Tagged Questions

Particle physics is the study of the fundamental forces of nature as they are embodied in the interactions of elementary and composite particles at high energies and short time and distance scales.

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Wavefunction of a system of particles

A three-dimensional volume $V$ contains a certain number $N$ of electrons and they can't escape the volume $V$. Assume for simplicity that the potential $\mathcal{V}(\mathbf{r})$ is zero in all the ...
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Lagrangian derivation of Thomson scattering cross section (ie photon-electron)

Does anyone know a quick way to obtain the classical Thomson scattering scattering cross section (for photons scattering on electrons) from quantum mechanics/quantum field theory, avoiding the lengthy ...
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How does Bremsstrahlung occur in a vacuumized particle accelerator?

In our electrodynamics course we have learned that accelerating a charged particle will lead to a loss of energy in the particle due to Bremsstrahlung. The exact amount of power radiated away is given ...
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Identical Particle Wavefunctions

Consider the process $$\rho^0\rightarrow\pi^0+\pi^0$$ The $\rho^0$ has $J=1$ whilst the two pions have $S_{tot}=0$ and thus require $L_{tot}=1$ by conservation of angular momentum. Consequently this ...
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How can $\Lambda^0$ and $\Sigma^0$ both have $uds$ quark content?

Title says it all: How can $\Lambda^0$ and $\Sigma^0$ both have $uds$ quark content? Doesn't this make them the same baryon?
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The highest photon energy ever measured and transplanckian energies

What is the highest energy of we have measured of a photon by any physical experiment? Has a transplanckian energy photon been measured? Can we study them -if they exist- with special relativity?
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Tree Level Feynman Diagrams of Electron Positron Interaction

Consider the interaction $$e^-+e^- \rightarrow e^-+e^-$$ The following is a tree level Feynman diagram for this: We can also make the paths of the two electrons on the right hand side cross over and ...
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Symmetry responsible for equality of masses of particles

During my studies of basic particle physics the following question came up. What symmetry is responsible for equality of masses of particles and their antiparticles? In particular, is this symmetry ...
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Topics important in electrodynamics for particle physics

Say I'm going to study Griffith's electrodynamics, what are the important topics in it, for particle physics? Like Maxwell equations etc.
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Helicity of massive particle at high enengy

We know that massless spin-1 particle like photon only has two helicity state (-1,1), what about the helicity of massive spin-1 particle (W boson) at very high energy? Does it have helicity 0 state ...
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How do single photons travel from here to there

I know there have been similar questions but I'm still unclear what the overall consensus is. (1) I assumed and have read that photons travel in straight lines unless deflected by gravity but there ...
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The energy of our universe [duplicate]

Is there a substantial basis for the claim that the total energy of our universe is zero? I just read a bit of Hawking's writing in which he comes to this conclusion through inflation theory, but i ...
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Finding the mixing angle for two-neutrinos

I am trying to answer the following question; Light Majorana neutrino masses can be generated by the see-saw mechanism. Consider a mass term which, in the simplest case of one active and one ...
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Why don't all the gluon's get converted into energy in an uranium atom undergoing fission?

I have following questions and arguments. why do only gluons get converted into energy in an uranium atom undergoing fission? why don't all the gluons get converted into energy? which conditions ...
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Appropriate fit function for $\phi$ meson mass from $K^{+}K^{-}$ pair

I am attempting to measure the mass of the $\phi$ meson using the decay mode $\phi \to K^{+}K^{-}$. I have isolated the $\phi$ meson candidates using this decay mode, and have constructed the graph ...
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Wave function of particle and antiparticle

The wave functions of particle and antiparticle are related by complex conjugation and wavefunction $Ψ$ must be complex for particle such as $n$, $p$. Is there way to prove this mathematically? Can we ...
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Is the back induced emf in inductive coil equal to the original? [duplicate]

I always thought that an inductor resists the change of magnetic flux to a CERTAIN EXTENT, that is it would generate a back emf that would provide only a percentage of obstruction to the original emf. ...
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What interaction shown in this Feynman diagram and is it possible?

I saw the following Feynman diagram in my textbook, not sure if a typo or something I don't know: Just to clarify, the "e" on the upper left does not have any superscript. I am not sure if such a ...
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DNA breaks with particles or photons (Radiation therapy)

When protons (or other particles) or photons are used in radiation therapy to treat cancer patients, the main effect is for it to make DNA breaks that hopefully will make the cancer cell die ...
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If dark energy is responsible for the expansion of the universe, is it possible that it is also the force which creates dark matter? [duplicate]

In a science fiction story I am writing humans travel through space (only our solar system) using dark energy. In my imagining of the future scientists discovered that dark energy exists in a field ...
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How to calculate probability of neutrino oscillation after a distance

I'm trying to calculate the probability of an detecting a muon neutrino after a certain distance, where the neutrino beam is entirely electron neutrinos as t = 0. I know I need to use the PMNS matrix ...
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Why do we need to build photon colliders? Since electron-position colliders are very “clean”

What's the advantage of gamma-gamma colliders? What new physics can be done with it? Reference: http://www.slac.stanford.edu/pubs/beamline/26/1/26-1-kim.pdf
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How do I go about understanding particle physics? [closed]

My science project has tasked me in creating a research paper on the standard model of particle physics, but I'm not in highschool yet. I don't know how to go about learning the math and the concepts ...
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What is the difference between “additive” quantum numbers and “multiplicative” quantum numbers?

What is the difference between "additive" quantum numbers and "multiplicative" quantum numbers? I think that this may have something to do with P and C Symmetry groups, but I may be mistaken. I’m ...
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Could we live if we were made of antimatter? If so, would there be any difference to experience?

Antimatter is material composed of antiparticles, which have the same mass as particles of ordinary matter but opposite charges, as well as other particle properties such as lepton and baryon numbers ...
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How can muons travel faster than light through ice?

When a neutrino traveling through ice hits and interacts with an oxygen atom, muons are created. Cherenkov radiation can be created when muons travel through ice faster than light and create a ...
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Why is there no fundamental force following from the $SU(4)$ symmetry?

I've understood that the three fundamental interactions described by the Standard Model (the electromagnetic, the weak and the strong force) are thought to correspond (roughly) to gauge invariances ...
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Trinification lepton Yukawa interactions

We have a trinification model of $SU(3)_c\otimes SU(3)_L\otimes SU(3)_R$, where the first is the usual colour group, the second a left $SU(3)$ and the third a right $SU(3)$. As usual, leptons and ...
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Higgs boson and dark matter.

In the standard model the Higgs boson gives the mass to other particles, but in the Universe we know that the 80% of mass is in form of dark matter, that is not constituted by known particles. The ...
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How do I form the four-momentum quantum operator?

I am trying to form the four-momentum quantum operator. These are the steps I have taken so far: The 3-momentum operator is given by $\hat{p}_{i} = -i\partial_{i}$. This is covariant because it is ...
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is the earth's atmosphere positivly charged? [duplicate]

Is the earth's atmoshere charged with positive ions? What are the effects of positive verses negative ions?
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How is Spin experimentally determined?

I know what spin is and how theories determine it for particles. What I don't understand yet, is how people, through experiments and data analysis or whatever, reach to confirm/say that the $X$ ...