[Clas_hadron] Slides for EUNPC

[Volker Burkert]

Hi Richard,

You have nice slides and I have only one basic comment:

Slide, bullet #3 says: "The proton mass radius is significantly different from the charge radius (0.84fm), suggesting  that ist 'gluon radius' is significantly smaller than its 'quark radius' [4]". (see also conclusions)

a) there is no such things as a "gluon radius" or a "quark radius". The size of an object can only be measured with a certain probe. Electromagnetic probe measures the "charge radius",  J/Psi probe can measure the "gluon mass radius" because it has spin=1, and it "conspires" with the incoming photon that also has spin=1 to form a system of spin=2. That is the same as the "graviton", which has spin=2. That is why it couples to "mass" as it looks like  gravity interaction. Its a bit more complicated, but that's the basic concept.

b) In order to measure the "quark mass radius" , one has to use an appropriate probe, e.g. DVCS, where one has 2 photons with spin 1 each coupling again to spin=2 .......

c) similar comment for conlusion slide.

Best,
Volker


 proton mass radius is significantly different from the charge radius (𝑅𝑐 = 0.8409 ± 4 ∙ 10−4 fm), suggesting that its gluon radius is significantly smaller than its quark radius [4].

________________________________
From: Clas_hadron <clas_hadron-bounces at jlab.org> on behalf of Richard Tyson (PGR) via Clas_hadron <clas_hadron at jlab.org>
Sent: Thursday, October 20, 2022 1:53 PM
To: CLAS Hadron <clas_hadron at jlab.org>
Subject: [Clas_hadron] [EXTERNAL] Slides for EUNPC

Hi All,

I'm going to give a talk at the EUNPC<https://urldefense.proofpoint.com/v2/url?u=https-3A__indico.cern.ch_event_1104299_&d=DwMFCQ&c=CJqEzB1piLOyyvZjb8YUQw&r=33hEheRcHuqzMP4K5hhMDPge6hQHiwXozGe7lR_eSfg&m=Xz6NFSC0nPCXJgDlknojl9AFKEY3vRTvtTRXRfBBasDZebXkxPWDIAkDuBZZd2r6&s=JVwTWKMQ4syAYDMkIbyYjjzuUSN3lcrEy59P-hfdkow&e=> Conference next week on J/ψ Near-Threshold Photoproduction off the Proton and Neutron with CLAS12 and wanted to check that this if fine with you all, sorry for the short notice. I've attached my slides; any feedback is welcome!

Thanks,
Richard

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