models:standard_model
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models:standard_model [2018/03/30 14:34] jakobadmin [Concrete] |
models:standard_model [2019/02/03 08:46] 77.180.211.234 [History] |
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| - | ====== The Standard Model ====== | + | ====== Standard Model of Particle Physics ====== |
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| **Particle Content** | **Particle Content** | ||
| - | {{ :models:standardmodel.png?nolink&400 |}} | + | {{ :models:paper.journal.40.png?nolink&800 |}} |
| + | |||
| ---- | ---- | ||
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| <tabbox Concrete> | <tabbox Concrete> | ||
| - | The Standard Model contains 12 vector fields, | + | At the heart of the Standard Model is the [[advanced_tools:gauge_symmetry|gauge symmetry]] |
| - | 45 Weyl fermion fields which describe 6 quarks and 6 leptons, | + | |
| - | and a complex doublet $H$ of scalar fields. | + | |
| - | + | ||
| - | The vector fields, denoted $A^a_\mu(x)$, are [[theories:gauge_theory|gauge fields]] of the [[advanced_tools:gauge_symmetry|local symmetry]] | + | |
| $$ | $$ | ||
| - | G\ =\ SU(3)_C\times SU(2)_W\times U(1)_Y\, , | + | G\ =\ SU(3)_C\times SU(2)_L\times U(1)_Y\, . |
| $$ | $$ | ||
| - | the $SU(3)_C$ mixes the three colors of the quarks and antiquarks, | + | The $SU(3)_C$ mixes the three colors of the quarks and antiquarks, |
| - | the $SU(2)_W$ the weak isospin, and the $U(1)_Y$ | + | the $SU(2)_L$ the weak isospin, and the $U(1)_Y$ |
| couples to the weak hypercharge $Y$. | couples to the weak hypercharge $Y$. | ||
| Line 45: | Line 43: | ||
| As a result, the $W^\pm$ and $Z^0$ vector particles become | As a result, the $W^\pm$ and $Z^0$ vector particles become | ||
| - | massive ($M_W\approx80.4$~GeV, $M_Z\approx91.2$~GeV) while the | + | massive ($M_W\approx80.4$ GeV, $M_Z\approx91.2$ GeV) while the |
| photon $\gamma$ remains massless. | photon $\gamma$ remains massless. | ||
| + | |||
| + | |||
| ---- | ---- | ||
| + | |||
| + | |||
| + | --> Standard Model Lagrangian# | ||
| + | |||
| + | |||
| + | [{{ :models:smlagshort.png?nolink&800 |Source: http://blogs.discovermagazine.com/cosmicvariance/2006/11/23/thanksgiving/ }}] | ||
| + | |||
| + | * A nice overview of the various terms in the __Standard Model Lagrangian__ can be found [[http://www.einstein-schrodinger.com/Standard_Model.pdf|here]]. A short non-technical discussion of the various terms can be found [[https://www.symmetrymagazine.org/article/the-deconstructed-standard-model-equation|here]]. | ||
| + | |||
| + | |||
| + | <-- | ||
| + | |||
| + | -->Particle Content# | ||
| + | |||
| + | {{ :models:sm-overview.pdf |The field content of the standard model is nicely summarized here}} | ||
| + | |||
| **The Gauge Bosons** | **The Gauge Bosons** | ||
| - | The photon couples to the electric charge which is a linear combination of hypercharge and weak isospin | + | |
| + | The __photon__ couples to the electric charge which is a linear combination of hypercharge and weak isospin | ||
| $$ | $$ | ||
| q\ =\ T^3\ +\ Y . | q\ =\ T^3\ +\ Y . | ||
| Line 58: | Line 75: | ||
| The photon is responsible for electromagnetic interactions. Since it is massless the electromagnetic forces are long-ranged. | The photon is responsible for electromagnetic interactions. Since it is massless the electromagnetic forces are long-ranged. | ||
| - | The $W^\pm$ and $Z^0$ bosons are responsible for the weak interactions. Since both are massive the weak force is short-ranged. | + | The __$W^\pm$ and $Z^0$ bosons__ are responsible for the weak interactions. Since both are massive the weak force is short-ranged. |
| - | The bosons responsible for the strong force are called gluons. This name stems from the fact that they ``glue'' the quarks and antiquarks together. Bound states made of quarks and antiquarks are called baryons and mesons. The strong forces become stronger with rising distance between two color-chared particles. As a result individual quarks, antiquarks, or gluons can't be isolated. This is known as confinement. Only $SU(3)_C$ singlets can be observed. | + | The bosons responsible for the strong force are called __gluons__. This name stems from the fact that they ``glue'' the quarks and antiquarks together. Bound states made of quarks and antiquarks are called baryons and mesons. The strong forces become stronger with rising distance between two color-chared particles. As a result individual quarks, antiquarks, or gluons can't be isolated. This is known as confinement. Only $SU(3)_C$ singlets can be observed. |
| ---- | ---- | ||
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| called `up', `down', `strange', `charm', `bottom', and `top'. | called `up', `down', `strange', `charm', `bottom', and `top'. | ||
| - | The left-handed quarks form 9 $SU(2)_W$ doublets: | + | The left-handed quarks form 9 $SU(2)_L$ doublets: |
| - | $$(u,d)_L$, $(c,s)_L$, $(t,b)_L$$ | + | $$(u,d)_L, (c,s)_L, (t,b)_L$$ |
| (3 for each color) | (3 for each color) | ||
| - | The right-handed quarks are $SU(2)_W$ | + | The right-handed quarks are $SU(2)_L$ singlets. |
| - | singlets. | + | |
| - | This curious difference between left-handed and right-handed quarks meanst that weak interactions disrespect the parity symmetry. The bosons $W^\pm$ only couple to the left currents $J^\mu_L=V^\mu-A^\mu$ | + | This curious difference between left-handed and right-handed quarks means that weak interactions disrespect the parity symmetry. The bosons $W^\pm$ only couple to the left currents $J^\mu_L=V^\mu-A^\mu$ |
| and don't care about the right currents $J^\mu_R=V^\mu+A^\mu$. | and don't care about the right currents $J^\mu_R=V^\mu+A^\mu$. | ||
| The same is true for the __leptons__ $e^-$, $\mu^-$, $\tau^-$, and the 3 neutrino species. | The same is true for the __leptons__ $e^-$, $\mu^-$, $\tau^-$, and the 3 neutrino species. | ||
| - | The left-handed leptons live in three $SU(2)_W$ doublets: | + | The left-handed leptons live in three $SU(2)_L$ doublets: |
| - | $$(\nu_e,e^e)_L$, $(\nu_\mu,\mu^-)_L$, $(\nu_\tau,\tau^-)_L$$. | + | $$(\nu_e,e^e)_L, (\nu_\mu,\mu^-)_L, (\nu_\tau,\tau^-)_L$$. |
| The right-handed charged leptons $e^-_R$, $\mu^-_R$, $\tau^-_R$ | The right-handed charged leptons $e^-_R$, $\mu^-_R$, $\tau^-_R$ | ||
| - | are $SU(2)_W$ singlets. So far right-handed neutrinos were never observed. | + | are $SU(2)_L$ singlets. So far right-handed neutrinos were never observed. |
| - | ---- | + | |
| - | + | ||
| - | + | ||
| - | --> Standard Model Lagrangian# | + | |
| - | + | ||
| - | + | ||
| - | [{{ :models:smlagshort.png?nolink&800 |Source: http://blogs.discovermagazine.com/cosmicvariance/2006/11/23/thanksgiving/ }}] | + | |
| - | + | ||
| - | * A nice overview of the various terms in the __Standard Model Lagrangian__ can be found [[http://www.einstein-schrodinger.com/Standard_Model.pdf|here]]. A short non-technical discussion of the various terms can be found [[https://www.symmetrymagazine.org/article/the-deconstructed-standard-model-equation|here]]. | + | |
| <-- | <-- | ||
| - | -->Particle Content# | + | -->Standard Model Interactions# |
| - | + | ||
| - | {{ :models:sm-overview.pdf |The field content of the standard model is nicely summarized here}} | + | |
| + | [{{ :models:586px-standard_model_feynman_diagram_vertices.png?nolink |Source: Image by Garyzx published under the [[https://creativecommons.org/licenses/by-sa/3.0|CC BY-SA 3.0]] licence}}] | ||
| <-- | <-- | ||
| ---- | ---- | ||
| Line 254: | Line 259: | ||
| <-- | <-- | ||
| - | --> Questions left open by the standard model?# | + | --> What questions are left open by the standard model?# |
| See [[:open_problems|Open Problems]] | See [[:open_problems|Open Problems]] | ||
| + | <-- | ||
| + | |||
| + | --> What symmetries do exist in the standard model and what is their experimental status?# | ||
| + | see https://physics.stackexchange.com/questions/97896/symmetries-of-the-standard-model-exact-anomalous-spontaneously-broken | ||
| <-- | <-- | ||
| <tabbox History> | <tabbox History> | ||
| * The Rise of the Standard Model: A History of Particle Physics from 1964 to 1979 by Lillian Hoddeson | * The Rise of the Standard Model: A History of Particle Physics from 1964 to 1979 by Lillian Hoddeson | ||
| * Resource Letter: The Standard Model and Beyond by Jonathan L. Rosner | * Resource Letter: The Standard Model and Beyond by Jonathan L. Rosner | ||
| + | * https://inference-review.com/article/the-standard-model by Sheldon Glashow | ||
| + | |||
| </tabbox> | </tabbox> | ||
models/standard_model.txt · Last modified: 2019/07/03 08:12 by jakobadmin
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