[Lowq] Solenoid field map - follow up

[Hovanes Egiyan]

Hi Eric,

thanks for following up on this issue. The normalization issue
is still standing and is important to solve. As far as the shift is 
concerned
I think it was a problem in how I was reading the map, but the  
reconstruction
code is consistent with the way the map is created. The map has a confusing
point -0.5cm in radial direction, but the code seems to be taking that into
account a proper manner.

Regards,
        Hovanes.



Eric Voutier wrote:
> Dear all,
>
> The problems of the solenoid field map used for CLAS
> analysis was discussed by the Saclay group, on the basis
> of our analysis meeting minuts.
>
> _Normalization factor_ :  the residual normalization factor
> might have different origins, particularly the current
> read-back is done at the power-supply level and not at
> the magnet level which leaves room for power losses and
> some 1-2 amps differences in the real current.  It might
> also be that the final current setting was set a little bit
> lower from the nominal for safety reasons... Jacques will
> trace back the history of this factor to make sure of this
> problem.
>
> _Shift_ : the observed shift should indeed have some consequences
> on slow particles, like DVCS protons. The effect might be small for
> asymetries but can be critical for cross sections, typically for the
> solid angle. The Saclay group is informed but it would be wise also
> to inform all DVCS groups about the problem. The question raised
> is about the real starting date of implementation of this map in
> the CLAS software. Additionnally it would be desirable to identify
> the person who did the implementation and should have all the
> history in hands. The Saclay group will try to look in this. Eg6
> on-site persons may also try to trace-back this issue.
>
> Regards, Eric
>
>