- #1
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- 465
The rapidity is defined as:
y = \frac{1}{2} ln(\frac{E+p_z}{E-p_z})
and for a hard event (hard scattering reaction/two partons reaction) we find that:
y'= \frac{1}{2} ln(\frac{x_A}{x_B})
If the invariant mass is zero the rapidity changes into the pseudorapidity n which depends only on the polar angle \theta:
n= -ln (tan(\frac{\theta}{2})) or cos (\theta) = tanh(n).
Since the pseudorapidity is just a (1-1) transformation of the polar angle theta, why is it prefered? I don't know but I'm losing geometrical intuition of the process when I try to think in n terms...
y = \frac{1}{2} ln(\frac{E+p_z}{E-p_z})
and for a hard event (hard scattering reaction/two partons reaction) we find that:
y'= \frac{1}{2} ln(\frac{x_A}{x_B})
If the invariant mass is zero the rapidity changes into the pseudorapidity n which depends only on the polar angle \theta:
n= -ln (tan(\frac{\theta}{2})) or cos (\theta) = tanh(n).
Since the pseudorapidity is just a (1-1) transformation of the polar angle theta, why is it prefered? I don't know but I'm losing geometrical intuition of the process when I try to think in n terms...