[Nps] NPS VTP Trigger thresholds for KinC_x60_4

[Peter Bosted]

Here is the efficiency of pi0 detection as a function
of momentum (row) and thw 2-pion trigger threshold.
I did this for a one-photon triger of 1.6 GeV and a cluster
readout threshold of 500 MeV.
It appears that we do loose some 1.8 to 2.2 GeV pi0's going
from 650 to 800 MeV threshold.

If we switch to running with HMS trig4 (elreal), then we would
gain some 1.6 to 2.2 GeV (column with 500 MeV). I hope you decide
on this strategy.

pi0 detection efficiency
distance target to back of NPS=  420. cm
          cluster threshold in GeV
   ppi  0.3  0.4 0.5  0.6  0.7  0.8  0.9  1.0
  1.80 0.07 0.07 0.06 0.05 0.04 0.02 0.00 0.00
  2.00 0.18 0.18 0.17 0.15 0.13 0.09 0.05 0.00
  2.20 0.27 0.27 0.27 0.27 0.22 0.18 0.13 0.09
  2.40 0.33 0.33 0.33 0.33 0.33 0.33 0.29 0.23
  2.60 0.38 0.38 0.38 0.38 0.38 0.38 0.38 0.38
  2.80 0.42 0.42 0.42 0.42 0.42 0.42 0.42 0.42


Prof. Peter Bosted
email: bosted at jlab.org
phone: (808) 315-1297 (cell)
P.O. Box 6254, Ocean View, HI 96737

On Tue, 6 Feb 2024, Charles Earl Hyde via Nps wrote:

>
> Hello,
> We are currently running with the following VTP thresholds
> Single Photon (NPS_T1) 1400 MeV
> TwoPhoton (each, NPS_T6) 650 MeV
> With 20 uA on LD2, the OR of these two triggers (with EDTM)
> is hTRIG1 = 1.9e6
> https://logbooks.jlab.org/entry/4248473
> The endpoint energy (gamma or pi0) of the current KinC_x60_3 setting is
> 4.4 GeV.
> So a symmetric pi0 decay of two photons of 650 MeV has a SIDIS
> z=1.3/4.4 =
>
> in NIM hardware, the output of hTRIG1 is fanned out with a 160 nsec pulse
> width.  Thus in current running on LD2 we have a 30% probability of
> pile-up in the trigger.
>
> In our next setting (starting tomorrow afternoon), KinC_x60_4,
> the endpoint energy will be 5.2 GeV.
> I would like to raise the NPS-VTP trigger thresholds as follows
> Single Photon raise to 1600 MeV
> Two photon raise to 800 MeV
> Looking at the cluster energy spectra, I think this will lower the NPS
> nTRIG1 rate by a factor of 2.
> The SIDIS range would be approximately 1.6/5.2 =0.31, so essentially
> unchanged.
>
>
> Sincerely
> Charles E. Hyde
> University Professor  and Eminent Scholar
> Department of Physics
> Old Dominion University
> www.odu.edu/~chyde
>
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