I have been looking at the flux of muons (as secondary cosmic ray particles) at the Earth's surface as a function of both energy and angle from the zenith. From what I have read, the flux follows a squared cos theta relationship with angle from the zenith and several attempts have been made to accurately parametrize the energy dependence. I am using a revision of the Gaisser parametrization, dN/dE=f(theta,E) [per square cm, per second, per steradian, per GeV]. My questions are as follows:(adsbygoogle = window.adsbygoogle || []).push({});

1. Do I just integrate f(theta,E) over an energy range to find the number of muons in that range? I have done this and it doesn't give what I expect (something that looks roughly like a Maxwell-Boltzmann spectrum in form) so I want to check I am doing the right thing.

2. How do I understand the 'per GeV' part of the untis of f(theta,E)? If for example, f(theta=10,E=20) = 2x10^-5, then it means that on average 2x10^-5 muons with energy 20GeV will flow through a square cm from a solid angle of 1 steradian centred around a point at 10 degrees from the zenith. Where does the 'per GeV' come into it?

Sorry if this doesn't make sense but I'd appreciate any help.

Thanks

**Physics Forums | Science Articles, Homework Help, Discussion**

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

# Need some help interpreting the muon energy spectrum

**Physics Forums | Science Articles, Homework Help, Discussion**