[d2n-analysis-talk] LHRS Trigger Efficiency Study

[David Flay]

On Tue, Jul 13, 2010 at 2:06 PM, Brad Sawatzky <brads at jlab.org> wrote:

> 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.
>

Wouldn't including the prescales give the latch pattern variable -- LTN =
ps*bitN?  Since bitN is after the prescale.

I know that we're missing events in that despite ps = 1 for T3 and T4 for
run 20676 (from the
logbook<http://www.jlab.org/%7Eadaq/halog/html/0903_archive/090314032236.html>):
the LT3 doesn't match bit3 (and more noticeable is the discrepancy of the T4
values) :

Trigger 3 [Bit]: 13870
Trigger 4 [Bit]: 10
Trigger 3 [Latch]: 13885
Trigger 4 [Latch]: 314
T3 Trigger Efficiency [using bit variables]:
Trigger 3: 99.9280 +/- 0.0228%

(where I count the number of entries in the histos for 'DL.bit3', etc.)

cuts used (applied to all histos):

    //one track from the target
    cut0 = Form("(L.tr.n==1)");
    //cut out the pulser, require either a T3 or a T4 trigger
    cut0 +=
Form("&&(DL.edtpl==0)&&(((DL.evtypebits&(1<<3))==(1<<3))||((DL.evtypebits&(1<<4))==(1<<4)))");

    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)");

PS -- should Cherenkov TDC cuts be used here?  I tried it out, and I get
eff_T3 ~ 99.96%, as compared to above, at 99.92%.
        I tacked on the TDC cuts since I do use them to define good
electrons in the Cherenkov.

        Also -- I was looking at Patricia's work on the trigger efficiency
-- her left arm results are comparable to mine (99.98%):
http://hallaweb.jlab.org/experiment/E01-012/reports/trig_vdc.pdf
        However, she is fairly brief on her description of the calculation.

-- 
-----------------------------------------------------------
David Flay
Physics Department
Temple University
Philadelphia, PA 19122

office: Barton Hall, BA319
phone: (215) 204-1331

e-mail: flay at jlab.org
            flay at temple.edu

website: http://www.jlab.org/~flay
              http://quarks.temple.edu
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