Re: cdcStrawHit vs. cdcTruthPoint

[Beni Zihlmann <zihlmann@jlab.org>]

Hi Mark,
answer to the first question: in hitCDC.c there is a threshold applied 
to Hits. This threhold is set to 1keV at the moment
                                             and any hit that deposited 
less then 1keV will be removed from the hit list.

what I do not understand yet is why there are 35 Truth hit in the CDC. 
while we have only 27 layers or less depending
on the geometry you used. The momentum of the particle is more than 1.5 
GeV in the y direction so I do not see how
one can get more than one Truthhit in the same layer from the same 
particle. The only way to get more hits is if the
timing separation between two hits is larger than the value defined by 
"TWO_HIT_RESOL" which is set to  250.
This means that whenever a second hit in the same volume happens to be 
250 (whatever units this is?) after the first
hit then this hit will be counted separately. This could explain why you 
have more Truthhits than layers.

cheers,
Beni



Mark M. Ito wrote:
> Folks,
>
> In the attached hdgeant output for a single event, there are 25 
> cdcStrawHit's but 35 cdcTruthPoint's. Why the difference?
>
> When I look in the jana event, for the same event, I get 41 
> DMCTrackHits after screening for FDC and CDC hits as follows:
>
>    if (mchit->system & (SYS_CDC | SYS_FDC) && mchit->primary == 1) {
>
> Why so many? (This is a backward going track so there should be no FDC 
> hits.) Do I need a binding lesson?
>
> Thought I'd ask before digging into the code.
>
>  -- Mark
>