[Clas12_first_exp] [EXTERNAL] J12-24-RunGroup A

Wed Jul 3 14:08:45 EDT 2024

Hi Latifa,

Attached are few slides I made for efficiency studies with the new tracking (DAV) compared with pass2. The last slide is the figure-of-merit graphs for 2 and 3-prong events in FD. This metric we used in the past to chose the luminosity. As we can see, with the current tracking we can easely run at 100 nA. This was the motivation to asses our expected charge with 100 nA beam current.
This is not for the PAC presentation, but I think it will help in the discussions if anyone asks.

Regards,
Stepan

On Jul 3, 2024, at 10:51 AM, Rafayel Paremuzyan via Clas12_first_exp <clas12_first_exp at jlab.org<mailto:clas12_first_exp at jlab.org>> wrote:

Hi FX,

Below are numbers that we discussed in today's meeting.

  *
The Collected charge including F18_In + F18_Out + S19 is 114 mC, which translates into 155 fb-1
  *
And, if we take data for 65 more days with 100 nA beam, we will collect 560 mC, which translates into 760 fb-1

Rafo
________________________________
From: Clas12_first_exp <clas12_first_exp-bounces at jlab.org<mailto:clas12_first_exp-bounces at jlab.org>> on behalf of Francois-Xavier Girod via Clas12_first_exp <clas12_first_exp at jlab.org<mailto:clas12_first_exp at jlab.org>>
Sent: Wednesday, July 3, 2024 10:31 AM
To: Latifa Elouadrhiri <latifa at jlab.org<mailto:latifa at jlab.org>>; clas12_first_exp at jlab.org<mailto:clas12_first_exp at jlab.org> <clas12_first_exp at jlab.org<mailto:clas12_first_exp at jlab.org>>
Subject: Re: [Clas12_first_exp] Fw: [EXTERNAL] J12-24-RunGroup A

Dear all

Could someone send either the collected charges for pass 2 run periods and expected collected charge for the proposed beamtime, or the corresponding luminosity?
I think it is important that we all use the same numbers in our projections

Thanks!

Best regards
FX

On Sun, Jun 30, 2024 at 10:04 PM Latifa Elouadrhiri via Clas12_first_exp <clas12_first_exp at jlab.org<mailto:clas12_first_exp at jlab.org>> wrote:
Dear All,

Below are the questions from Marco Radici, our PAC reader, along with the attached TAC report and the theory report. We need to address all the questions in a written document this week and update the presentation, accordingly and taking into account the comments and questions made during the CLAS collaboration meeting.

I will work with the deep exclusive process to address the related questions. Harut, please coordinate with the SIDIS group to address the questions in your section. The comments in other sections are minor.

Our CLAS12-first experiment meeting on Wednesday morning will focus on these issues.

Best regards,

Latifa

________________________________
From: Marco Radici <marco.radici0 at gmail.com<mailto:marco.radici0 at gmail.com>>
Sent: Sunday, June 30, 2024 2:24 PM
To: Latifa Elouadrhiri <latifa at jlab.org<mailto:latifa at jlab.org>>
Cc: Markus Diehl <markus.diehl at desy.de<mailto:markus.diehl at desy.de>>; Ilieva, Yordanka <ILIEVA at sc.edu<mailto:ILIEVA at sc.edu>>
Subject: [EXTERNAL] J12-24-RunGroup A

Dear Latifa,
   I'm writing to you as the contact person for the Jeopardy RunGroup A  J12-24-RunGroupA, entitled
"11 GeV Polarized Electrons on Liquid Hydrogen Target to Study Proton Structure, 3D Imaging, and Gluonic Excitations"
to be considered at the upcoming JLab PAC52 meeting.

You should have already received the Theory report, and I'm sorry of being late with respect to that one.
But overall I must confirm some of the remarks contained in that report.
While the very broad physics program covered by the proposal is still central to the physics agenda of JLab12, and its scientific motivation remain strong since the last Jeopardy review (if I'm not mistaken, it is PAC48, where the scientific rating was "A"), I share the opinion of Theory report's authors that some parts of the proposal should be completed with a more detailed analysis of the expected statistical impact from the remaining beam time (65 PAC days of the total 139).

An explicit example of it is given in Sec. 3.1 on TCS: comparison of "blue points" with "gray points" in Fig.10 gives a visual estimate of what will be gained with the remaining beam time w.r.t. data collected in the 2018 and 2019 runs.

This kind of information is missing in most of the discussion on Deep Exclusive Processes:

- in Sec. 1.3 (E12-06-108) where in Fig.2 it would be particularly useful in comparison with the displayed theoretical calculations

- in Sec. 1.4 (E12-12-007) where there is no plot of the t-dependence of the cross section nor of the estimate of its error with accumulated and remaining statistics

- in Sec. 1.5 in hard exclusive rho electroproduction, where there is a vague reference to SDMEs: are they measurable with expected total statistics or not? Incidentally, it might be interesting to look also at the sigma_L / sigma_T ratio, where other data exists and show a puzzling deviation from the perturbative QCD prediction (see the Compass publication E.P.J. C83 (23) 924)

- in Sec. 1.6 (DVMP with pions to study TDA), where an order of magnitude increase in statistics is wished but there is no study of the statistical impact of remaining PAC days on the errors indicated in Fig. 5

- in Sec. 1.7 (Sullivan process for pion GPDs), where there is no indication of the statistical impact on errors in Fig. 6; incidentally, where does the blue curve come from? Neither caption nor text mention it

- in Sec. 1.8 (N* DVCS): there is a statement (".. Based on the statistics already collected with RG-A, a differential study is only possible in one kinematic variable, in addition to the phi-dependence, with relatively large uncertainties..") which is not supported by any figure. So that it's hard first to convince of the mentioned agreement with theoretical predictions, and secondly to estimate the impact on uncertainties from accumulating the remaining statistics.

Also, about DVCS (E12-06-119) and Fig. 1 in Sec. 1.2, I think it would be useful to refine the comparison with more updated theoretical calculations, as suggested also in the Theory report.
KM15 has been now superseeded by KM20 (P.R.L. 125 (20) 232005, with flavor separation of CFFs); it could be useful to have a look also at calculations with NLO corrections (JHEP 12 (23) 192), as well as to the results in the PARTON framework (Moutarde et al., E.P.J. C79 (19) 614). Both groups use modern analysis techniques, based on Neural Networks.
P.S. In Fig. 1 both labels VGG and GK are not explained in the caption.

As for Sec. 2 on pion SIDIS (E12-06-112 and E12-06-112A), I share the general comment of the Theory report.
In SIDIS at low Q2, there are important questions that need to be addressed, like the validity of TMD factorization, the separation between current and target fragmentation, the role of vector meson decays, etc..
I'm convinced that the best observable to attack these problems is the differential cross section. Azimuthal/spin asymmetries, as ratios of cross sections, can indeed hide the answer to above questions. Even multiplicities, as ratios to the collinear inclusive cross section, can show deviations from theoretical expectations that are not directly related to the elementary mechanisms to be explored (see, for example, the "SIDIS normalization problem" in recent global extractions of TMDs).
Given the potential of exploring the 5-dim. phase space in (x,z,Q2,PhT,phi), the RunGroup A should concentrate in extracting the cross section differential in these variables at the best accuracy provided by the attainable total statistics.

I have also a couple of questions on the text of Sec.2:

- Eq.(1) is anticipated by a paragraph warning about the lack of information related to the part of the unpolarized structure function F_UU related to the longitudinal polarization of the exchanged virtual photon: F_UU,L.
However, Eq.(1) shows an ambiguous F_UU notation and its expression includes twist-3 contributions (A_UUcosphi and A_LUsinphi). Does this mean that F_UU includes only the photon-transverse contribution F_UU,T, since F_UU,L is at twist 4? The text should better clarify the point

- when building the multiplicities, NLO collinear PDFs and FFs are used, while the comparison with theory calculations is claimed to be done at LO. Why?

- in the discussion of Fig.8, there is no mention of the x variable; the plots are for a specified Q-y bin...

- about Dihadron Fragmentation Functions (DiFFs), there is a misleading statement in the text. The claim about G1perp is made that ".. Extending this analysis with a partial wave expansion will give access to the correlation between the fragmenting quark angular momentum with the angular momentum of the dihadron...".
This is not correct. G1perp means that the fragmenting quark is always longitudinally polarized. And the partial-wave expansion gives information on the relative orbital momentum inside the hadron pair.

- DiFFs are mentioned as tools to access the chiral-odd PDF e(x). But the A_LU asymmetry at twist 3 contains several other contributions that are not mentioned. Are they small and negligible?

I find Secs. 4,5,6 clearly written and self-comprehensive.
I have only these small remarks:

- Fig.14: no color code is mentioned to identify the different contributions to the total curve

- Fig. 15: the caption says that the Partial-Wave Amplitudes are plotted as functions of the four-momentum transfer squared. Is this the meaning of the label "r" in the plots? It is an unusual notation...

Best regards,
Marco Radici

--
============================================

Marco Radici

INFN - Sezione di Pavia
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