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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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24 views

A question on 't Hooft's paper “Computation of the quantum effects due to a four-dimensional pseudo-particle”

In the avove paper 't Hooft considers the following (rotation invarinat) operators on the Euclidean space $\mathbb{R}^4$: \begin{eqnarray} \mathcal{M}_0=-\left(\frac{\partial}{\partial r}\right)^2-\...
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39 views

Spinless $e^{-}\gamma\rightarrow e^{-}$ Cross section

I was trying to figure out the cross section $\frac{d\sigma}{d\Omega}$ for spinless $e^{-}\gamma\rightarrow e^{-}$ scattering. First I wrote the terms associated with each component. Vertex: $$ie(...
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22 views

Could ultrasound pings and triangulation really help de-scatter diffuse red light for imaging?

Does the science explanation in the latest OpenWater TED talk make sense in principle? The claim involves taking advantage of the doppler effect. Could someone give a more detailed explanation as to ...
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1answer
34 views

Can Compton scattering increase a photon's energy?

I've read (in Hagai Netzer's book The Physics and Evolution of Active Galactic Nuclei) that "Comptonization in the [black hole's accretion] disk atmosphere can increase the energy of some photons..." [...
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1answer
33 views

Brillouin scattering in multimode fibers

Fiber ring resonators made up of single mode fibers often incorporate an optical isolator to suppress the build-up of Brillouin scattering. However, ring resonators made of multimode fibers generally ...
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1answer
32 views

1D string reflection and transmission phase

Ok, I must be missing something very obvious here. After applying the boundary conditions, we can write: $$ A_R e^{i \delta_R} = (\frac{v_2 - v_1}{v_1 + v_2}) A_I e^{i \delta_I} $$ and $$ A_T e^{...
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1answer
55 views

Does the electron act as point charge in scattering theory?

We know that an electron behaves like a point charge, and the probability density of its position is given by the Born rule. Now suppose that we shoot an electron toward an atom, so the electron gets ...
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1answer
75 views

Necessity to consider the square of Four Momentum

Why do we often need to consider the square of four momentum transfer $Q$ in scattering experiment or particle physics/cosmology instead of just the $Q$ itself?
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How to write the Rutherford differential cross section in terms of the momentum transfer?

The Rutherford differential cross section is: $$\frac{d\sigma}{d\Omega} = \frac{Z^2 \alpha^2}{4E^2 \sin^4 (\theta/2)}.$$ I need to write this in terms of the momentum transfer $\frac{d\sigma}{d(Q^...
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1answer
28 views

Integral convergence in scattering problem

Consider the scattering of a particle by a central time-independent potential $V$, that is limited to a finite region in the space. the hamiltonian is $H = H_{0} + V$. Using the Moller operators, we ...
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1answer
268 views

Maximum scattering angle for relativistic elastic collision

In Landau Classical theory of fields, in the section of elastic collision(chapter 2, section 13), he mentions that for $m_1>m_2$, the scattering angle $\theta_i$ cannot exceed a maximum value, and ...
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74 views

A Question about In/Out States in Quantum Field Theory

When I was reading the lecture notes Advanced Quantum Field Theory by Jorge Crispim Romao, I accidentally found the following thing that I don't understand. On page 56, section 2.2, the author ...
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Polarized structure functions and Bjorken sum rule

I'm trying to understand what the Bjorken sum rule and the polarized structure functions entering it are. I will use equation (2.3) here as a reference for asking the question. In Peskin, I've only ...
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2answers
55 views

Calculating the charge density from a form factor

For an atomic form factor $F(\textbf q)$, the corresponding charge density distribution is given by $$ \rho(\textbf r) = \frac{1}{(2\pi)^3}\int\text{d}^3 \textbf q \,F(\textbf q)\,\text{e}^{-\text{i}\...
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1answer
56 views

How do we see if light scatters in all directions?

This may be a silly question, but I'm not sure how we see an object in front of us. If light hits the points of the object and scatters in all directions, how come we are able to form an image of the ...
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S-matrix branch cuts properties

I'm trying to formally understand some non-perturbative results in scattering theory but the material available on the topic are not too friendly, so there are some very simple and essential facts I ...
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1answer
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Why are number changing interactions inelastic?

Inelastic processes are those in which the kinetic energy of the initial particles and final particles are not the same. Is this true also for number changing processes such as pair creation or pair ...
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100 views

Example of calculating phase shifts in scattering theory

I have an extended question to this post: Phase shifts in scattering theory I have read it and also went over the formalism in Sakurai's, Shankar's, and Griffith's. I am now trying to look for ...
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57 views

Neutrino scattering cross-section in high energy limit

I've come across a problem in out particle physics lecture notes that I have been unable to resolve on my own. I've paraphrased the bits of the notes that are giving me so much trouble: The notes ...
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19 views

How to evaluate the Feynman gauge photon propogator in coordinate space?

In coordinate space the Feynman gauge looks like: $$\frac{g_{\mu\nu}}{\partial^2} .$$ Without fourier transforming, how does this operator act on currents? In general for inverse derivative operators ...
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1answer
62 views

Direction of propagating wave in quantum barrier

Consider a step potential $V(x)$ where \begin{align} V(x) & = 0; \quad x\leq 0 \\ V(x) & = V_0; \quad x> 0 \end{align} Now consider the case where $E_0<V_0$. The solutions of the ...
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How to transform a function form planar symmetry to spherical symmetry? [closed]

I'm checking some derivation in photon scattering, where there's a phrase like: "...transform planar symmetry to spherical symmetry...$\Psi_{sp}(r)=\frac{1}{2\pi r} \frac{d}{dr}[\varphi_{pl}(r)]$" ...
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59 views

Why is the extent of scattering of light by particles inversely proportional to the fourth power of the wavelength of the light wave?

When I first came across this, I speculated this law is experimental. However, later I came to know that this is not the case. A concise answer, with some reasoning as to why the negative fourth power ...
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1answer
44 views

Qualitative understanding of negative step potential problem

In QM textbooks the single step potential problem is explained in great detail. However, it is hard to understand what happens when $V_{0}<0$. Could anyone please explain qualitatively, how the ...
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1answer
91 views

Transmission coefficient and transmission probability

Are transmission coefficient and transmission probability the same terms? If not, could you please explain how they are related to each other?
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1answer
107 views

quantum mechanical treatment of rayleigh scatterring

Is there a quantum mechanical explanation of light scattering by atmospheric gases? Classically, treating the atmospheric particles as excited dipole antennas, we know that the amount of scattering is ...
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117 views

How can I use the Wronskian to show the following relation? [closed]

I cannot solve the part(a) and (b) mathematically. Have no idea how to start solving the problem by using the property of wronskian.
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How to prove that the scattering amlitude of bi-adjoint scalar field theory admits a Cachazo-He-Yuan (CHY) representation?

How to prove that the scattering amlitude of bi-adjoint scalar field theory admits a Cachazo-He-Yuan (CHY) representation?
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1answer
53 views

Thomson's Plum Pudding and Rutherford's scattering [duplicate]

Why did Rutherford's scattering experiment disprove the plum pudding? Assuming a gold-atom to be a large homogeneous ball and hitting it with small homogenuous $\alpha$-balls should lead to the ...
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38 views

Why is a diagonal scattering matrix preferable?

Maybe it is a trivial question, but it is not so clear to me why (if it is so) I would rather want a diagonal S-Matrix. Thanks
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26 views

electron free mean path understanding

I am having difficulties to grasp the idea that the probability a particle is absorbed between $x$ and $x + dx$ is given by $$dP(x) = \frac{I(x) - I(x+dx)}{I_0} = \frac{1}{l} e^{-\frac{x}{l}}dx$$ ...
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2answers
41 views

Division by 0 when calculating wave transmission and reflection coefficients

Perhaps more like a mathematical issue here... When we consider a wave propagating from medium 1 to a medium 2, boundary located at $x=0$, we have the following wave equations for the incident, ...
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61 views

Elastic X-ray diffraction: Where does the Photon Momentum go to?

lately I was discussing the following situation. Let's suppose you are doing X-Ray diffraction experiments on a crystal. So what you basically do is shooting a high energy photon with a wave vector $k$...
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83 views

Are all collisions involving photons and electrons elastic?

In my textbook it asks me to calculate the energy gained by an electron that scatters an incoming x ray through a given angle. Using the Compton scattering equation you can work out the change in ...
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Can I consider electron scattering with grain boundaries in metal as a tunneling process?

I am reading about the Mayadas-Shatzkes model (MS model). when electrons are scattered with the grain boundary, there is a probability that it will be transmitted to the other side of the grain ...
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19 views

Elastic electron scattering

In an electron diffraction pattern, the elastically scattered electrons are distributed over resolutions in the pattern corresponding to resolutions considerably higher than 1 Å. What does this ...
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3answers
266 views

Why does the frequency of a wave does not change on reflection and on transmission? [duplicate]

I wanted to know why the frequency of a wave does not change even on reflection or transmission and does it only depends on the source only.
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58 views

How do you do partial wave analysis with spin?

The derivations of the partial wave expansion I've seen have assumed spinless particles. However, when spin is involved, $l$ (orbital angular momentum) is no longer a good quantum number. What are ...
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1answer
43 views

Thickness of a target bombarded with deuterium

I need to calculate de thickness of a sheet of Zinc that is being bombarded by deuterium nuclei. I'm given that the fraction of nuclei dispersed below $\theta=90º$ with $T=8MeV$ is $0.9999$ and the ...
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72 views

The relation between the electric field and magnetic field?

I was wondering under what condition the relationship between the electric and the magnetic field holds: $\overrightarrow{B} =−\frac{\overrightarrow{𝑘}}{𝜔}×\overrightarrow{𝐸_0}𝑒^{𝑖(𝑘⃗ ⋅𝑥⃗ −𝜔𝑡)...
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1answer
67 views

Where is the missing energy in the Debye-Waller effect?

X-ray/neutron scattering from crystals and liquids is well-described by the scattering theory to give the (dynamic) structure factor which is a function of momentum and energy: $$S(\mathbf{k},\omega)=...
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1answer
73 views

Does sky luminance really decrease in steps as the Sun goes deeper under the horizon?

Playing with some atmospheric scattering simulations, I've come across a fact that, as the Sun goes lower under the horizon, sky luminance (neglecting sources of light other than the Sun) appears to ...
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Why did recombination make the universe transparent?

It is commonly said that after the universe cooled enough for ionized Hydrogen to settle down into neutral Hydrogen, i.e. recombination, the universe became transparent. A reason I have heard for this ...
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2answers
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If the probability that an alpha will deflect is $1/10000$, for $n$ layers, is the probability is only $1/10000n$?

I have attached a picture of an extract I read on Wikipedia (also in the AQA A-Level Physics specification and textbook). It says that 1/10000 alpha particles deflected in the alpha particle ...
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109 views

1D Potential Barrier Boundary Conditions (tunneling)

I'm trying to solve the boundary conditions of a 1D potential barrier for a free particle. The boundary conditions on the continuity of the wave function and its first derivatives leads to four ...
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16 views

Radiative Transport Equation scattering phase density probability term question

The development of Radiative Transport Equation has a contribution term called the scattering phase density probability function. It account to scattering events from photons from a different solid ...
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1answer
31 views

Reduced absorption coefficient question

I came across a paper that reads It is noteworthy that for a sample without lateral light propagation in the material, i.e. [reduced scattering] $\mu_s' = \infty$ and [absorption] $\mu_a=0$, ... ...
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1answer
49 views

Size of transversal momenta in Multi-Regge kinematics?

Considering a scattering process in which $2$ incoming particles annihilate and produce $n-2$ other particles, one can consider the particle momenta $p_i^\mu$ (with $i=1,2,3,...,n$) to be in so called ...
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$ e^+e^- \longrightarrow \mu^+\mu^-$ probability density function of $\theta$ strange trend

I'm considering the process: $$ e^+e^- \longrightarrow \mu^+\mu^-$$ The cross section in the center-of-mass frame: \begin{equation} \left( \frac{d \sigma}{d \Omega} \right)_{CoM}= \frac{\alpha^2}{4 s}...
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1answer
144 views

Why we don't need to normalize the scattering states?

I am new to QM, have find some wavefunction in different potentials, but there we need to normalize the wave function, for a reason that - particle should be found somewhere . So a wave-function, to ...