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

[Shepherd, Matthew]

Richard,

The DFCALShower object (which is stored in REST) does not have a member called "shower RF time."  Without more information as to what you are plotting, I can't comment on it.

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 19, 2019, at 4:24 PM, Richard Jones <richard.t.jones at uconn.edu> wrote:
> 
> 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%7Cadd23819a49f404ad61208d6ad672868%7Cb4d7ee1f4fb34f0690372b5b522042ab%7C1%7C0%7C636887055900668936&sdata=j6tJ79vLuJqrSrBvWKMfn%2F5xEmNzlhauCwYsKkuge%2BQ%3D&reserved=0
> > 
> > -Richard Jones
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