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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121 views

What is the rigorous description of scattering in relativistic QFT?

The first conundrum is what picture of QM to choose, in order to describe such a scattering. Unlike in non-relativistic QM, in RQFT the three all-known pictures are not at all equivalent. The ...
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0answers
67 views

The second order scalar quartic field theory Feynman diagrams

I'm trying to find the second order Feynman diagrams for the scattering of a scalar phion, described by the Lagrangian $$ L = L_0 + L_I \\ L_0 = \frac{1}{2}[\partial_{\mu} \phi(x)]^2 - \frac{1}{2}m^2 ...
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1answer
61 views

Evidence for standard model description of neutrons

as I don't know too much about experiments I have the following question concerning the evidence about the quark constituents in neutrons. After a quick google investigation I found some sentences ...
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0answers
21 views

What's the electromagnetic boundary condition on axis for a 2D axisymmetric problem?

I have a basic but also kinda confusing question here. We know for electromagnetic scattering from a body of rotation symmetry it's possible to reduce the 3D problem to 2D axisymmetric ones, which ...
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0answers
14 views

Canonical treatment of thermalization of two gases at different temperatures

I'd like to understand the thermalization process when two gases of different species and different temperatures are allowed to mix in an insulated container, interacting only through an elastic ...
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1answer
48 views

minimum hyperbolic distance for Rutherford Scattering

I saw in a textbook that gave the minimum distance for a hyperbolic trajectory in Rutherford scattering is given by $$r_{min}= ...
2
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1answer
142 views

Normalization of potential barrier solution

I don't understand a point in the solution attached to this barrier potential problem. Below equation 4.209, they say Assume first that the wave function on the right side of the barrier in the ...
2
votes
1answer
97 views

S-matrix in Weinberg QFT

I'm a bit confused by Weinberg's discussion of scattering. He defined the in and out states $|\Psi^{\pm}_\alpha\rangle$ with particle content $\alpha$ as states that transform under the Poincare group ...
4
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0answers
113 views

Pole in reflection/transmission coefficient and bound states

I was working on a scattering problem in a quantum mechanical system with Hamiltonian $$H_1=A^{\dagger}A=(-\partial_x+W(x))((\partial_x+W(x))).$$ One can show that a 'supersymmetric' partner to this ...
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4answers
727 views

Why is the sky blue: For a 3-year old [duplicate]

My nephew asked me yesterday why the sky was blue. I tried to explain it to him as best and as dumbly I could, but I failed. I tried to explain the concept of scattering of light using an analogy of ...
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0answers
38 views

Derivation of the dynamical master equation for collisional decoherence of a massive particle

I'm working on the problem of collisional decoherence of a massive particle interacting with an environment of light particles. The problem. I have some confusion regarding the derivation of the ...
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1answer
94 views

Rutherford scattering in Quantum Mechanics terms?

Rutherford scattering stands as the first evidence of atoms having the positive charge concentrated in a small nucleus. While the classical description of the phenomenon is satisfactory, it puzzles ...
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1answer
240 views

Converting between $\frac{d \sigma}{d t}$ and $\frac{d \sigma}{d \Omega}$

I'm performing some simulation where I require the integration of a cross section of the form $$\sigma = \int_{-s}^{0}dt \frac{1}{(t-\mu^2)^2} f(\theta,\phi)$$ where $s$ and $t$ are the usual ...
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2answers
157 views

Rectangular potential barrier

Take the usual rectangular potential barrier, that is: $$V(x)=0 \: \text{if} \: x<0 \: \text{or}\: \: x>a$$ $$V(x)=V_0 \: \text{if} \: 0\leq x \leq a.$$ I've looked at several notes and books ...
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1answer
84 views

Compton's formula for change in wavelength [closed]

I want to measure the shift in wavelength predicted by Compton's formula. I find that I cant measure a shift of less than 5% and that I also cannot measure at angles greater than 150 degrees. What is ...
1
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1answer
53 views

Bragg Scattering of Thermal Neutrons [closed]

I'm currently reviewing Bragg scattering. The particular problem below has me slightly confused on whether I'm thinking about it correctly. Questions Is the problem below referring to the kinetic ...
0
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1answer
83 views

Lippmann-Schwinger equation and $T$ expansion

Lippmann-Schwinger equation, in operator form, is: $$ T=V+V\frac{1} {E-H_0+i \hbar \varepsilon} T=:V+V\Theta_0T, $$ where $H_{tot}=H_0+{V}$ is the hamiltonian ($H_0$ is the free particle hamiltonian ...
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1answer
420 views

What would the sky look like if the sun was a different type of star?

Barring, of course, all other issues that wold naturally arise from the following question - if we made the sun a cooler, red star or a hotter, blue star, what impact would that have on the colour of ...
-1
votes
1answer
68 views

Photon energies and attenuation [closed]

I hope you can help. I am trying to understand which attenuation effect (photoelectric, compton scatter and pair production) is dominant at which level of photon energy and why. The levels are 10keV, ...
4
votes
1answer
161 views

Strange use of complex analysis in Weinberg QFT 1?

In the beginning of chapter 3 on scattering theory in Weinberg's QFT book there is a use of the Cauchy residual theorem that I just cannot get. First some notation, we are looking at states that are ...
3
votes
1answer
57 views

What type of matrices do we mean by $I_{D2}$ and what is Chandrasekhar decomposition?

Suppose that $A_{2\times 2}$ is a hermitian matrix, so it has real eigenvalues $\lambda_1$ and $\lambda_2$ and corresponding orthonormal eigenvectors $\underline u_1$ and $\underline u_2$ and we know ...
2
votes
1answer
80 views

Difference between scattering amplitude and scattering lenght

I'm studying neutron scattering theory and I noticed that one usually writes the scattered wave as a spherical wave: $$\psi \sim \frac{-b} {r}e^{ikr}$$ where $b$ is known as scattering lenght. From ...
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0answers
21 views

How is the frequency unchanged in elastic wave scattering with a crystal?

it makes sense that with an inelastic scattering process, a wave approaches a crystal, and then some energy is imparted to the phonons, so that the outgoing wave has a different frequency from the ...
0
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1answer
62 views

Is this possible to determine exactly the scattering angle for inverse-cube force?

I am trying to determine the scattering cross section for the potential $$ V= \frac{a}{r} + \frac{b}{r^2}$$ As I am completely stuck while determining the scattering angle (I don't see a way to ...
3
votes
1answer
64 views

Rate of interaction of free electron with photons from sunlight

How many photons does a free electron (in sunlight say) interact with per second? I did a rough calculation assuming the electron interacts with any photon that enters through an area the size of ...
0
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1answer
25 views

Non-square transfer matrix from square scattering matrix

I'm trying to construct the transfer matrix for an arbitrary system with 1 input and 2 outputs, like a splitter (shown below) or 1x2 multi-mode interferometer. (Image borrowed from ...
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2answers
58 views

Why conductors don't scatter light?

Air molecules can be oscillated by E field and re-radiate EM waves in different directions. However, if light is shined to a conductor the E field oscillate the free charges but the effect is to ...
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votes
2answers
84 views

Will neutral particles be affected by EM waves?

Air molecules scatter sunlight and makes the sky blue. Many books say that the air molecules are oscillated by E field and so they become sources of EM waves. Is it because the air molecules have ...
0
votes
0answers
36 views

Relaxation time approximation in anisotropic potential scattering event

In relaxation time approximation (RTA) of Boltzmann transport theory, the relaxation time is calculated by $\frac{1}{\tau(\mathbf{k})}=\frac{2 \pi}{\hbar V}\sum_{\mathbf{k^{'}}} \delta ...
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1answer
183 views

Direct vs. Compound reactions

I know there are different types of direct reactions like inelastic scattering and such. But is the main difference between direct and compound reactions that one excites (Or at least can) the whole ...
2
votes
1answer
101 views

Dirac delta function definition in scattering theory

I'm studying scattering theory from Sakurai's book. In the first pages he gets to the following expression: $$\langle n|U_I(t, t_0)|i\rangle=\delta_{ni}-\frac{i}{\hbar}\langle ...
3
votes
0answers
190 views

One-particle scattering: LSZ vs Feynman [duplicate]

This question is about Klein-Gordon theory (the field is hermitian). If I calculate the amplitude for the process $\phi\to\phi$, I get two different results depending on whether I use Feynman rules ...
5
votes
2answers
860 views

Why is space black? [duplicate]

We on earth see the space black only at night. But on moon it observed that the space is black in both day and night even though the source is same for both ( the sun).Why? And also there are many ...
7
votes
3answers
259 views

Contradictory result for scalar-field propagator from Feynman rules and LSZ formula

I am trying to learn how to calculate scattering amplitudes in a Klein-Gordon theory. I am getting stuck with the simplest of the examples: $\phi\to\phi$ in a free scalar-field theory. If I calculate ...
2
votes
1answer
74 views

Difference between Rayleigh scattering and fluorescence spectroscopy [closed]

How can we differentiate Rayleigh scattering from fluorescence spectrum?
3
votes
1answer
310 views

How is Lippmann-Schwinger equation derived?

I'd like to know the derivation of Lippmann-Schwinger equation (LSE) in operator formalism and on what assumptions it is based. I consulted the Ballentine book as advised in this Phys.SE post, but I ...
0
votes
1answer
181 views

X-ray diffraction on thin film

As far as I am concerned, when we perform an X-ray diffraction experiment using a Bragg-Brentano diffractometer using the "powder method" we have that the scattering pattern depends on only one angle ...
3
votes
1answer
196 views

Plane wave expansion of cylindrical functions:Summation of the Hankel functions

I understand that; in cylindrical coordinates, the basic solutions of the Helmholtz equation are of the form Hankel function of integer order times a complex exponential term ...
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votes
0answers
25 views

Optimal wavelength for low IR attenuation under normal atmospheric conditions?

I can't find any good data about the transmit attenuation of infrared light in the atmosphere transmitted horizontally (there is a bunch of stuff detailing penetration of radiation from space, but ...
3
votes
2answers
412 views

Why can't gravitons be created in traditional particle accelerators?

I've heard that it is incredibly difficult to detect a graviton, but I don't quite understand why. With all of the knowledge I have at the present time it seems like it should be possible to create a ...
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vote
1answer
46 views

Coulomb collision

I was reading an article by N. Bohr and came upon the following problem (the following wording is actually taken from a book by Thompson - Conduction of Electricity Through Gases): Let $M_1, M_2$ ...
3
votes
0answers
102 views

False sunset and false sunrise time estimation

False sunset and false sunrise are described . Here is a sample day rise and set time according to AccuWheather site and calculated value of sunrise and sunset in my country. Could you please help ...
3
votes
1answer
102 views

Interactions and scattering length in Feshbach resonances

In the context of cold atoms, one can make use of the Feshbach resonance mechanism to alter the sign and value of the two-particle scattering length by applying and varying an external magnetic field. ...
4
votes
0answers
126 views

Will a black hole cause scattering of a gravitational wave?

In my GR textbook, it states that gravitational waves can undergo interference but not scattering. I am just starting the chapter on linearised gravity concepts (weak field approximation) and my ...
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1answer
95 views

Deformation parameters of a nucleus

How are the deformation parameters (quadrupole, hexadecapole etc) of a nucleus mathematically related to the reduced transition probabilities $B(El)$ values obtained experimentally?
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0answers
19 views

Undirected scattering is named fluorescence. What is directed scattering named?

Undirected scattering is named fluorescence. What is directed scattering named? Also, does fluorescence = spontaneous emission?
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1answer
43 views

Multiparticle Mandlestam Variables Extension

So in 4D we have three Mandlestam variables for a 4-particle scattering process. This corresponds to $p_i^\mu$ giving us 16 degrees of freedom. Momentum conservation reduces this by 4, and we have 4 ...
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0answers
101 views

Fermion - Antifermion (annihilation) scattering amplitude

I'm trying to get the scattering of the diagrams described here in the "annihilation, part ii" (fermion/antifermion - scalar/scalar) ...
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0answers
44 views

Scalar spherical wave in terms of Cylindrical coordinates

I am looking at a problem where a scalar spherical wave is scattered by an uncharged cylinder. I want to work in cylindrical coordinates in order to simplify it. Can anyone tell me how to expand the ...
0
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0answers
70 views

Incoherent Intermediate Scattering Function from Molecular Dynamics Simulations

I want to calculate the incoherent intermediate scattering function (ISF) using the self-part of the van Hove function. When I plot the ISF as a function of time, should I consider the modulus of the ...