# Questions tagged [scattering]

Scattering is a general term for several physical processes in which radiation of some sort changes direction due to an interaction with a particle. Scattering can be classified by the type of radiation (ie, electromagnetic, x-ray, neutron), or by the relative sizes of the wave and the particle (ie, Rayleigh, Mie, geometric).

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### The radiation power of an electromagnetic wave scatter due to the magnetic field

In studying the scattering of an electromagnetic wave by a single charge, it seems typically we consider the motion driven only by the electric field, as is presented in Section 32-5 Scattering of ...
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### How many relativistically invariant degrees of freedom in $n$-particle scattering?

Suppose we have a scattering process with $n$ external legs with four-momenta $p_1, \cdots, p_n$. Naively there are $4n$ degrees of freedom, however most of these putative degrees of freedom are not ...
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### Proving that the interference current integrated over a small cone does not depend on the angle of the cone

I'm studying quantum mechanical scattering and I have gotten to $$\psi=\psi_{in}+\psi_{scattering}=e^{ikrcos\theta}+f(\theta,\phi)\frac{e^{ikr}}{r}$$ and when calculating the current, i get three ...
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### Effective field theory of massive spin-1 and spin-2

I'd like to understand what could be the use of an effective field theory (EFT) of a single massive particle of spin 1 or 2, or simple modification of these (see below). By EFT, I mean the most ...
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### What exactly does the quantity $\sigma(\theta)$ represent in scattering problems? What is the interpretation of the differential cross section?

So I don’t understand intuitively what the scattering cross section is. The equation also seems quite random to me. I have looked at derivations but I cannot wrap my head around. I am looking for some ...
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### Compton Scattering Angle Distribution, and the Klein-Nishina Model

I have a Geant4 simulation where 662keV photons are going into a detecting volume (Germanium). As expected, when I look at the output of the simulation, these photons undergo Compton scattering and ...
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### Discontinuities in the $u$ channel

if we consider a 2-to-2 scattering, we have normally an $s$ channel a $t$ channel and $u$ channel. In CMS frame $s$ is positive and $t$ and $u$ negative, by crossing symmetry there are kinematics ...
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### Relation between matrix element of a process with its crossed processes

Consider a process in particle physics denoted by, $$(1) \quad a+b\to c+d$$ which is related to the reverse process $$(2)\quad c+d\to a+b.$$ By virtue of the hermiticity of the interaction Hamiltonian,...
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### CPT invariance and Soft Theorems

I am reading the paper IR Dynamics and Entanglement Entropy, written by Toumbas and Tomaras and I have a question on using the CPT invariance of the QED $S$-matrix elements in order to derive the ...
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### Rutherford's experiment

I have read everywhere that the gold foil experiment performed by Rutherford was done hoping that the alpha particles face only a little deflection/no deflection however this doesn't sit right with me,...
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### Making sense of Scattering of Impulsive Gravitational Waves

Consider the space-time diagram of KP-wave as shown below: We see that two transverse plane fronted GW waves intersect at the point ($u,v$)=(0,0). The curvature comes with a delta function, except in ...
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### How an autocorrelation function is calculated experimentally in a Dynamic Light Scattering experiment

As said in the title, I would like to know how an autocorrelation function of scattered light intensities defined as $G(\tau)=\langle I(t)I(t+\tau)\rangle$ is computed experimentally. Let's say we ...
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### The blue sky — is the simple Rayleigh explanation wrong?

Reading various answers here (, , ), Wikipedia, nasa.gov, and other places, the common explanation of our blue sky is Rayleigh Scattering due to gases and particles in the air, maybe with ...
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### First EXPERIMENTAL proof of indistinguishability of electrons

Fairly early on in Thermodynamics there was a suggestion that particles are generally indistinguishable because of entropy paradoxes. Later on, my recollection is that somebody in the 1920's shot ...
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### How to calculate a scattering matrix numerically for 1D localized potential?

I want to calculate a scattering matrix numerically for an arbitrary localized potential for the 1D Schrödinger equation. I want to do this to get a better feel for the scattering matrix. I can solve ...
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### How can I calculate the reflectivity of an electron gas with Thomson scattering?

I have to do a seminar presentation about the topic of using relativistic mirrors in integrated laser ion accelerator systems. The idea is (for context sake) to accelerate an electron bunch to ...
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### Order of fields in scattering amplitude

Given the lagrangian $$\mathcal L=-\dfrac{1}{4}F_{\mu\nu}F^{\mu\nu}+(D_{\mu}\phi)^*(D^{\mu}\phi)-M^2|\phi|^2+\bar\psi(i\gamma^{\mu}D_{\mu}-m)\psi.$$ I tried to compute some first order scattering ... 