# Narrow-width approximation

by Safinaz
Tags: approximation, narrowwidth
 P: 35 Hi all, I try to understand the difference which can made by using or not using NWA .. I have a process have cross section (p p > x x) ~ 10^-5 pb , where x is a paricle have mass mx = 2 TeV and dominant decay channel (x > b b~) with Gamma (x > b b~) ~ 6 * 10^2 GeV , while sigma ( p p > x x , x > b b~) ~ 10^-6 pb (I calculate this with a program not using the NWA).. It's clear that if NWA is used sigma ( p p > x x , x > b b~) will just ~ 10^-5 pb since BR (x > b b~) =1, so what does mean 10^-5 (NWA) and 10^-6 (non- NWA) Is that what meant by that NWA has ## \Gamma/m ## approximation ? Regards, Safinaz
 P: 77 Let me try to understand more. Are you pair producing these two new particles? Then looking at the final state of 4 bs? And your partial width of x>b bbar is 5% of the mass of x?
 P: 35 Hi, I think I get it, thanks. S.

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