1. Overview

First step is to access the PRDF data : you do this using the ONCS Event package[Pur] and the famous Eventiterator class, which returns you an Event object. Only then the EMCAL software come into the game.

Then, you will ask an emcRawDataAccessor object (figure 1) to process the Event. In this step, the RawDataAccessor (RDA hereafter) will decode the Event, i.e. fetch the high-pre, high-post, low-pre, low-post and tac values for each and every channels, and store them into a emcRawDataObject (RDO hereafter). The channels are those belonging to one of the FEMs described in a configuration file which is needed to initialize the RDA.

  

Figure 1: Overview of calibration process

You will then pass this RDO to an emcCalibrator which will convert it into an emcMixedDataObject (MDO hereafter), where you'll get only 2 values per channel : an ADC value and a TAC value, i.e. the Calibrator will make the pre-post subtraction and choose between high and low gain values.

The same calibrator can then convert the MDO into an emcCalibratedDataObject (CDO hereafter) where ADC and TAC values will be converted into GeV and ns. Note that the calibrator can go directly from the RDO to the CDO, with a slight lost in performance (see section 3 for details).

The calibrator needs to fetch some calibration data to perform its work. Those data are provided by the emcDataManager. They can come from files or from Objectivity Federation (except time-zero calibration which are by now only on files).

Once you get a CDO, you are free to do whatever you'd like with its data : fill another object (e.g. an old STAF table), clusterize it, or store it directly using PHOOL (the CDO is a child of TObject and as such can be put in a PHIODataNode).

In the following section we describe in some more (technical) details the above steps, giving code examples and some design considerations and issues. If you just need to know how to calibrate EMCAL raw data, see sections 2 to 4. Those are the only section you really need to know about. But if you would like to know more about how calibrations are stored into DB, see sections 5, or if you would like to fill yourself some calibration objects, see section 6. Section 7 gives insight into plugins, and section 8 gives an alphabetical index of classes used.