[Hybrid baryons] Presentation uploaded on wiki page

Thu Mar 17 14:52:35 EDT 2016

  Dear All,

 Again, I can not understand how with zero contribution from hybrid to P3, P4,5 moments we have so sizable interference? What is the exact value of hybrid contribution to the moments? Is it possible to provide the numbers

P3 moment W=2.2 GeV Q^2=0.192 GeV^2 J=1/2:
Value of moment for hybrid only,
Value of moment for Ghent amplitude only,
Value of moment Ghent+hybrid

 I never have idea to add hybrid at cross section level. I am unable to understand such strong interference effect.

 Best Regards,
                 Victor 

----- Original Message -----
From: "annalisa dangelo" <annalisa.dangelo at roma2.infn.it>
To: "hybrid baryons" <hybrid_baryons at jlab.org>
Sent: Thursday, March 17, 2016 2:12:21 PM
Subject: Re: [Hybrid baryons] Presentation uploaded on wiki page

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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-- 
================================================
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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