# Homework Help: Particle physics lab: techniques

1. Nov 16, 2008

### audreyh

Hi all,

I'm measuring multiple coulomb scattering by using 4 chambers filled with He gas, and lead plates between the top 2 chambers and bottom two. The chambers have a potential difference across the plates so when the muons ionize the He gas, a spark is produced. A camera marks the pixels of the sparks.

1. The problem statement, all variables and given/known data

The computer program written in root plots number of events (y) vs scattering angle (x). The fit to the data points is a double gaussian.

$f(x)= e^{- \frac {x^2} {2 \sigma_1^2}} + e^{- \frac{x^2} {2 \sigma_1^2}}$

We'd like to see, for more lead plates a larger scattering angle distribution (i.e. Sigma to increase). The problem is, the experiment with zero lead plates produced non-zero scattering angles (expected), so I'd like to subtract the straight through data (zero lead plates) from the data that has a non-zero number of lead plates. This is what I'm not sure how to do.

2. Relevant equations

3. The attempt at a solution

From my limited understanding of probability: if X is a continuous random variable that is normally (gaussian) distributed with parameters mu and sigma^2, then
$Y= \alpha X+ \beta$
with parameters
$\alpha \mu + \beta$
and
$\alpha^2 \sigma^2$
So can I somehow linearly convert the non-zero lead plate distributions to one that has the zero-plate scatter distribution subtracted?