[Halld-cpp] tagger overlapping counters and CPP target density

[Justin Stevens]

Hi Ilya,

Thanks for the numbers.  I updated the target values in CCDB and also the python script in hd_utilities https://github.com/JeffersonLab/hd_utilities/tree/master/psflux that we use to histogram the flux.

As for the overlapping counters, I would suggest you start by performing the analysis separately for the TAGM and the TAGH.  Along those lines, I added separate histograms to the plot_flux_ccdb.py script that are filled with the tagged flux vs beam energy for the two tagger detectors separately.  This way you can do the physics analysis with only one tagger detector or the other and use the appropriate flux to normalize the yield.

The instructions to run the flux script can be found on the wiki page https://halldweb.jlab.org/wiki/index.php/PS_acceptance_and_luminosity_determination#Instructions_for_obtaining_measured_fluxes_from_CCDB and an example output can be found at /work/halld2/home/jrsteven/home/forCPP/flux_100000_109999.root

-Justin

On Feb 17, 2025, at 3:44 PM, Ilya Larin <ilarin at jlab.org> wrote:


Hi Justin,
According to my records (Rory may correct me), the values are:

  *   Density: 11.39 g/cm³
  *   Thickness (average): 305.9 microns
  *   Thickness variation: 0.38%
  *   Lead-208 mass fraction: 99.09%
  *   Number of atoms per unit of transverse square: 1.009 × 10²¹ cm⁻²

My estimation for the uncertainty in (density × thickness) was 0.39%.
By the way, for the CPP flux calculations, it might be important to exclude the part of the flux associated with tagger hodoscope counters that geometrically overlap with microscope counters, if they coincide in time as well. We need to find a way to address this issue.
Below is the table I am currently using to eliminate this double-counting.

 Best,
Ilya

TAGH counter;   TAGM min overlapping counter; TAGM maximum overlapping counter

222 1 3
223 5 7
224 8 12
225 12 15
226 17 19
227 20 25
228 25 27
229 29 33
230 32 37
231 36 42
232 41 45
233 45 49
234 48 54
235 53 57
236 57 63
237 62 65
238 65 70
239  0  0
240 72 77
241 79 82
242  0  0
243 86 91
244 90 94
245 95 96




________________________________
From: Halld-cpp <halld-cpp-bounces at jlab.org<mailto:halld-cpp-bounces at jlab.org>> on behalf of Justin Stevens via Halld-cpp <halld-cpp at jlab.org<mailto:halld-cpp at jlab.org>>
Sent: Monday, February 17, 2025 14:44
To: halld-cpp at jlab.org<mailto:halld-cpp at jlab.org> <halld-cpp at jlab.org<mailto:halld-cpp at jlab.org>>
Subject: [Halld-cpp] CPP target density?

Hi All,

I’m working on adding the photon flux to CCDB so that we can use our standard tools to compute the flux for each run.  Part of that process for our typical LH2 runs is to store the target density (g / cm^3) in CCDB so that we can convert the flux to luminosity.  My question is: what is the density of the lead target for CPP that I should put in this table https://halldweb.jlab.org/cgi-bin/ccdb/versions?table=/TARGET/density ?

-Justin

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