Cross section Definition and 315 Threads

Homework Statement The problem concerns the collision of a particle on a rigid, fixed disk of radius R. The coefficient of friction is zero, and the coefficient of restitution is 0 < ε < 1, such that vperpendicular, final = εvperpendicular, initial . A) Show that tanαincident = εtanαfinal...

Hi all, Could anyone help for calculating the hadronc production cross section for example for tree level : p p > t t~ process, I try to calculate, but the first problem I meet is a negative value of the matrix element amplitude (and so cross section ) and a negative ## \hat{t} ## Mandelstam...

I'm currently doing some research at the moment for my professor, and he gave me a list of things to look at. Before he had me calculate the "real center of mass cross section." Now, starting at point 0 for publication, he's having me go through and do some other things. In his list of things to...

Dear Forum : I'm reading a cross section data of 20MeV proton + 16O reaction from ICRU 63. ( as attachment and link http://ppt.cc/qf-9 ) The total cross setion of (p,n) reaction is 4.372mb However, the cross section of emitting neutron of energy between 0 to 1.5MeV is 0.91 mb / MeV. The...

I want to use a rectangular cross section to act as a torsion spring that can be adjusted. The idea is that the adjustment would be made via rotating the rectangular cross section about it's center at an angle theta. I've used parallel axis theorem before, but I don't think that is applicable...

I have a question about cross section probability for a positron (e+) to interact with the electron (e-) that would be bound to three different atomic systems (1) hydrogen atom: H(e-), (2) deuterium atom: D(e-), (3) tritium atom: T(e-). My hypothesis is that a positron (e+) would have the...

I have a book on nuclear reactions which details the mean free paths for thermal neutron scattering as: 0.37cm for water and 2.2cm for heavy water The transport cross sections are listed as 0.45cm for water and 2.6cm for heavy water. Does anyone know how to calculate these from the thermal...

e+e- --> gamma f0 --> gamma pi0 pi0 cross section with VMD Homework Statement Find the cross-section of ##e^+e^- \to \gamma f_0(980) \to \gamma \pi^0 \pi^0## using the vector meson dominance model. Homework Equations Some Feynman's rules: The photon propagator is -i...

Hello. When you have a plot of the cross section in function of the centre of mass energy of an e+e- -> hadrons collision, you get a graph with a few peaks which are due to the resonances (ρ, ω, J/ψ...). But I don't understand why at a resonance, the cross section goes up? Or other way...

If a metal rod of 20 cm is charged with 10 μC, then what should be its cross section area so as to prevent electric discharge (electric breakdown) ?

I have a question. From this government reference: http://www.ncnr.nist.gov/resources/n-lengths/ the thermal neutron cross section for stable isotope Be-9 = 0.0076 barns. This means Be-9 is not expected to absorb a thermal neutron, the probability of this is very, very low. The Be-9...

I'm trying to get started on this project but am totally confused about how to find the volume of the solid. All the information I was given was the following: y= √x boundaries: 0,9 cross sections: isosceles right triangle how the hell do I get started?!

I am looking for the derivation to an approximation formula for the differential cross section for hard sphere scattering in the limit of high energy. The paper that mentioned this had referred to Methods of Theoretical Physics, PM Morse and H. Feshbach page 1484 but I have no access to the...

Homework Statement Please visit my flickr link for a scanned image of the problem statement. http://www.flickr.com/photos/93763273@N05/8815418518/lightbox/ Homework Equations M/I = σ/y = E/R This is the flexure or bending formula. The Attempt at a Solution a) = 8.333 kN...

Hey everyone, So I've been killing myself trying to find a good reference that talks about the wavelength dependence of dust grains when the size of the grain is about the size of the incoming light, or s~lambda. I have numerous references for when s<<lambda (absorption dominates with a...

I am doing a research on activation radionuclides resulting from thermal neutron(2200 m*s-1 or 0.0253eV) capture. The activation cross section of some nuclides(H-3,C-14,54Mn,58Co), still can't be found even many efforts were taken. The related reactions...

Homework Statement Consider the spherical well such that V(r<a) = -V0 and V(r≥a) = 0. Calculate the l = 0 partial wave scattering cross section in the low energy limit for this potential. Homework Equations σ = \frac{4 \pi}{k^2} * \Sigma (2l+1)*sin^2(\delta_l) The Attempt at a...

Octagonal Cross Section with Parabolically Increasing "Span" Hi all, could some one tell me what I am doing wrong in my analysis in the attached file? Its a parabolical flare column with an octagonal cross section. The effect of the parabolic flare simply stretches the octagon so that the...

Homework Statement Two curves/functions make up one side of a tunnel (the tunnel is symmetrical, so the other side is the same) Function 1: y = 5 + (2/((x-4)^3)) Function 2: y = (x -1)^3 - 5 I need to find the area of the tunnel, so I can find the amount of dirt that needs to be removed...

Homework Statement A plane monochromatic electromagnetic wave (polarized in x-direction and propagating in the z direction) is scattered by a free electron initially at rest. Homework Equations \vec{E}=E_0 \exp(i(kz-wt)) \hat{x} \vec{B}=\frac{E_0}{c} \exp(i(kz-wt)) \hat{y} The...

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 center of mass frame dσ/dΩCM; I now have to go into the lab frame, where the nucleus is initially at...

I was reading Wikipedia article on Rayleigh scattering and came upon this: "...the major constituent of the atmosphere, nitrogen, has a Rayleigh cross section of 5.1×10^(−31) m^2 at a wavelength of 532 nm (green light). This means that at atmospheric pressure, about a fraction 10^(−5) of...

Which wood cross sectioπ caπ carry hïghest uπiform load Homework Statement Homework Equations Moment of inertia for rectangle I=(1/12)bh3 τ=(VQ)/(I*b) σ=(MV)/I The Attempt at a Solution I started by finding reactions at B and C Then drew the sheer and moment diagrams (to save...

Hello! I´m confused about this concept.. It seems rather trivial, but my teacher is not that pedagogical and describes it as a rather diffcult concept so maybe I misunderstood it. Given the definition in Sakurai and the scattering of only one particle it seem to be a kind of "denisty" per...

Hi I need to plot the (differential) Rutherford cross section as a function of the scattering angle in the CM frame. the reaction is a typical projectile on stationary target. I know the projectile energy in the lab, θcm and the masses. I am confused over which energy to use though. I know...

Lagrangian I have is little bit massy so I don't write in here. Like in ψψ(dagger) , or ψ∅ -> ψ∅, How can I calculate the differential cross section or total, or amplitudes?

I'm learning scattering theory from Griffiths' book, and I don't really understand the meaning of differential cross section; it's one of those things that I find hard to conceptualize and give a physical meaning to. The most intuitive description he gives is "the proportionality factor between...

Hello, I've found in some of the articles on experimental quantum physics the term "Topological cross section" Now I'm trying to understand what is it and in particular what the difference between topological and differential cross section? Thanks in advance for suggestions on any reading...

qq- --->qq- differential cross section and mandelstam variables Homework Statement for the problem statement please look the attachement Homework Equations The problem is asking to express the mandelstam variables in temrs of the scattering angle θ.I would like to ask the quastion...

Hi, I'm reading an article called SuperSymmetric Dark Matter, by G. Jungman et al. doi:10.1016/0370-1573(95)00058-5 and in section 3.2, he claims that <σv> ≈ \alpha^{2}(100 GeV)^{-2} \approx10^{-25} cm^{3} s^{-1},[\itex] for \alpha \approx \frac{1}{100}. When I run through the calculation...

hello , can anyone give the formula of the differential cross section and the macro cross section because in each web i see a different notation thank you

Consider the cross section of two beams of same material as shown in the file attached. The area moment of inertia I about the central axis is equal for both the c/s. I have calculated it. Can somebody explain why the second c/s (2 in the figure ) is preferred for the design?

Homework Statement Find σ , the differential cross section, starting from the expression below and integrating over solid angle Ω Homework Equations dσ/dΩ = r2sin2θ The Attempt at a Solution dσ = r2sin2θ dΩ I remember that dΩ = sinθ dθ dμ and doing the μ integral from 0...

I wish to verify a couple of assertions. From the NNDC and other references, it appears that the neutron capture cross section of 3H (Tritium) is zero to a first approximation. This holds true for all neutron energies, including cold neutrons. These statements are equivalent to asserting that 4H...

'Ello, I have a question regarding the results in this paper (and another which I will mention later) http://arxiv.org/abs/hep-ph/0212199 Now, I'm not so concerned about the 'braney' bit, but more their definition of the cross section in Eqn. (46). They have included the usual (2j+1)...

Hello, currently I work on 2->3 scattering process. So there exist five external momenta and in my case 5 different Feynman diagrams, for which I have already calculated the full matrix element. The matrix element is a function of various scalar products of the four-momenta. This scattering...

Homework Statement Find the volume of the solid obtained by rotating the region bounded by the given curves about the specified axis. Homework Equations y = \sqrt{x-1} , y = 0, x = 5; about y = 3 The Attempt at a Solution I already completed graphing it, but not really sure how...

Homework Statement A beam has a solid square cross section of 100mm and is simply supported by two supports 3m apart. Calculate the dead load that can be safely supported when applied to the middle of the beam. Homework Equations Solid square cross section of beam: 100mm Material...

the higher the energy of the photon, the more powerful it can ionize an atom but why then the absorption cross section decreases with the photon energy?

a basic problem but i have no idea how to measure it

Hello. I was hoping someone could help me understand some units. In several papers, I have seen the two photon LIF signal written as: S = n*(Ω/4π)*T*G*σ*(E/hv)^2*η*a where the units are n (density of measured atom): #/cm3 Ω/4π (solid angle fraction): unitless T (optical transmission...

Homework Statement The only given data is that the cross section is 1m^2, the shape is circular (like a cut wire/rod) and i have to find the volume. Homework Equations from what I've searched, i found the equation: but i have no idea what to do with it, i still haven't learned it at...

Homework Statement What is the volume if the area bounded by y=x^2 and y=9 and the cross sections are perpendicular to the y axis Homework Equations The Attempt at a Solution I have no idea

I'm just wondering what the difference is between a cross section and a scattering cross section? Or is there any? I can't seem to find anywhere that clears it up, in fact there's a whole section on scattering cross sections in Kibble and Berkshire but they don't define it once :P

I am reading chapter three of Huang's Statistical Mechanics and I have a problem with equation (3.22). Having discussed the derivation of the classical cross section for a scattering process, Huang moves on to the quantum version of it. He states that in quantum mechanics the fundamental...

what is the cross section area of the water?? Homework Statement Determine an expression for the cross sectional area A of the fluid in the tank as a function of D and H. Homework Equations A=pi*r2 The Attempt at a Solution i try to let the radius equal to the height but then the...

Homework Statement A supernova can produce a neutron star with typical radius 10km. Assume the neutron star matter consists of iron nuclei (A=56), produced by the electron capture reaction: e^{-}+Co\rightarrowFe+\nu_{e} The matter density is \rho=10^{5} tonne mm^{-3} and the neutrino...

Hi all. This is my first time in the Physics Forums. I would like to ask for guidance in a calculation of a cross section of a process. I know the Feynman graph but I'm completely lost on how to start the calculation.. For example.. p p -> Z -> μμ Many thanks in advance..

Hi all, I'm trying to understand the solution to a problem from a textbook. We're asked to find the proportionality constant for $$\frac{d\sigma_{\rm elastic}}{dq^2}\propto e^{bt},$$ where q is the momentum transfer in a scattering process, defined in elastic scattering as...

I recently saw the Evaluated Nuclear Data File provided by Brookhaven national lab., where in i saw the plot of "Neutron Energy Vs cross section (total)" for different elements. http://www.nndc.bnl.gov/sigma/index.jsp?as=1&lib=endfb7.0&nsub=10 Now what i am interested in is, can we derive or...