Unformatted text preview: Then, d3p = p2 dp d = c13 E 2dE d : So, for photons in a xed energy interval dE around E , d3p is proportional to
the solid angle element d that encompasses their directions and to E 2dE .
We should here say a word about the notation d for solid angle; it is
measured in steradians, a unit such that the full 2-sphere is 4 steradians,
d = 4 :
Z In spherical polar coordinates, d decomposes into the two orthogonal directions,
d = sin dd' = d(cos )d' :
sin θ d ϕ If we consider photons moving in one direction and normally incident on
a detector, then d3x is related to their ux: 27 ...
View Full Document
- Fall '09
- Topology, Coordinate system, Polar coordinate system, Solid angle