[Rgc_analysis] [EXTERNAL] Re: note on the extraction of pDVCS asymmetries

[Hayward, Timothy]

Dear Tony,

I believe (but am not positive!) that this is an effect of Noémie using the following definition for the beam-spin asymmetry (which is the “most correct” way to do it in light of the target polarizations etc.),

[cid:6ca0e944-ab91-478a-b62a-29d4ccc41799 at namprd05.prod.outlook.com]

Because there is a large charge difference between negative target helicities and positive target helicities and Pt+ != Pt- it manifests as a large difference away from 0 offset even for the beam-spin asymmetry without normalizing to the charge. If Noémie started from the more familiar


then there would be a negligible difference as you allude to between putting in raw counts or counts normalized by accumulated charge. This has been observed quite frequently in all RGA (unpolarized H2 target) asymmetry extractions. I believe the original definition is safer and more general though.

Regards,
Timothy

On Sep 12, 2023, at 6:09 AM, Tony Forest via Rgc_analysis <rgc_analysis at jlab.org<mailto:rgc_analysis at jlab.org>> wrote:

*Message sent from a system outside of UConn.*


Noémie

The program "FCup_reading.cc<https://urldefense.proofpoint.com/v2/url?u=http-3A__fcup-5Freading.cc_&d=DwIGaQ&c=CJqEzB1piLOyyvZjb8YUQw&r=aSEBncnFTdfouxOejKajYG--Ygz0DFQolIcHUhF20pw&m=qq3_RyxYgjlcOM_HJIv2M_kC5XxNWqAePVeIBkdQTNERhV0wRQMrujPSO4kpe0Ti&s=ddNaiviCn4LVC-ZVd4RRg8kpHXXsEZTvUOOJQckQ9xs&e= >" reports FC asymmetries that are on the order
of 0.001 in natural units.  Figures 16-18 show asymmetries that are on the
order of 0.1.

Why do the FC corrections shift the asymmetry so much when the FC
asymmetry is so small?

Tony



Dear all,
Please find attached a note I wrote on the preliminary DVCS results I got
with the NH3 runs that were cooked, with the intent of asking the DPWG for
a release in order to talk at SPIN. The first part relates to the
extraction of the target polarization and the second part to the
extraction of pDVCS asymmetries. I would be happy to take any feedback
into consideration !
Best regards, Noémie._______________________________________________
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