[G12] energy corrections

[Saini, Mukesh]

Thing that is throwing me off here is that the numbers differ in the 4th and 5th decimal places too. and also it seems for the same tagger-id they are rounded off to different numbers. I would expect the rounding error to be on the 6th digit of 1.

Anyways, If a1c accounted for the changing electron beam energy during our cooking pass for different runs ( Let's say electron energy between 5.710 - 5.720 ),
then is the single tagger-id to photon-energy conversion posted still valid?

If yes, then how did the a1c account for the shift in electron energies?
If the tagger paddle gives me the same energy back for an incoming electron of 5.71 GeV as well as 5.72 GeV then I have a lack of understanding of this process and the way a1c accounted for the incoming electron energy-change during our cooking pass.

I am trying to code this in my ntuple-maker and this is throwing me off. We should explain this in a small section/note on the wiki. Also please reply with your insights.

Thanks,
Mukesh.








________________________________
From: g12-bounces at jlab.org [g12-bounces at jlab.org] on behalf of Paul Eugenio [eugenio at fsu.edu]
Sent: Thursday, February 16, 2012 10:36 AM
To: g12
Subject: Re: [G12] energy corrections


Yes, this makes sense.  Floats have precision of 6 decimals whereas doubles have 15 decimal precisions.  While we are performing our calculations as double precisions, we are saving them to disk as floats.


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Prof. Paul Eugenio
Florida State University
Department of Physics
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On Feb 16, 2012, at 8:47 AM, Johann Goetz wrote:

Actually those differences you see are because the 32bit floating point numbers in the BOS files are only good to 5 digits at best, and the paddles' widths are about 5 MeV anyways.

On Wed, Feb 15, 2012 at 3:03 PM, Mukesh Saini <msaini at admin.fsu.edu<mailto:msaini at admin.fsu.edu>> wrote:
Hello,

I checked a few runs in my data and compared the photon energies in my
data-ntuples against  the energies provided in the file:

/group/clas/parms/pcor/g12/tagger_energies_reported_by_tagr_bank.txt

Some of the photon energies in my data-ntuples are off by fractions of
MeV (at most 0.5 MeV) from those in the file. I am guessing that is due
to some tage correction function applied in CLASEvent. I couldn't find
one during the first lookup of the code I did and I will look into this
further.

In case, anyone is aware where this further correction gets applied, and
if its necessary, We might have to add this correction in
post-processing Beam Energy Corrections also. To reverse lookup and
correct the tage paddle seems cumbersome if the photon-energies in the
data-ntuple's don't match the ones in the table provided. I think I will
just reskim my data to include the tage paddle number, if that is the case.

Mukesh.

On 02/15/2012 01:32 PM, Johann Goetz wrote:
>
> It describes the files and how to interpret them. Currently I only had
> enough statistics to do 481 of the runs. I'm working on getting the
> rest right now. Tomorrow, I intend to address momentum corrections and
> I should have most of the


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