[d2n-analysis-talk] Pion Rejection Factors in the LHRS Gas Cerenkov

[David Flay]

Hi all,

I've been working on the pion rejection factors for the gas Cerenkov over
the past few days, attached are some plots of what I have.

The procedure is as follows:

I choose the pion region in the L.prl1.e:L.prl2.e plot (see attached) and
see how many of those events trigger the Cerenkov.  Then, I place a cut in
the gas Cerenkov and see how many events pass the cut.  I take the ratio
(call it r) of the events that pass the cut to those events I chose in the
2D shower plot.  Then r is the 'pi detection efficiency'.  Therefore, 1 -
r is our pion rejection efficiency.  Subsequently, 1/r is the pion
rejection factor, since this reflects the amount of pions that we remove
when making the Cerenkov cut.

I have attached the plots of the 2D shower, and a sample Gas Cerenkov with
and without the graphical cut on the shower.  These two plots are subject
to the 'standard' cuts:

     L.tr.n==1&&(DL.evtypebits&(1<<3))==(1<<3)&&DL.edtpl==0;
   //cuts on target windows
    cut0 += Form("&&(abs(L.tr.tg_y)<0.04)");
    //VDC cuts -- requirement of one track reconstruction
    cut0 += Form("&&(L.vdc.u1.nclust==1)&&(L.vdc.v1.nclust==1)");
    cut0 += Form("&&(L.vdc.u2.nclust==1)&&(L.vdc.v2.nclust==1)");
    //cut on acceptance
    cut0 += Form("&&(abs(L.tr.tg_dp)<0.035)");
    cut0 += Form("&&(abs(L.tr.tg_th)<0.05)&&(abs(L.tr.tg_ph)<0.03)");

The last three plots show the pion rejection factor as a function of cut
position in the Cerenkov, each for a different momentum setting (the three
plots cover the whole kinematic range).

Dave

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

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

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

website: http://www.jlab.org/~flay
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