# I have a problem with units

1. Sep 17, 2007

### stakhanov

I have a problem with units....

I have been looking at energy loss of muons in matter (from both ionizations and radition processes like bremsstrahlung). I have used an equation for the mean energy loss (for a muon of specified energy in a specified material) which gives an answer in units of g/cm^2/MeV. I am ok with converting this to cm/MeV I think (just divide by the density), but my problem is what does the 'per MeV' bit mean?

I have 50GeV muons going into concrete and from what I have read the mean range is ~45m. The equation I am using gives me an answer of 6.58cm/MeV (or 16.44g/cm^2/MeV) and I'm puzzling over how this gets converted into 45m.

Any help?

2. Sep 17, 2007

### mgb_phys

MeV is million electron volts. Electron volts is the energy to raise a electron of charge through 1 volt and so 1ev= 1.6E-19J ( ie the charge on the electron in Coloumbs)
It is a more convenient sized unit of energy and mass when dealing with particles.