Re: cdcStrawHit vs. cdcTruthPoint

[Beni Zihlmann <zihlmann@jlab.org>]

Hi Again,
sorry forget the second part of the mail below that is bull....

cheers,
Beni
> 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
>>
>