Read about cross section | 30 Discussions | Page 1

  1. qnach

    A Software for cross section calculations using .cif files

    Is there any software available to calculate cross section using .cif file?
  2. Adesh

    I How can generatrices be parallel to the y-axis?

    CONTEXT: We are finding the the buoyancy force on a boat which is upright in a still water (Fluid at rest) and the only gravity is acting as the external force. So, first we go for imaging a proper geometry of our boat. See this figure : For this figure the book writes: Fig 8 represents...
  3. W

    I Cross Section Formula in Peskin and Schroeder

    On page 105 of Peskin and Schroeder's book it says that the integral over ##d^2b## in the expression: $$d\sigma = \left(\Pi_f \frac{d^3 p_f}{(2\pi)^3}\frac{1}{2E_f}\right) \int d^2b\left(\Pi_{i=A,B} \int \frac{d^3 k_i}{(2\pi)^3}\frac{\phi_i(k_i)}{\sqrt{2E_i}} \int \frac{d^3...
  4. A

    A How do soft Pomerons become hard?

    The exchange of soft Pomerons (and Reggeons) (##\alpha_R(0)=0.55## and ##\alpha_P(0)=1.08##) seem to describe total hadron-hadron cross sections pretty well in the Regge limit. See, for example: https://arxiv.org/abs/hep-ph/9209205 In this limit, QCD is of very little use since the exchanged...
  5. A

    B Differential cross sections in Pythia

    Dear Users, I would like to ask you how can I plot d_sigma/d_omega and d_sigma/d_theta for any collision (for instance, proton and proton) using pythia event generator. I would be greatful if you could tell me how make it. Any ideas would be appreciated. Kind regards.
  6. C

    I Are resonances formed in the scattering of a baryon and a meson?

    Consider the following reaction of strong interaction (in a scattering process) $$n+\pi^+\to \Lambda_0+K^+\tag{1}$$ Then the particle ##\Lambda_0## formed decays with weak interaction $$\Lambda_0\to \pi^+ +p\tag{2}$$ For each decay process I measure the four momenta of ##K^+##, ##\pi^+##...
  7. C

    I Measuring characteristic time of strong and weak interaction

    Consider a scattering between two particles a and b that produces two particles c and d: d is stable, while c decays in two other different particles e and f. The first interaction is by strong force (time of interaction ##t_1\sim 10^{-23}s##, which is also the time of generation of c and d)...
  8. O

    Effective cross-section of catching a comet with the Sun

    Hello. 1. Homework Statement I have to find formula for effective cross-section (σ) of catching a comet with the Sun. I know mass of the Sun (M), radious of the Sun (R) and initial velocity (v) of the comet (at a big distance from the Sun). Homework Equations σ=πb^2, where b is on the...
  9. O

    Effective cross-section of catching a comet with the Sun

    Hello. 1. Homework Statement I have to find formula for effective cross-section (σ) of catching a comet with the Sun. I know mass of the Sun (M), radious of the Sun (R) and initial velocity (v) of the comet (at a big distance from the Sun). Homework Equations σ=πb^2, where b is on the...
  10. Kirk Truax

    Neutron fission cross section

    Hey all, Does anyone happen to know the value of ν∑f for natural uranium? Here ν is the average number of neutron released from fission and ∑f is the macroscopic fission cross section of uranium. Kirk
  11. chandrahas

    A What is wrong with particle acceleration based fusion?

    Recently, I was thinking about fusion and this thought struck my mind. In tokamaks, the plasma is heated to extremely high temperatures in order to supply enough energy to the ions for them to fuse. But since, the plasma follows a boltzmann maxwell distribution curve,only a few ions have have...
  12. chandrahas

    I How large is the collision cross section compared to nuclear fusion cross section

    Most Fusion reactors, and the leading ones like JET, use high temp. plasma and confine it. So, the plasma would approximate the Maxwell- Boltzmann distribution. This means that only a small portion of the plasma has enough energy to fuse. But, collisions are much more often, right? Since not all...
  13. D

    I A question about momentum integrals and lengths

    I've been making my way through Matthew Schwartz's QFT book "Quantum Field Theory and the Standard Model". In chapter 6 he derives the differential cross-section for a ##2\rightarrow n## interaction. As part of the derivation, he introduces the Lorentz invariant phase space measure (LIPS), and...
  14. kiwaho

    A Equivalence equation between cross section & half life?

    Is there equivalence equation between cross section & half life? For beta decay, we usually use half life to describe how fast or slow the decay undergo. For nuclear reaction, we use cross section to describe the possibility of reaction. In a sense, they reflect the same root physics spirit. Is...
  15. kiwaho

    A Why so big of a difference in cross section by different sources?

    if you look up the cross section in Janis books, usually for same reaction, different cross sections are quoted by different laboratories. For example, the values of thermal neutron capture reaction 9Be(n, r)10Be: EAF-2010, 0.0075b ENDF/B-VII.1, 0.01b JEFF-3.1.2, 0.0088b JENDL-4.0, 0.0085b...
  16. lippyka

    Rutherford Scattering

    Hi I am revising for an exam and am a bit confused with Rutherford Scattering - Finding the cross section (is the cross section different to the differential cross section?) - Finding the solid angle. So here is a past question: A beam of 6MeV alpha particles is incident on a platinum foil. A...
  17. M

    Calculating Cross Section

    Homework Statement I have a problem in calculating cross-section in elektron-positron -> muon-antimuon scattering. Homework Equations In the relativistic limit, we find the differential cross-section of {e}+{e^-} -> {μ}+{μ^-} is \frac{d\sigma}{d\Omega}=\frac{\alpha^2}{4s}*(1+cos^2{\theta})...
  18. X

    I Lambda baryon decays

    I've been asked to find the ratio between the cross sections of the two folowing decais: Using the CKM matrix and the feynman diagrams for both decays, I reach the conclusion that the Ratio is exactly 1. However, consulting this document...
  19. kiwaho

    How many barns at least for a commercial nuclear reactor?

    The conventional commercial fission reactors use uranium-235 as fuel. Its cross section of (n, fission) reaction at thermal neutron is about 585 barns. My question is: Is there a known threshold of the cross section that makes a nuclear reaction not sustainable if the minimal cross section is...
  20. kiwaho

    I How many barns above could make nuclear reaction rate 100%?

    All guys know the importance of cross section. In a sense, it stands for the possibility of a reaction. I am wondering how many barns above could make nuclear reaction rate almost 100%? Generally speaking, the cross section can span a couple of decades order of magnitude, e.g. 10^-10 to 10^6...
  21. S

    Preferential bending loading direction of a beam

    Hi All, I'm trying to think through a problem and was hoping to ping the community for guidance. Suppose you have a beam that's symmetric about 2 axes (like a u channel or a triangular extrusion). Is it better to load the beam in compression on the side with material furthest away or should you...
  22. ORF

    What causes a plateau in the cross section of neutrons?

    Hello It seems to me that the nuclei have a flat elastic scattering cross section of neutrons, for neutron energies from eV to MeV. http://www.nuclear-power.net/wp-content/uploads/2015/11/Elastic-Scattering-Cross-section-light-elements-min.png I thought that maybe it was caused because the...
  23. parazit

    FLUKA Code : Total Cross Section Calculation

    Hi folks, I'm working on Fluka nowadays which you can found from here if you are not familiar. It's a very useful and widely used Monte Carlo simulation package. My main goal is to be able to perform total cross section calculation with it. So far, please consider I'm a rookie, I've done some...
  24. Z

    Question about Resonance Cross Sections

    Hi All, I have a question about resonance cross sections. I have been doing the design work on the reactor I want to propose for testing at Oak Ridge National Labs, and have run into a problem. It is an accelerator driven reactor transmuting thorium into uranium, then burning the uranium by...
  25. thegirl

    Rutherford Scattering model geometry

    Hi, I was just wondering if someone could help clarify how pi - theta = phi? That is the link to the youtube video I was watching, the guys pretty good check him out if you want to learn how to derive the differential scattering cross section.
  26. W

    Differential cross-section for partonic collisions

    I am trying to calculate differential cross-section for partonic collisions (QCD) like q + q \rightarrow q +q q + \bar{q}\rightarrow q + q g + g \rightarrow g + g I can't find those calculations done anywhere, just the results and maybe some middle tips, thats all. As you may know those...
  27. U

    Scattering Cross Section - At high energies

    Homework Statement Why does ## \frac{ e^+ + e^- \rightarrow \mu^+ + \mu^- }{e^+ + e^- \rightarrow \tau^+ + \tau^- } \rightarrow 1## at high energies? Would it be the same if it was ## \frac{ e^+ + e^- \rightarrow \mu^+ + \mu^- }{e^+ + e^- \rightarrow e^+ + e^- }##? Homework Equations The...
  28. E

    Cross Section for Asteroid Impact

    Homework Statement In this problem, you will estimate the cross section for an earth-asteroid collision. In all that follows, assume that the earth is fixed in space and that the radius of the asteroid is much less than the radius R of the earth. The mass of the earth is M_e, and the mass of...
  29. Prof. 27

    Current through Point or Cross Sectional Area

    Homework Statement I'm finding conflicting statements. One says that current is measured as the amount of charge per time that enters through a cross sectional area. Another says that current is measured as the amount of charge per time that passed through a point. Could someone clarify this...
  30. L

    Cross Section: Quark-Gluon vs. Quark-Photon

    This isn't a homework problem. I am preparing for a particle physics exam and although I understand the theoretical side of field theory, I have little idea how to approach practical scattering questions like these. THE PROBLEM: Dark matter might be observed at the LHC with monojet and...
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