GlueX Phase III 31-Aug-23

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Meeting Coordinates

The meeting will be on Thursday, August 31, 2023 at 1:00 PM ET. For those in-person at JLab F326 is reserved

Connecting

To connect to the meeting, please go to the listing of Zoom meetings on the private Wiki and select the GlueX/Hall D Biweekly Meeting link at the top of the list.

Agenda

  • open kickoff discussion and brainstorming (all)

Links

Minutes

(prepared by Matt and Justin)
Present: Zisis, Eugene, Simon, Justin, Matt, Sean (online), Sasha (online)

Introduction

We anticipate that the current PAC-approved GlueX running will end around 2025. There are other approved experiments in Hall D, like KLF, but the readiness for running in 2025 is uncertain due to a variety of external factors. Therefore, it is advantageous to have the PAC approve additional GlueX running that could happen as soon as 2025.

Short Term

Sasha proposed a short term plan where we try to run perhaps up to 1x - 2x higher than current GlueX luminosities. We should evaluate if this is possible – we can use data collected in early 2023 for this evaluation. There are some areas where we might expect issues:

lifetime of PMTs and general usability of TOF for paddles near the inner region trigger rate/bandwidth could require retuning of the trigger capability of inner FCAL insert channels will depend on yet unknown rates in these channels occupancy and pileup in tagger counters? (Sasha says TAGH may be OK)

If this is feasible, this could make an attractive option for 2025. Continued running at similar or slightly higher intensities provides significant incremental gains for the physics program that uses the new calorimeter insert. If CEBAF energy is higher in the future and enhanced electron ID capability exists via a TRD, the charmonium program would also experience better than sqrt(N) gains with additional running.

TRD: Lubomir was not able to make the meeting, but it is known that there is a program of TRD R&D and development ongoing.

Long Term

In the long term we will need hardware upgrades to push to higher intensities which we consider to be 2x - 4x current GlueX luminosity. During the meeting we discussed a couple of areas of hardware development that will be required for a high intensity program in the future. Eugene stressed that it is important to start R&D on these activities now. There may even be a small window of 4 days in March 2024 to put prototype detector elements in Hall D. It will be important to demonstrate in our 2024 PAC proposal that we have an active R&D program that is preparing for high intensity running in the future. Areas for hardware development (in addition to the TRD) include:

Time of Flight

The main line of discussion here seemed to be to open the central hole in the present time of flight to be the size of FCAL insert. A fine granularity scintillator detector could then be placed immediately upstream of the FCAL insert. The desired timing resolution of this detector depends on its application: charged particle veto, particle identification, and/or aiding tracking algorithms. Several possible implementations were discussed like a scintillating fiber matrix or scintillating pixels with embedded wavelength shifting fiber.

Tagger

We briefly discussed that Richard is investigating FPGA algorithm upgrades that better accommodate multiple hits in the tagger. This could be deployed in the context of the existing hardware and provide benefits.

Pileup and tagger rates will eventually require that the tagger hodoscope be built with finer granularity. We have also observed that the microscope has a lifetime due to apparent radiation damage. There was less discussion about practical solutions, but it seems accepted that the tagger will need to be overhauled for high intensity. Maybe a larger microscope-style detector is appropriate to span the coherent edge to the endpoint.

Physics Objectives

It will be important to understand the compatibility between the rare eta and di-electron physics programs. The ideal situation would be one in which a common data set can be used for both applications. The rare eta program prefers less material. It is also anticipated that there will be a balance between increasing beam intensity to access rare processes and pileup in the calorimeter that comes with higher rate. The di-electron program prefers to enhance electron ID with the addition of a TRD, but this increases photon conversions. Could the effects of this be offset, for example, by the previously mentioned charged particle veto that might replace the inner TOF? The trigger will also need modification and this must be done with target physics channels in mind.

Simulations

There were two broad areas of simulation that were discussed. (1) Try to learn how material and rates negatively affect the rare eta program. This is probably a lower limit on the true impact as typically backgrounds are worse than anticipated. One may also explore how a charged-particle veto might be helpful in reducing these backgrounds. (2) Understand how global PID (pion/kaon) might be affected by a change in time-of-flight resolution for the inner region of the detector.

Next Steps and Action Items

We agreed to try to focus on two intensities: 2x and 4x nominal GlueX rates. Probably for critical subsystems identified above (trigger, TOF, tagger), the appropriate questions to address are:

  • Could the system be operated at 2x nominal rate?
  • What hardware modifications would be required so that the system operates at 4x nominal rate?

There were some volunteers to explore a few other things.

  • Simon with Igal will brainstorm on various simulation studies that can be done to understand how to optimize hardware for a variety of physics objectives.
  • Zisis and Sasha will look at scintillating fiber options for an inner TOF
  • Justin will look at Hall B developments of a 2D array of scintillating tiles

While not at the meeting, both Richard and Paul indicated interests in microscope and TOF development.


Next Meeting

It may be helpful to have a more structured discussion with some slides or data from the test running that took place in early 2023. The afternoon of Monday, September 18 is suggested – indicate availability here:

Possible agenda items for brief reports:

  • approximate schedule/plan for TRD R&D (Lubomir)
  • operating the tagger at 2x rates (Richard)
  • TOF at 2x rates (Beni?, Paul?, Sean?)
  • trigger at 2x nominal intensity (Sasha)
  • simulation brainstorming/discussion (Simon, Igal?)
  • scintillating fiber R&D thoughts (Sasha, Zisis)
  • scintillating tile R&D thoughts (Justin)
  • discussion of scenarios: what might a PAC proposal for 2025 look like? (All)
    • 100 (?) days of running at 1x-2x (?) GlueX-II
      • primary physics emphasis: rare eta and charmonium
      • secondary physics emphasis: rate limited spectroscopy studies
    • hardware configuration: informed by simulation
    • dedicated detector high intensity R&D – additional beam time for testing?
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