Description of the ECAL online pi0 calibration

The aim of the following document is to provide description of pi0-online calibration from the expert usage point of view. The structure, programs called and their command line parameters are summarized here. Please, consult a Shift Manual for shift instruction how to run pi0 calibration.

The scheme( PS) presents main steps of pi0 calibration. It includes :


pi0 Server program


Control histograms

Control histograms are filled on-line for the monitoring purposes. The numeration is defined by standard DQ-rules.  Any histogram (its number)  should be defined in the database (consult DAQ expert). The definitions are given in /afs/desy.de/group/hera-b/ECAL/pi0/common/include/pi0_hist.h
 
Histogram name Description
CLusterX vs ClusterY 2-dimensional histogram with the coordinates of clusters which gave an entry in pi0-ntuple.
Invariant mass - all channels together Invariant mass in the pi0 ntuple, sum for all channels
Background - all channels together Invariant mass for pairs where one cluster comes from the current event and another one from previous event, sum for all channels
Number of clusters in event Clusters multiplicity in an event
Cluster energy, all found Energy spectrum of all clusters found
Cluster energy, in mass region Energy spectrum of clusters which are included in pairs with the invariant mass in the pi0 region
Number of events processed, accepted First bin of the histogram shows the number of events processed by pi0 program, 
the second bin is the number of events where at least one pi0 candidate is found.
Number of clusters versus BX The number of clusters versus BX.
Number of triggers versus BX The number of triggers versus BX.

The histograms are read out by the gatherer program and then can be viewed on-line with HbDisplay program (PI0 expert option)
or be extracted  afterwards from database with hbrowser program.

(28.06.2002: Go to hb-cr** as hbshift. Then to /online/DISPLAY/pro/Linux_intel_glibc/bin/ directory and Start hbrowser ../../etc/hbrowser.   Select DQ_PROD_4/ECAL. At the very end of the list there are PI0 histograms.  Choose one. Select below the appropriate run. Hbrower takes time)

For any problems ask DAQ expert assistance.


pi0 gatherer


pi0 fit


Cross-Check with ARTE


pi0 Update of DataBase information

After the calibration constants checked with latest ARTE version the information is passed to the ECAL database (/ECAL_CALIB). At the same time it is distributed with keytable. To avoid conflict with data taking the update of database is done manually between HERA luminosity runs ( when no run is being taken).
The update is performed by means of the /afs/desy.de/group/hera-b/ECAL/publisher code. 

Meaning of database tables ECPI0SLT, ECPI0ONL

As the output of the program the tables ECPI0SLT, ECPI0ONL are updated in the /ECAL_CALIB database. They contains Table discription TabInfo and row ECpi0 for each channel.

For each raw there are several parameters in addition to the status, sensitivity and error on sensitivity. Most of parameters are obtained from the fit of final iteration so they include calibration contants of previous iterations performed on the same set of data. However the latest correction is made on this bases (except channels with fit=0).
The fitting function is Gaussian (pi0 signal) + background (mixed events). The parameters meaning is following :
 
Parameter Meaning
mass mean of Gaussian (final fit)
emass error of mean of Gaussian (final fit)
sigma width of Gaussian (final fit)
esigma error of width of Gaussian (final fit)
nevents Number of pi0 in the signal (final fit)
enevents error of the number of pi0 in the signal (final fit)
back Normalization of background histograms, 4 parameter in the fit (final fit)
eback error of Normalization of background histograms (final fit)
chisq Chi-squared of final fit
ndf number of degree of freedom.
factor Ratio of obtained sensitivity to the one used for the data collection
efactor 2*emass/0.135 * OldSensitivity
fit Internal variable, 0 means that the calibration constant was fixed during previous iterations
flag type of final fit : -1 - means channels was not considered
0 - no fit found 
1 - fit with background histogram
2 - fit with polinomial of second power




Last update 26.04.2000
Olya Igonkina, Dima Rusinov