Re: BCAL timing for a mip

[Elton Smith <elton@jlab.org>]

HI Alex,

Just a note on your comment (1) Stefano said that KLOE achieved 320 ps
for mips.

My understanding of his statement (as well as in discussions following) is
that the 320 ps was for a single 4x4 cm2 cell measurement (very close to
our segmentation in the beam test).  Their resolution for a mip would be
~320/sqrt(6)=130 ps for 6 radial readout segments. This number is
consistent with the statistical term in their timing resolution (assuming
200 MeV of equivalent energy for a muon) of sigma~56/sqrt(E) =
56/sqrt(0.2) = 125 ps.

Looking back at the notes on cosmic ray timing (e.g. GlueX-doc836 and
summary GlueX-doc-842), I see that the time resolution quoted from our
cosmic-ray tests (see GlueX-doc-842, p 27) of sigma_cell~426 ps is also
for a single cell.  Therefore, to estimate the resolution for a mip, one
should also divide by sqrt(6), namely sigma_mip ~ 426/sqrt(6) = 173 ps.

So these two results are not too different, but both need to be
extrapolated to the expectation for a particle traversing the entire bcal
module as a measure of the estimated resolution for a mip.

Cheers, Elton.

Elton Smith
Jefferson Lab MS 12H5
12000 Jefferson Ave
Suite # 16
Newport News, VA 23606
elton@jlab.org
(757) 269-7625
(757) 269-6331 fax

On Tue, 26 Feb 2008, Alex Dzierba wrote:

> 	Hi All
>
> At Friday's phone conference we are meant to be having a discussion
> of timing for charged particles from BCAL.   Since some work has been
> done with cosmic rays - can someone take responsibility for coming up
> with a number for BCAL?   As far as I know, the current estimate is
> of order 420 ps based on Christine's cosmics analysis and a followup e-mail
> exchange between Christine and Elton.  Andrei - have you done any
> independent analysis with cosmics?  Maybe a two-page note summarizing
> what we know and how we know it would be appropriate.
>
> I am currently working on the analysis of the fiber emission spectra
> I received from Blake last night.   After that I will produce 2-3 slides
> showing how 420 ps allows to separate pi/proton but not pi/K
> for the reactions of interest.
>
> Two other comments:  (1) Stefano said that KLOE achieved 320 ps for
> mips and (2) Zisis is doing work on understanding BCAL response to
> protons (apart from timing).
>
> Cheers
> Alex
> --
> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> Alex R. Dzierba
> Chancellor's Professor of Physics (Emeritus)
> Department of Physics / Indiana U / Bloomington IN 47405 / 812-855-9421
> JLab Visiting Fellow
> Jefferson Lab / 12000 Jefferson Ave / Newport News, VA 23606 / 757-269-7577
> Home Phone: 812-825-4063  Cell:  812-327-1881  Fax: 866-541-1263
> http://www.dzre.com/alex
> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>