[d2n-analysis-talk] LHRS Trigger Efficiency Study

[Brad Sawatzky]

On Tue, 13 Jul 2010, David Flay wrote:

> efficiencies:
> Trigger 3: 99.9280 +/- 0.0228%
> Trigger 4: 0.0720 +/- 0.0228%
> 
> with the statistical error given as:
> 
> de = sqrt((bit4)/(bit3)*1.0/((bit3)+(bit4)));  (for trigger 3)
> 
> for trigger 4, let bit3 <-> bit4 in the above equation.

The 'eff' value for T4 doesn't really mean much.  (It isn't really an
efficiency by any standard definition -- I wouldn't worry about it.)

Now that I think about it a bit more (and I'm suspicious that the
efficiency seems too good to be real), I forgot a some factors in the
expression I gave you.  The trigger counts really ought to be multiplied
by the prescale factors
  eff_3 = bit3*ps1/(bit3*ps1 + bit4*ps4)

You'll need to grab the prescales from the ROOT file on every run since
they can change, of course.

> The cuts used:
> 
>     //one track from the target
>     cut0 = Form("(L.tr.n==1)");
>     //cut out the pulser, T8 trigger
>     cut0 += Form("&&(DL.edtpl==0)&&(((DL.evtypebits&(1<<8))!=(1<<8)))");

Rather than cutting out the T8 events, you should change the cut to
explicitly require only a T3.or.T4 -- that way your calculation won't
get confused if some other trigger type gets thrown in the mix for some
run.

>     cut1 = cut0;
>     //VDC cuts -- requirement of one track reconstruction
>     cut1 += Form("&&(L.vdc.u1.nclust==1)&&(L.vdc.v1.nclust==1)");
>     cut1 += Form("&&(L.vdc.u2.nclust==1)&&(L.vdc.v2.nclust==1)");
> 
>     cut2 = cut1;
>     //PID cuts
>     cut2 += Form("&&(L.cer.asum_c>300)&&(prl_E_P>0.54)&&(L.prl1.e>200)");
> 
> I wanted to show you these numbers before I do this for all the kinematics.

That should be fine.  You may want to pick one or two runs and vary the
cuts a bit to see how sensitive your efficiency is to those parameters.

-- Brad

-- 
Brad Sawatzky, PhD <brads at jlab.org>  -<>-  Jefferson Lab / Hall C / C111
Ph: 757-269-5947  -<>-  Fax: 757-269-5235  -<>- Pager: brads-page at jlab.org
The most exciting phrase to hear in science, the one that heralds new
  discoveries, is not "Eureka!" but "That's funny..."   -- Isaac Asimov