Difference between revisions of "Feynman Diagram"
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===Constructing a Feynman Diagram=== | ===Constructing a Feynman Diagram=== | ||
| − | : '''Feynman Diagrams''' can be constructed from the equations representing a [[Subatomic Particle|particle]] [[Fundamental | + | : '''Feynman Diagrams''' can be constructed from the equations representing a [[Subatomic Particle|particle]] [[Fundamental Interactions|interaction]]. |
: The [[Subatomic Particle|particles]] at the start of the [[Nuclear Equation|equation]] are written at the bottom of the '''Feynman diagram''' while the [[product]]s are written at the top. | : The [[Subatomic Particle|particles]] at the start of the [[Nuclear Equation|equation]] are written at the bottom of the '''Feynman diagram''' while the [[product]]s are written at the top. | ||
| + | {| class="wikitable" | ||
| + | |+[[Electron Capture]] | ||
| + | | style="height:20px; width:200px; text-align:center;" | | ||
| + | <math>p + e^-</math> | ||
| + | | style="height:20px; width:200px; text-align:center;" | | ||
| + | <math>p + e^- \rightarrow n + \nu_e</math> | ||
| + | | style="height:20px; width:200px; text-align:center;" | | ||
| + | <math>p + e^- \xrightarrow{W^+} n + \nu_e</math> | ||
| + | |- | ||
| + | |[[File:FeynmanDiagramElectronCapturePt1.png|center|200px]] | ||
| + | |[[File:FeynmanDiagramElectronCapturePt2.png|center|200px]] | ||
| + | |[[File:FeynmanDiagramElectronCapture.png|center|200px]] | ||
| + | |- | ||
| + | | style="height:20px; width:200px; text-align:center;" |The [[Subatomic Particle|particles]] prior to the [[Fundamental Interactions|interaction]] are drawn first at the bottom of the '''Feynman diagram'''. Both the [[proton]] and [[electron]] in this '''diagram''' are drawn with a steep [[gradient]] to show their relatively small [[velocity]] compared to the [[Speed of Light|speed of light]]. | ||
| + | | style="height:20px; width:200px; text-align:center;" |The [[Subatomic Particle|particles]] after the [[Fundamental Interactions|interaction]] are drawn at the top of the '''Feynman diagram'''. It should be recognised that [[Conservation of Baryon Number|baryon conservation]] means a [[baryon]] becomes another [[baryon]] and [[Conservation of Lepton Number|lepton conservation]] means that a [[lepton]] is transformed from one type of [[lepton]] into another. The [[Electron-neutrino|electron-neutrino]] in this [[diagram]] is drawn with a shallow [[gradient]] to show that it travels close to the [[Speed of Light|speed of light]]. | ||
| + | | style="height:20px; width:200px; text-align:center;" |Finally the [[boson]] mediating the [[Fundamental Interactions|interaction]] is added as a [[wave]] between the two points of [[Fundamental Interactions|interaction]]. In this case a [[proton]] loses its [[Positive Charge|positive charge]] therefore it is carried away to the [[electron]] via the [[W-boson|W<sup>+</sup> boson]] transforming the [[electron]] into an [[Electron-neutrino|electron-neutrino]]. | ||
| + | |} | ||
| + | |||
| + | {| class="wikitable" | ||
| + | |+Neutron Decay | ||
| + | | style="height:20px; width:200px; text-align:center;" | | ||
| + | <math>n \rightarrow</math> | ||
| + | | style="height:20px; width:200px; text-align:center;" | | ||
| + | <math>n \rightarrow p + \beta^- + \bar\nu_e</math> | ||
| + | | style="height:20px; width:200px; text-align:center;" | | ||
| + | <math>n \xrightarrow{W^-} p + \beta^- + \bar\nu_e</math> | ||
| + | |- | ||
| + | |[[File:FeynmanDiagramNeutronDecayPt1.png|center|200px]] | ||
| + | |[[File:FeynmanDiagramNeutronDecayPt2.png|center|200px]] | ||
| + | |[[File:FeynmanDiagramNeutronDecay.png|center|200px]] | ||
| + | |- | ||
| + | | style="height:20px; width:200px; text-align:center;" |The [[Subatomic Particle|particles]] prior to the [[Fundamental Interactions|interaction]] are drawn first at the bottom of the '''Feynman diagram'''. The [[neutron]] in this '''diagram''' is drawn with a steep [[gradient]] to show it has a relatively small [[velocity]] compared to the [[Speed of Light|speed of light]]. | ||
| + | | style="height:20px; width:200px; text-align:center;" |The [[Subatomic Particle|particles]] after the [[Fundamental Interactions|interaction]] are drawn at the top of the '''Feynman diagram'''. It should be recognised that [[Conservation of Baryon Number|baryon conservation]] means a [[baryon]] becomes another [[baryon]] and [[Conservation of Lepton Number|lepton conservation]] means that if a [[lepton]] comes into existence there must also be an [[antilepton]]. The [[antielectron-neutrino|antielectron-neutrino]] in this [[diagram]] is drawn with a shallow [[gradient]] to show that it travels close to the [[Speed of Light|speed of light]]. | ||
| + | | style="height:20px; width:200px; text-align:center;" |Finally the [[boson]] mediating the [[Fundamental Interactions|interaction]] is added as a [[wave]] between the two points of [[Fundamental Interactions|interaction]]. In this case a [[neutron]] loses a [[Negative Charge|negative charge]] therefore it is carried away to produce the [[electron]] via the [[W-boson|W<sup>-</sup> boson]] also producing an [[antielectron-neutrino]]. | ||
| + | |} | ||
===Examples=== | ===Examples=== | ||
Latest revision as of 15:58, 8 March 2021
Contents
Key Stage 5
Meaning
A Feynman diagram is a type of graph used to represent the interactions between subatomic particles.
About Feynman Diagrams
- Feynman diagrams have time on the y-axis and space on the z-axis.
- Feynman diagrams are used to simplify complex equations used to represent subatomic particle interactions.
- Particles with a high velocity are seen as having shallow gradients on a Feynman diagram since they travel a large distance in space over a short duration of time.
Constructing a Feynman Diagram
- Feynman Diagrams can be constructed from the equations representing a particle interaction.
- The particles at the start of the equation are written at the bottom of the Feynman diagram while the products are written at the top.
|
\(p + e^-\) |
\(p + e^- \rightarrow n + \nu_e\) |
\(p + e^- \xrightarrow{W^+} n + \nu_e\) |
 |
 |
 |
| The particles prior to the interaction are drawn first at the bottom of the Feynman diagram. Both the proton and electron in this diagram are drawn with a steep gradient to show their relatively small velocity compared to the speed of light. | The particles after the interaction are drawn at the top of the Feynman diagram. It should be recognised that baryon conservation means a baryon becomes another baryon and lepton conservation means that a lepton is transformed from one type of lepton into another. The electron-neutrino in this diagram is drawn with a shallow gradient to show that it travels close to the speed of light. | Finally the boson mediating the interaction is added as a wave between the two points of interaction. In this case a proton loses its positive charge therefore it is carried away to the electron via the W+ boson transforming the electron into an electron-neutrino. |
|
\(n \rightarrow\) |
\(n \rightarrow p + \beta^- + \bar\nu_e\) |
\(n \xrightarrow{W^-} p + \beta^- + \bar\nu_e\) |
 |
 |
 |
| The particles prior to the interaction are drawn first at the bottom of the Feynman diagram. The neutron in this diagram is drawn with a steep gradient to show it has a relatively small velocity compared to the speed of light. | The particles after the interaction are drawn at the top of the Feynman diagram. It should be recognised that baryon conservation means a baryon becomes another baryon and lepton conservation means that if a lepton comes into existence there must also be an antilepton. The antielectron-neutrino in this diagram is drawn with a shallow gradient to show that it travels close to the speed of light. | Finally the boson mediating the interaction is added as a wave between the two points of interaction. In this case a neutron loses a negative charge therefore it is carried away to produce the electron via the W- boson also producing an antielectron-neutrino. |
Examples
 |
|
| This Feynman diagram shows the electromagnetic interaction between two protons via the virtual photon. | This Feynman diagram shows the weak interaction in which a neutron decays into a proton.
\(n \rightarrow p + \beta^- + \bar\nu_e\) |
|
 |
| This Feynman diagram shows the weak interaction in which a proton captures an electron to become a neutron.
\(p + e^- \rightarrow n + \nu_e\) |
This Feynman diagram shows the weak interaction in which an up-quark decays into a down-quark, which is observed as a proton decaying into a neutron via beta emission.
\(u \rightarrow d + \beta^+ + \nu_e\) |