Sept. 20th, 2022

TCS meeting, Sept 20th, 2022

Discussion: Going through PAC/TAC and other comments we got since PAC, discussing how to address them

• (PAC comments) It must be shown that the GEMs to be used can operate at the luminosities of the experiment without a negative impact on their resolution and efficiency.

- UVA + JLab have the expertise, SBS will give us some responses

- should be fine with extra layers of GEM

- From TAC: raise threshold on signal to lower low energy background - but then we won’t have tracking for e+e- (only good for the proton) / need to check with experts, to put also in simulations. (resolution?) (something to try at least)

- Not sure we can do e+e- reconstruction without GEM tracking.

- Will try to reconstruct e+e- with simple regression only with calo and hodo signal: check if possible (will discuss first with other people then do simulation)

- We should discuss with people working on SBS, people with experience on the analysis with the tracking (will contact this week)

• (PAC comments) The radiation damage on the hodoscope and on the photosensors used in the different subdetectors has to be assessed.

- We put only for calorimeter, need to do study for other parts

• (PAC comments) The proposal must discuss the required level and stability of calibration of the different subdetectors that will allow one to measure the kinematic variables to the precision discussed in the proposal.

- To do with full MC

- Calibration with pi0 decay for calo (once per day in DVCS conditions)

- Gain monitors

- Option to look: pi+pi- from rho or heavier mesons to use for GEM/hodo proton track resolution?

- Looking for other options

• (PAC comments) It should be demonstrated that the particle identification for the e+e− pair suppresses the non-resonant exclusive and the SIDIS π+π− backgrounds enough to cleanly isolate the small TCS signal.

- Full MC with background, need to be done with accurate cross sections (to do very soon)

- Rely on “good” model (which one?), other experiments measurement, or parallel./complmentary measurement of meson or uncorellated pi+pi- pairs (Hall B did the measurement, see if anything public now)

- Hall B people have MC, not sure yet if they have an actual measurement

- SIDIS: Pythia but not very reliable near exclusivity peak (or assuming large model uncertainty) - build “homemade” code with cross section at high z + extra 4-momentum (looking at z dependent TMD related measurements at JLab to normalize) (will look if it works by doing this for existing measurements, for instance pion data)

• (PAC comments) The plan to realize the modifications to the NPS needed for the experiment should be specified in detail.

- Action plan with timelines

- More GEMs layers, feasibility…

- We need to optimize the hodoscope design

- Need to put more details if we come back to PAC

• (PAC comments) The PID response and its fluctuations should be simulated in a full GEANT simulation of the detectors

- Digitization in GEM to add (only energy deposition) - need to be added

• (PAC comments) Deeper review of the experimental issues raised above is required

- We need to communicate more with JLab in advance of proposal submission

• (PAC comments) The collaboration needs to increase their workforce focusing on the challenging technical issues of this proposal.

- Trying to talk to more people

• (PAC comments) Other things that came up:

- Full GEANT needed

- Expertise with high background environment

- “ERR” like procedure (we need to do the rest fierst, trying to go to that no later than Jan 2023)

- Simulations of full background (physics + low energy)

To do list & timelines

Next meeting: Oct. 4th but will be confirmed (or the following Tuesday)

• By mid-October:

• • Marie: working on the physics simulations and trying to get a homemade model for SIDIS at large z into the simulations

• • Vardan: writing instruction for the GEANT code (Marie + Deb will look at it, Deb learning from Petr so we can have some cross check)

• • Vardan: check compatibility with newer versions of GEANT & multiprocessor computers

* Objectives:

• By November:

- GEM tracking & threshold,

- Physics background

• By December

- Full MC

- PID, high background

- updated counting rates if there is update

- updated physics outcome if there is with more realistic simu

• By January

- Having the “ERR like” readiness review (close to the Hall C collab meeting)

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