Re: [Beamtest Analysis] - Attn:Dave and Simon - odd tphoton spectra

[Elton Smith <elton@jlab.org>]

Hall D barrel calorimeter:


One further note:

If the T-counters have been lined up relative to the veto (as Simon
suggested). This should be checked, but once calibrated, any T-counter can
be used as a reference and will significantly enhance statistical samples
for tests.

Cheers, Elton.




Elton Smith
Jefferson Lab
elton@jlab.org
(757) 269-7625

On Mon, 27 Nov 2006, David Lawrence wrote:

>
> Hi,
>
>     Just to add a little to Simon's comment. The production trigger(bit 4 for run 2334) had the
> MOR in it which I believe was delayed so that it determined the trigger time. This means that the
> jitter between T-counter channels would appear in the trigger time.
>
>     I agree that we'd like to have nicely lined up timing spectra, however, I want to make sure we
> don't get caught chasing a red herring here. The only thing we really need good timing from the
> tagger for is to match it up with the event seen in the downstream detectors (veto and BCAL). My
> understanding is that generally, you apply a cut that Nphotons==1 so there is no ambiguity as to
> what photon caused the event. Thus, your cuts on the tagger timing can be very loose. In this case
> +/-10ns.
>
>     The most vital information about the BCAL comes from the BCAL itself. If I look at the time
> difference between N8 and S8 for the recent 2334 DST, I get:
>
> root [53] bcal->Fit("gaus","tn8-ts8","abs(tn8-ts8)<10 && Nphotons==1")
>  FCN=13346 FROM MIGRAD    STATUS=CONVERGED      94 CALLS          95 TOTAL
>                      EDM=8.04063e-09    STRATEGY= 1  ERROR MATRIX UNCERTAINTY   1.9 per cent
>   EXT PARAMETER                                   STEP         FIRST
>   NO.   NAME      VALUE            ERROR          SIZE      DERIVATIVE
>    1  Constant     5.29003e+04   1.55913e+02  -6.24633e-01   1.42340e-06
>    2  Mean        -1.11402e-01   8.19901e-04   1.57801e-06  -4.41226e-02
>    3  Sigma        3.86152e-01   7.91046e-04  -9.46867e-07   4.28185e-01
>
> Which says the timing difference has a sigma of 386ps (which includes resolution due to spot
> size). If you want to look at absolute timing resolution of the BCAL relative to an external
> detector, you should place cuts on Ephoton such that you're looking at a single T-counter.
>
> Regards,
> -David
>
>
> Simon Taylor wrote:
>
>  Hi, Blake.
>
> I believe the explanation is this:
> The last timing calibration for the tagger counters was done relative to
> signals in the veto (using one of the special veto-triggered runs).  The
> times you plot are relative to the (presumably) production trigger.  The
> T-counters are not guaranteed to be exactly in time in hardware at the
> trigger level.
>
> Simon
>
> On Fri, 24 Nov 2006, Blake Leverington wrote:
>
>
>
>  Hi Dave and Simon,
>
> Hope you guys had a good weekend stuffing yourselves!
>
> I've been doing some more analysis looking at the tdc and so on to try
> and clean up the adc spectra for the BCal. I noticed when I plot adcsumN
> vs. tphoton and Ephoton vs. tphoton I get the plots at the bottom of
> http://www.jlab.org/Hall-D/software/wiki/index.php/BCAL_Beam_Test_Plots%2C_November_20%2C_2006
>
> The scale is blown up but I think something strange is going on like the
> offsets aren't correct for the tagger. Or is this normal and something I
> have to live with?
>
> Thanks,
> -Blake
>
>
>
>
>  --
>
> ------------------------------------------------------------------------
>   David Lawrence Ph.D.
>   Staff Scientist                 Office: (757)269-5567   [[[  [   [ [
>   Jefferson Lab                   Pager:  (757)584-5567   [  [ [ [ [ [
>   http://www.jlab.org/~davidl     davidl@jlab.org         [[[  [[ [[ [[[
> ------------------------------------------------------------------------
>
>
>