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, ...

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8
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1answer
437 views

Green's function in path integral approach (QFT)

After having studied canonical quantization and feeling (relatively) comfortable with it, I have now been studying the path integral approach. But I don't feel entirely comfortable with. I have the ...
3
votes
0answers
78 views

Delta normalization and density of states in the Golden rule of Fermi

In the text-book derivation of first order inelastic scattering amplitude, box normalization is usually used to calculate the result. This leads to a correct result through the Golden Rule of Fermi, ...
0
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0answers
74 views

Dynamic light scattering of rods at low q

In dynamic light scattering (DLS), I understand that for spherical particles it is their diffusive motions which cause the intensity fluctuations that are correlated. And that the scattering vector ...
2
votes
1answer
128 views

Phase Shift of Tunneling Wave

What is the phase shift of a wave that tunnels through a barrier, meaning the difference in phase between the incoming (in front of the barrier) and the outgoing (behind the barrier) waves? For ...
2
votes
1answer
69 views

Any difference between “Mueller matrix” and “Scattering matrix”?

I find in some references 4x4 Mueller matrix and in other references 4x4 Scattering matrix. Are they different or identical? If they are different, I would like to know the book or any research ...
3
votes
1answer
607 views

s-wave, p-wave or d-wave collisions in scattering theory

In scattering theory, what is a good intuitive picture to think of s-wave, p-wave or d-wave collisions ? What is their importance and what are the examples where a particular one is assumed to be the ...
1
vote
1answer
81 views

What do they mean with: photon scattering with $q^2=-Q^2\leq 0$

In a scattering problem, let q denote the four-momentum of the photon. Is $q^2=-Q^2\leq 0$ simply a statement of what metric one uses and simultaneously a definition of $Q^2$?
2
votes
3answers
288 views

Naive question about the S-matrix

In quantum field theory, the elements of the S-matrix are defined as the amplitude describing the transition from an initial $n$-particle state (the "in" state) to an final $m$-particle state: ...
0
votes
1answer
78 views

Why does the Debye-Scherrer procedure work (powder diffractometer)

In the Debye-Scherrer procedure a sample of crystalline powder is hit by a beam of monochromatic photons. The diffracted photons are measured with a detector. We have constructive interference of the ...
0
votes
0answers
13 views

Form factor and Guinier regime [duplicate]

sorry for reposting. I dont get why it is such a good idea to plot the logarithm of the form factor vs $Q^2$ in Guinier plots. It seems arbitrary to me.
0
votes
1answer
93 views

Guinier regime for form factor

Why is it such a good idea to plot the logarithm of the form factor vs $Q^2$ in Guinier plots. It seems arbitrary to me.
3
votes
3answers
178 views

Bound States clarification

Our professor hasn't explained what bound states are. Could you give me an idea of what they mean and their importance in quantum-mechanics problems with potential (e.g. a potential described by a ...
1
vote
1answer
60 views

Photon number conservation during scattering

I was reading this writeup on the Kompaneets equation and the Sunyaev-Zel'dovich effect. On page 3, section 2 the author states There is no way to increase the mean energy of a planckian ...
2
votes
0answers
49 views

How to prove the equivalence of two definitions of the scattering cross section

I have noticed that there are two definitions of differential scattering cross section in non-relativistic quantum mechanics. One of them is the most popular, particularly it is used in the book of ...
4
votes
0answers
130 views

Calculating Forces via Feynman diagrams?

How would one go about calculating forces that test objects feel using Feynman diagram methods? For example, say we have a massive object in GR so that the metric takes on the standard ...
0
votes
0answers
44 views

What is the importance of the Odderon?

From hep-ph/0001149v1: (1) an Odderon contribution is absolutely necessary to reproduce quantitatively well the data; while its presence is not explicitly needed at $t = 0$, its inclusion is ...
4
votes
2answers
253 views

Are all scattering states un-normalizable?

I am an undergraduate studying quantum physics with the book of Griffiths. in 1-D problems, it said a free particle has un-normalizable states but normalizable states can be obtained by sum up the ...
6
votes
4answers
366 views

Is forward scattering = no scattering?

What is forward scattering? If it is equivalent to no scattering, then why not call it "no scattering"?
1
vote
2answers
141 views

Why an infinitely measuring apparatus in gravity is not possible?

In the discussion of the amplituhedron paper (arXiv:1312.2007), there is the following discussion in paragraph 14.outlook (page 28): Quantum mechanics forces us to divide the world in two pieces - ...
4
votes
1answer
293 views

Connected and strongly connected Feynman diagrams

Recently I read, that only connected Feynman diagrams give contribution of nonzero values into the scattering amplitude. Why it is so and what is the physical sense of connected diagrams (due to ...
1
vote
0answers
157 views

Derivation of Scattering Equation 9.88 in Thornton & Marion

I am confused as to how a particular equation in Thornton & Marion's 'Classical Dynamics of Particles and Systems' was derived. It is equation 9.88, on page 354 of the fifth edition. An incoming ...
15
votes
2answers
630 views

Why Cronin Effect Happens?

I'm looking for explanation on Cronin effect but unfortunately there's no Wikipedia entry or self-contained paper to start from. The statement of this effect is that: "At leading order, multiple ...
2
votes
0answers
93 views

Partial waves and the velocity expansion of a scattering cross section

I'm confused about the relation between the velocity expansion of a scattering cross section and the angular momentum (partial wave) expansion. For example, for dark matter annihilation, we write ...
3
votes
0answers
45 views

Scattering theory on Schrodinger and Feynman languages

Recently I heard that both of "languages" of scattering theory (formal solution by method of classical scattering theory and its reworking by Feynman with his rules) predict virtual particles. But for ...
1
vote
1answer
43 views

What are the criteria to have rutherford backscattering?

Assuming there is an incident beam(i.e. $p$ or $\alpha$) and a target. How can I be sure if a rutherford backscattering will take place? I know that for high $Z$ it more likely to happen as well as ...
4
votes
2answers
142 views

What is the sense of introducing generating functional to the summands of expansion of S-matrix?

Let's have generating functional $Z(J)$: $$ Z(J) = \langle 0|\hat {T}e^{i \int d^{4}x (L_{Int}(\varphi (x)) + J(x) \varphi (x))}|0 \rangle , \qquad (1) $$ where $J(x)$ is the functional argument ...
2
votes
0answers
354 views

Radial Wave Function for Spherical Squared Well Potential and $S$-Matrix

I have a problem with this exercise because I really don't know how to proceed. It's related with the "S-matrix". In class we saw this example: Consider the spherically symmetric potential: ...
1
vote
0answers
58 views

Some strange transformation [closed]

In a lecture (look at the chapter "The fermion determinant in a constant field", p. 5) I found some strange transformation, which is given by eq. 18. How to prove it? Exactly, I don't understand the ...
6
votes
1answer
137 views

Importance of MHV amplitudes

Why are MHV amplitudes so important? How/where are they used and why do people keep trying to rederive them in many different ways?
4
votes
1answer
196 views

Do higher frequency EM waves travel longer than lower EM frequency waves?

In radio communication, the distance traveling seems to be an important parameter before we choose the frequency band of communication. There is also a path-loss model that describes a distance ...
4
votes
2answers
100 views

Is ocean color affected by Rayleigh Scattering?

We know that sky color is due primarily to Rayleigh scattering. Is Rayleigh scattering the dominant effect for ocean color too?
4
votes
1answer
173 views

How does light pass through rough glass?

Light incident on a rough surface will be diffuse after passing it. Angular intensity depends on the grinding of the glass surface. I'm trying to find information about the scattering indicatrix of ...
1
vote
0answers
48 views

How common is compromised reference data for physical properties of materials and elements?

This question concerns Monte Carlo simulation of electron scattering in complex material structures, especially the reliability of publicly available source codes and reference data for physical ...
2
votes
0answers
99 views

Møller scattering: twisted?

I am studying the Møller scattering, but I don't know how to get the twisted diagram from the S-matrix. Has anybody a good explanation?
5
votes
1answer
398 views

Scattering amplitude and LSZ formula

I'm arriving at a contradiction. To calculate the scattering amplitude, one usually follows the prescription given by the Feynman rules that you only consider fully connected diagrams with the ...
0
votes
0answers
58 views

Electron scattering

I'm trying to figure out the missing step here, in a problem about X-ray crystallography. I am referring to the attached image: In the image, $A =$ electron density, $Z =$ distance traveled, ...
2
votes
1answer
194 views

Virtual particles and S-matrix

One of methods of introducing of virtual particles is using perturbation theory. We say that scattering matrice amplitude $M_{in \to out}$ contains of $\delta(P_{out} - P_{in})$, which realizes ...
1
vote
1answer
349 views

Transparence of an infinite square well? [closed]

What does it mean by an infinite square well being transparent? I have been doing the calculation of the infinite square well and I came up with an answer $T = 1$ where $T$ for Transmission ...
2
votes
0answers
312 views

QM Question about the Dirac Delta Potential

I just wrote down the solution for the bound state of the Dirac delta potential well, for $E<0$, and apparently there is only one specific energy for the bound state, and it is negative. I solved ...
5
votes
1answer
313 views

Quantum tunneling effect in a potential of the kind $V(x)=A\frac{x^2}{1+x^4}$

Given a potential: $$V(x)=A\frac{x^2}{1+x^4}$$ with $A\gt 1$ and a quantum particle inside the well around the point $x=0$. I'm stuck on the calculation of the transmission and reflection coefficients ...
-2
votes
1answer
102 views

Why do planets other than earth have colours?

I know Mars has many red rocks and mountains. But since it does not have any atmosphere, it shouldn't have any color. So, why does it appear red?
1
vote
1answer
42 views

Decrease in Intensity [closed]

A beam of particles pass through a target made of thin foil of a very small thickness $\Delta x$ having $N$ particles per unit volume. Let the collision cross section be $\sigma$ . If the intensity of ...
2
votes
1answer
119 views

Why multiply by volume when integrating over final momenta in scattering amplitude calculations?

I am learning about calculating decay rates from quantum field theory amplitudes from David Tong's lecture notes (page 74 in the notes, 24 in document). However, I have some doubts: When he says the ...
1
vote
0answers
208 views

What happens to the amplituhedron in a non-peturbative context?

The Amplituhedron has recently been popular; it supposedly encodes perturbative scattering amplitudes in a simple, geometric fashion. What happens to it in a non-perturbative context? Is there ...
7
votes
1answer
152 views

Does QED provide a closed form for Coulomb logarithms?

The classical models for the integrand as well as the cut-offs in computing the Coulomb logarithm are pretty rough. Does quantum electrodynamics have definite expressions for the quantity ...
0
votes
0answers
93 views

Collision of 2 neutrons

If two neutrons collide in 3D space and we want to determine the final velocities of both nuetrons (3 components for each neutrons), we can use the conservation of momentum equations and the ...
11
votes
2answers
323 views

Locality in the scattering amplitude

Early in this talk by Nima Arkani-Hamed, he describes what locality means for scattering amplitudes. "Locality tells you that the only poles in the scattering amplitude occur when the sum of a subset ...
4
votes
0answers
904 views

How does one actually compute the amplituhedron?

I was watching Nima's very popular talk (download if you're using chrome) (also mirrored at youtube here) about the "Amplituhedron", which has suddenly become very popular recently. He talks all ...
2
votes
1answer
468 views

Why depolarization of light by scattering

I am trying to understand the concept of depolarization of light by various particle shapes. For example, depolarization light scattered (re radiated) from a sphere illuminated with vertically ...
1
vote
1answer
219 views

Classical Rutherford scattering (partial) derivation

I am having trouble answering the following question, please could you help! Thank you in advance for any assistance you can give. Consider classical Rutherford scattering of a particle with mass $m$ ...