Outline 1 From the trigger point of view it is convenient to put - - PowerPoint PPT Presentation

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HPS Collaboration meeting, Nov. 18-19, Jefferson Lab

Outline

NO signal NO signal Must have Must have signal Must have signal NO signal

Probe channel From the trigger point of view it is convenient to put the same threshold cut for all tiles Gains are chosen such that signal from each distribution to be peaked at 1000 (An almost arbitrary unit)

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Before installation, the Hodoscope was tested in EEL building and for each channel cosmic gains are

• btained

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Note: gains and HV settings were obtained with cosmics: Pretty low rate environment! Things become quite different when the it was placed under the beam

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𝜈 𝜈 It is probably the photons from walls of vacuum chamber (or any other material) hit fibers. Quote from H8711 datasheet So this apparently forced us to reduce the HV on PMTs, otherwise the anode current goes too high

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𝜈 The beam current was rumped up to 220 nA

• This was the max luminosity we were

thinking at that time Chose the highest HV setting, that will not exceed the 5% limit too much. The Top 800 V, and Bot 740V was chosen

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For tiles with stat < 200, the mean value is taken for the peak position.

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500 < L < 1100 1100 < L < 1300 1300 < L < 1800 1800 < K < 2500

1600 1400 1600 1600 640 800 1200

• Higher Luminosity Higher gains
• Gain drop during the time

We might consider obtaining new PMTs for next runs to compensate the gain drop.

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Not good!

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Requirements on clusters and tracks

• About 2% failed

≈ half of failed events failed “XHodo ⨂ XECal“ See next slide for these failed events

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Events that failed “XHodo ⨂ XECal“ cut This led to loosen a bit “XHodo ⨂ XECal“ matching cut Trigger efficiency with new “XHodo ⨂ XECal“ table Inefficiency is 1.3%