[Hybrid baryons] Presentation uploaded on wiki page
burkert
burkert at jlab.org
Thu Mar 17 14:26:07 EDT 2016
Hi all,
I think it would be useful to normalize all Legendre moments to the
zero-moment P0, which is the total cross section. This will reduce the
absolute effect of the addition of one hybrid state and can be more
easily interpreted in terms of sensitivity given the statistical
precision that can be achieved.
Best regards,
Volker
On 3/17/16 2:12 PM, Annalisa D'Angelo wrote:
> 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
>
>
> This body part will be downloaded on demand.
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