

1 Electromagnetic forces (EM): are responsible for thebinding of electrons and protons in atoms, and they lead tothe process of photon emission from atoms and nuclei.

2 Weak Interactions: are responsible for electron emission andneutrino emission (β-decay) from a nucleus - see nuclearphysics course.

3 Strong interactions: are responsible for the binding ofquarks in hadrons and are also responsible for the binding ofprotons and neutrons into the nuclei.

4 Gravity: is so weak that we ignore it (at microscopic level).

4/21 Particle Physics - lecture 1

Classification of particles and forcesElementary particles and fundamental forcesLeptons and conservation lawsHadrons (Baryons and Mesons)

Elementary particles and fundamental forcesFundamental forces:

Fundamental Forces There are four fundamental forces of nature:

1 Electromagnetic forces (EM): are responsible for thebinding of electrons and protons in atoms, and they lead tothe process of photon emission from atoms and nuclei.

2 Weak Interactions: are responsible for electron emission andneutrino emission (β-decay) from a nucleus - see nuclearphysics course.

3 Strong interactions: are responsible for the binding ofquarks in hadrons and are also responsible for the binding ofprotons and neutrons into the nuclei.

4 Gravity: is so weak that we ignore it (at microscopic level).

4/21 Particle Physics - lecture 1

Classification of particles and forcesElementary particles and fundamental forcesLeptons and conservation lawsHadrons (Baryons and Mesons)

Elementary particles and fundamental forcesFundamental forces:

Fundamental Forces There are four fundamental forces of nature:

1 Electromagnetic forces (EM): are responsible for thebinding of electrons and protons in atoms, and they lead tothe process of photon emission from atoms and nuclei.

2 Weak Interactions: are responsible for electron emission andneutrino emission (β-decay) from a nucleus - see nuclearphysics course.

3 Strong interactions: are responsible for the binding ofquarks in hadrons and are also responsible for the binding ofprotons and neutrons into the nuclei.

4 Gravity: is so weak that we ignore it (at microscopic level).

4/21 Particle Physics - lecture 1

Classification of particles and forcesElementary particles and fundamental forcesLeptons and conservation lawsHadrons (Baryons and Mesons)

Elementary particles and fundamental forcesFundamental forces:

Fundamental Forces There are four fundamental forces of nature:

1 Electromagnetic forces (EM): are responsible for thebinding of electrons and protons in atoms, and they lead tothe process of photon emission from atoms and nuclei.

2 Weak Interactions: are responsible for electron emission andneutrino emission (β-decay) from a nucleus - see nuclearphysics course.

3 Strong interactions: are responsible for the binding ofquarks in hadrons and are also responsible for the binding ofprotons and neutrons into the nuclei.

4 Gravity: is so weak that we ignore it (at microscopic level).

4/21 Particle Physics - lecture 1

Classification of particles and forcesElementary particles and fundamental forcesLeptons and conservation lawsHadrons (Baryons and Mesons)

Elementary particles and fundamental forcesSummary

There are four types of particles: three of them are elementary(leptons, quarks, gauge bosons) and one of them is composed(Hadrons). There are three fundamental interactions (strong,weak, EM) + gravity.

5/21 Particle Physics - lecture 1

Classification of particles and forcesElementary particles and fundamental forcesLeptons and conservation lawsHadrons (Baryons and Mesons)

Leptons and conservation lawsLeptrons

Leptons are elementary spin-half particles with no stronginteractions. There are six known leptons which are grouped intothree generations:(

νee−

),

(νµµ−

),

(νττ−

)so we have three charged leptons: the electron e−, the muon µ−

and the tauon τ−, all of negative chargeQ = −e = −1.602× 10−19C,and three neutrinos: electron neutrino νe, muon neutrino νµ andtauon neutrino ντ which are electrically neutral and have verysmall mass (order eV/c2). Hence the neutrinos do not interactelectromagnetically (only weak interactions).

6/21 Particle Physics - lecture 1

Classification of particles and forcesElementary particles and fundamental forcesLeptons and conservation lawsHadrons (Baryons and Mesons)

Leptons and conservation lawsLeptrons

Leptons are elementary spin-half particles with no stronginteractions. There are six known leptons which are grouped intothree generations:(

νee−

),

(νµµ−

),

(νττ−

)so we have three charged leptons: the electron e−, the muon µ−

and the tauon τ−, all of negative chargeQ = −e = −1.602× 10−19C,and three neutrinos: electron neutrino νe, muon neutrino νµ andtauon neutrino ντ which are electrically neutral and have verysmall mass (order eV/c2). Hence the neutrinos do not interactelectromagnetically (only weak interactions).

6/21 Particle Physics - lecture 1

Classification of particles and forcesElementary particles and fundamental forcesLeptons and conservation lawsHadrons (Baryons and Mesons)

Leptons and conservation lawsLeptrons

Leptons are elementary spin-half particles with no stronginteractions. There are six known leptons which are grouped intothree generations:(

νee−

),

(νµµ−

),

(νττ−

)so we have three charged leptons: the electron e−, the muon µ−

and the tauon τ−, all of negative chargeQ = −e = −1.602× 10−19C,and three neutrinos: electron neutrino νe, muon neutrino νµ andtauon neutrino ντ which are electrically neutral and have verysmall mass (order eV/c2). Hence the neutrinos do not interactelectromagnetically (only weak interactions).

6/21 Particle Physics - lecture 1

Classification of particles and forcesElementary particles and fundamental forcesLeptons and conservation lawsHadrons (Baryons and Mesons)

Leptons and conservation lawsLeptrons

Leptons are elementary spin-half particles with no stronginteractions. There are six known leptons which are grouped intothree generations:(

νee−

),

(νµµ−

),

(νττ−

)so we have three charged leptons: the electron e−, the muon µ−

and the tauon τ−, all of negative chargeQ = −e = −1.602× 10−19C,and three neutrinos: electron neutrino νe, muon neutrino νµ andtauon neutrino ντ which are electrically neutral and have verysmall mass (order eV/c2). Hence the neutrinos do not interactelectromagnetically (only weak interactions).

6/21 Particle Physics - lecture 1

Classification of particles and forcesElementary particles and fundamental forcesLeptons and conservation lawsHadrons (Baryons and Mesons)

Leptons and conservation lawsLeptrons

Leptons are elementary spin-half particles with no stronginteractions. There are six known leptons which are grouped intothree generations:(

νee−

),

(νµµ−

),

(νττ−

)so we have three charged leptons: the electron e−, the muon µ−

and the tauon τ−, all of negative chargeQ = −e = −1.602× 10−19C,and three neutrinos: electron neutrino νe, muon neutrino νµ andtauon neutrino ντ which are electrically neutral and have verysmall mass (order eV/c2). Hence the neutrinos do not interactelectromagnetically (only weak interactions).

6/21 Particle Physics - lecture 1

Classification of particles and forcesElementary particles and fundamental forcesLeptons and conservation lawsHadrons (Baryons and Mesons)

Leptons and conservation lawsanti-leptons

In addition there are six anti-particles:(νee+

),

(νµµ+

),

(νττ+

)e+ is the anti-electron (also known as the positron), νe is theanti-electron neutrino, µ+ is the anti-muon, νµ is the anti-muonneutrino, τ+ is the anti-tauon and ντ is the anti-tauon neutrino.

7/21 Particle Physics - lecture 1

Classification of particles and forcesElementary particles and fundamental forcesLeptons and conservation lawsHadrons (Baryons and Mesons)

Leptons and conservation lawsanti-leptons

In addition there are six anti-particles:(νee+

),

(νµµ+

),

(νττ+

)e+ is the anti-electron (also known as the positron), νe is theanti-electron neutrino, µ+ is the anti-muon, νµ is the anti-muonneutrino, τ+ is the anti-tauon and ντ is the anti-tauon neutrino.

7/21 Particle Physics - lecture 1

Classification of particles and forcesElementary particles and fundamental forcesLeptons and conservation lawsHadrons (Baryons and Mesons)

Leptons and conservation lawsanti-leptons

In addition there are six anti-particles:(νee+

),

(νµµ+

),

(νττ+

)e+ is the anti-electron (also known as the positron), νe is theanti-electron neutrino, µ+ is the anti-muon, νµ is the anti-muonneutrino, τ+ is the anti-tauon and ντ is the anti-tauon neutrino.

7/21 Particle Physics - lecture 1

Classification of particles and forcesElementary particles and fundamental forcesLeptons and conservation lawsHadrons (Baryons and Mesons)

Leptons and conservation lawsConservation laws for leptons

Lepton numbers: are conserved quantum numbers associatedwith each generation. They include the electron number Le, themuon number Lµ and the tauon number Lτ :

Le = N(e−) +N(νe)−N(e+)−N(νe)

Lµ = N(µ−) +N(νµ)−N(µ+)−N(νµ)

Lτ = N(τ−) +N(ντ )−N(τ+)−N(ντ ),

where N(e−) is the number of electrons present in a state, etc.For example a state which has just an electron has Le = +1,Lµ = Lτ = 0. A state with just an anti-muon has Lµ = −1 andLe = Lτ = 0.Non-leptons (p, n , γ, π, ...) have all lepton numbers equal to zero.

Lepton numbers are conserved in all known interactions

8/21 Particle Physics - lecture 1

Classification of particles and forcesElementary particles and fundamental forcesLeptons and conservation lawsHadrons (Baryons and Mesons)

Leptons and conservation lawsConservation laws for leptons

Lepton numbers: are conserved quantum numbers associatedwith each generation. They include the electron number Le, themuon number Lµ and the tauon number Lτ :

Le = N(e−) +N(νe)−N(e+)−N(νe)

Lµ = N(µ−) +N(νµ)−N(µ+)−N(νµ)

Lτ = N(τ−) +N(ντ )−N(τ+)−N(ντ ),

where N(e−) is the number of electrons present in a state, etc.For example a state which has just an electron has Le = +1,Lµ = Lτ = 0. A state with just an anti-muon has Lµ = −1 andLe = Lτ = 0.Non-leptons (p, n , γ, π, ...) have all lepton numbers equal to zero.

Lepton numbers are conserved in all known interactions

8/21 Particle Physics - lecture 1

Classification of particles and forcesElementary particles and fundamental forcesLeptons and conservation lawsHadrons (Baryons and Mesons)

Leptons and conservation lawsConservation laws for leptons

Lepton numbers: are conserved quantum numbers associatedwith each generation. They include the electron number Le, themuon number Lµ and the tauon number Lτ :

Le = N(e−) +N(νe)−N(e+)−N(νe)

Lµ = N(µ−) +N(νµ)−N(µ+)−N(νµ)

Lτ = N(τ−) +N(ντ )−N(τ+)−N(ντ ),

where N(e−) is the number of electrons present in a state, etc.For example a state which has just an electron has Le = +1,Lµ = Lτ = 0. A state with just an anti-muon has Lµ = −1 andLe = Lτ = 0.Non-leptons (p, n , γ, π, ...) have all lepton numbers equal to zero.

Lepton numbers are conserved in all known interactions

8/21 Particle Physics - lecture 1

Classification of particles and forcesElementary particles and fundamental forcesLeptons and conservation lawsHadrons (Baryons and Mesons)

Leptons and conservation lawsConservation laws for leptons

Lepton numbers: are conserved quantum numbers associatedwith each generation. They include the electron number Le, themuon number Lµ and the tauon number Lτ :

Le = N(e−) +N(νe)−N(e+)−N(νe)

Lµ = N(µ−) +N(νµ)−N(µ+)−N(νµ)

Lτ = N(τ−) +N(ντ )−N(τ+)−N(ντ ),

where N(e−) is the number of electrons present in a state, etc.For example a state which has just an electron has Le = +1,Lµ = Lτ = 0. A state with just an anti-muon has Lµ = −1 andLe = Lτ = 0.Non-leptons (p, n , γ, π, ...) have all lepton numbers equal to zero.

Lepton numbers are conserved in all known interactions

8/21 Particle Physics - lecture 1

Classification of particles and forcesElementary particles and fundamental forcesLeptons and conservation lawsHadrons (Baryons and Mesons)

Leptons and conservation lawsConservation laws for leptons

Lepton numbers: are conserved quantum numbers associatedwith each generation. They include the electron number Le, themuon number Lµ and the tauon number Lτ :

Le = N(e−) +N(νe)−N(e+)−N(νe)

Lµ = N(µ−) +N(νµ)−N(µ+)−N(νµ)

Lτ = N(τ−) +N(ντ )−N(τ+)−N(ντ ),

where N(e−) is the number of electrons present in a state, etc.For example a state which has just an electron has Le = +1,Lµ = Lτ = 0. A state with just an anti-muon has Lµ = −1 andLe = Lτ = 0.Non-leptons (p, n , γ, π, ...) have all lepton numbers equal to zero.

Lepton numbers are conserved in all known interactions

8/21 Particle Physics - lecture 1

Classification of particles and forcesElementary particles and fundamental forcesLeptons and conservation lawsHadrons (Baryons and Mesons)

Leptons and conservation lawsConservation laws for leptons

Lepton numbers: are conserved quantum numbers associatedwith each generation. They include the electron number Le, themuon number Lµ and the tauon number Lτ :

Le = N(e−) +N(νe)−N(e+)−N(νe)

Lµ = N(µ−) +N(νµ)−N(µ+)−N(νµ)

Lτ = N(τ−) +N(ντ )−N(τ+)−N(ντ ),

where N(e−) is the number of electrons present in a state, etc.For example a state which has just an electron has Le = +1,Lµ = Lτ = 0. A state with just an anti-muon has Lµ = −1 andLe = Lτ = 0.Non-leptons (p, n , γ, π, ...) have all lepton numbers equal to zero.

Lepton numbers are conserved in all known interactions

8/21 Particle Physics - lecture 1

Classification of particles and forcesElementary particles and fundamental forcesLeptons and conservation lawsHadrons (Baryons and Mesons)

Leptons and conservation lawsConservation laws for leptons

Lepton numbers: are conserved quantum numbers associatedwith each generation. They include the electron number Le, themuon number Lµ and the tauon number Lτ :

Le = N(e−) +N(νe)−N(e+)−N(νe)

Lµ = N(µ−) +N(νµ)−N(µ+)−N(νµ)

Lτ = N(τ−) +N(ντ )−N(τ+)−N(ντ ),

where N(e−) is the number of electrons present in a state, etc.For example a state which has just an electron has Le = +1,Lµ = Lτ = 0. A state with just an anti-muon has Lµ = −1 andLe = Lτ = 0.Non-leptons (p, n , γ, π, ...) have all lepton numbers equal to zero.

Lepton numbers are conserved in all known interactions

8/21 Particle Physics - lecture 1

Classification of particles and forcesElementary particles and fundamental forcesLeptons and conservation lawsHadrons (Baryons and Mesons)

Leptons and conservation lawsExamples

In electromagnetism we have the vertices:

e− e−

and the vertex

µ− µ−

9/21 Particle Physics - lecture 1

Classification of particles and forcesElementary particles and fundamental forcesLeptons and conservation lawsHadrons (Baryons and Mesons)

Leptons and conservation lawsExamples

but not the vertex:

e− µ−

10/21 Particle Physics - lecture 1

Classification of particles and forcesElementary particles and fundamental forcesLeptons and conservation lawsHadrons (Baryons and Mesons)

Leptons and conservation lawsExamples

Consider the weak interaction:

νµ + n → µ− + p

Lµ = 1 + 0 → 1 + 0

Here Lµ = 1 in the initial state and Lµ = 1 in the final state.Thus Lµ is conserved and the reaction is readily observed withintense high energy ν beams.Examples of unobserved reactions:

νµ + n → e− + p

Lµ = 1 + 0 → 0 + 0

Le = 0 + 0 → 1 + 0

where both Le and Lµ are violated

11/21 Particle Physics - lecture 1

Classification of particles and forcesElementary particles and fundamental forcesLeptons and conservation lawsHadrons (Baryons and Mesons)

Leptons and conservation lawsExamples

Consider the weak interaction:

νµ + n → µ− + p

Lµ = 1 + 0 → 1 + 0

Here Lµ = 1 in the initial state and Lµ = 1 in the final state.Thus Lµ is conserved and the reaction is readily observed withintense high energy ν beams.Examples of unobserved reactions:

νµ + n → e− + p

Lµ = 1 + 0 → 0 + 0

Le = 0 + 0 → 1 + 0

where both Le and Lµ are violated

11/21 Particle Physics - lecture 1

Classification of particles and forcesElementary particles and fundamental forcesLeptons and conservation lawsHadrons (Baryons and Mesons)

Leptons and conservation lawsExamples

Consider the weak interaction:

νµ + n → µ− + p

Lµ = 1 + 0 → 1 + 0

Here Lµ = 1 in the initial state and Lµ = 1 in the final state.Thus Lµ is conserved and the reaction is readily observed withintense high energy ν beams.Examples of unobserved reactions:

νµ + n → e− + p

Lµ = 1 + 0 → 0 + 0

Le = 0 + 0 → 1 + 0

where both Le and Lµ are violated

11/21 Particle Physics - lecture 1

Classification of particles and forcesElementary particles and fundamental forcesLeptons and conservation lawsHadrons (Baryons and Mesons)

Leptons and conservation lawsExamples

Consider the weak interaction:

νµ + n → µ− + p

Lµ = 1 + 0 → 1 + 0

Here Lµ = 1 in the initial state and Lµ = 1 in the final state.Thus Lµ is conserved and the reaction is readily observed withintense high energy ν beams.Examples of unobserved reactions:

νµ + n → e− + p

Lµ = 1 + 0 → 0 + 0

Le = 0 + 0 → 1 + 0

where both Le and Lµ are violated

11/21 Particle Physics - lecture 1

Classification of particles and forcesElementary particles and fundamental forcesLeptons and conservation lawsHadrons (Baryons and Mesons)

Leptons and conservation lawsExamples

Consider the weak interaction:

νµ + n → µ− + p

Lµ = 1 + 0 → 1 + 0

Here Lµ = 1 in the initial state and Lµ = 1 in the final state.Thus Lµ is conserved and the reaction is readily observed withintense high energy ν beams.Examples of unobserved reactions:

νµ + n → e− + p

Lµ = 1 + 0 → 0 + 0

Le = 0 + 0 → 1 + 0

where both Le and Lµ are violated

11/21 Particle Physics - lecture 1

Classification of particles and forcesElementary particles and fundamental forcesLeptons and conservation lawsHadrons (Baryons and Mesons)

Leptons and conservation lawsExamples

νµ + p → µ+ + n

Lµ = 1 + 0 → −1 + 0

violates Lµ conservation.

No lepton-number–violating interactions have ever been

observed despite extensive searches

12/21 Particle Physics - lecture 1

Classification of particles and forcesElementary particles and fundamental forcesLeptons and conservation lawsHadrons (Baryons and Mesons)

Leptons and conservation lawsExamples

νµ + p → µ+ + n

Lµ = 1 + 0 → −1 + 0

violates Lµ conservation.

No lepton-number–violating interactions have ever been

observed despite extensive searches

12/21 Particle Physics - lecture 1

Classification of particles and forcesElementary particles and fundamental forcesLeptons and conservation lawsHadrons (Baryons and Mesons)

Leptons and conservation lawsExamples

νµ + p → µ+ + n

Lµ = 1 + 0 → −1 + 0

violates Lµ conservation.

No lepton-number–violating interactions have ever been

observed despite extensive searches

12/21 Particle Physics - lecture 1

Classification of particles and forcesElementary particles and fundamental forcesLeptons and conservation lawsHadrons (Baryons and Mesons)

Leptons and conservation lawsThe first generation

(νee−

) (νee+

)Le = 1 Le = −1

(Historically) the electron neutrinos are emitted in nuclear-βdecays (via weak interactions):

(Z,A)→ (Z + 1, A) + e− + νe

(Z + 1, A)→ (Z,A) + e+ + νe

and in neutron decays:

n→ p+ e− + νe

13/21 Particle Physics - lecture 1

Classification of particles and forcesElementary particles and fundamental forcesLeptons and conservation lawsHadrons (Baryons and Mesons)

Leptons and conservation lawsThe first generation

(νee−

) (νee+

)Le = 1 Le = −1

(Historically) the electron neutrinos are emitted in nuclear-βdecays (via weak interactions):

(Z,A)→ (Z + 1, A) + e− + νe

(Z + 1, A)→ (Z,A) + e+ + νe

and in neutron decays:

n→ p+ e− + νe

13/21 Particle Physics - lecture 1

Classification of particles and forcesElementary particles and fundamental forcesLeptons and conservation lawsHadrons (Baryons and Mesons)

Leptons and conservation lawsThe first generation

(νee−

) (νee+

)Le = 1 Le = −1

(Historically) the electron neutrinos are emitted in nuclear-βdecays (via weak interactions):

(Z,A)→ (Z + 1, A) + e− + νe

(Z + 1, A)→ (Z,A) + e+ + νe

and in neutron decays:

n→ p+ e− + νe

13/21 Particle Physics - lecture 1

Classification of particles and forcesElementary particles and fundamental forcesLeptons and conservation lawsHadrons (Baryons and Mesons)

Leptons and conservation lawsThe first generation

Neutrinos are usually not detected experimentally.Their existenceis inferred by Pauli to satisfy the energy and angular momentumconservation.The neutrino mass is inferred from observed electron energies.Thebest results from Tritium decay:

H3 → He3 + e− + νe

(pnn→ ppn +e− + νe)which gave an experimental bound on theneutrino mass: mνe < 3 eV/c2 ∼ 6× 10−6me (i.e. mνe me)and thus often assumed to be zero.Note that neutrino oscillations require that mν 6= 0.

14/21 Particle Physics - lecture 1

Classification of particles and forcesElementary particles and fundamental forcesLeptons and conservation lawsHadrons (Baryons and Mesons)

Leptons and conservation lawsThe first generation

Neutrinos are usually not detected experimentally.Their existenceis inferred by Pauli to satisfy the energy and angular momentumconservation.The neutrino mass is inferred from observed electron energies.Thebest results from Tritium decay:

H3 → He3 + e− + νe

(pnn→ ppn +e− + νe)which gave an experimental bound on theneutrino mass: mνe < 3 eV/c2 ∼ 6× 10−6me (i.e. mνe me)and thus often assumed to be zero.Note that neutrino oscillations require that mν 6= 0.

14/21 Particle Physics - lecture 1

Classification of particles and forcesElementary particles and fundamental forcesLeptons and conservation lawsHadrons (Baryons and Mesons)

Leptons and conservation lawsThe first generation

Neutrinos are usually not detected experimentally.Their existenceis inferred by Pauli to satisfy the energy and angular momentumconservation.The neutrino mass is inferred from observed electron energies.Thebest results from Tritium decay:

H3 → He3 + e− + νe

(pnn→ ppn +e− + νe)which gave an experimental bound on theneutrino mass: mνe < 3 eV/c2 ∼ 6× 10−6me (i.e. mνe me)and thus often assumed to be zero.Note that neutrino oscillations require that mν 6= 0.

14/21 Particle Physics - lecture 1

Classification of particles and forcesElementary particles and fundamental forcesLeptons and conservation lawsHadrons (Baryons and Mesons)

Leptons and conservation lawsThe first generation

Neutrinos are usually not detected experimentally.Their existenceis inferred by Pauli to satisfy the energy and angular momentumconservation.The neutrino mass is inferred from observed electron energies.Thebest results from Tritium decay:

H3 → He3 + e− + νe

(pnn→ ppn +e− + νe)which gave an experimental bound on theneutrino mass: mνe < 3 eV/c2 ∼ 6× 10−6me (i.e. mνe me)and thus often assumed to be zero.Note that neutrino oscillations require that mν 6= 0.

14/21 Particle Physics - lecture 1

Classification of particles and forcesElementary particles and fundamental forcesLeptons and conservation lawsHadrons (Baryons and Mesons)

Leptons and conservation lawsThe first generation

Neutrinos are usually not detected experimentally.Their existenceis inferred by Pauli to satisfy the energy and angular momentumconservation.The neutrino mass is inferred from observed electron energies.Thebest results from Tritium decay:

H3 → He3 + e− + νe

(pnn→ ppn +e− + νe)which gave an experimental bound on theneutrino mass: mνe < 3 eV/c2 ∼ 6× 10−6me (i.e. mνe me)and thus often assumed to be zero.Note that neutrino oscillations require that mν 6= 0.

14/21 Particle Physics - lecture 1

Classification of particles and forcesElementary particles and fundamental forcesLeptons and conservation lawsHadrons (Baryons and Mesons)

Leptons and conservation lawsThe first generation

Neutrinos are usually not detected experimentally.Their existenceis inferred by Pauli to satisfy the energy and angular momentumconservation.The neutrino mass is inferred from observed electron energies.Thebest results from Tritium decay:

H3 → He3 + e− + νe

(pnn→ ppn +e− + νe)which gave an experimental bound on theneutrino mass: mνe < 3 eV/c2 ∼ 6× 10−6me (i.e. mνe me)and thus often assumed to be zero.Note that neutrino oscillations require that mν 6= 0.

14/21 Particle Physics - lecture 1

Classification of particles and forcesElementary particles and fundamental forcesLeptons and conservation lawsHadrons (Baryons and Mesons)

Leptons and conservation lawsThe first generation

Neutrinos are usually not detected experimentally.Their existenceis inferred by Pauli to satisfy the energy and angular momentumconservation.The neutrino mass is inferred from observed electron energies.Thebest results from Tritium decay:

H3 → He3 + e− + νe

(pnn→ ppn +e− + νe)which gave an experimental bound on theneutrino mass: mνe < 3 eV/c2 ∼ 6× 10−6me (i.e. mνe me)and thus often assumed to be zero.Note that neutrino oscillations require that mν 6= 0.

14/21 Particle Physics - lecture 1

Classification of particles and forcesElementary particles and fundamental forcesLeptons and conservation lawsHadrons (Baryons and Mesons)

Leptons and conservation lawsNeutrino detection

We use the inverse-β decay:

νe + n→ e− + p

orνe + p→ e+ + n

to detect neutrinos emitted in β-decay. This experiment is typicallyvery difficult because the cross-section for this reaction is verysmall.For solar neutrinos the energy of a neutrino is of orderEν ∼ 1 MeV, and this cross-section is σ ∼ 10−47 m2 on protons.The mean-free-path of these neutrinos (l = 1/(σρ) ∼ 2 light yearsin iron).However with massive detectors this can be done (∼ 5interactions/sec in 1m3 of Fe)

15/21 Particle Physics - lecture 1

Classification of particles and forcesElementary particles and fundamental forcesLeptons and conservation lawsHadrons (Baryons and Mesons)

Leptons and conservation lawsNeutrino detection

We use the inverse-β decay:

νe + n→ e− + p

orνe + p→ e+ + n

to detect neutrinos emitted in β-decay. This experiment is typicallyvery difficult because the cross-section for this reaction is verysmall.For solar neutrinos the energy of a neutrino is of orderEν ∼ 1 MeV, and this cross-section is σ ∼ 10−47 m2 on protons.The mean-free-path of these neutrinos (l = 1/(σρ) ∼ 2 light yearsin iron).However with massive detectors this can be done (∼ 5interactions/sec in 1m3 of Fe)

15/21 Particle Physics - lecture 1

Classification of particles and forcesElementary particles and fundamental forcesLeptons and conservation lawsHadrons (Baryons and Mesons)

Leptons and conservation lawsNeutrino detection

We use the inverse-β decay:

νe + n→ e− + p

orνe + p→ e+ + n

to detect neutrinos emitted in β-decay. This experiment is typicallyvery difficult because the cross-section for this reaction is verysmall.For solar neutrinos the energy of a neutrino is of orderEν ∼ 1 MeV, and this cross-section is σ ∼ 10−47 m2 on protons.The mean-free-path of these neutrinos (l = 1/(σρ) ∼ 2 light yearsin iron).However with massive detectors this can be done (∼ 5interactions/sec in 1m3 of Fe)

15/21 Particle Physics - lecture 1

Classification of particles and forcesElementary particles and fundamental forcesLeptons and conservation lawsHadrons (Baryons and Mesons)

Leptons and conservation lawsNeutrino detection

We use the inverse-β decay:

νe + n→ e− + p

orνe + p→ e+ + n

to detect neutrinos emitted in β-decay. This experiment is typicallyvery difficult because the cross-section for this reaction is verysmall.For solar neutrinos the energy of a neutrino is of orderEν ∼ 1 MeV, and this cross-section is σ ∼ 10−47 m2 on protons.The mean-free-path of these neutrinos (l = 1/(σρ) ∼ 2 light yearsin iron).However with massive detectors this can be done (∼ 5interactions/sec in 1m3 of Fe)

15/21 Particle Physics - lecture 1

Classification of particles and forcesElementary particles and fundamental forcesLeptons and conservation lawsHadrons (Baryons and Mesons)

Leptons and conservation lawsNeutrino detection

We use the inverse-β decay:

νe + n→ e− + p

orνe + p→ e+ + n

to detect neutrinos emitted in β-decay. This experiment is typicallyvery difficult because the cross-section for this reaction is verysmall.For solar neutrinos the energy of a neutrino is of orderEν ∼ 1 MeV, and this cross-section is σ ∼ 10−47 m2 on protons.The mean-free-path of these neutrinos (l = 1/(σρ) ∼ 2 light yearsin iron).However with massive detectors this can be done (∼ 5interactions/sec in 1m3 of Fe)

15/21 Particle Physics - lecture 1

Classification of particles and forcesElementary particles and fundamental forcesLeptons and conservation lawsHadrons (Baryons and Mesons)

Leptons and conservation lawsNeutrino detection

We use the inverse-β decay:

νe + n→ e− + p

orνe + p→ e+ + n

to detect neutrinos emitted in β-decay. This experiment is typicallyvery difficult because the cross-section for this reaction is verysmall.For solar neutrinos the energy of a neutrino is of orderEν ∼ 1 MeV, and this cross-section is σ ∼ 10−47 m2 on protons.The mean-free-path of these neutrinos (l = 1/(σρ) ∼ 2 light yearsin iron).However with massive detectors this can be done (∼ 5interactions/sec in 1m3 of Fe)

15/21 Particle Physics - lecture 1

Classification of particles and forcesElementary particles and fundamental forcesLeptons and conservation lawsHadrons (Baryons and Mesons)

Leptons and conservation lawsNeutrino detection

We use the inverse-β decay:

νe + n→ e− + p

orνe + p→ e+ + n

to detect neutrinos emitted in β-decay. This experiment is typicallyvery difficult because the cross-section for this reaction is verysmall.For solar neutrinos the energy of a neutrino is of orderEν ∼ 1 MeV, and this cross-section is σ ∼ 10−47 m2 on protons.The mean-free-path of these neutrinos (l = 1/(σρ) ∼ 2 light yearsin iron).However with massive detectors this can be done (∼ 5interactions/sec in 1m3 of Fe)

15/21 Particle Physics - lecture 1

Classification of particles and forcesElementary particles and fundamental forcesLeptons and conservation lawsHadrons (Baryons and Mesons)

More generationsMore generations

(νµµ−

),

(νττ−

)Lµ = 1 Lτ = 1

Le = Lτ = 0 Le = Lµ = 0

The charged leptons have masses:

me = 0.511 MeV/c2

mµ = 106 MeV/c2

mτ = 1777 MeV/c2

(1)

16/21 Particle Physics - lecture 1

Classification of particles and forcesElementary particles and fundamental forcesLeptons and conservation lawsHadrons (Baryons and Mesons)

More generationsMore generations

(νµµ−

),

(νττ−

)Lµ = 1 Lτ = 1

Le = Lτ = 0 Le = Lµ = 0

The charged leptons have masses:

me = 0.511 MeV/c2

mµ = 106 MeV/c2

mτ = 1777 MeV/c2

(1)

16/21 Particle Physics - lecture 1

Classification of particles and forcesElementary particles and fundamental forcesLeptons and conservation lawsHadrons (Baryons and Mesons)

More generationsMore generations

and life times:

τe > 1034s(stable)

τµ = 2.2× 10−6s

ττ = 3× 10−13s

(2)

Electromagnetic interactions of leptons:EM interactions areidentical to those of the electron provided the masses are takeninto account, for example the µ− is much more penetrating thanthe electron because it is heavier.

17/21 Particle Physics - lecture 1

Classification of particles and forcesElementary particles and fundamental forcesLeptons and conservation lawsHadrons (Baryons and Mesons)

More generationsMore generations

and life times:

τe > 1034s(stable)

τµ = 2.2× 10−6s

ττ = 3× 10−13s

(2)

Electromagnetic interactions of leptons:EM interactions areidentical to those of the electron provided the masses are takeninto account, for example the µ− is much more penetrating thanthe electron because it is heavier.

17/21 Particle Physics - lecture 1

Classification of particles and forcesElementary particles and fundamental forcesLeptons and conservation lawsHadrons (Baryons and Mesons)

More generationsMore generations

and life times:

τe > 1034s(stable)

τµ = 2.2× 10−6s

ττ = 3× 10−13s

(2)

Electromagnetic interactions of leptons:EM interactions areidentical to those of the electron provided the masses are takeninto account, for example the µ− is much more penetrating thanthe electron because it is heavier.

17/21 Particle Physics - lecture 1

Classification of particles and forcesElementary particles and fundamental forcesLeptons and conservation lawsHadrons (Baryons and Mesons)

More generationsMore generations

and life times:

τe > 1034s(stable)

τµ = 2.2× 10−6s

ττ = 3× 10−13s

(2)

Electromagnetic interactions of leptons:EM interactions areidentical to those of the electron provided the masses are takeninto account, for example the µ− is much more penetrating thanthe electron because it is heavier.

17/21 Particle Physics - lecture 1

Classification of particles and forcesElementary particles and fundamental forcesLeptons and conservation lawsHadrons (Baryons and Mesons)

Hadrons (Baryons and Mesons)Quarks

Quarks are fundamental spin-half fermions. They have weak,strong and EM interactions (c.f. leptons have no stronginteractions).Quarks are not observed as isolated free particles, instead theyexist in multi-quark bound states, known as hadrons.There are six types of quarks (quark flavours) grouped in threegenerations:(

ud

),

(cs

),

(tb

), with charges

(+2

3e−1

3e

)they are respectively up (u) down (d) charm (c) strange (s) top (t)bottom (b).

18/21 Particle Physics - lecture 1

Classification of particles and forcesElementary particles and fundamental forcesLeptons and conservation lawsHadrons (Baryons and Mesons)

Hadrons (Baryons and Mesons)Quarks

Quarks are fundamental spin-half fermions. They have weak,strong and EM interactions (c.f. leptons have no stronginteractions).Quarks are not observed as isolated free particles, instead theyexist in multi-quark bound states, known as hadrons.There are six types of quarks (quark flavours) grouped in threegenerations:(

ud

),

(cs

),

(tb

), with charges

(+2

3e−1

3e

)they are respectively up (u) down (d) charm (c) strange (s) top (t)bottom (b).

18/21 Particle Physics - lecture 1

Classification of particles and forcesElementary particles and fundamental forcesLeptons and conservation lawsHadrons (Baryons and Mesons)

Hadrons (Baryons and Mesons)Quarks

Quarks are fundamental spin-half fermions. They have weak,strong and EM interactions (c.f. leptons have no stronginteractions).Quarks are not observed as isolated free particles, instead theyexist in multi-quark bound states, known as hadrons.There are six types of quarks (quark flavours) grouped in threegenerations:(

ud

),

(cs

),

(tb

), with charges

(+2

3e−1

3e

)they are respectively up (u) down (d) charm (c) strange (s) top (t)bottom (b).

18/21 Particle Physics - lecture 1

Classification of particles and forcesElementary particles and fundamental forcesLeptons and conservation lawsHadrons (Baryons and Mesons)

Hadrons (Baryons and Mesons)Quarks

Quarks are fundamental spin-half fermions. They have weak,strong and EM interactions (c.f. leptons have no stronginteractions).Quarks are not observed as isolated free particles, instead theyexist in multi-quark bound states, known as hadrons.There are six types of quarks (quark flavours) grouped in threegenerations:(

ud

),

(cs

),

(tb

), with charges

(+2

3e−1

3e

)they are respectively up (u) down (d) charm (c) strange (s) top (t)bottom (b).

18/21 Particle Physics - lecture 1

Classification of particles and forcesElementary particles and fundamental forcesLeptons and conservation lawsHadrons (Baryons and Mesons)

Hadrons (Baryons and Mesons)Quarks

Quarks are fundamental spin-half fermions. They have weak,strong and EM interactions (c.f. leptons have no stronginteractions).Quarks are not observed as isolated free particles, instead theyexist in multi-quark bound states, known as hadrons.There are six types of quarks (quark flavours) grouped in threegenerations:(

ud

),

(cs

),

(tb

), with charges

(+2

3e−1

3e

)they are respectively up (u) down (d) charm (c) strange (s) top (t)bottom (b).

18/21 Particle Physics - lecture 1

Classification of particles and forcesElementary particles and fundamental forcesLeptons and conservation lawsHadrons (Baryons and Mesons)

Hadrons (Baryons and Mesons)Quarks

There are six anti-quarks(ud

),

(cs

),

(tb

), with charges

(−2

3e+1

3e

)The masses of these quarks are inferred from properties ofhadrons.Their approximate masses are respectively (in GeV/c2):(

0.0030.006

),

(1.30.1

),

(1754.3

)The top quark is too heavy to form stable hadrons, and its mass isinferred from its decay products.These masses cannot be observeddirectly because they are never isolated as free particles.

19/21 Particle Physics - lecture 1

Classification of particles and forcesElementary particles and fundamental forcesLeptons and conservation lawsHadrons (Baryons and Mesons)

Hadrons (Baryons and Mesons)Quarks

There are six anti-quarks(ud

),

(cs

),

(tb

), with charges

(−2

3e+1

3e

)The masses of these quarks are inferred from properties ofhadrons.Their approximate masses are respectively (in GeV/c2):(

0.0030.006

),

(1.30.1

),

(1754.3

)The top quark is too heavy to form stable hadrons, and its mass isinferred from its decay products.These masses cannot be observeddirectly because they are never isolated as free particles.

19/21 Particle Physics - lecture 1

Classification of particles and forcesElementary particles and fundamental forcesLeptons and conservation lawsHadrons (Baryons and Mesons)

Hadrons (Baryons and Mesons)Quarks

There are six anti-quarks(ud

),

(cs

),

(tb

), with charges

(−2

3e+1

3e

)The masses of these quarks are inferred from properties ofhadrons.Their approximate masses are respectively (in GeV/c2):(

0.0030.006

),

(1.30.1

),

(1754.3

)The top quark is too heavy to form stable hadrons, and its mass isinferred from its decay products.These masses cannot be observeddirectly because they are never isolated as free particles.

19/21 Particle Physics - lecture 1

Classification of particles and forcesElementary particles and fundamental forcesLeptons and conservation lawsHadrons (Baryons and Mesons)

Hadrons (Baryons and Mesons)Quarks

There are six anti-quarks(ud

),

(cs

),

(tb

), with charges

(−2

3e+1

3e

)The masses of these quarks are inferred from properties ofhadrons.Their approximate masses are respectively (in GeV/c2):(

0.0030.006

),

(1.30.1

),

(1754.3

)The top quark is too heavy to form stable hadrons, and its mass isinferred from its decay products.These masses cannot be observeddirectly because they are never isolated as free particles.

19/21 Particle Physics - lecture 1

Classification of particles and forcesElementary particles and fundamental forcesLeptons and conservation lawsHadrons (Baryons and Mesons)

Hadrons (Baryons and Mesons)Quarks

There are six anti-quarks(ud

),

(cs

),

(tb

), with charges

(−2

3e+1

3e

)The masses of these quarks are inferred from properties ofhadrons.Their approximate masses are respectively (in GeV/c2):(

0.0030.006

),

(1.30.1

),

(1754.3

)The top quark is too heavy to form stable hadrons, and its mass isinferred from its decay products.These masses cannot be observeddirectly because they are never isolated as free particles.

19/21 Particle Physics - lecture 1

Classification of particles and forcesElementary particles and fundamental forcesLeptons and conservation lawsHadrons (Baryons and Mesons)

Hadrons (Baryons and Mesons)Hadrons

Hadrons are composed particles (not elementary) with integercharge.They can either be fermions or bosons. There are morethan 200 known types of hadrons and they exist in two types:Baryons (and anti-baryons): are qqq bound states. Examplesinclude:

Proton (p = uud) with mass 938 MeV/c2 and charge +1eand spin-1/2.Neutron (n = udd) with mass 940 MeV/c2 and neutral chargeand spin-1/2.Anti-proton (uud) with same mass as proton and charge −1eand spin-1/2.Ω− (Omega particle = sss) with electric charge −1e andmass 1672 MeV/c2 and spin 3/2.

and many others.20/21 Particle Physics - lecture 1

Classification of particles and forcesElementary particles and fundamental forcesLeptons and conservation lawsHadrons (Baryons and Mesons)

Hadrons (Baryons and Mesons)Hadrons

Hadrons are composed particles (not elementary) with integercharge.They can either be fermions or bosons. There are morethan 200 known types of hadrons and they exist in two types:Baryons (and anti-baryons): are qqq bound states. Examplesinclude:

Proton (p = uud) with mass 938 MeV/c2 and charge +1eand spin-1/2.Neutron (n = udd) with mass 940 MeV/c2 and neutral chargeand spin-1/2.Anti-proton (uud) with same mass as proton and charge −1eand spin-1/2.Ω− (Omega particle = sss) with electric charge −1e andmass 1672 MeV/c2 and spin 3/2.

and many others.20/21 Particle Physics - lecture 1

Classification of particles and forcesElementary particles and fundamental forcesLeptons and conservation lawsHadrons (Baryons and Mesons)

Hadrons (Baryons and Mesons)Hadrons

Hadrons are composed particles (not elementary) with integercharge.They can either be fermions or bosons. There are morethan 200 known types of hadrons and they exist in two types:Baryons (and anti-baryons): are qqq bound states. Examplesinclude:

Proton (p = uud) with mass 938 MeV/c2 and charge +1eand spin-1/2.Neutron (n = udd) with mass 940 MeV/c2 and neutral chargeand spin-1/2.Anti-proton (uud) with same mass as proton and charge −1eand spin-1/2.Ω− (Omega particle = sss) with electric charge −1e andmass 1672 MeV/c2 and spin 3/2.

and many others.20/21 Particle Physics - lecture 1

Classification of particles and forcesElementary particles and fundamental forcesLeptons and conservation lawsHadrons (Baryons and Mesons)

Hadrons (Baryons and Mesons)Hadrons

Hadrons are composed particles (not elementary) with integercharge.They can either be fermions or bosons. There are morethan 200 known types of hadrons and they exist in two types:Baryons (and anti-baryons): are qqq bound states. Examplesinclude:

Proton (p = uud) with mass 938 MeV/c2 and charge +1eand spin-1/2.Neutron (n = udd) with mass 940 MeV/c2 and neutral chargeand spin-1/2.Anti-proton (uud) with same mass as proton and charge −1eand spin-1/2.Ω− (Omega particle = sss) with electric charge −1e andmass 1672 MeV/c2 and spin 3/2.

and many others.20/21 Particle Physics - lecture 1

Classification of particles and forcesElementary particles and fundamental forcesLeptons and conservation lawsHadrons (Baryons and Mesons)

Hadrons (Baryons and Mesons)Hadrons

Hadrons are composed particles (not elementary) with integercharge.They can either be fermions or bosons. There are morethan 200 known types of hadrons and they exist in two types:Baryons (and anti-baryons): are qqq bound states. Examplesinclude:

Proton (p = uud) with mass 938 MeV/c2 and charge +1eand spin-1/2.Neutron (n = udd) with mass 940 MeV/c2 and neutral chargeand spin-1/2.Anti-proton (uud) with same mass as proton and charge −1eand spin-1/2.Ω− (Omega particle = sss) with electric charge −1e andmass 1672 MeV/c2 and spin 3/2.

and many others.20/21 Particle Physics - lecture 1

Classification of particles and forcesElementary particles and fundamental forcesLeptons and conservation lawsHadrons (Baryons and Mesons)

Hadrons (Baryons and Mesons)Hadrons

Hadrons are composed particles (not elementary) with integercharge.They can either be fermions or bosons. There are morethan 200 known types of hadrons and they exist in two types:Baryons (and anti-baryons): are qqq bound states. Examplesinclude:

Proton (p = uud) with mass 938 MeV/c2 and charge +1eand spin-1/2.Neutron (n = udd) with mass 940 MeV/c2 and neutral chargeand spin-1/2.Anti-proton (uud) with same mass as proton and charge −1eand spin-1/2.Ω− (Omega particle = sss) with electric charge −1e andmass 1672 MeV/c2 and spin 3/2.

and many others.20/21 Particle Physics - lecture 1

Classification of particles and forcesElementary particles and fundamental forcesLeptons and conservation lawsHadrons (Baryons and Mesons)

Hadrons (Baryons and Mesons)Hadrons

Hadrons are composed particles (not elementary) with integercharge.They can either be fermions or bosons. There are morethan 200 known types of hadrons and they exist in two types:Baryons (and anti-baryons): are qqq bound states. Examplesinclude:

Proton (p = uud) with mass 938 MeV/c2 and charge +1eand spin-1/2.Neutron (n = udd) with mass 940 MeV/c2 and neutral chargeand spin-1/2.Anti-proton (uud) with same mass as proton and charge −1eand spin-1/2.Ω− (Omega particle = sss) with electric charge −1e andmass 1672 MeV/c2 and spin 3/2.

and many others.20/21 Particle Physics - lecture 1

Classification of particles and forcesElementary particles and fundamental forcesLeptons and conservation lawsHadrons (Baryons and Mesons)

Hadrons (Baryons and Mesons)Hadrons

Hadrons are composed particles (not elementary) with integercharge.They can either be fermions or bosons. There are morethan 200 known types of hadrons and they exist in two types:Baryons (and anti-baryons): are qqq bound states. Examplesinclude:

Proton (p = uud) with mass 938 MeV/c2 and charge +1eand spin-1/2.Neutron (n = udd) with mass 940 MeV/c2 and neutral chargeand spin-1/2.Anti-proton (uud) with same mass as proton and charge −1eand spin-1/2.Ω− (Omega particle = sss) with electric charge −1e andmass 1672 MeV/c2 and spin 3/2.

and many others.20/21 Particle Physics - lecture 1

Classification of particles and forcesElementary particles and fundamental forcesLeptons and conservation lawsHadrons (Baryons and Mesons)

Hadrons (Baryons and Mesons)Hadrons

Hadrons are composed particles (not elementary) with integercharge.They can either be fermions or bosons. There are morethan 200 known types of hadrons and they exist in two types:Baryons (and anti-baryons): are qqq bound states. Examplesinclude:

Proton (p = uud) with mass 938 MeV/c2 and charge +1eand spin-1/2.Neutron (n = udd) with mass 940 MeV/c2 and neutral chargeand spin-1/2.Anti-proton (uud) with same mass as proton and charge −1eand spin-1/2.Ω− (Omega particle = sss) with electric charge −1e andmass 1672 MeV/c2 and spin 3/2.

and many others.20/21 Particle Physics - lecture 1

Classification of particles and forcesElementary particles and fundamental forcesLeptons and conservation lawsHadrons (Baryons and Mesons)

Hadrons (Baryons and Mesons)Hadrons

Since there are three spin-half constituents in baryons they mustbe fermions.Mesons are qiqj bound states.Examples include:

Pion (π+ = ud) with mass 140 MeV/c2 and charge +1e andspin-0.

Neutral-pion (π0 = uu or dd) with mass 135 MeV/c2 andneutral charge and spin-0.

B-zero (B0 = db) with mass 5.279 GeV/c2 and neutral chargeand spin-0.

Since Mesons are composed of two quarks they are bosons ofspin-0 or spin-1.

21/21 Particle Physics - lecture 1

Classification of particles and forcesElementary particles and fundamental forcesLeptons and conservation lawsHadrons (Baryons and Mesons)

Hadrons (Baryons and Mesons)Hadrons

Since there are three spin-half constituents in baryons they mustbe fermions.Mesons are qiqj bound states.Examples include:

Pion (π+ = ud) with mass 140 MeV/c2 and charge +1e andspin-0.

Neutral-pion (π0 = uu or dd) with mass 135 MeV/c2 andneutral charge and spin-0.

B-zero (B0 = db) with mass 5.279 GeV/c2 and neutral chargeand spin-0.

Since Mesons are composed of two quarks they are bosons ofspin-0 or spin-1.

21/21 Particle Physics - lecture 1

Classification of particles and forcesElementary particles and fundamental forcesLeptons and conservation lawsHadrons (Baryons and Mesons)

Hadrons (Baryons and Mesons)Hadrons

Since there are three spin-half constituents in baryons they mustbe fermions.Mesons are qiqj bound states.Examples include:

Pion (π+ = ud) with mass 140 MeV/c2 and charge +1e andspin-0.

Neutral-pion (π0 = uu or dd) with mass 135 MeV/c2 andneutral charge and spin-0.

B-zero (B0 = db) with mass 5.279 GeV/c2 and neutral chargeand spin-0.

Since Mesons are composed of two quarks they are bosons ofspin-0 or spin-1.

21/21 Particle Physics - lecture 1

Classification of particles and forcesElementary particles and fundamental forcesLeptons and conservation lawsHadrons (Baryons and Mesons)

Hadrons (Baryons and Mesons)Hadrons

Since there are three spin-half constituents in baryons they mustbe fermions.Mesons are qiqj bound states.Examples include:

Pion (π+ = ud) with mass 140 MeV/c2 and charge +1e andspin-0.

Neutral-pion (π0 = uu or dd) with mass 135 MeV/c2 andneutral charge and spin-0.

B-zero (B0 = db) with mass 5.279 GeV/c2 and neutral chargeand spin-0.

Since Mesons are composed of two quarks they are bosons ofspin-0 or spin-1.

21/21 Particle Physics - lecture 1

Classification of particles and forcesElementary particles and fundamental forcesLeptons and conservation lawsHadrons (Baryons and Mesons)

Hadrons (Baryons and Mesons)Hadrons

Since there are three spin-half constituents in baryons they mustbe fermions.Mesons are qiqj bound states.Examples include:

Pion (π+ = ud) with mass 140 MeV/c2 and charge +1e andspin-0.

Neutral-pion (π0 = uu or dd) with mass 135 MeV/c2 andneutral charge and spin-0.

B-zero (B0 = db) with mass 5.279 GeV/c2 and neutral chargeand spin-0.

Since Mesons are composed of two quarks they are bosons ofspin-0 or spin-1.

21/21 Particle Physics - lecture 1

Classification of particles and forcesElementary particles and fundamental forcesLeptons and conservation lawsHadrons (Baryons and Mesons)

Hadrons (Baryons and Mesons)Hadrons

Since there are three spin-half constituents in baryons they mustbe fermions.Mesons are qiqj bound states.Examples include:

Pion (π+ = ud) with mass 140 MeV/c2 and charge +1e andspin-0.

Neutral-pion (π0 = uu or dd) with mass 135 MeV/c2 andneutral charge and spin-0.

B-zero (B0 = db) with mass 5.279 GeV/c2 and neutral chargeand spin-0.

Since Mesons are composed of two quarks they are bosons ofspin-0 or spin-1.

21/21 Particle Physics - lecture 1