Questions tagged [standard-model]
A model of the basic particles and forces featuring six quarks, three charged leptons, three massless neutral leptons and four fundamental force carrying bosons. The twelve fermions are arranged into three generations, while the bosons serve to explain the electromagnetic interaction plus the strong and weak nuclear forces (and the Higgs mechanism). Do NOT use this tag for the standard model of cosmology, etc..
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When is the Lagrangian a Lorentz scalar?
The Lagrangian $\mathcal{L}$ can be defined as the Legendre transform (when it exists) of the Hamiltonian $\mathcal{H}$, a non-Lorentz scalar quantity (as $\mathcal{H} =T^{00}$). My questions are,
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What force or field is associated with the weak hypercharge?
So what is the force or field associated with the weak hypercharge in post-SSB?
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Parity transformation of the $\pi^{0}\rightarrow\gamma\gamma$ process
I want to prove that the amplitude
$$\mathcal{M}^{\mu\nu}=\epsilon^{\mu\nu\alpha\beta}q_{1\alpha}q_{2\beta}$$
is violating parity. Here $q_{i=1,2}$ are the external momenta of the photons. The total ...
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$ \pi^0\to \gamma\gamma$ parity conservation
Let's consider the decay process $\pi^0\to \gamma \gamma$. After we spontaneously broke the chiral symmetry of QCD coupled to an abelian gauge field $A^\mu$, we end up with the Goldstone boson ...
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What is the associated charge for the weak neutral current?
So for the strong force, there's color charge; for electromagnetism, there's electric charge; and for weak charged current, there's weak isospin. How about the weak neutral current? Is there an ...
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Standard Model Generational Disparity [closed]
This may appear to be opinion based at first glance, but I believe it has conceptual merit.
The Standard Model contains 3 generations of particles: $e~–\mu~–\tau$, Up–Charm-Top, etc. But the 2nd and ...
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Parity violation via symmetry breaking?
(Apologies in advance for a poorly formulated question.) In Physics, if something can be equally well found in state A or state B, but for whatever reason is in state A, we sometimes observe the ...
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Jet events and Deeep Inelastic Scattering (Scaling Behavior) at the same time?
I am a philosopher of physics, so I already apologize for potential ignorance. I have also graduated in physics, but I now analyze problems on another level and also forgot some of the mathematical ...
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Checks of anomaly cancellation
In a textbook I read that if $G$ is a global symmetry of the classical Lagrangian, then one has to check $G\times H^2$ anomalies, where $H$ is one of the SM gauge groups.
For example, when $G$ refers ...
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Does electroweak theory have mass gap (not just Higgs mechanism)?
I am extremely confused by seemingly contradictory statements.
In this PE answer, the electroweak sector in the Standard Model does NOT have a mass gap (or at least not observed). In fact, the gauge ...
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How to add a non-chiral lepton doublet to the Standard Model?
How would the Standard Model Lagrangian (before symmetry breaking) change if we were to add a non-chiral lepton doublet $\ell_{L,R}$ with weak hypercharge $y=-\frac{1}{2}$ to the $SU(2)\times U(1)$ ...
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How can a virtual $W$ boson turn into an electron and electron antineutrino?
This is specifically with regard to beta decay. My current understanding is that in one type of beta decay, a neutron turns into a proton, an electron, and an electron antineutrino. In order to change ...
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Is there a sigma for unexplained hypothetical discoveries?
I recently read that the Koide formula relating electronic leptons rest masses is often considered to be numerologic, since unexplained, even though recent years experiment data tend to narrow the ...
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Could there be states of matter that could avoid "matter decay"?
Regular structures of matter may decay over extremely long periods of time (especially if proton decay occurs, which is not proven but it remains a possibility)
Even if that happens, are there any ...
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Why does the up and anti-up quark combine into a pion and not a photon?
im currently studying a level particle physics and im confused about this. Particle annihilation occours when a particle meets its corresponding particle, converting their mass energy into two photons,...
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