Cross section Definition and 315 Threads

How does the emission cross section of an emitting atom (such as Yb atoms in glass) affect the laser performance, namely the slope efficiency (signal power vs absorbed pump power) and laser threshold? Thanks a lot

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^+##...

I am working on HFSS and designing Antennas for LOW RCS , in all previous works they calculate the S11 parameter for the unit cell then make an array form this unit cell and calculate the RCS , my question is what is the relation between S11 and RCS and why we calculate S11 for the unit...

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)...

Homework Statement Consider scattering of a particle of mass ##m## on the potential $$U(r) = \begin{cases} 0, & r \geq b\\ W, & r < b \\ \end{cases}$$ Where ##W## is some arbitrary chosen constant, and the radius ##b## is considered a small parameter. Find the cross section ##\sigma## in the...

I have found answers on how to calculate the self-inductance of toroid of rectangular cross section, however my question says that "The winding are seen as a thin homogeneous currentlayer around the core" (excuse the translation). What does that mean for N? Does it mean N=1?

Hi everyone, I was wondering, is the cross section at Eq 50.25 in http://pdg.lbl.gov/2017/reviews/rpp2017-rev-cross-section-formulae.pdf correct? Because I see a term in the denominator with \frac{1}{s\Gamma} whereas in several other references, the propagator term in the matrix element comes...

I am working on deriving expression for deflection of a tapered beam with an elliptic cross-section. Hence, area moment of inertia is a linear function of the beam length. The beam is fixed at one end, and a concentrated force F is applied on its tip at the free end. I am using the known...

Good day all I'm looking for the proof of stress generated in case of skew bending applied in acircular cross section ( I browsed internet the whole day without finding anything convincing) we use with many thanks in advance!

I was doing the calculations for this: http://fermi.la.asu.edu/PHY531/cylinder/index.html But I can't figure out how to go from \frac{d\sigma}{d\phi} to the total cross section. My guess was that you did the integral from \phi=0 to \phi=2\pi, but that's not helping since I can't tell either how...

Homework Statement There is a conductor with the square-shaped area. the Radii are r1 , r2 with width b and resistivity ## \rho_R##. Find the resistance R between A and B 2. Homework Equations ##I = \iint_A\vec J \cdot d \vec A## ## \vec J = \kappa \vec E ## ## \vec E = \rho \vec J## ## V =...

I have come across the term quiet often, but I find it difficult to explain it to myself (or others) and even interpret it... So what is a fiducial cross section? Is it the measured cross section once you factor out the detector acceptance and the different cut-efficiencies (mainly motivated by...

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...

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...

Hey guys, if I consider a Bernoulli-Beam with a constant jump in cross- section as shown below Then I get the two differential equations for the bending mentioned above. Let us now assume that a traveling wave from the left w_incident = C*cos(k_1*x - ωt) arrives at t = 0 at the jump of...

Homework Statement [/B] Using n-Pb collision experimental data, find sigma_0 in units of 1/keV^2 and convert to cm^2 (I'm copy-pasta'ing from Mathematica, sorry for mess) \[Alpha]n = 7*10^-49m^3; mn = 939565; <--- Neutron mass in keV/c2 \[HBar] = 1*10^-3; <--- Natural units and again keV*s b...

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

Homework Statement The current in a wire varies with time according to the equation I(t) = 6.00 A + (4.80 A/s)t, where t is in seconds. How many coulombs of charge pass a cross section of the wire in the time period between t = 0.00 s and 3.00 s Homework Equations I=dq/dt The Attempt at a...

Title says it all. Made a few google searches and couldn't find any information. Is there a reason why it is so large, or is it just a coincidence of nature?

Dear Forum: I have a question about atmospheric photodissociation. I use methane as an example, but any atmospheric gas molecule would suffice. Methane, CH4, has a photodissociation energy of 439 kJ/mole at 298oK, meaning that CH4 + hv --> CH3 + H , hv<274nm. It also has an “absorption cross...

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...

Homework Statement In an experiment carried out with a beam of thermal neutrons it is found that on traversing a 2mm thick foil of 197Au, some 70% of the neutrons are removed. What is the total thermal neutron cross-section for this isotope of gold? Comment on the result of the 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...

Homework Statement Hi, I'm trying to figure out how to calculate the stresses in my beam. The cross section varies (shown in the picture), and I don't know how I'm supposed to think to find the maximum stress. I appreciate tips or links to learn how to do it. Thanks. Sorry if the picture is...

Homework Statement In PIXE (Proton-Induced X ray Emission), if you increase the beam energy from 2 MeV to 4 MeV, do you expect that the factor of increase in the cross section for the K X ray production from Ni is higher than that from S, or vice-versa? Homework EquationsThe Attempt at a...

Homework Statement My homework involves calculating the amount of energy the Earth receives from the Sun in a given year. I actually have the answer, but what I'm confused with is that the calculation says that the Sun "sees the cross section of the Earth, a circle". So in the calculation, we...

Homework Statement I am trying to derive the 2 body cross section, as given in https://web2.ph.utexas.edu/~schwitte/PHY362L/QMnote.pdf dσ/dΩ Homework Equations I am stuck on d√s/dp=v where √s=(Ea+Eb)=E The Attempt at a Solution p=Ev (relativisitic energy-momentum relationship) √s=E...

Homework Statement A beam of ##^{50}##Ti nuclei impinged on a ##0.5 mg/cm^2## thick ##^{208}##Pb target in an experiment lasting 176 hours. During that time a total of ##3260 \; ^{257}##Rf nuclei were detected. The beam intensity was throughout the experiment constant at ##6.6\mu A##. Each...

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...

I am looking for free solved exercises about: right angle projections, (cross) section views Here are some pictures of my book so you can understand what I am looking for http://1.1m.yt/3cNNDl-.jpg http://1.1m.yt/FekMn6x.jpg http://1.1m.yt/1t3KEer.jpg http://1.1m.yt/urA5V2_.jpg...

Homework Statement In the notes , I don't understand why the shear stress is maximum at the edge ( circle part) . Homework EquationsThe Attempt at a Solution I think it's wrong . Refer to another diagram attached , i found that the shear stress varies parabolically across the vertical length...

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...

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...

Consider the real emission correction to the tree level process ##e^+ e^- \rightarrow q \bar q## involving a final state gluon emitted from either the outgoing quark or antiquark line. The differential cross section for producing a quark with fractional energy ##x_1## in the ##q \bar q g##...

If given the cross section for ZZ* to two leptons, is it possible to work out the cross section for ZZ* to just electrons or muons from it? So excluding the tau decay mode, unless ##ZZ^{*} \rightarrow \tau + \tau## can't happen anyway? I'm guessing it wouldn't just be two thirds of the ##ZZ...

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...

Homework Statement [/B] (Note: this is not strictly homework, but it is related to one course I'm doing, and I can't find a useful solution anywhere) Find the analytical expression for the scattering cross section of two longitudinally polarized electrons at tree level. Homework Equations...

Is there any measure for cross section of η′→γγ? Or has anyone did the calculation??

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})...

Hi all, Do any has an idea how to give a rough estimation for this process's cross section: g g -> H -> h h, (h -> b b~), ( h -> b b~) ? where h is SM Higgs and H is a heavy Higgs boson with BR (H > hh) ~ Gamma (H > hh) ~ 10^-3 GeV and sigma (g g > H ) ~ 10 pb .. When I calculated it by...

Hi all, Do anyone familiar with these analysis of cross section ? I wonder how to find the cross section of ( p p ## \to \gamma \gamma## b b~) (blue region) in the opposite plot, the y-axis is the number of events divided by 100 GeV with luminosity = 100 ##\mbox{fb}^{−1 }##.. The Fig. from...

Hey, working on something for a personal project and was wondering if you could point me in the right direction. I have a 47 inch hollow steel tube that I'm going to cut the end 6 inches into a half circle tube . I have a load of 200 lb at the top and am wondering how about I would quickly...

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...

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...

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...

In the research,it is found there is significant difference of B-10(n,2a)H-3 reaction cross section between ENDF/B-V and ENDF/B-VI (http://www.nndc.bnl.gov/).The cross section in ENDF/B-V is 10 times less than ENDF/B-VI when neutron energy...

Hi! On page 12 of http://pdg.lbl.gov/2009/reviews/rpp2009-rev-cross-section-plots.pdf one can see the total cross section increasing beyond a certain treshold. At higher energy protons (and their quarks) have a shorter wave length and so they can become closer an closer and the strong force...

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...

Hi all, I try to find the exact calculated gluon- gluon fusion cross section for the SM- Higgs with mass 125 GeV, for instance at CME = 14 TeV. I found on twiki page: " https://twiki.cern.ch/twiki/bin/view/LHCPhysics/CERNYellowReportPageAt1314TeV#s_14_0_TeV " ##\sigma(gg \to h) = 49.47~ pb##...

In chapter 1 of Peskin and Schroeder, the reaction ##e^{+}e^{-}\rightarrow \mu^{+}\mu^{-}## is studied in detail. The related following paragraph is taken from page 4 of Peskin and Schroeder: Both the electron and the muon have spin ##1/2##, so their spin orientations must be specified. It is...