What is Standard model: Definition and 273 Discussions

The Standard Model of particle physics is the theory describing three of the four known fundamental forces (the electromagnetic, weak, and strong interactions, and not including gravity) in the universe, as well as classifying all known elementary particles. It was developed in stages throughout the latter half of the 20th century, through the work of many scientists around the world, with the current formulation being finalized in the mid-1970s upon experimental confirmation of the existence of quarks. Since then, confirmation of the top quark (1995), the tau neutrino (2000), and the Higgs boson (2012) have added further credence to the Standard Model. In addition, the Standard Model has predicted various properties of weak neutral currents and the W and Z bosons with great accuracy.
Although the Standard Model is believed to be theoretically self-consistent and has demonstrated huge successes in providing experimental predictions, it leaves some phenomena unexplained and falls short of being a complete theory of fundamental interactions. It does not fully explain baryon asymmetry, incorporate the full theory of gravitation as described by general relativity, or account for the accelerating expansion of the Universe as possibly described by dark energy. The model does not contain any viable dark matter particle that possesses all of the required properties deduced from observational cosmology. It also does not incorporate neutrino oscillations and their non-zero masses.
The development of the Standard Model was driven by theoretical and experimental particle physicists alike. For theorists, the Standard Model is a paradigm of a quantum field theory, which exhibits a wide range of phenomena including spontaneous symmetry breaking, anomalies and non-perturbative behavior. It is used as a basis for building more exotic models that incorporate hypothetical particles, extra dimensions, and elaborate symmetries (such as supersymmetry) in an attempt to explain experimental results at variance with the Standard Model, such as the existence of dark matter and neutrino oscillations.

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  1. diegzumillo

    This wikipedia article on the standard model is really good

    I just wanted to get this out of my system. I'm not talking about the main article on SM but the mathematical formulation one: https://en.wikipedia.org/wiki/Standard_Model_(mathematical_formulation) Very, very hard to find good summarized material on SM out there. It's either good coverage but...
  2. heavybuilder

    I Standard Model (Forces interacting with Matter)

    Not the best at physics but trying to understand the standard model. So can someone please tell me if this is right or not and if not, can you explain me why? Higgs bosons reacts with everything that has mass. Electromagnetic force reacts with everything that has charge. Weak force reacts with...
  3. S

    A How can the LRS model for leptons incorporate the Standard Model group?

    This is a homework problem in a course in particle physics at Cornell University. Assume the Left Right Symmetric (LRS) model for leptons. The gauge group is GLR = SU(2)L×SU(2)R×U(1)X. The Standard Model group SU(2)L×U(1)Y has to be included in the LRS group. Namely, U(1)Y ⊂ SU(2)R×U(1)X. Find...
  4. mollwollfumble

    A My T-shirt and the Standard Model

    This T-shirt I bought at a physics conference displays the following equation. It looks like the Lagrangian of the Standard Model of particle physics but I only recognise lines 1 (electroweak) and 3 (Higgs mechanism). What are lines 2 and 4 and what is/isn't included? eg. are quarks, gluons...
  5. S

    A Covariant derivative in Standard Model

    The covariant derivative in standard model is given byDμ = ∂μ + igs Gaμ La + ig Wbμ Tb + ig'BμYwhere Gaμ are the eight gluon fields, Wbμ the three weak interaction bosons and Bμ the single hypercharge boson. The La's are SU(3)C generators (the 3×3 Gell-Mann matrices ½ λa for triplets, 0 for...
  6. TAKEDA Hiroki

    I Double sided arrow notation in Dirac Field Lagrangian

    In a thesis, I found double sided arrow notation in the lagrangian of a Dirac field (lepton, quark etc) as follows. \begin{equation} L=\frac{1}{2}i\overline{\psi}\gamma^{\mu}\overset{\leftrightarrow}{D_{\mu}}\psi \end{equation} In the thesis, Double sided arrow is defined as follows...
  7. C

    B Electroweak spontaneous symmetry breaking

    This is a question that I have tried to pose several times without any success but, anyway, I would like to try again for the very last time. Asume for a moment that EW-SSB (electroweak spontaneous symmetry breaking) actually happened in our early universe. Imagine that our Standard Model of...
  8. S

    A How do we know the spins of elementary particles?

    How do we know the spin of an elementary particle? For example, a fermion has spin 1/2; a photon has spin 1; and even the ficticious graviton has spin 2. How do we know these spins? In other words, how are these spins determined?
  9. ohwilleke

    I Do these equations have a non-trivial solution?

    I was reading the following article that tries to use some equations originally proposed by Pauli in 1951 to reason from one of two reasonably plausible axions that there are tight constraints on the fundamental particle content and mass spectrum of the Standard Model together with BSM...
  10. D

    What's the Latest Theory on the Structure of an Atom?

    Hi I'm Dan and new to Physics forums! I'm planning on posting something tomorrow on an alternate theory for the structure of an atom... I thought I would start with something light ;-) By day I'm a Product Owner and have established several successful and unsuccessful companies! I'm...
  11. G

    B How many equations is the standard model composed of

    Roughly speaking General Relativity is summarized with one equation but 15 or so equations are packed within it. Sorry if that's wrong, but I'm not an expert or anything. (If I could get an answer to that questions I would appreciate it to). I saw once a physicist show me a finite list of how...
  12. G

    A Divergent Diagrams in the Standard Model

    It is my understanding that the task of enumerating all of the divergent diagrams in a quantum field theory can be reduced to analyzing a hand full of diagrams (well, at the moment I know that this is at least true for QED and phi^4 theory), and that all other divergent diagrams are divergent...
  13. sunrah

    A What are the implications of time constraints in the standard model?

    What are the constraints (if there are any) placed on time by the different theories in the standard model and what are their potential implications?
  14. diegzumillo

    A Supplementary material for standard model

    Hi all So I took graduate level courses of QFT, Quantum Gauge theories and a course on standard model of particle physics. I struggled a lot but got decent grades, so why does it all still look greek to me? It's becoming very frustrating to read sentences like "the theory is invariant under an...
  15. J

    I What is mass according to the standard model?

    All particles get their mass from the higgs field. But how? According to the standard model what is "mass" and how do particles get it?
  16. Sophrosyne

    I Why are gluons considered to be elementary particles?

    Gluons are often depicted as fundamental particles in the Standard Model. But in looking at their mechanism, it seems they are not really fundamental particles in the sense that they are fundamental, indivisible, building blocks. They are mesons- a composite quark-antiquark pair, where their...
  17. S

    A Dimension-5 interaction beyond the standard model

    Consider the following dimension-5 interaction: $$\bar{\psi}D^{2}\psi.$$ Why is this interaction not consistent with either Lorentz invariance, the standard model field content or gauge invariance?
  18. T

    I Standard Model SU(2) singlets and doublets

    I know that for SU(2), weak interaction, in the standard model the right handed leptons are singlets, (and right handed neutrinos don't exist). For right handed quarks are they singlets or doublets in the standard model. So is it (u d)R or is it just u(R) and d(R)
  19. S

    A Bar on a fermion field, arrows on fermion lines and particle-antiparticle nature of a fermion

    This question is about the use of bar on a fermionic field in a Lagrangian, the use of arrows on external fermion lines and the particle-antiparticle nature of a fermion. For illustration of my question, I will use the following the charged-current interaction of the Standard model...
  20. S

    A Deducing decay processes and Feynman diagrams using Lagrangian and conservation laws

    The decay processes of the ##W## bosons are completely governed by the charged current interaction terms of the Standard model: $$\mathcal{L}_{cc} = ie_{W}\big[W_{\mu}^{+}(\bar{\nu}_{m}\gamma^{\mu}(1-\gamma_{5})e_{m} + V_{mn}\bar{u}_{m}\gamma^{\mu}(1-\gamma_{5})d_{n})\\...
  21. S

    A Matching interaction terms and decay processes in standard model

    I would like to consider the interaction terms in the Standard Model which allow the following decay process: The only interaction terms in the Standard Model which allow this decay process are contained in the charged current interactions: $$\mathcal{L}_{cc} =...
  22. smodak

    Particle The Standard Model in a Nutshell - Goldberg

    Just found this new book on amazon. Looks interesting. I purchased. https://www.amazon.com/dp/0691167591/?tag=pfamazon01-20 The TOC, Preface, and intro could be found here http://press.princeton.edu/titles/11050.html I wish they included a sample chapter as well (the book in not cheap), but I...
  23. C

    B Standard model particle properties

    In the Standard Model, for any particle, I have only found properties related to electromagnetic and gravitational (in fact mass does not necessarily mean it is a property related to gravity, but to emergy)forces like charge and mass. Why there isn't anything about the other two interactions...
  24. L

    Other Graduate Research topic involving QFT and General Relativity

    Last year I finished the undergraduate course in Mathematical Physics. This year, more precisely in March, I'm going to start the graduate course to acquire a master's degree in Physics. Now, for this course I must choose a research topic and find an advisor. This is being a little bit...
  25. Q

    Unruh Effect for Standard Model Fields

    I have seen the derivation for Unruh radiation for a massless, non-interacting scalar field (Carroll). Are there interesting differences that arise for more realistic standard model cases. For example, what does QCD look like for an accelerating observer? Any papers that detail this would be...
  26. wolram

    B Beyond the standard model through 'mini spirals'

    https://www.sciencedaily.com/releases/2016/12/161215080856.htm Can anyone provide the origin of this article.
  27. wolram

    B Does antimatter fit into the standard model

    AFAIK antimatter was produced equality in the big bang, and in the matter antimatter fight the matter won . Does antimatter react to gravity the same as matter, surly if it does then the antimatter will be annihilated due to matter antimatter mixing IF matter repels antimatter how did the...
  28. Urs Schreiber

    Insights Spectral Standard Model and String Compactifications - Comments

    Urs Schreiber submitted a new PF Insights post Spectral Standard Model and String Compactifications Continue reading the Original PF Insights Post.
  29. S

    I Local Gauge Invariance Explained: Physics & Math Insight

    Hello! Can someone explain to me what exactly a local gauge invariance is? I am reading my first particle physics book and it seems that putting this local gauge invariance to different lagrangians you obtain most of the standard model. The math makes sense to me, I just don't see what is the...
  30. john baez

    Insights Struggles with the Continuum - Conclusion - Comments

    john baez submitted a new PF Insights post Struggles with the Continuum - Conclusion Continue reading the Original PF Insights Post.
  31. john baez

    Insights Struggles with the Continuum - Part 7 - Comments

    john baez submitted a new PF Insights post Struggles with the Continuum - Part 7 Continue reading the Original PF Insights Post.
  32. A

    I Is the SM of particles physics and Cosmology SM

    I'm in a deep discussion with a friend. He says that the Standard Model of particle physics is actually known by Standard Model of cosmology and that both are the same and that the SM of particle physics is in the Minkousky geometry... I disagree about this, I do think that the SM of particle...
  33. Luca_Mantani

    A Custodial Symmetry in the Standard Model

    Hi, I am reading about this symmetry but I'm struggling to have a deep understanding of it. Would somebody please explain this symmetry to me from a conceptual point of view? Thanks in advance, Luca
  34. mfb

    Insights LHC Part 4: Searching for New Particles and Decays - Comments

    mfb submitted a new PF Insights post LHC Part 4: Searching for New Particles and Decays Continue reading the Original PF Insights Post.
  35. scientepid

    I How can you visualize the Higgs field, or can you?

    Just when I thought I had finally wrapped my brain around relativity, Quantum theory took off. Then the Higgs Boson was discovered. How does the Higgs field under-pin relativity, namely space-time? How is the Higgs field distributed? Does it have curvature like space time, or is omnipresent...
  36. F

    How Do You Diagonalize the Chiral Symmetry Breaking Term for Pion Masses?

    Homework Statement I want to diagonalize the quadratic form $$ m_0((m_u+m_d)\pi^3\pi^3+\frac{2}{\sqrt{3}}(m_u-m_d)\pi^3\pi^8+\frac{1}{3}(m_u+m_d+4m_s)\pi^8\pi^8)$$ which can be found under equation 5.47, in order to get the mass of the η and ##\pi^0## pions. This quadratic form is produced by...
  37. dschwie

    Gravity and massless particles

    Just finished reading Sean Carroll's "The Higgs Boson and Beyond". I would be grateful if someone could explain how gravity, which I understand to be a function of mass, can interact with massless particles as evidenced by the phenomenon of gravitational lensing. I understand that gravity is a...
  38. T

    I Ratio of abundance of sub-atomic particles in the universe?

    I was wondering if there is a current hypothesis about the quantities of which matter particles were created? I'm not completely au fait with the standard model, but I've seen the picture...
  39. Samy_A

    Particle Books about the Standard Model (with math)

    I've been trying to learn more about the standard model. Leonard Susskind's lectures have been very helpful for SR, GR and QM. His lectures about the standard model are interesting, I learned a lot, no question. But he doesn't really cover in any depth the mathematical side of it. He mentions...
  40. unknown1111

    A Computing the pole mass from a given MS mass?

    Given a Yukawa coupling as a function of scale and a vev, how can I compute the corresponding pole mas? Understandably most paper explain how from a measured pole mass one can compute the running mass, for example, Eq. 19 here. However I want to compute the pole mass from the running mass. In...
  41. unknown1111

    Top quark mass mt at energy scales μ<mt?

    Does it make sense to talk about the top mass at energies below mt, although in all processes the corresponding energy scale is above mt because of the rest mass energy of the top quark? Using an effective field theory approach, the top quark decouples at energies below the top quark mass and...
  42. thegirl

    Basic interactions in the Standard Model

    Hi, Is there a list of basic interactions in the standard model? Does anyone know where I can find this list of basic interactions in the standard model?
  43. R

    Standard model says 17 particals, M theory says 18?

    Hi. I've only just started reading on M-theory. I'm otherwise a lay person so I'm going to have some basic questions. Here's my first. Standard Model has 17 elementary particles right? But doesn't M-theory say there's 18? Or 36 if you include the symetrical ones. So am I missing one particle...
  44. S

    Standard Model, Mass in QFT - Is There Consensus?

    I realize that Wiki is not the preferred reference source here, but I'll go ahead with this question anyway... In the latest iteration of the article on the Standard Model is the statement, "We see that the mass-generating interaction is achieved by constant flipping of particle chirality." Is...
  45. K

    Neutrino miminal standard model vs string/M-theory

    back ground http://arxiv.org/abs/0912.0208 Asymptotic safety of gravity and the Higgs boson mass Mikhail Shaposhnikov, Christof Wetterich (Submitted on 1 Dec 2009 (v1), last revised 12 Jan 2010 (this version, v2)) There are indications that gravity is asymptotically safe. The Standard Model...
  46. K

    If Sterile neutrino and axions exist, is that standard model

    it's commonly stated that the standard model has no dark matter candidate. axions and/or sterile neutrions are well motivated extensions of the standard model. if experiments show they exist and are a part of dark matter, would this still be within the framework of the standard model, or is it...
  47. wolram

    I Cosmology looks beyond the standard model

    http://phys.org/news/2015-07-cosmology-standard.html The most popular candidate for the elusive particles that give the Universe extra mass is Cold Dark Matter (CDM). CDM particles are thought to move slowly compared to the speed of light and interact very weakly with electromagnetic radiation...
  48. M

    Hello, my name is Mark, and I'm not an alcoholic....

    Hello, my name is Mark, and I am joining here because I have always been interested in theoretical physics but I know almost nobody I can discuss this with. I am guessing many people join with questions, and a number of people join to share/test ideas, and I am a little of both.. I will start by...
  49. Anchovy

    Standard Model decompositions of larger group representations?

    When reading about GUTs you often come across the 'Standard Model decomposition' of the representations of a given gauge group. ie. you get the Standard Model gauge quantum numbers arranged between some brackets. For example, here are a few SM decompositions of the SU(5) representations...
  50. T

    Total mass-energy v nature of forces, particles

    What does the standard model have to say about the relationship between the total mass-energy of the universe and the characteristics of forces and force-carrier particles? That is, if the total mass-energy were different, would the nature, strength, … of the forces and force-carrier particles...
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