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malawi_glenn

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**[SOLVED] Lifetime & Branching ratio**

Hi!

In my book Particle Physics by Martin & Shaw, eq 2.15:

Lifetime:

[tex] \tau _l = \dfrac{B(l^- \rightarrow e^-\bar{\nu }_e\nu _l )}{\Gamma (l^-\rightarrow e^-\bar{\nu }_e\nu _l )} [/tex]

Where B is branching ratio and Gamma the decay rate and l is a lepton.

Why is B included? :S I thought the lifetime just was the inverse of the decay rate...