- #1
_Matt87_
- 15
- 0
Homework Statement
hi, so I've got this distribution function:
[tex]f(z,p,t)=\frac{1}{2\pi\partial z\partial p}exp(-\frac{[z-v(p)t]^2}{2\partial z^2})exp(-\frac{[p-p_0]^2}{2\partial p^2})[/tex]
where:
[tex]v(p)=v_0+\alpha(p-p_0)[/tex]
[tex]v_0=\frac{p_0}{m\gamma_0}[/tex]
[tex]\alpha=\frac{1}{m\gamma_0^3}[/tex]
I have to calculate the mean position as a function of time[tex]\langle z \rangle[/tex]
Homework Equations
I've got a hint too which doesn't help me at all to be honest ;] :
All the integrals over z required to calculate the averages can be expressed in therms of [tex]I_\nu =\int_{-\infty}^{+\infty}\,ds \ s^\nu exp(-s^2)[/tex] with [itex]I_0=\sqrt{\pi}, I_1=0,\ and \ I_2=\sqrt{\pi}/2[/itex], by substitution and a suitable choice of the order of integration.
The Attempt at a Solution
Presented function is I think distribution of particles in a beam in longitudinal phase space, and in that case
[itex]\int \,d^3p\ f(z,p,t)=n(z,t)[/itex] which is the particle density and [itex] \int \,d^3z\ n(r,t)=N[/itex] which is particles number.
So I think that mean position should look like this:
[tex] \langle z \rangle=\frac{\int\,d^3z\int\,d^3p \ z\ f(z,p,t)}{N}[/tex]
so
[tex] \langle z \rangle=\frac{\int\,d^3z\int\,d^3p \ z \ f(z,p,t)}{\int\,d^3z\int\,d^3p\ f(z,p,t)}[/tex]
am I right? if yes, how to start solving this kind of integral. I mean something like even this :
[tex] \int\,d^3z\frac{1}{2\pi\partial z\partial p} ...[/tex] those partials go before the integral .. or what?
btw. I attached two files with the actual assignment, and a slide from lecture that is supposed to tell me everything ;)