# Tag Info

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Charge means that the body experiences a force in an electric field. A charge generates an electric field, which generates a force on other charges particles. Two bodies are said to repel if they force each other away and two bodies are said to attract if they force each other closer together. Now, I'm not really answering your question here of "why," I ...

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Yes, you could set up a series of multiple SG experiments so that the electrons leaving one experiment entered the next. If you're absolutely determined to use just the one piece of SG kit you'd need some form of magnetic guide to route electrons round in a circle back to the starting point. A bit like putting the SG experiment in the beam line of a (very ...

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From an experimentalist point of view, I had done something very similar to that for a different decay channel. For each particle the four momentum in the laboratory frame was stored in the experiment. The analysis proceeds using only these four momenta as input. Due to the helicity amplitudes formalism every momentum has to be boosted back from the ...

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You have done all the hard steps, what remains is to remember that $(\vec{p}\cdot\vec{\sigma})^2=\vec{p}^2=E^2-m^2$ so that \begin{align} (|E|+m) - (|E|+m)\left(\frac{\vec{p}\cdot\vec{\sigma}}{E+m}\right)^2 &= (|E|+m) - (|E|+m)\frac{\vec{p}^2}{(E+m)2}\\ &= (|E|+m) - (|E|+m)\frac{(|E|+m )(|E|- m)}{(E+m)2} \\ &= (|E|+m) - (|E|-m) \\ &=2m ...

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Expanding on what Couchyam said: To some extent, this is actually the definition of what it is to be a "particle." Intuitively, a particle should have some particular definite energy, and be stable enough that it can exist in its own right. These two requirements are linked by energy-time uncertainty. The natural "clock" to compare against when asking if ...

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He's relying on isospin symmetry. The integrals you exhibit are for the proton, but the the form factors in the ratio are proton in the denominator and neutron in the numerator. The claim is that the up-distribution of the proton is a good proxy for the down-distribution of the neutron and vice versa, and that the sea distributions are identical. That ...

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To measure the mass of a charged particles like electron we use mass spectroscopy. What about uncharged particles? For the neutron there exists a wiki paragraph as mentioned in the comments. One has to use interactions and conservation laws. The mass of the pi0 is the invariant mass of the two gammas it decays into. K0 has a pi+pi- decay mode. Lamda a ...

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To answer this question, you need to make decomposition of quantum states. Lets define protons has total isospin 1/2 and projection 1/2: $|1/2, 1/2>$, while neutron has the same isospin but projection -1/2: $|1/2, -1/2>$. Lets combine all four options. To help with it, we use Clebsch-Gordon coeffiicients for (1/2, 1/2) states: ...

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There are 4 combinations of 2 nucleons. These are pp, np, pn, nn. It is possible to see that pp, nn are both symmetrical whilst the other two have not got a defined symmetry. It is possible to produce 3 symetric combinations, which will form an spin=1 triplet: pp, $\frac{1}{2}(np+pn)$, nn These have the Isospin values 1,0,-1. A single antisymetric ...

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This is something I never really understood, but Glen Knoll Offers the following in pp. 116 of his book "Radiation Detection and Measurement": "The energy resolution of the detector is conventionally defied as the FWHM divided by the location of the peak centroid H_0 The energy resolution R is thus a dimensionless fraction conventionally expressed as a ...

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One has to distinguish between fields and particles. Fields are a mathematical construct , similar to a coordinate system, defined at all (x,y,z,t) points . Quantum mechanical fields are at the same time operators with expectation values. Particles are excitations on the fields and their interactions are measurable in the laboratory. If no electron exists, ...

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There is a single Higgs field that fills all of space and always has. Similarly there is a single electron field filling all of space. And an up quark field, and a photon field and a $W^+$ field and a Z field and a gluon field and a $W^-$ field and some neutrino fields and fields for down quarks and top and bottom quarks and charm and strange quarks and ...

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Since I can't comment, I can't ask for specification. Most probably problem is following. In the lab system $\Lambda$ with total energy $E= 10~GeV$ flies along x axis and after some time decays into proton and pion. In the $\Lambda$ rest frame, which is oriented the same way (x, y, z coordinates), those daughter particles must fly back to back isotropically, ...

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Have you met the conservation rules of a feynmann diagram? They basically say the following: "At each vertex (that is every point on the feynmann diagram you see more than one branch touching that point) there are several quantities that must be conserved" The rules slightly differ in QCD (that's roughly speaking the study of quarks and weak interaction) ...

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Gauss's law relates the integral of the electric field over a closed surface with the amount of charge inside the volume enclosed by this surface. It does not state anything about magnetic fields or about changes in time. So unfortunately I would not consider either to be 'safe'.

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Start by thinking about single-function magnets, e.g. dipoles. A real-world dipole is designed such that the dipole field quality is good in the center aperture of the magnet. However there will always be some higher-order field components due to design/manufacturing tolerances and saturation effects; in other words a dipole will have quadrupole and ...

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Potential energy is wrong. Even in Newtonian Mechanics it only works if the force is 1) purely a function of position and also 2) is conservative. Magnetic forces depend on velocity so they fail. And electric forces are not conservative if you aren't in statics. What you really have is kinetic energy and rest energy for the charged particle, some energy ...

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Don't forget about the rest energy, $E=mc^2$. Since a particle's intrinsic spin cannot be changed, it doesn't make sense to distinguish "intrinsic spin energy" $\frac12 I\omega^2$ (as you would compute for, say, a spinning flywheel) and the rest energy. A particle which is moving in an electric field will see a motional magnetic field. Charged particles ...

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(sorry, I couldn't write this in the comment section) Have you met the postulates of quantum mechanics? Here is a summary of them http://vergil.chemistry.gatech.edu/notes/quantrev/node20.html Postulate 3 says if an observable has associate a (hermitian) operator, the only values we would observe for one photon the spin-angular momentum are the eigenvalues ...

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Being "near by" means that there is (unavoidably) an interaction between them. The problem is no longer $$\gamma \to e^+ + e^- \,,$$ but $$\gamma + A \to e^+ + e^- + A\,,$$ (here $A$ represents the spectator nucleus) and there is now a way to share out the energy and momentum. The interaction is generally thought of as mediated by the electromagnetic ...

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Originally radioactive elements come from nature where they were very diluted and that's why they were secure. When these naturally radioactive materials like Uranium are used in processes like civilian nuclear energy production the resulting waste becomes many, many times more radioactive than the raw materials one started off with. Even after the ...

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Probably too expensive and disruptive to try to deal with nuclear waste that way. You're talking about processing through an enormous amount of earth and/or seawater. Note that nuclear waste includes not just material that was initially radioactive when it came out of the ground (e.g., uranium ore), but a lot more material as well. If a nuclear plant worker ...

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One on the problem is re-concentration, by the help of water circulation in the soil (possibly up to water sources) or by the help of small animals (then to food chain up to us). The stability of geological layers is not so easy to predict. Beside, the radio-activity of wastes can be a lot higher, and spreaded through a huge variety of chimical species, ...

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Yes, the requirement for at least two photons is because a single photon would violate conservation of momentum. See my answer to Particle anti-particle annihilation and photon production for a (very simple!) proof of this. Annihilation can produce more than three photons. In fact the decay of ortho-positronium to two photons is forbidden, and it (mostly) ...

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The answer is yes. There are hundreds of facilities all over the world called synchrotron radiation sources where electromagnetic radiation with different wavelengths (ranging from IR to hard X-rays) is produced by circulating electric currents. However, I would not call them antennas.

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The presence of gamma rays and positrons associated with lightning strikes suggests that the strikes are capable of accelerating particles with enough energy for D-H or D-D fusion. However I'd expect that even in a pure deuterium atmosphere the energy released by D-D fusion would be negligible compared to the energy released in the lightning strike itself.

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In its rest frame an electron is always equal parts left- and right-handed chirality.

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This is not unique to light. For this behavior there are 2 kinds of "particles", the fermions and the bosons. The first have the "Pauli exclusion" phenomena: 2 identical fermions can't have the same state (quite close to saying "not be at the same place"), while 2 bosons can. This relates to their spin: fermions' spins are half-integers while bosons are ...

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