Hello!

I am looking for a way to better understand scattering of 1-5GeV/c electrons on thin targets (given that the Highland formula comes with some uncertainties).

For this, I noticed in the physics reference manual (page 91 or see the formula I attach below) the treatment of MCS in G4 using the Urban Model. Something does not click for me and I was hoping you can help me.

As you can see in modified Highland-Lynch-Dahl formula, the angle is calculated using the square root of **y** multiplied by a correction term **c** . The correction term is given below the formula, as a function of the atomic number. Similarly, the **y** term is the logarithm of the material budget expressed in units of radiation length.

Here is where my problem lies. Usually, this quantity is smaller than 1 (eg: 50um of Silicon would correspond to **t/X0** = 0.0005). Taking the natural log of such a number would yield a negative **y**.

The square root of a native **y** plugged into the angle formula …

Am I getting something wrong?

Thank you very much!

Wishing you all a pleasant weekend!

NB: My goal is to find a better description (formula) of the multiple scattering than the Highland formula, which contains a dependence on the material budget. I have some scattering angle data from which I would then like to calculate the material budget of an unknown sample.

I started asking myself if the Highland formula is also appropriate for electrons (since it has no dependence on the projectile mass) or if I should look for a better description or corrections.