Brian Jackson edited Whether_or_not_we_detect__.tex  almost 9 years ago

Commit id: 03912f634d0604e9fdbc30cc8d1986f3a4cc9f12

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Whetheror not we detect  a devil with a given $P_{\rm act}$, act}$ is detected,  the the fact that $b$ probably won't be isn't  zero means the devil will usually be detected with $P_{\rm obs} < P_{\rm act}$. From the encounter geometry, we can see that the infinitesimal probability $dp$ for the center of a devil to pass within a certain range of radial distances, between $b$ and $b + db$, is proportional to the infinitesimal area of the corresponding disk, giving $dp = 2 b\ db/b_{\rm max}^2$. Outside of $b_{\rm max}$, the probability is assumed zero. For the Lorentz profile, we can relate the differential range of distances $db$ to $dP_{\rm obs}$: \begin{equation}  db = \frac{1}{2}\Gamma_{\rm act}\left[ \dfrac{P_{\rm act}}{P_{\rm obs}} - 1 \right]^{-1/2} \left( \dfrac{P_{\rm act}}{P_{\rm obs}^2} \right) dP_{\rm obs} = \frac{1}{2}\left( \dfrac{\Gamma_{\rm act}}{2} \right)^2\dfrac{P_{\rm act}}{P_{\rm obs}^2} \dfrac{ dP_{\rm obs} }{b},  \end{equation}