<div dir="ltr">Hello Matt,<div><br></div><div>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.</div><div><br></div><div>-Richard J.</div></div><br><div class="gmail_quote"><div dir="ltr" class="gmail_attr">On Tue, Mar 19, 2019 at 3:37 PM Shepherd, Matthew <<a href="mailto:mashephe@indiana.edu">mashephe@indiana.edu</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><br>
Richard,<br>
<br>
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?<br>
<br>
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.<br>
<br>
Matt<br>
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> On Mar 14, 2019, at 12:15 PM, Richard Jones <<a href="mailto:richard.t.jones@uconn.edu" target="_blank">richard.t.jones@uconn.edu</a>> wrote:<br>
> <br>
> 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.<br>
> <br>
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