[Psqateic] [EXTERNAL] Re: PSQ at EIC White Paper

Mon Aug 22 09:15:00 EDT 2022

Dear All
Yet you cannot throw it out without discussing all
these very valid points.
Simonetta

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________________________________
From: Psqateic <psqateic-bounces at jlab.org> on behalf of Xiangdong Ji <xji at umd.edu>
Sent: Monday, August 22, 2022 3:10:28 PM
To: Keh-Fei Liu <liu at g.uky.edu>
Cc: psqateic at jlab.org <psqateic at jlab.org>
Subject: Re: [Psqateic] [EXTERNAL] Re: PSQ at EIC White Paper

hi, All,
 C-bar is a twist-4 form factor, hard to measure in high-energy scattering where
one probes quarks and gluons directly. Moreover, it depends on how does one
define teh separation of trace parts of the quarks and gluons. In the simplest scenario,
they are related to the form factors of the scalars, F^2 and \psi-bar\psi.
   C-bar generates  a part of the momentum-current density of the quarks and gluons separately.
but cancels in the sum.  In the present writing, no separation
of the momentum-current density is made because such separation has additional
scheme dependence due to different ways of deriving the trace anomaly.

Xiangdong

On Wed, Aug 17, 2022 at 4:00 PM Keh-Fei Liu <liu at g.uky.edu<mailto:liu at g.uky.edu>> wrote:
Dear Volker:

       In a simple scheme, the forward matrix elements are \bar{C}_q = 1/4 (quark condensate - <x>_q (\mu) M)
and \bar{C}_g = 1/4 (trace anomaly - <x>_g (\mu) M). The \pi N sigma term can be obtained from \pi N scattering, the strangeness
sigma term can be obtained from the lattice. The momentum fractions can be obtained from global fitting of DIS. How to obtain
the trace anomaly experimentally is a challenge. All of them can be and have been obtained in lattice calculations. The current
challenge for lattice is to calculate their form factors including the quark and glue parts of B (t) and C(t). In other words, all the
gravitational FFs including \bar{C}.

Best,
Keh-Fei

On 8/17/22 6:59 AM, Volker Burkert wrote:
Dear Keh-Fei and Oleg,

I like the idea to acknowledge the existence of additional terms that cancel when summing quarks and gluons, but don't discuss them in any detail.
I have not seen a description of how \bar{C} can be measured in experiment, either for quarks or for gluons, separately. If there are such proposals we could refer to them in the WP.
 Perhaps we could mention that \bar{C} may be computed in LQCD and then used as correction to the EMT for quarks and gluons separately?

Volker

________________________________
From: teryaev <teryaev at jinr.ru><mailto:teryaev at jinr.ru>
Sent: Wednesday, August 17, 2022 4:16 AM
To: Keh-Fei Liu <liu at g.uky.edu><mailto:liu at g.uky.edu>
Cc: Volker Burkert <burkert at jlab.org><mailto:burkert at jlab.org>; psqateic at jlab.org<mailto:psqateic at jlab.org> <psqateic at jlab.org><mailto:psqateic at jlab.org>
Subject: Re: [Psqateic] [EXTERNAL] Re: PSQ at EIC White Paper

Dear Keh-Fei,

You are completely right, there are terms cancelling when the when quark
and gluon contributions are summed (due to equivalence principle, whose
extension may be used to explain their smallness even separately),
including C\bar ("proton cosmological constant")  together with
anomalous gravitomagnetic moment, and often forgotten gravitoelectric
dipole moment. violating also CP. Indeed, C \bar is crucially important
when (separate) traces are calculated.

Maybe in the text one can add after (6) something like "There are also
terms cancelling
in the sum of quark and gluons due to conservation laws and equivalence
principle"?

best regards,
Oleg

Keh-Fei Liu писал(а) 2022-08-13 08:56:
> Dear Volker:
>
>        Now that we agree that there are \bar{C} terms in Eq. (6), take
> the trace of the GFF in the rest frame, one
> has the expression <T_{\mu\mu}> = [(A_q(0) + A_g(0)]M + Tr-Anomaly +
> chiral condensate - [(A_q(0) + A_g(0)]M = Tr-Anomaly
> +chiral condensate which is the correct expression. The last three
> terms come from \bar{C} which is zero (for a good reason because
> it is the stability condition). If one drops them first, one ends up
> with the expression of [(A_q(0) + A_g(0)]M. Please explain why
> it is acceptable and not wrong with an expression where the trace of
> EMT does not contain trace anomaly. \bar{C} exists in many
> publications in the literature, I don't understand the rationale for
> dropping it in this document. It leads to (unintended) consequences.
>
> Best,
> Keh-Fei
>
> On 8/12/22 4:07 PM, Volker Burkert wrote:
>
>> Dear Keh-Fei,
>>
>> * There is agreement for eq.(6) which deals with quark and gluon
>> EMT separately, and the \bar{C} is needed (with opposite sign for q
>> and g).
>> * For eq.(19), which deals with the full EMT (quark + gluons} the
>> \bar{C} terms should cancel out to zero, and the term \bar{C} should
>> not appear.
>>
>> *
>>
>> *
>> * Volker
>>
>> *
>>
>> -------------------------
>>
>> From: Keh-Fei Liu <liu at g.uky.edu><mailto:liu at g.uky.edu>
>> Sent: Friday, August 5, 2022 8:35 AM
>> To: Volker Burkert <burkert at jlab.org><mailto:burkert at jlab.org>; psqateic-request at jlab.org<mailto:psqateic-request at jlab.org>
>> <psqateic-request at jlab.org><mailto:psqateic-request at jlab.org>
>> Cc: Lorcé Cédric (M.) <cedric.lorce at polytechnique.edu><mailto:cedric.lorce at polytechnique.edu>
>> Subject: [EXTERNAL] Re: [Psqateic] PSQ at EIC White Paper
>>
>> Dear Volker and Latifa:
>>
>> Thank you for your tremendous effort in organizing this
>> valuable whitepaper for the community.
>>
>> I now have a firm argument to show that one cannot drop
>> the \bar{C} term in Eqs. (6) and (19). Take the
>> forward FF of the trace T_{\mu\mu}, they give (A_q(0) + A_g(0))M.
>> This is a trivial and meaningless result. It relates
>> the matrix element of the trace to the mass via a sum rule of
>> traceless matrix elements. It does not have the anomaly.
>> Only when the \bar{C} is retained, do you get the correct expression
>> with the anomaly. We should put the \bar{C} term back
>> in these equations.
>>
>> Best,
>> Keh-Fei
>>
>> On 8/3/22 4:33 PM, Volker Burkert wrote:
>>
>>> Dear Colleagues,
>>>
>>> We are sending you this email because you have registered to
>>> participate in at least one of the workshops presented below,
>>> which were held on December 15-16, 2020, March 17-19, 2021, and
>>> July 19-23, 2021.
>>>
>>> One of the main goals of these workshops was to develop a white
>>> paper focused on high-impact science requiring high integrated
>>> luminosity at the low-to-medium center-of-mass energy of the U.S.
>>> Electron-Ion Collider project.
>>>
>>> This white paper is ready to be submitted for publication. As a
>>> participant in the workshop series, we invite you to become a
>>> co-author of this white paper, which can be found at this link:
>>>
>>
> https://www.femtocenter.org/sites/default/files/docs/PSQ_EIC_White_Paper.pdf
>>> [1]
>>>
>>> Please visit this link and review the scope and content of the
>>> white paper. If you decide to co-author the WP, please send an
>>> email to burkert at jlab.org<mailto:burkert at jlab.org> no later than August 12.  You may also
>>> suggest minor changes to the text, acknowledgements, and
>>> references, or make comments that would improve the WP.
>>>
>>> We have an agreement with a journal to publish the paper and we
>>> need to submit the final version by August 20.
>>>
>>> With best regards,
>>>
>>> Volker & Latifa
>>>
>>> https://urldefense.proofpoint.com/v2/url?u=https-3A__indico.bnl.gov_event_9794&d=DwIDaQ&c=CJqEzB1piLOyyvZjb8YUQw&r=vVqGQabj76hiyFv-SdFNhS9JnbDxELkn2szNoXMYQyo&m=Qy-CQv_msBooo8cd6Jy97FsQwD8soQkuCbKcwOzXyRURXIXufQPQRH2VFLMnTGww&s=S77fnwvL0qr9S0UjhFrOn1UKkpBtmyd0ngSd30jkvnM&e=   [2]
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>
>
>
> Links:
> ------
> [1]
> https://www.femtocenter.org/sites/default/files/docs/PSQ_EIC_White_Paper.pdf
> [2]
> https://urldefense.proofpoint.com/v2/url?u=https-3A__indico.bnl.gov_event_9794&d=DwMDaQ&c=CJqEzB1piLOyyvZjb8YUQw&r=vVqGQabj76hiyFv-SdFNhS9JnbDxELkn2szNoXMYQyo&m=5AYW9vwxxp8DN9axYcgThaO2tDVhNhrtj-XHvMm22kfS_MbCzGceMTTjt26SJakY&s=4daDQQx1-C0DPsG0iFTkbWjsPATQb5ZddY_N9OGquj0&e=
> [3]
> https://urldefense.proofpoint.com/v2/url?u=https-3A__indico.bnl.gov_event_10677&d=DwMDaQ&c=CJqEzB1piLOyyvZjb8YUQw&r=vVqGQabj76hiyFv-SdFNhS9JnbDxELkn2szNoXMYQyo&m=5AYW9vwxxp8DN9axYcgThaO2tDVhNhrtj-XHvMm22kfS_MbCzGceMTTjt26SJakY&s=vIOR4EUCQxbO8iay3K1a8zheeXLc26lrKytTPA4AF_U&e=
> [4]
> https://urldefense.proofpoint.com/v2/url?u=https-3A__indico.bnl.gov_event_11669&d=DwMDaQ&c=CJqEzB1piLOyyvZjb8YUQw&r=vVqGQabj76hiyFv-SdFNhS9JnbDxELkn2szNoXMYQyo&m=5AYW9vwxxp8DN9axYcgThaO2tDVhNhrtj-XHvMm22kfS_MbCzGceMTTjt26SJakY&s=ULJyvLIlwTDZWjvQsqoes6fwCcIVQE67gO8XWJup3aI&e=
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