[Hybrid baryons] Presentation uploaded on wiki page

Thu Mar 17 14:29:26 EDT 2016

Dear All,

the plots we have just sent assume S1/2=0.
The plots we uploaded on the wiki page assume S1/2=A Q as in the LoI.
Tomorrow we will double check the importance of this additional 
interference effect in the L>4 moments.
Ciao
Annalisa

Il 17/03/16 18:30, Viktor Mokeev ha scritto:
>   Dear All,
>
>   I was not surprised to see the interference effects in the W-dependencies of the Legendre moments. Interference plays very important role also in two-pion photo-/electroproduction allowing us to establish the contributions from resonances with small and intermediate electrocouplings. The interference is of particular importance for the extraction of resonance photocouplings from Npipi photoproduction with maximal (in comparison with electroproduction) non-resonant contributions.
>
>   What was surprised me is the SIZE of interference effects in L4 and in L>4 moments to which the hybrid contributions shown in red in Lucilla talk are ZERO within accuracy seen by eyeball. I expect that actual hybrid contributions are more than order of magnitude smaller than the contribution from Ghent amplitudes. How so small hybrid amplitude may generate so sizable interference effect?
>
>   Another point of my confusion is:such sizable interference effects are seen at A1/2=0.004 GeV^-1/2, which is very small amplitude. If instead we will use ``regular" N* amplitudes A1/2 of 0.040-0.050 GeV^2, the interference effecst should in be increased by a factor of 10, resonant cross section should be increased by a factor 100!  I have doubt that regular resonances would be so pronounced in KY channel...
>
>    Best Regards,
>                         Victor
>
> ----- Original Message -----
> From: "burkert" <burkert at jlab.org>
> To: "hybrid baryons" <hybrid_baryons at jlab.org>
> Sent: Thursday, March 17, 2016 8:15:18 AM
> Subject: Re: [Hybrid baryons] Presentation uploaded on wiki page
>
> Dear all,
>
> I am not at all surprised that the effect of  L_i(Ghent + Hybrid) is
> different from L_i(Ghent) + L_i(hybrid), i=1,2,3,4,5,6...
> This is due to interference effects. Even if one L_i =0 for some
> individual contribution, it does not have to be zero if amplitudes are
> added, and L_i of the sum is evaluated. We have been making use of
> interference effects for all our UIM and DR analyses.  It is also well
> known that interferences enhance very small effects, e.g. the S1+/M1+
> and E1+/M1+  multipole ratios for the Delta(1232) can only be extracted
> due to interference effects because in the cross section their effects
> are just much too small.
>
> That does not mean, we should not verify the size of the effect in the
> L_i moments as Victor suggests.
>
> Regards,
> Volker
>
>
>
> The other question is , On 3/16/16 4:13 PM, Viktor Mokeev wrote:
>> Hi All,
>>
>>    In Legendre moments we may observe the structures in W-dependencies existing simultaneously for both blue and black curves.
>>
>>    In my view, the common structures we observed in W-dependence of both blue and black curves come from Ghent amplitudes (not from hybrid!), since they are persistent with/without hybrid.
>>
>>    The hybrid signal is the difference between blue and black curves.
>>
>>    What is difficult for me to comprehend is: for L5 and L6 moments the hybrid moments in red look as zero within any conceivable accuracy in the J=1/2 case. I would expect the hybrid contributions to the moments L5,L6 should be more than order of magnitude smaller in comparison with contributions from Ghent model amplitudes converted to the cross sections. From the other hand, the difference between between the blue and black curves is sizable for the L5, L6 moments , J=1/2. I am surprised to see that hybrid-Ghent amplitude interference at list order of magnitude bigger than hybrid contribution.
>>
>>    I would propose to show superimposed in the single plot, computed for exactly the same W and Q^2, espl, differential dsigma_U/d(-cos\theta_K) cross sections
>> from Golovach ans Annalisa/Luchilla. In this plot also it is worth to show separately hybrid contribution, Ghent contribution (resonances + background) and coherent sum hybrid+Ghent.
>>
>>     Best Regards,
>>                       Victor
>>
>> ----- Original Message -----
>> From: "Viktor Mokeev" <mokeev at jlab.org>
>> To: "hybrid baryons" <hybrid_baryons at jlab.org>
>> Sent: Wednesday, March 16, 2016 10:44:16 AM
>> Subject: Re: [Hybrid baryons] Presentation uploaded on wiki page
>>
>> Dear Annalisa and Lucilla,
>>
>>    Would it be possible to re-evaluate the Wigner moments in the pp. 3-4 for
>>
>> A1/2=0.030 (or 30 in your notation) GeV^-1/2 for J=1/2+ hybrid
>> A1/2=A3/2=0.021 (0r 21 in your notation) GeV^-1/2 J=3/2+ hybrid
>>
>>    THese values correspond to the threshold for hybrid observation in observables. Nsaively. I would expect the pronunced signal in moments with the afirementioned couplings, since the cross hybrid cross section shpould be increasesd in comparison with A1/2=0.004 GeV^2 you presented by a factor of (30/4)^2=56!
>>
>>      Best Regards,
>>                         Victor
>> ----- Original Message -----
>> From: "Lucilla Lanza" <lucilla.lanza at roma2.infn.it>
>> To: "hybrid baryons" <hybrid_baryons at jlab.org>
>> Sent: Tuesday, March 15, 2016 7:09:07 AM
>> Subject: [Hybrid baryons] Presentation uploaded on wiki page
>>
>> Dear all,
>>
>> we uploaded our last presentation on the Hybrid Baryons wiki page.
>>
>> Best regards,
>>
>> Annalisa and Lucilla
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-- 
================================================
Prof. Annalisa D'Angelo
Dip. Fisica, Universita' di Roma "Tor Vergata"
INFN Sezione di Roma Tor Vergata, Rome Italy
email:annalisa.dangelo at roma2.infn.it
Jefferson Laboratory, Newport News, VA USA
Email: annalisa at jlab.org
Tel: + 39 06 72594562
Fax: + 39 06 2040309