Re: systematic contributions to time-of-flight resolution (fwd fromBeni)

[Elton Smith <elton@jlab.org>]

Hall D PID Mail List:


---------- Forwarded message ----------
Date: Wed, 26 Mar 2008 05:28:08 -0400 (EDT)
From: Benedikt Zihlmann <bzihlman@hep.physics.indiana.edu>
To: Simon Taylor <staylor@jlab.org>
Cc: Matt <bellis@ernest.phys.cmu.edu>, halld-pid@jlab.org
Subject: Re: systematic contributions to time-of-flight resolution


Hi Simon,
the time on the y-axis in ns is the time difference between the true
path length and the path-length given by the swimming routine.
If this is true then the actual contribution to the TOF resolution
is not this time but you should plot the time difference lets say
between a pion and a kaon of the same mometum for the path-length
difference between true and swimming routine. I think this is the time
that contributes to the resolution.
I  hope this number will be much smaller than what you have plotted.
Otherwise we would have a hard time using tof for PID.

cheers,
Beni


On Tue, 25 Mar 2008, Simon Taylor wrote:

> Hall D PID Mail List:
>
> Hi, Matt.
>
> You are right, this is not a study of the intrinsic resolution of the
> time-of-flight counters, which is assumed to be perfect for the purpose of
> the study.    Rather this is a study of the contributions due to momentum
> resolution and path length variations to the uncertainty in calculated flight
> time for a particular particle type.   This impacts the interpretation of the
> time measured in the TOF or BCAL.
>
> Simon
>
> Matt wrote:
>>  Hi Simon,
>>
>>      Is this a study of resolution of TOF? Or a study of the resolution on
>>  how we will reconstruct the path length? The time-of-flight will just be
>>  the time-of-flight as calculated from the start time (accelerator RF) and
>>  the stop time from some detector (BCAL/forward TOF), independent of what
>>  path it took to get there. Resolution on the TOF will be dependent on
>>  those quantities as well.
>>
>>      Isn't it more accurate to say this study is looking at the resolution
>>  of our swimming routine and the path length that it returns. I might be
>>  too picky...I wasn't sure if this was for the review or just some internal
>>  study. Or perhaps I missed something.
>>
>>  Matt B.
>>
>>
>>  On Tue, Mar 25, 2008 at 9:06 AM, Simon Taylor <staylor@jlab.org
>>  <mailto:staylor@jlab.org>> wrote:
>>
>>      Hi, everyone.
>>
>>      I have started looking at the contribution to the time-of-flight
>>      resolution due to the momentum resolution, path length variations, and
>>      z-vertex position variations.  I have attached a plot of
>>      resolution in the difference between the true flight time to
>>      either the BCAL
>>      or the TOF (as determined from the MC truth points) and the
>>      reconstructed
>>      flight time using the path length derived from swimming the
>>      reconstructed
>>      track from the vertex position to either the first TOF plane or
>>      the inner
>>      BCAL radius.  I threw 1.0, 2.0, and 3.0 GeV/c pions from the
>>      center of the
>>      target uniformly in phi and flat in theta from 126 degrees to ~0.5
>>      degrees.  I find that the time resolution does not depend on the
>>      momentum
>>      in the barrel region but does for tracks that would hit the TOF.
>>      Comments welcome.
>>
>>      Simon
>>
>>
>>
>>
>>  --
>>  --
>>  ----------------------------
>>  Matt Bellis
>>  Carnegie Mellon University
>>  (office) 412-268-6949
>>  (cell) 412-310-4586
>>  ----------------------------
>
>