[Halld-cal] forward shower systematics from MC, new timing comparison

[Richard Jones]

Hello Matt,

I don't compute the shower RF time, I just read the value directly from the
REST event record. I suppose someone else who is the expert on the
in-memory FcalShower object that holds the corresponding field in its data
can answer the question as to how it is computed.

-Richard J.

On Tue, Mar 19, 2019 at 3:37 PM Shepherd, Matthew <mashephe at indiana.edu>
wrote:

>
> Richard,
>
> Can you explain exactly how you compute the expected RF time for these
> showers?  Specifically, do you extrapolate to the z position recorded in
> the shower or to the front face of the FCAL?
>
> The photon should propagate to the (x,y,z) position of the shower at the
> speed of light.  If the evolution of z is not considered, then this will
> produce an apparent time walk with energy.
>
> Matt
>
> ---------------------------------------------------------------------
> Matthew Shepherd, Professor
> Department of Physics, Indiana University, Swain West 265
> 727 East Third Street, Bloomington, IN 47405
>
> Office Phone:  +1 812 856 5808
>
> > On Mar 14, 2019, at 12:15 PM, Richard Jones <richard.t.jones at uconn.edu>
> wrote:
> >
> > I have added a side-by-side comparison of the timing (Fcal only for the
> moment) from hdgeant and hdgeant4 to my MC shower systematics study. See
> slide 8 in the attached document, posted to docdb. The agreement between
> the two simulations is acceptable (30ps difference in the fit p0,
> probabably within MC systematics. The primary message of this plot is the
> large time-walk that exists in the simulated shower times after all
> corrections have been applied. This is the time recorded in REST within the
> fcalShower objects.
> >
> >
> https://gcc01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fhalldweb.jlab.org%2Fdoc-private%2FDocDB%2FShowDocument%3Fdocid%3D3852&data=02%7C01%7Challd-cal%40jlab.org%7C5a052d3500e9435f03d608d6aca8e9b0%7Cb4d7ee1f4fb34f0690372b5b522042ab%7C1%7C0%7C636886238811112492&sdata=4Mo94XSFqvxYBLbRua8wwKLIXglyut%2FsjwaXZkPkOg4%3D&reserved=0
> >
> > -Richard Jones
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