# Question about differential cross section

• Clara Chung
In summary, the conversation discusses the disappearance of target particles in a physical system and the mismatch in units for flux and cross-sectional area. The solution is to insert the target particle number into a given equation to ensure consistent units on both sides. It is also noted that when the target particles completely disappear, the flux should be zero regardless of the incident flux.
Clara Chung
Homework Statement
Attached below
Relevant Equations
Attached below

I have attached the two pages in my notes and I have the following question.
1. Where have the n_t*l gone in 9.9? (According to 9.5 why do they disappear?)
2. Why J_s=sigma_tot J_i? The dimension of flux is per m^2 and sigma is per area too, the dimension is not right...

Clara Chung said:
View attachment 242124
View attachment 242125
I have attached the two pages in my notes and I have the following question.
1. Where have the n_t*l gone in 9.9? (According to 9.5 why do they disappear?)
2. Why J_s=sigma_tot J_i? The dimension of flux is per m^2 and sigma is per area too, the dimension is not right...
Looks like an error to me...

Clara Chung
Yes, insert ##n_t l## into (9.9) in such a way that the units are consistent on both sides.

A physical reality check: if ##l = 0## or ##n_t = 0##, i.e. the target disappears completely, what should we expect ##J_s## to be, regardless of ##J_i##?

Clara Chung
jtbell said:
Yes, insert ##n_t l## into (9.9) in such a way that the units are consistent on both sides.

A physical reality check: if ##l = 0## or ##n_t = 0##, i.e. the target disappears completely, what should we expect ##J_s## to be, regardless of ##J_i##?
Yes, it should be zero :)

## 1. What is a differential cross section?

A differential cross section is a measure of the probability of a particle interacting with another particle in a given direction and energy. It is commonly used in particle physics to study the scattering of particles.

## 2. How is a differential cross section calculated?

The differential cross section is calculated by taking the ratio of the number of particles scattered in a particular direction to the incident flux of particles. It is then normalized by the solid angle and the target density.

## 3. What is the significance of the differential cross section in particle physics?

The differential cross section provides valuable information about the internal structure of particles and the nature of their interactions. It can also be used to test theoretical models and make predictions about future experiments.

## 4. Can the differential cross section be measured experimentally?

Yes, the differential cross section can be measured experimentally by detecting the scattered particles in different directions and energies. This data is then used to calculate the differential cross section and compare it to theoretical predictions.

## 5. How does the differential cross section depend on the energy of the particles?

The differential cross section generally increases with increasing energy of the particles. This is because higher energy particles have a greater chance of interacting with other particles. However, the exact dependence on energy can vary depending on the type of interaction and the properties of the particles involved.

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