Re: 1/N*dN/d(pt) and 1/sigma* dsigma/d(pt)

Hello, Wajid!

I would add that dsigma/dX is used to refer to a real cross section, i.e. a quantity corrected for all experimental effects like resolution, shape-effect of selection cuts etc.
dN/dX usually relates to the raw quantity measured by the detector (with finite acceptance, after cuts, and in terms of e.g. smeared energy). So, dN or dsigma are used as notations for different quantities. In case of ideal detector with 100% acceptance, delta-function resolutions and no cuts used for the distribution extraction, the shapes 1/s ds/dX and 1/N dN/dX would be the same, while in reality they never are.

Jiri

On 01/04/2010 06:32 AM, Wajid Ali Khan wrote:
> Dear Root Experts,
>
> I need your help. Any body can explain me what is the main
> difference between the following
>
> 1/N*dN/d(pt) and 1/sigma* dsigma/d(pt)
>
> Is the same N=luminosity*Sigma. If I want to normalize my histogram
> per entry per unite of Xaxis with say pt. What would be the quantity
> plotted on Y axis will it be 1/N*dN/d(pt) or some other quantity.
>
> One thing more I want to get the area under the fitted histogram how
> can I get that area.
>
>
>
> I would be indeed thank full to you.
>
> Best Regards
>
> Wajid Ali National Center for Physics, Islamabad Phone: 051-2077336
>
>

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