[Hybrid baryons] Presentation uploaded on wiki page

Annalisa D'Angelo annalisa.dangelo at roma2.infn.it
Thu Mar 17 14:12:21 EDT 2016 

Dear all,

Lucilla and I agree with Volker.
Adding a resonance at the amplitude level results in a much different 
angular behavior in the cross section
than adding the resonance at the cross section level.
Moreover Victor has already shown that the s1/2 resonance alone provides 
an isotropic contribution to the
unpolarized cross section dsigma u/domega, so that only P0 legendre 
moment is expected to be non-zero
for the hybrid resonance alone.
Lucilla has been working on:
1. comparing her code with Evgeny's to make sure we find the same results.
In attachment you find the plot of the differential cross section 
dsigma_u/d(cos_theta) for Q2=0.567 GeV2
and W=2.2 GeV for the Ghent model. They are in perfect agreement now. 
file: Lucilla_Evgeny_comp.pdf
2. Producing plots of Legendre moments for dsigma_u/domega with 
different values of A_1/2 for J=1/2
and A_1/2 and A_3/2 for J=3/2 with s_1/2=0.
In attachment you may find the plots
A1/2=0.020  and A1/2=0.040  GeV^-1 for J=1/2+ hybrid: files 
Leg_A1/2=20J=1/2.pdf and Leg_A1/2=40J=1/2.pdf
and
A1/2=A3/2=0.020 GeV^-1^^for J=3/2+ hybrid File: Leg_A1/2=A3/2=20J=3/2.pdf
A1/2=0.020 GeV^-1 A3/2=0 for J=3/2+ hybrid file: Leg_A1/2=20_A3/2=0J=3/2.pdf
A1/2=0 GeV^-1 A3/2=0.02 for J=3/2+ hybrid file: Leg_A1/2=0_A3/2=20J=3/2.pdf

Many more combinations of A1/2 and A3/2 fixed values are available.


3. She is also producing plots of the Legendre moments for 
dsigma_TT/domega and dsigma_LT/domega
We need to check the results yet, but it looks like dsigma_TT/domega 
legendre moments are NOT sensitive
to the addition of the hybrid resonance, while dsigma_LT/domega legendre 
moments are VERY SENSITIVE
to the hybrid resonance.

We hope to show you the results tomorrow.
All the best
Lucilla and Annalisa

Il 17/03/16 13:15, burkert ha scritto:
> 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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>
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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

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