Questions tagged [scattering-cross-section]
A cross-section is the name given to a hypothetical unit of area (often in units of Barns) for measuring the probability of scattering events in particles collisions. DO NOT USE THIS TAG for a physical non-probabilistic cross-section of a macroscopic object.
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Why, in spin sums, we sum over final spin states and average over initial states?
I am reading Halzen's book about quarks and leptons and on page 120 he talks about spin sums.
He says that in order to calculate the amplitude between unpolarized states we have to sum over FINAL ...
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Where to find cross section data for $e^{-}$ + $p$ $\longrightarrow$ $p$ + $e^{-}$?
Where to find cross section data for $e^{-}$ + $p$ $\longrightarrow$ $p$ + $e^{-}$ ?
PDG's cross-section data listing does not include it.
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Cross-section in relativistic limit: Fermi's golden rule still valid?
In order to calculate the cross-section of an interaction process the following formula is often used for first approximations:
$$
\sigma = \frac {2\pi} {\hbar\,v_i} \left| M_{fi}\right|^2\varrho\...
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Why is the laboratory frame energy always greater than the center of mass frame energy?
I have been looking for an answer to 'Why is the laboratory frame energy always greater than the center of mass frame energy during collisions?'.
A lot of resources provided mathematical explanations....
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Physical interpretation of infinite total cross section
What does it tell us about a process, say A+B->C+D, if the calculated total cross section is infinite?
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Cross Section Peskin vs Srednicki
in Peskin Schroeder after the derivation of the differential cross section there is a comment for the central mass system (CMS), which says:
In the special case, where all four particles have ...
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Interpreting the Cross Section Ratio $R$
Below is experimental data for the ratio $$R=\frac{\sigma(e^+e^-\rightarrow hadrons)}{\sigma(e^+e^-\rightarrow\mu^+\mu^-)}$$ as a function of the centre of mass energy $\sqrt s$.
I am interested in ...
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Differential Cross Section
I would like to know what exactly the term differential cross section means. It comes from electron scattering experiments which are used to deduce the charge distribution of a nucleus and the cross ...
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Exclusion limits on particle dark matter
I'm trying to make sense of how the upper limits of the cross-section of particle dark matter (WIMPs) are computed, like in the figure below. This is taken from an article on dark matter searches.
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What is the relationship between Mie scattering amplitudes, incident intensity and outgoing intensity?
Wikipedia's Mie scattering Mathematics discusses the scattering amplitudes $S_1(\theta), \ S_2(\theta)$ for each outgoing polarization of an incident EM plane wave on a uniform sphere.
It defines the ...
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Cross-sectional area of a Gaussian beam of particles
On page 47 of the seventh edition of Particles and Nuclei, the authors write the following:
For a Gaussian distribution of the beam particles around the beam centre (with horizontal and vertical ...
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Mass dimension of an $n$-particle scattering amplitude in 4D
For the 4-dimensional case, and using the cross-section formula, how can we show that the mass dimensions of an $n$-particle amplitude must be $$[A_n] = 4-n~?\tag{2.99}$$
My understanding is that the ...
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Form factor for Proton
To find the charge distribution of proton , we study electron proton scattering and compute the form factor to find the cross section. The form factor comes out to be Fourier transform of charge ...
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Why does Gadolinium have the highest neutron cross section?
Gadolinium-157 has the highest thermal-neutron capture cross-section among any stable nuclide. Based on my layman's understanding of neutron capture – particularly the fact that (I assume) neutrons ...
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Understanding scattering cross section
I think I might have a serious misunderstanding of some concepts to do with scattering cross sections and would really appreciate any help.
As far as I can tell the differential cross section is ...
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