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

Wed Jul 3 10:31:51 EDT 2024

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> 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>
> *Sent:* Sunday, June 30, 2024 2:24 PM
> *To:* Latifa Elouadrhiri <latifa at jlab.org>
> *Cc:* Markus Diehl <markus.diehl at desy.de>; Ilieva, Yordanka <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
> via Bassi 6
> I-27100 Pavia
> Italy
>
> tel. +39 0382 987451
> fax  +39 0382 423241
>
> email  marco.radici at pv.infn.it
> web    http://www.hadronicphysics.it/hasqcd/ <https://urldefense.proofpoint.com/v2/url?u=http-3A__www.hadronicphysics.it_hasqcd_&d=DwMDaQ&c=CJqEzB1piLOyyvZjb8YUQw&r=IbWk8zxXqrZbowqRjbpcbQ&m=wy7ywUoNnXbEYGUFZqbP0pA7eB80d_G9j8I3Nct5DaNMq0XIHw87-2OUsJRw97vx&s=wAmE6TFBFp3-1HWc3sxmC69UwhUF65SN9cB9Ygx6T4c&e=>
>
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