[G14_run] Fwd: HA: pi+pi- Asymmetries

Mon May 18 03:59:38 EDT 2015

Dear Collaborators,
We have just received  the predictions by FIX on asymmetries for two 
pion production on the proton and the neutron.
You may find the results in attachment.
Best regards
Annalisa & Irene

-------- Messaggio Inoltrato --------
Oggetto: 	HA: pi+pi- Asymmetries
Data: 	Mon, 18 May 2015 07:24:23 +0000
Mittente: 	Aleksandr I. Fiks <fix at tpu.ru>
A: 	Annalisa D'Angelo <annalisa.dangelo at roma2.infn.it>
CC: 	irene.zonta at roma2.infn.it <irene.zonta at roma2.infn.it>

Dear Annalisa,
Dear Irene,

thank you for the explanation. Attached are 2 files with callculations for free protons and neutrons. The asymmetries are averaged over the photon energy in each energy bin. I calculated only up to Egamma=1.5 GeV. Above this energy the model does not work, I guess. Please have a look. If something is unclear or seems strange, please tell me.

Best regards
Alexander
________________________________________
От: Annalisa D'Angelo [annalisa.dangelo at roma2.infn.it]
Отправлено: 15 мая 2015 г. 14:36
Кому: izonta; Aleksandr I. Fiks
Тема: Re: pi+pi- Asymmetries

Dear Alexander,
thank you for your prompt reply and for your kind availability to do the
calculations.
Results on free nucleon target would certainly teach us a lot.

As Irene already well specified, the z-axis direction in the frame where
phi' is defined as you say,
according to Strauch's paper.

The picture describing the kinematic variables, taken from Irene's
thesis, is attached.
It may help to get a general picture of the kinematic she has considered.

My best regards
Annalisa

Il 15/05/15 09:51, izonta ha scritto:
> Dear Professor Fix,
> yes, the direction of the z-axis in the helicity frame is along the
> total pi+pi- momentum
> in the overall c.m frame. The formalism is the same used in the paper
> by S. Strauch.
> Thank you in advance.
>
> Best regards
>
> Irene Zonta
>
>
> Il 2015-05-15 05:09 Aleksandr I. Fiks ha scritto:
>> Dear Annalisa,
>>  Dear Irene,
>>
>>  sure I can do the required calculation, but only on free (not bound)
>> protons and neutrons. Firstly a small question. You write:
>>
>>  - ... asymmetry I_dot as a function of the azimuthal helicity angle
>> phi' of the pi+ in the center of mass frame ...
>>
>>  Which direction has the z-axis in the frame, where the angle phi' is
>> determined? I guess it is along the total pi+pi- momentum in the
>> overall c.m. frame like in the paper by S.Strauch at al (PRL 95 (2005)
>> 162003, FIG.1). Am I right?
>>
>>  Best regards
>>  Alexander
>>
>>  P.S. You can use this e-mal address (fix at tpu.ru).
>>
>>
>> ------------------------------------------------------------------------------------------------------------------------------
>>
>>
>> Dear Alexander,
>>
>> my PhD student Irene Zonta and myself are presently working within the
>> CLAS
>> collaboration at Jlab on the analysis of g14 run, which uses
>> longitudinally polarized protons
>> and deuterons from frozen spin HD polarized target and circularly
>> polarized photons.
>>
>> Irene has analyzed the data for two charged pion production on the
>> both nucleons:
>> gamma p -> pi+ pi- p
>> gamma p (+n) -> pi+ pi- p (+n)
>> gamma n (+p) -> p+ pi- n (+p)
>> in the free or quasi-free kinematics.
>>
>> She has extracted the dependence of the observables:
>> - single beam circular polarization asymmetry I_dot as a function of
>> the azimuthal helicity angle phi' of the pi+ in the center of mass
>> frame with respect to the plane containing the incident photon and the
>> scattered target, at fixed incoming photon energies and integrated
>> over all other kinematics variables;
>>
>> - single target longitudinal polarization observable Pz as a function
>> of the azimuthal helicity angle phi' of the pi+ in the center of mass
>> frame with respect to the plane containing the incident photon and the
>> scattered target, at fixed incoming photon energies and integrated
>> over all other kinematics variables;
>>
>> - double longitudinal beam target polarization asymmetry Pz_dot as a
>> function of the azimuthal helicity angle phi' of the pi+ in the center
>> of mass frame with respect to the plane containing the incident photon
>> and the scattered target, at fixed incoming photon energies and
>> integrated over all other kinematics variables;
>>
>> for both free and quasi-free proton and quasi-free neutron.
>>
>> She has results for incoming photon beam energies from E_gamma = 0.9
>> GeV to E_gamma = 2.3 GeV at intervals
>> of 100 MeV.
>>
>> Would it be possible for you to send us your predictions for all
>> available incoming photon energies of your model ?
>> Could you send us predictions for both proton and neutron targets?
>>
>> Thank you very much for your attention
>> My best regards
>> Annalisa D'Angelo
>>
>> --
>> ================================================
>> 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
>

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