# Narrow-width approximation

1. Nov 22, 2013

### Safinaz

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

Last edited: Nov 22, 2013
2. Nov 22, 2013

### RGevo

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?

3. Nov 22, 2013

### Safinaz

Hi,
I think I get it, thanks.
S.

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