c
CRMESS=' EID_init was called !!!'
CALL RECMES(CRNAME,'I',CRMESS)
c
c Initialization of some constants for the
c FAST ELECTRON IDENTIFICATION (eid0)
c ==========================================
c
CCecthr = 150 ! EC deposited energy threshold (in MeV)
CCscthr = 50 ! 10 * SC deposited energy threshold (in MeV)
CCscecy = 15 ! Possible difference in Y (Sector) coord.(cm)
CCicoor = 35 ! Possible deviation in I - coord in EC (cm)
CCscpn = 30 ! 10 * Possible deviation in SC paddle #
c
RETURN
END
c
All tcl variables and output variables for eid0 are stored
in eidcontrol.inc file
.
c
c Variables contained in EIDCONTR common block
c --------------------------------------------
c
integer maxeid0
parameter (maxeid0 = 20)
c
integer CCecthr, ! EC deposited energy threshold (in MeV)
& CCscthr, ! SC deposited energy threshold (in 0.1 MeV)
& CCscecy, ! Possible deviation in Y (Sector) coord.
c ! in EC and SC detectors (cm)
& CCicoor, ! Possible deviation in I - coord in EC (cm)
& CCscpn ! 10 * Possible deviation in SC paddle #
c
integer jeidsec, ! Sector # for electron candidate
& jCC_eid, ! Pointer to the hit in CCRC bank
& jEC_eid, ! Pointer to the hit in ECHB bank
& jSC_eid ! Pointer to the hit in SCRX bank
c_end_var
c
COMMON /EIDCONTR/ CCecthr, CCscthr, CCscecy, CCicoor, CCscpn
COMMON /CCEID0/ jeidsec(maxeid0), jCC_eid(maxeid0),
& jEC_eid(maxeid0), jSC_eid(maxeid0)
c
....
c=============================================
c
c CC eid0 information
c
c=============================================
c
call eid0(nelectr)
if(nelectr.ge.1) then
s = ievent
call hf1(1005,s,1.)
c ==> 1005
end if
c=== Fill the histogram with event numbers with electron candidates.
c
do i = 1,nelectr
c ================
c
NHIS = 100 * jeidsec(i)
c === NHIS is the Sector number * 100
c
j = jCC_eid(i)
c === j is the pointer to the CCRC bank.
k = jSC_eid(i)
c === k is the pointer to the SCRX bank. ( Number of ROW in SCRX bank)
c Now you can use SCRX information for histogram filling or
c any other event analysis.
a1 = sc_r(2,k)
c
c === a1 is the Y-coordinate of the hit in SCRX bank for hit number k.
c ( I extract data from SCRX bank and store them in CCSCHB common
c block in cc_sch.F subroutine - see ccschb.inc file )
c
s = 0.1 * nrsegm(j)
c === s is the weighted mean hitted CC segment number for the cluster
c number j
call hf2(NHIS + 24,s,a1,1.)
c === This histogram stores segment number and Y coordinate in
c Sector ref. system for a CC cluster .
c
c ==> 24
a = 0.1 * nrphe(j)
c === a is the estimated number of photoelectrons for that cluster
call hf2(NHIS + 25,s,a1,a)
c === This histogram stores segment number and Y coordinate in
c Sector ref. system for a CC cluster weighted by number
c of photoelectrons.
c ==> 25
c +++ So, after these (24 & 25) histograms will be filled, then
c +++ the ratio of hist. 25 to hist. 24 will show the mean number
c +++ of photoelectrons as a 2-dimension plot : CC segment and Y
c +++ coordinate.
c +++
end do
This program is based mostly on GEANT simulations of detectors responses for initial electron and comparing with those from pions. These simulations were made at Full magnetic field of Torus and Mini-torus .
One of the most important features, allowed to identify electron, is the fact that for initial electron the CC segment and I coordinate in EC calorimeter are strongly correlated for ALL electron energies. Next picture shows the I-coordinate dependence on a CC segment number. One can see that for different initial energies of electrons this dependence could be described as a straight line :
Another feature, helped to identify electron , is the deposited energy in EC. Typically electron should deposit about 27% of its energy. But if you don't know the initial particle momentum, you can assume the low threshold of deposited energy, which depends mostly on magnetic field value. At full magnetic field electrons with energy more then 0.5 GeV can achieve EC calorimeter, so the threshold in that case should be about 0.15 GeV. In other cases you can redefine the tcl variable CCecthr .
Deposited energy distribution in EC for 1.6 GeV electrons and pions. Vertical line shows the cut range . The cut 0.15 GeV means 0.5 GeV electrons threshold for FULL magnetic field.
Other cuts for identifying electrons are :
Next picture shows the correlation between CC segment number and SC paddle number. Left 2 figures are for all hits in the event, right - the SC paddle number, nearest to the CC cluster. Bottom figures show the difference between "expected" SC paddle number and number in the simulated events.
One can see that in case of electron it is possible to predict what SC paddle numbers could be hitted.
Next figure shows the SC deposited energy distribution. More precisely in case of two sequential paddles hitted the plotted value is the maximum deposited energy. Mostly this energy stands for minimum ionization value for corresponding path length in the plastic scintillator (depending on the angle).
Some events had low deposited energy in SC - see next figure.
The case of low (<0.004 GeV) deposited energy events was investigated. Detailed analysis of these events shows, that
Next figure shows the GEANT simulation of the number of events passed the cuts for secondary 1.6 GeV electrons.
Cut #3 is the existence of hits in the CC,EC and SC in the same sector. The difference between cuts #3 and #9 (last) is less than 1% of events. So, applied cuts do not diminish the number of electrons.
The result of applying this program to four pions of 1.6 GeV events ( I generate events with 4 pions with fixed energy 1.6 GeV , targeted to CC detector ) is shown on the next figure :
It is evident, that this program can reject events without electron with high efficiency and low CPU time.