Lesson 30
Scattering Cross Sections

Name:faculty Section:M2 Start Time:16:3:12 Instructor:pate Course:355

1) Consider a scattering process. You have a target (red mass m2 in the figure). You shoot a bunch of particles of mass m1 in the general direction of the target and observe what happens to each of the shot particles. If there's some sort of interaction that occurs between the target and the particles you shoot at it, the shot particles will undergo some deflection.

What factors should affect the scattering distribution (where the shot particles end up)?

How should that distribution be characterized? That is, in terms of what parameters would you characterize the distribution?

Also, how would you characterize the incoming particles (in terms of what parameters?)?

(Please be sure to explain, in your own words, exactly what parameters you pick and what they actually are. Please don't just use "textbook-speak." Thanks.)





2) Suppose you are trying to scatter light masses off of a target made of somewhat more massive particles. The differential cross-section s(y) in the LAB frame is different than the differential cross-section s(q) in the CM frame. (Why?) For a given scattering angle (as observed in the LAB frame), estimate by about what factor the two differential cross-sections differ. Which differential cross section is bigger? Please briefly explain your steps and assumptions.



3) Suppose you throw a 2.0 kg ball at an Acme ballcatcher. The Acme ball catcher consists of a massless orange disk which is free to rotate about its axis, and two massless ball-catching clips, shown in blue in the figure. The orange disk has a radius of 2.0 m, and one of the clips is 2.0 m from the center of the disk, while the other is just 1.0 m from the disk's center. Once the ball hits a blue ball-catching clip, it sticks in the clip, causing the disk to spin about its axis. (What will those Acme folks think of next?!)

Suppose you throw the ball at 10 m/s. Which of the following choices represents the amount of time it would take the Acme ballcatcher to rotate once around its axis if (i) you hit the top clip and (ii) you hit the bottom clip?

  1. (i) 1.26 sec (ii) 0.63 sec
  2. (i) 5.0 sec (ii) 10.0 sec
  3. (i) 0.2 sec (ii) 0.1 sec
  4. (i) 0.796 sec (ii) 1.59 sec



Below is a space for your thoughts, including general comments about today's assignment (what seemed impossible, what reading didn't make sense, what we should spend class time on, what was "cool", etc.):

You may change your mind as often as you wish. When you are satisfied with your responses click the SUBMIT button.

I received no help from anyone on this assignment.
I received help from someone on this assignment (document in comments section).