[d2n-analysis-talk] LHRS Scintillator Study

[Brad Sawatzky]

It is the _ADC_ signals that might be useful for particle ID (this is
also the case in BigBite).  The dt over any flight-path inside the
LHRS/BB detector stack will be very small -- almost certainly below
the TDC resolution.

> I have examined an elastic run as well -- attached as the second plot
> (run 1229).  We see that the electron cut (GC>600) picks out this main
> peak -- there is only one peak in this TDC spectrum.
> 
> Based on this double peak structure in the first plot, I'm thinking
> that maybe we could benefit from a calibration of the time offsets of
> the left and right TDCs, since this has a direct effect on the
> resolution of S1 (and hence, wouldn't that imply that we could
> possibly discern electrons from pions, based on timing information --
> considering the (main) trigger requires a coincidence between S1 &
> S2?)  A calibration of S2 will provide for a more accurate beta as
> well.

I doubt we'll have sufficient timing resolution, but it would be nice to
understand the time structure in the histogram.  As with the other
base classes, the THaScintillator class only exposes a single TDC hit.
It would be interesting to see if the outliers are correlated with
multiple hits in a given TDC channel (you'll have to use the DecData
class to check that).

> Other insightful variables I've been looking at (for the calibration)
> are L.s1.nthit -- this tells us the number of paddles with a L&R TDC
> coincidence.  Another is the related quantity L.s1.t_pads -- this
> tells us which paddle has a L&R TDC coincidence...  I was thinking of
> using these as cuts -- such that if we require S1, S2 to have a
> coincidence in 1 paddle -- that is effectively an 'extra' trigger cut
> for good electrons (?)  Of course, this fuels my interest in a
> calibration of the time offsets in S1 and S2.

The LHRS T3 trigger is S1.and.S2

The LHRS T4 trigger is any 2 of 3 using S1, S2, Cer.

Each of the S1 and S2 sub-triggers an OR of L+R coincidences in each
paddle.

-- Brad

-- 
Brad Sawatzky, PhD <brads at jlab.org>  -<>-  Jefferson Lab / Hall C / C111
  Ph: 757-269-5947 -<>- Pager: 757-584-5947 -<>- Fax: 757-269-7848
The most exciting phrase to hear in science, the one that heralds new
  discoveries, is not "Eureka!" but "That's funny..."   -- Isaac Asimov