[Hybrid baryons] Fwd: Theory support for hybrid baryon search with the CLAS12

[Viktor Mokeev]

Dear Colleagues,

 Please see the S.Capstick answer.

  Best Regards,
                       Victor

----- Forwarded Message -----
From: "Simon Capstick" <scapstick at fsu.edu>
To: "Viktor Mokeev" <mokeev at jlab.org>
Cc: "Simon Capstick" <scapstick at fsu.edu>, "burkert" <burkert at jlab.org>, "Johnathan Gross" <jlg12d at my.fsu.edu>
Sent: Sunday, January 24, 2016 7:53:14 AM
Subject: Re: Theory support for hybrid baryon search with the CLAS12

Hi Viktor,

Johnathan told me about your questions (sorry I couldn’t make the meeting) and I will discuss this further with him. The spectrum (masses and J^P values) will come along with the wave functions, as the latter will come from a calculation of the spectrum. It will then be possible to get some idea of the strong-decay amplitudes. I think electroproduction amplitudes will, unfortunately, come last, as these are the hardest to calculate. We could do a non-relativistic calculation fairly easily, but at these energies I would not trust the results.

I expect that we will get some useful result for the spectrum and wave functions before this time next year.

Cheers, Simon

On Jan 18, 2016, at 3:05 PM, Viktor Mokeev <mokeev at jlab.org<mailto:mokeev at jlab.org>> wrote:



Dear Simon,

As you know, we are preparing the proposal on hybrid baryon search with the CLAS12 in exclusive KY, pi^+pi^-p electroproduction at low Q^2. The text of the LOI encouraged by PAC for the full proposal preparation is attached.

I want to let you know on the needs for theory support of this work, which were discussed at the last group Meeting, Jan 15 2016.

First, I want to pay your attention to our strategy for the hybrid baryon state search explained in the pp. 26-28 of the attached LOI. We are looking for ``missing" (or known) resonance state(s) in mass range from 2.0 to 2.5 GeV of spin-parities 1/2^+ and/or 3/2^+ based on the LQCD evaluation of the lowest mass hybrids. The refs are mentioned in LOI. In order to identify the ``missing" (or known) resonance as the hybrid, we need the theory expectations on:
a) masses of hybrid-N*\Delta^* with glue as extra constituent in comparison with the masses of known N*/Delta* states;
b) particular features in Q^2 evolution of hybrid electrocouplings;
c) specific pattern of hadronic decays for the hybrid states.

In my view, there are two major reasons, which require distinctively different behavior of the hybrid electrocouplings in comparison with conventional N*/Delta* states. First, the quark counting rules require faster evolution with Q^2 of the hybrid electrocouplings in comparison with those of regular N*/Delta* states because of the presence of the extra glue-constituent (my guess is: the glue incorporates qq-bar pairs with which virtual photon can interact). Secondly, in regular baryons qqq component should be in color singlet state, while in hybrid-baryons the qqq-component should be in the color octet state. Such distinctive differences in qqq configurations likely should result in pronounced differences in Q^2-evolutuin of hybrid and conventional N*/Delta* state electrocouplings. I appreciate your comments on my naive expectations.

Your new PhD student you assigned for the hybrid baryon studies, informed us on your group plans to compute the wave functions of the hybrid states. Perhaps these studies will also provide the hybrid spectrum: masses/spin-paritites? Would it be possible to compute also the hybrid electrocoupling evolution with Q^2 in the range up to 1.0 GeV^2? Could you see the possibility to compute the hybrid hadronic decay widths predicting the most promising channels for the hybrid search?

I appreciate it very much, if you may let us know on possible contributions from your group to the aforementioned research tasks, which are of particular importance for our proposal as well as on the expected time line.


  Thank you very much!


 With Best Regards,
                              Victor   <LOI_hybrid_baryons.pdf>

________________________________________
Simon Capstick                                   capstick at fsu.edu<mailto:capstick at fsu.edu>
Department of Physics
Florida State University
Tallahassee, FL 32306-4350
(850) 644 4478 (fax)                  (850) 339 4797 (cell)

“It doesn't matter how beautiful your theory is, it doesn't matter how smart you are. If it doesn't agree with experiment, it's wrong.”...Richard Feynman
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