Yep. That makes it a log easier esp. if you're going to do the fits a bunch
of times.
----- Original Message -----
From: "Ahmed Al-Jamel" <ahmed1@rcf.rhic.bnl.gov>
To: "Arthur E. Snyder" <snyder@slac.stanford.edu>
Cc: <ahmed_jamel@yahoo.com>; <roottalk@pcroot.cern.ch>
Sent: Sunday, February 29, 2004 7:25 PM
Subject: Re: [ROOT] statistical error of Intergation
>
> Thank you Arthur. What I really did to avoid this is to re-define my
> Gaussian function so that the constant N is now the number of J/psis:
>
> Gassian = N/srqrt(2*pi*sigma)
> EXP[-0.5((x-\bar x)/sigma)^2].
>
> Then, we have the statistcial error on N is the statistical error of
> the J/psi counts., which is COMPUTED directly by root and shown on the
> statistical window of the Canvas. Does this sound correct?.
>
> Sorry if my questions look elementary, but this is the first of my work
> with root.
>
> Best Regards, Ahmed
>
> Arthur E. Snyder wrote:
>
> >This not really a root problem ... just propagation of errors. The peak P
> >(par[0])) is related to area by A=P*sigma*sqrt(2pi) (no integral function
> >needed!), so given error matrix on P and sigma it easy to compute error
on
> >A.
> >
> >
> >----- Original Message -----
> >From: "Ahmad" <ahmed_jamel@yahoo.com>
> >To: <roottalk@pcroot.cern.ch>
> >Cc: <ahmed1@rcf.rhic.bnl.gov>
> >Sent: Friday, February 27, 2004 6:18 PM
> >Subject: [ROOT] statistical error of Intergation
> >
> >
> >
> >
> >>Dear Rooters,
> >>
> >> I am new to the list, and I have the following which I coud not figure
> >>
> >>
> >out
> >
> >
> >>how to do it under root. I'm fitting my J/psi peaks by a Gaussian
function
> >>
> >>
> >:
> >
> >
> >>f=N*Exp[-(x-\bar{x})^2/2 sigma^2]. Then I utilized the function
> >>Integral(min,max) to find the area or the number of counts under this
fit.
> >>.
> >>.
> >>.
> >>n[j]->Fit("Gaus","R");
> >>G->SetParameters(par[0],par[1],par[2]);
> >>float mean = par[1];
> >>float sigma = par[2];
> >>float mlo = mean-3.0*sigma;
> >>float mhi = mean+3.0*sigma;
> >>cout <<mean<<" and "<<sigma<<" and " <<mlo<<"and "<<mhi<<endl;
> >>float binw = n[j]->GetBinWidth(1);
> >>double COUNTS = G->Integral(mlo,mhi)/binw;
> >>.
> >>.
> >>.
> >>
> >>
> >>I need to know how to find the statistical error of the integral, i.e.
> >>
> >>
> >"COUNTS"
> >
> >
> >>in root.
> >>
> >>Thank you very much
> >>
> >>Ahmed.
> >>
> >>
> >>
> >>
> >>
> >>=====
> >>"EAST OR WEST, HOME IS BEST".
> >>
> >> Ahmed Al-Jamel
> >> Physics Department(http://www.physics.nmsu.edu)
> >> New Mexico State University
> >> Box 30001, MSC 3D
> >> Las Cruces, NM 88003-8001
> >> Tel (off): (505)-646-7614.
> >> http://www.feynman.nmsu.edu
> >> http://www.phenix.bnl.gov/phenix/WWW/publish/ahmed1/
> >>
> >>__________________________________
> >>Do you Yahoo!?
> >>Get better spam protection with Yahoo! Mail.
> >>http://antispam.yahoo.com/tools
> >>
> >>
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