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.

learn more… | top users | synonyms

1
vote
1answer
48 views

From a cross section to a probability

This is homework problem: Given the cross-section of a neutrino-electron scattering, what is the probability for a solar neutrino to scatter with a electron as it goes through the center of the Earth? ...
5
votes
1answer
71 views

How to sum over final, and average over initial color states?

Consider the $s$-channel mediated top quark production process $$ d + \overline d \rightarrow t + \overline t$$ Using the Feynman rules for QCD, the amplitude contains a color factor $$[c^\dagger ...
1
vote
1answer
20 views

Energy dependent cross sections for neutrons

Do you know where I can find a table with energy dependent cross sections for neutrons? Thanks!
2
votes
0answers
36 views

Conversion of QCD cross section formula

I'm writing a program to calculate NLO cross sections for semi-inclusive high-$p_T$ pion production in proton-proton-collisions for my bachelor thesis. I've got a paper describing the production ...
0
votes
1answer
19 views

Internuclear Binding Force: Experimental geometric detail

I am looking for the most precise currently available deuterium potential energy curve (generated purely by experimental data) on the nucleon-nucleon scale. This is crucial. I need a radial ...
2
votes
2answers
40 views

Do molecular bounded systems shield or reduce neutron cross-sections?

When talking about neutron cross-sections, literature is usually investigating isolated cases of Neutron + Atom. Here, the abundance of hydrogen is dominating neutron fluxes through material. I ...
2
votes
1answer
116 views

Rutherford Experiment - practical and theoretical questions

I performed the Rutherford experiment the other day, using Au thin foil of $2\,\mathrm{\mu{}m}$, a source/gun of α particles (241Am) and a detector/counter. α particles were shot from the source ...
2
votes
0answers
38 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 ...
1
vote
0answers
29 views

Trouble evaluating an integral arising from particle collision

Assume we have two charged particles colliding. He have particle 1 with mass $m_1$, charge $Z_1 \cdot e$ which travels in $x$-Direction passing by a STATIONARY particle 2 (mass $m_2$, charge $Z_2 ...
4
votes
3answers
88 views

Do nuclear reaction cross sections depend on the angle between incident beam and target-crystal?

Shouldn't the absorption rate of a beam of particles strongly depend on the angle between the beam and the target material's crystal-axis (if the target material is a monocrystal)? At certain angles, ...
3
votes
0answers
97 views

List of cross sections?

Sometimes I need to look up a certain cross section, say the inclusive Z production cross section at $\sqrt{s}$ = 7 TeV. Is there a place where 'all the' cross sections are tabulated ...
2
votes
0answers
93 views

Parton Distribution Functions, average cross section of the nucleon

Say we are given the scattering cross section for neutrinos from $d$ and $\bar{u}$ quarks as $\frac{d\sigma^{d}}{dQ^2}=\frac{G_F^2}{\pi}$, $\frac{d\sigma^{\bar{u}}}{dQ^2}=\frac{G_F^2}{\pi} (1-y)^2$, ...
3
votes
1answer
234 views

Why is the total interaction cross section larger for incident particles with lower energy?

The cross section of a nuclear interaction is a measurement of the probability of that interaction occuring. These probabilities are typically presented in terms of barns ($10^{-28}$ m$^2$) as a ...
1
vote
0answers
150 views

QFT: differential cross section from center of mass to lab frame

I have the following process: two ingoing particles, a photon hitting a nucleus, and two outgoing particles, the nucleus and a pion. I have computed $|M|^2$ and the differential cross section in the ...
2
votes
0answers
57 views

Literature value of forward-backward asymmetry on the Z resonance?

I did a Standard Model calculation and I want to compare my answer to a measured value. Does anyone know the literature value for the forward-backward asymmetry $\frac{\sigma_F - \sigma_B}{\sigma_F + ...
1
vote
1answer
232 views

Integral in Peskin and Schroeder

I'm having a bit of a slow day, and can't see how to do the following integral in Peskin and Schroeder (page 107 for anyone with the book). We've derived in the centre of mass frame the integral over ...
6
votes
1answer
218 views

SUSY, ways to boost Chargino/Neutralino production?

Does anybody know a good reference that works out the equations for the Chargino/Neutralino production cross section in SUSY? I'm trying to understand if there are any tricks for boosting the ...
1
vote
1answer
99 views

Definition of scattered particle?

Compare the number of scattered particles: $N_s=Fa\int\sigma(\theta)d\Omega$ With the total number of incident particles: $N_{in}=Fa$ Here, F is the flux of incoming beam, a the area. sigma the ...
1
vote
1answer
97 views

What is the spectrum of the Earth's albedo?

I was recently discussing climate change with a friend and was surprised (and embarrassed) to learn that the heat capacity of CO${}_2$ is not higher than that of nitrogen contrary to my assertions. ...
1
vote
1answer
172 views

How do particle scattering cross sections scale with energy in colliders?

How do particle scattering cross sections scale with energy in colliders? Particularly photons, electrons, protons, and gold or lead nucleii? (If necessary, break this into four separate questions.) ...
5
votes
0answers
167 views

What statistical test should I use?

I have two differential cross sections $d\sigma_{1,2}/dM$ ($M$ is some invariant mass) corresponding to different hypothesis. What I want is to calculate how well the appropriate experiment would do ...
1
vote
2answers
211 views

Where to find cross section data for e- + p -> p + e-?

Where to find cross section data for e- + p -> p + e-? PDG's cross section data listing does not include it.
3
votes
2answers
429 views

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?
5
votes
1answer
224 views

Inelastic nucleon-nucleon cross section at LHC energies

I am trying to reproduce the number of participants $N_{part}$ in Pb-Pb Collisions at LHC using a Glauber Monte Carlo simulation, specifically aiming to reproduce the values given in Phys. Rev. Lett. ...
11
votes
1answer
754 views

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| ...
5
votes
1answer
177 views

Cross section fon non-collinear beams

If I have two collinear beams with opposite velocities the cross section is defined by the formula: $\frac{dN}{dtdV}=\sigma \rho_1 \rho_2 |\underline{v}_1-\underline{v}_2|$ where $\sigma$ is the ...
3
votes
1answer
92 views

estimating ion collisions from Vlasov equations

Suppose you have a distribution function $ f_{\alpha}( \vec{r} , \vec{p} , t)$ obtained from Vlasov equations for a certain $\alpha$ species, say some ions. Is there a rigorous way (in the domain of ...
4
votes
2answers
567 views

Quantum Field Theory cross sections integrals

Where can I find some examples of cross sections calculations in QFT done step-by-step? Those integrals are a little horror. For example - a simple scalar+scalar -> scalar+scalar at the tree level in ...