Re: [GlueX] Hall-B beamtest

[Elton Smith <elton@jlab.org>]

Hi Rafael,

Thanks for producing the plots on energy resolution. For the purpose of
that study the following does not make any difference, but you should
consider using E = sqrt(Ea*Eb) as the measure of the energy instead of the
average of exponentially corrected energies. The geometric mean removes
the energy and the attenuation length dependence to the energy measure so
it makes it a very robust quantity. If you use other form, you introduce
both a dependence on both the position and the attenuation length.

Cheers, Elton.




Elton Smith
Jefferson Lab
elton@jlab.org
(757) 269-7625

On Mon, 24 Jul 2006, Rafael Hakobyan wrote:

> HI Elton,
>
> I have obtained the resolution VS the beam position in a rough way,
> namely I took the entry position
> instead of the energy-weighted average position (EWAP) for each cell
> separately (just in order to speed up the
> procedure, but later I'll redo it with the EWAP).
>
> Please find the results on the web site
>                           http://www.jlab.org/~rafael/Beamtest/
> cleaking on the last link, i.e. "Energy Resolution VS the Beam Position".
>
> Let me inform you, briefly, that  the distribution of the deposited
> energy in the scintillating fibers is obtained
> for the cases when the incident photons with the energy of 500 MeV and
> spot size of 18.7mm (2.6mm collimated beam) are entring the BCAL
> perpedicularly from different positions ( 0 cm(centre), 0.5cm, .....).
> The fitted sigmas are for the  distributions  of the average energy at
> the both ends after the attenuation (atten. length is 3m).
>
> Details we can discuss tomorrow at the teleconference.
> Best regards,
> Rafael
>
>
> Elton Smith wrote:
>
> >HI Rafael,
> >
> >Thanks for the addition. It looks like the curve has a slope even at the
> >center, perhaps implying that we in fact do have sensitivity even to the
> >smallest change in the the beam position. However the amount of leakage is
> >very small, so I assume that the resolution is not much affected. Do you
> >have a plot of the resolution as a function of the beam position?
> >
> >Cheers, Elton.
> >
> >
> >
> >Elton Smith
> >Jefferson Lab
> >elton@jlab.org
> >(757) 269-7625
> >
> >On Tue, 18 Jul 2006, Rafael Hakobyan wrote:
> >
> >
> >
> >>Hi Elton,
> >>
> >>In the plots that have been presented today, I have added the points
> >>corresponding to the percentage of the energy leakage (WRT the incident
> >>photon energy) when the photon beam enters the BCAL from the centre.
> >>Please find the improved plots on the web site
> >>                       http://www.jlab.org/~rafael/Beamtest/misalignment/
> >>Thanks for the relevant comment.
> >>Rafael
> >>
> >>Rafael Hakobyan wrote:
> >>
> >>
> >>
> >>>Hi All,
> >>>
> >>>Please find some more simulation results on the web site
> >>>                  http://www.jlab.org/~rafael/Beamtest/
> >>>Two more links are added, namely
> >>>  a). shower energy leakage from the BCal module when the beam is
> >>>misaligned
> >>>        from the BCal centre
> >>>  b). distribution of the Up and Down time difference for the
> >>>collimated (2.6mm)
> >>>         beam and for the pencil beam
> >>>about which Zisis and I want to discuss with you during today's
> >>>teleconference.
> >>>
> >>>Time always has been calculated in two ways: taking the energy
> >>>weighted time and  the very first
> >>>photon time. Our investigations always show that the sigma is smaller
> >>>for the energy weighted
> >>>time. From the beging for the calculation of the time, I have had very
> >>>useful and productive discussions
> >>>with Richard Jones about the energy weighted time, and I want to
> >>>express my thankfulness  to Richard for  the  useful discussions.
> >>>
> >>>Cheers,
> >>>Rafael
> >>>
> >>>
> >>>
> >>>
> >>>
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> >>
> >>
> >>
>
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