[G12] energy corrections, I'm confused

[Saini, Mukesh]

Thanks Lei. I had forgotten how I had done the corrections earlier.

I assume a single stretch factor defined by:

New and Improved electron Beam Energy 
/ Assumed Beam Energy for that run during cooking by a1c 

suffice?

We can then simply multiply our current Beam Photon Energy by this Number to get the correct beam photon energy.

Old E_gamma = Old_electron_energy ( 1 - fraction of electron energy left mapped to tagger paddle )

If we have a new incoming electron energy, since the Tagger paddle remains the same for the beam photon, we should be able to get the New E_Gamma with a single multiplicative/stretch factor for each other.


______________
From: Lei Guo [lguo at jlab.org]
Sent: Thursday, February 16, 2012 2:32 PM
To: Saini, Mukesh
Cc: Eugenio, Paul; g12
Subject: Re: [G12] energy corrections, I'm confused

I'm equally confused by the tagger-id dependent corrections. I thought
the run-dependent correction is only supposed to correct the overall
electron beam energy. Did I miss something?

Lei
On Feb 16, 2012, at 1:50 PM, Saini, Mukesh wrote:

> 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.
>
>
> --
> Prof. Paul Eugenio
> Florida State University
> Department of Physics
> Tallahassee, Florida,  USA 32306
>
> (850) 325-0314
> eugenio at fsu.edu<mailto:eugenio at fsu.edu>
>
>
>
>
> 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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> --
> Johann T. Goetz, PhD.<http://sites.google.com/site/theodoregoetz/>
> jgoetz at ucla.edu<mailto:jgoetz at ucla.edu>
> Nefkens Group, UCLA Dept. of Physics & Astronomy
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