# Tag Info

## Hot answers tagged conservation-laws

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Since $\pi^0$ is a pseudoscalar particle, we have $$\langle 0|J^\mu_{em}|\pi^0 \rangle =0,$$ and the pion cannot decay into two leptons with a simple photon exchange. In the Standard Model, the leading-order contributions for this process are a box diagram and a $Z^0$ exchange, as you can see in fig. 1 of arXiv:0806.4782 (replacing a $c$ quark by a light ...

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An energy conservation law only arises when the system studied has a Lagrangian which is invariant under time translations up to total derivatives, due to Noether's theorem. More generally, a quasi-symmetry under spacetime translations gives rise to an entire host of conserved quantities, encoded in the stress-energy tensor. Consider a scalar field; under ...

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The abstract of that paper mentions the annihilation of the previously measure photons, where now, they aren't totally conserved, but not totally annihilated. Further down, they mention survival probability, and without access to the whole article, I can only conjecture, but I would go so far as to say that that is them implying that not ALL of their photons ...

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According to this article (the choice of article has no significance other than it came up first in my Google search): Remington's 12-gauge 2 3/4-inch Premier Magnum turkey load has 1 1/2 ounces of shot and a 1260 fps muzzle velocity Converting these figures to metric, $m_{\text{shot}} = 0.0425$ kg and $v_{\text{shot}} = 384$ m/sec, so the momentum of ...

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the simple answer is that a quantum state has several variables (degrees of freedom), so if you measure only one of them and leave the others unchanged, then you detect the photon , change its state but do not destroy it completely. this is what they say in introduction Second, nondestructive detection can serve as a herald that signals the presence ...

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There exists elastic scattering where only directions are changed , momentum is conserved and energy is conserved. There exists elastic scattering of photons: In Thomson scattering a photon interacts with electrons. Thomson scattering is the elastic scattering of electromagnetic radiation by a free charged particle, as described by classical ...

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I dont now about this system but i have had a lecture about a similar non destructive measurement aperatus. they trap a photon in a cavity and have a atom move throw the cavity. right throw the destructive interference spot (there where the photon has low change of being so low change of destroying it) They trick lies in the atom. When that atom moves throw ...

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