[Tensor] [EXTERNAL] Re: Tensor Experiments meeting today at 4pm (ET)

Tue May 2 15:05:59 EDT 2023

Hi b1 fans,

I've taken a look at the question of higher-twists in A_zz and extracting b_1. Starting with eq. (27) of the Cosyn et al. paper, and the longitudinal target field configuration, one can substitute for the tensor polarization in (27) using the expressions in (28). The result is a straightforward derivation of eq. (47). For convenience, the paper is at

https://urldefense.proofpoint.com/v2/url?u=https-3A__doi.org_10.1103_PhysRevD.95.074036&d=DwIF-g&c=CJqEzB1piLOyyvZjb8YUQw&r=mbL-4Mr65FbyCWqCw73luw&m=Vj5drvJX7Z_gyCUF_2iKu0Mi7eOULh0MCQOGNlYgfpmTTruh0PqqesVQYxcftkko&s=ibS067Ltz-cuaIP4p2nMgCptNX4vVLIuBYMe35G6cz8&e= 

As seen in (32), the only polarized structure functions that depend on b_1 are F_UT_{LL}L and F_UT_{LL}T.  But the contribution of b_1 to the combined term, see line 2 of (47), is in the form
(1 - {\epsilon}) b_1. Since {\epsilon} (defined in eq. 30) at our kinematics is very close to 1, ranging from 0.88 at low x to 0.936 at x = 0.452, there is an almost total cancellation of b_1. 

On the other hand, the terms with the HT tensor SF's b_{2,3,4} become kinematically dominant, since there is only partial cancellation between the last term of F_UT_{LL}L and the second term of F_UT_{LL}T, see eq. (32). The coefficients of the different terms at our proposal's kinematics are shown in the attached file. The >1 factor (1+gamma^2)^2 in front of the second term of F_UT_{LL}L (shown in the last column in attached table), in which all the HT SF's add their contributions and there are no matching cancellations, can further complicate a direct connection between A_zz and b_1.

The question is whether these HT terms can be as large as the leading twist one. On the second attachment I've plotted the values of b_i shown on Table 1 of the paper, at the same scale. b_3 and b_4 dominate. Since the expectation is that HT terms are supressed by (1/Q)^(twist-2) powers and both Hermes and our proposal measure a region where Q^2 > 1, it's not clear how the HT dominance   comes about. Other models, such as the one presented in the following paper by Hoodbhoy, Jaffe and Sather, "Twist-four corrections to deep-inelastic lepton scattering from a polarized spin-one target"

 https://urldefense.proofpoint.com/v2/url?u=https-3A__doi.org_10.1103_PhysRevD.43.3071&d=DwIF-g&c=CJqEzB1piLOyyvZjb8YUQw&r=mbL-4Mr65FbyCWqCw73luw&m=Vj5drvJX7Z_gyCUF_2iKu0Mi7eOULh0MCQOGNlYgfpmTTruh0PqqesVQYxcftkko&s=c8RwmKBfsTcjE5SWzQZQPISVQYqWyDOJ4ZJTGMzRyxg&e= 

finds that at Q^2 ~ 1 GeV^2 the HT contributions would be just a 5% correction. The paper by Cosyn et al.  doesn't include this work in their references.

Since aligning the target field along the q vector to supress HT would be a major undertaking impacting the experiment installation and running, it seems a better understanding of the HT contributions is needed. Of course, everyone should feel free to verify the numbers and plot in the attachments.

Cheers,

Oscar

___________________________
From: Tensor <tensor-bounces at jlab.org> on behalf of Karl Slifer via Tensor <tensor at jlab.org>
Sent: Tuesday, April 25, 2023 7:44 PM
To: tensor at jlab.org; Fernando, M. A. Ishara Priyasad (cee9hc)
Subject: [Tensor] [EXTERNAL] Re: Tensor Experiments meeting today at 4pm (ET)

Minutes of today’s meeting

2023-04-25
Present: Carlos Yeros, WC, EL, KS, MM, AZ, NS, DR

1) Carlos Yeros gave an overview of a proposal he is working on with Nathaly S and Mark Jones (and others?) to measure electro-disentigration with tensor target.  He has done some rate calculations, but they don't expect to have a proposal ready for this PAC.  The rate estimates indicate it is doable for Q2 about 2.1-2.9 using the Hall C SHMS electron trigger and HMS proton trigger. But they still need clearer motivation and methods for extraction of exclusive from inclusive.  i.e. They need more theory support to justify putting more work in.

2) We attempted to recap/summarize last week's theory discussion. The biggest takeaways (atleast the biggest relevant to the jeopardy review) were:
-There is continued high interest in b1 as probe of non-conventional/exotic components of the deuteron.
-We were asked to plot Azz vs light cone variable
-there were several statements to the effect that polarized D is the best way to access S/D.
-There was suggestion to show how does Azz fit in with recent SRc measurements
-Interesting to access a new twist-2 pdf.  Deuteron is "disappointing and interesting" target. Unconventional contributions will be striking.
-Several suggestions for new channels to measure
-much much more.... Thanks to our theory colleagues!

3) Ellie crafted templates for the review documents based on recent jeopardy reviews.  These are still just skeletons but we aim to share with the full collaboration by next week's meeting so that everyone can start contributing.

4) Wim discussed the B-field orientation calculation:
--b1,b2,b3,b4 contributioins must be cleanly separated
--if you polarize along the photon beam, we will have less mixing
--however the additional contribution can have opposite signs that cancel. So along electron beam he found it was closer to the real b1 than not. Polarizing along electron direction did not make it terribly worse
--Wim students used our Q2, and a wide range in x at lower Q2.  He does not think it will take much to run again at our exact kinematics, but it is much more work to establish the model dependence of the calculation.  He's aiming to have this done "to some level" before the Jeopardy review.
-Allison Zec is working on this in parallel.  She has started coding, but does not yet have a working program.

5) David Ruth briefly discussed the g2p proposal and we discussed the pros and cons of submitting to this PAC.

--
Prof. Karl Slifer
Nuclear Physics Group
University of New Hampshire
Department of Physics & Astronomy

From: Tensor <tensor-bounces at jlab.org> on behalf of Karl Slifer via Tensor <tensor at jlab.org>
Date: Tuesday, April 25, 2023 at 10:36 AM
To: tensor at jlab.org <tensor at jlab.org>, Fernando, M. A. Ishara Priyasad (cee9hc) <cee9hc at virginia.edu>
Subject: [Tensor] [EXTERNAL] Tensor Experiments meeting today at 4pm (ET)
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Reminder of Tensor experiments meeting Today at 4pm (ET)

https://urldefense.proofpoint.com/v2/url?u=https-3A__unh.zoom.us_j_97641757857&d=DwIF-g&c=CJqEzB1piLOyyvZjb8YUQw&r=mbL-4Mr65FbyCWqCw73luw&m=Vj5drvJX7Z_gyCUF_2iKu0Mi7eOULh0MCQOGNlYgfpmTTruh0PqqesVQYxcftkko&s=cABE6PNF7CT3iug3MypDmQWzXpdYmBW4AESDmJQfyDc&e= <https://urldefense.proofpoint.com/v2/url?u=https-3A__nam12.safelinks.protection.outlook.com_-3Furl-3Dhttps-253A-252F-252Furldefense.proofpoint.com-252Fv2-252Furl-253Fu-253Dhttps-2D3A-5F-5Funh.zoom.us-5Fj-5F97641757857-2526d-253DDwMFAg-2526c-253DCJqEzB1piLOyyvZjb8YUQw-2526r-253DmbL-2D4Mr65FbyCWqCw73luw-2526m-253DmO2KcBS32FUa51mzNtpWHFfa-5FLSkM77Nqd2sdCU1GFPOlXTYORNdKqVag5pZdUE3-2526s-253DOWJFhL6DTu5zeeemfdmzsRmY-5FB6ywmFmGP5RDKuLSek-2526e-253D-26data-3D05-257C01-257Ckarl.slifer-2540unh.edu-257Cd2128e807f2d43b5f0ac08db27091521-257Cd6241893512d46dc8d2bbe47e25f5666-257C0-257C0-257C638146692213753801-257CUnknown-257CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0-253D-257C3000-257C-257C-257C-26sdata-3D8tFreWg7qrB7Vl5zpyLqCG6ydMjy4FivNRPp9Y0tWns-253D-26reserved-3D0&d=DwMFAg&c=CJqEzB1piLOyyvZjb8YUQw&r=mbL-4Mr65FbyCWqCw73luw&m=u1Fzm3KVZCl-5pm_pTmS7yeIk0A27_vZYa0_xrgerzUrhEapfc_UTm6_I7NYpKUe&s=L-j5WmVQ5dhIUILvW9h_jH0oZbQ9ekdY4S1_ydVBVVc&e=>

Please send any items to add to the agenda.

Draft Agenda

  1.  Brief summary of ECT* preparations
  2.  Jeopardy Review Prep
  3.  Discussion/Summary of theorist input
  4.  AOB

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