[Pwg] Reader 1 PR12-21-006 review

[Xiaochao Zheng]

Dear All:

We received some questions and comments from Steven Dytman on the proposal, please see his email below.  (Shufang Su is the 2nd reader and we may receive more questions from her later).

To the positron team (Joe, Yves, Jay, et al): could you please provide some insights to 1b and 1c?

To my theory colleagues: any suggestion on 2? (I can probably make a draft sketch on its answer.  And I may also expand the last theory update in my other 4-page PDF answer to theory/tech comments).

I think I can answer 5, but suggestions are welcome.

I am not sure I understand 3 and 4.. Any ideas?   I think since both e- and e+ are secondary beams, we can't use polarized e-, so we can only do "unpolarized DIS measurement" but I can't figure out how to use it as a "cross check".

I hope to draft a full answer over the weekend and send it back to our readers by Tuesday next week.

Best regards,

Xiaochao

________________________________
From: Steven Dytman <dytman at pitt.edu>
Sent: Friday, July 9, 2021 11:26 AM
Subject: [EXTERNAL] PR12-21-006 review

Xiaochao,
I hope I have your name correct.  Here are my questions on your proposal.

1.  The main issue is the positron beam.
     a.  What parameters are most important properties to control, how well?
     b.  Proposal emphasizes importance of *equality* of beam energies.
Is this a strong limitation on the lab?  TAC report also mentions this.
What if the consistency was 50% worse than you request?  What is your
estimate of how much the systematic errors would increase?
     c.  What is earliest time you plan to have a suitable e+ beam for
your experiment?
     d.  What is the maximum time separation between e+ and e- beam
running you seek?

2.  Since DIS has no sharp signal, backgrounds must be calculated (high
twist, radiative corrections seem most difficult).  How will those be
controlled?

3.  Will you do unpolarized or single polarized DIS measurements as a
cross-check?

4.  How does this relate to other positron experiments? Why was this
chosen to be first?

5. What are the differences between your proposal and the existing CERN
measurement?  I think that comes from the fact that their beam was
polarized and yours will be unpolarized.

regards,
Steve



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