Re: [Brahms-dev-l] D1 swim status

Hi djamel,

Thanks for pointing this out - I am also embarassed since I checked part of
this code , and  naively but incorrectly
assumed that radius2 had been set to radius**2 ; Coewritting wise it points
to the old ideom that one should NEVER
define variable until they are used initialized. E.g
Doulble_t Radius2 = Radius*Radius; \and not the fortran like statement used
some places.

On the physics issue - there are probably a class of tracks with high
momentum at larger angles
that out to have swim status set from this constraint.

flemming


----------------------------------------------------------------
Flemming Videbaek
Physics Department
Brookhaven National Laboratory

e-mail: videbaek@bnl.gov
phone: 631-344-4106
----- Original Message ----- 
From: "Djamel Ouerdane" <ouerdane@nbi.dk>
To: "Brahms Devel List" <brahms-dev-l@lists.bnl.gov>
Sent: Thursday, July 29, 2004 6:09 AM
Subject: [Brahms-dev-l] D1 swim status


> I think there's a serious mistake (at least software-wise) in
> BrMagnet::GetSwimStatus for D1.
>
> Indeed, here's an extract from the code :
>
>  Double_t x0, z0, Radius, Radius2;
>
>  ...
>
>  // D1 case (due to Cu block)
>
>  Radius = TMath::Abs(Radius);
>
>  Double_t outerPos = -112.7; //outer addge of the D1 front field clamp?
>  Double_t innerPos = outerPos + 38.1;
>  Double_t InnerX = TMath::Sqrt(Radius2 - (innerPos-z0)*(innerPos-z0)) +
x0;
>  Double_t OuterX = TMath::Sqrt(Radius2 - (outerPos-z0)*(outerPos-z0)) +
x0;
>
>  if (InnerX < (-3.56 + FiduCutX) || OuterX < (-1.81 + FiduCutX))
>    TrackTransported=kFALSE;
>  }
>
>
> Look at it carefully, the variable Radius2 is defined, not initialized,
> and then used in the D1 equations. I checked the code in between (the
> three dots I've put here), Radius2 is never set to anything. I checked
> some older revision (namely before some recent cleaning) : same thing.
>
> How important is it ??
>
> Djam
>
>
> -- 
> Djamel Ouerdane ------------------------------------------o
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