Tutorial: performing an Example Partial Wave Analysis for e+ e- data

For testing and benchmarking purposes, an example PWA of Monte Carlo toy data is located in the directory Pawian/Examples/benchmark/epem . It is an analysis of the e+ e- annihilation to a J/psi charmonium with a radiative decay to the final state particles omege omega gamma via two intermediate resonances, the f2(1910) and the eta(2225).

This is a step by step tutorial on running this example.

Relevant Files

The following files should be located in the "benchmark" folder:

File	Description
JpsiGamOmegaOmega.cfg	The configuration file. The fitted model is defined and all options set here
toyDataSignal.dat	The "experimental" toy data as an ASCII file containing four-vectors
toyMC.dat	The phasespace distributed toy Monte Carlo data as an ASCII file containing four-vectors
startparams.dat	A list of default start parameters for the fit
benchmarkGam2Omega_runscript	A shell script to run the PWA in client/server-mode

Setting the Environment

If not yet done, the relevant environment variables have to be set. An example for the Bochum site is given in the file "SetEnv_rub" in the top directory of the PAWIAN installation.

Starting the Server and the Clients

This example PWA is performed using the client/server mode with two clients, each one using two threads. The relevant configuration file options are

serverPort = 50003
serverAddress = localhost
noOfClients = 2
noOfThreads = 2

To start the server run

$TOP_DIR/bin/singleChannelApp --epemFiles $TOP_DIR/Examples/benchmark/epem/JpsiGamOmegaOmega.cfg --mode server !>& server.log &

Wait some seconds and then start the two clients on the same machine:

$TOP_DIR/bin/singleChannelApp --epemFiles $TOP_DIR/Examples/benchmark/epem/JpsiGamOmegaOmega.cfg --mode client !>& client1.log &
$TOP_DIR/bin/singleChannelApp --epemFiles $TOP_DIR/Examples/benchmark/epem/JpsiGamOmegaOmega.cfg --mode client !>& client2.log &

In the server.log, lines similar to the following should appear:

INFO: ********* Server mode ****************
INFO: Listening on port 50003
INFO: Number of clients for channel 0 : 2
INFO: Waiting for 2 clients ...
INFO: Client pc14 logged in (ID 0).
INFO: Client pc14 logged in (ID 1).
INFO: All clients ready.
INFO: start migrad

During the minimization, the current values of the likelihood are printed

INFO: current LH = -3298.143159127945

while the current parameter values are frequently dumped into a file named currentResult.dat. After the minimization has finished, the logfile should show

**************** Minuit FunctionMinimum information ******************
INFO: Function minimum is valid.
INFO: Covariance matrix is valid.
INFO: Final LH: -6184.421575
INFO: # of function calls: 1329
INFO: minimum edm: 1.288794568e-06

The file finalResult.dat now holds the list of final fit parameters with proper errors. Another file serializedOutput.dat is created in which (currently only) the covariance matrix is stored for later use.

Plotting the Result and Calculating the Contributions of the Intermediate Resonances

For this purpose it is needed to start the QA mode by running

$TOP_DIR/bin/singleChannelApp -c $TOP_DIR/Examples/benchmark/epem/JpsiGamOmegaOmega.cfg --mode qaMode --paramFile finalResult_epem.dat --serializationFile serializedOutput_epem.dat !>& logQA.log &

-- BertramKopf - 10 Feb 2015