[Primex2] group tdc in silicon runs

[gasparan at jlab.org]

  Hi Yang,

 That was expected, the 0.5 GeV for a TDC opening is still rather
 low energy (including non uniformity of the gains). Try to increase
 the energy threshold, say up to 1 GeV and see if we apply for those
 events how much the background is getting better, without
 compromising the error on efficiencies.

 Ashot


> Dear collaborators,
>
> In the following link are group tdc timing distribution against tagger
> timing and the multiplicity with hycal cluster energy cut at 0.5 GeV. The
> efficiency doesn't improve with the cut. But I will use it anyway like in
> the veto situation, whenever group tdc works I will exclude out of timing
> (group tdc - tagger timing) pi0s and see if the background can be reduced.
>
> https://www.jlab.org/primex/weekly_meetings/primexII/slides_2015_03_13/gtdc_dist_w_energy_cut.pdf
>
> Best
>
> Yang
>
> On Thu, Mar 12, 2015 at 1:08 AM, Yang Zhang <yzhang132 at gmail.com> wrote:
>
>> Dear collaborators,
>>
>> The file in the following link are some plots for group tdc behind
>> crystals from all silicon production runs.
>>
>>
>> https://www.jlab.org/primex/weekly_meetings/primexII/slides_2015_03_13/gtdc_dist.pdf
>>
>> For each Hycal cluster, the program looks for the corresponding group
>> tdc
>> timing information. If there is a group tdc hit for this cluster, it is
>> then paired with tagm timing to get group tdc t - tagm. The tagm timing
>> is
>> selected in such a way that it has coincidence with hycal trigger and
>> the
>> tdiff between these two is within -6 to 6 ns. The distributions of the
>> group tdc t-tagm are plotted on the left of each page in the file.
>>
>> On the right are the multiplicity, meaning the number of group tdc
>> timing
>> and tagm timing pair for each corresponding hycal cluster (so the
>> entries
>> in the statistic box are total number of clusters on this group tdc).
>> From
>> those plots we can see the group tdc efficiency is not very good.
>>
>> Please let me know if you have any comment.
>>
>> Best
>>
>> Yang
>>
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