10 - H1 - Desy

Chapter 4
Event reconstruction and
preselection
This chapter provides the basic informations about the reconstruction of general event
properties as well as criteria requested to obtain basic data selection. Section 4.1 gives an
overview of the data on which this analysis is based. Section 4.2 explains the reconstruction
of the basic event properties, particularly explains the jet reconstruction algorithm.
The triggering issues are explained in details in section 4.3, while additional requirements
aimed to reject non-ep background are discussed in section 4.4.
4.1 Data overview
The analysis presented in this thesis is based on the data collected by the H1 detector
in the years 2004-2007 and represents the whole HERA II data sample. The data taking
strategy of the H1 experiment groups the collected events into runs of of approximately
1 hour duration. Depending on the quality of collision environment and the experimental
hardware status the runs are classified offline as good, medium or poor. The analysis
presented in this thesis does not use runs degraded as poor. In addition it is required
that the high voltage of all the essential subdetectors is at its nominal value and their
readout is functional. The essential subdetectors for this analysis include: CJC1, CJC2,
LUMI, LAr calorimeter, SPACAL, CIP, BPC, TOF and VET systems (see section 3.2 for
systems description).
Table 4.1 contains the detailed information about used H1 data periods, including the
charge of the lepton beam and its helicity. The polarisation of the electrons has not been
used in this analysis, but since it is commonly used to define data taking periods, it is
included in the table. The total integrated luminosity of all considered HERA run periods
amounts to 340.1 pb −1 .
In figure 4.1 the event yield for inclusive prompt photon selection (selection criteria will
be discussed later and are summarized in section 5.4) is presented. The yield is stable over
the time and amounts to roughly 440 events per 12 pb −1 of integrated luminosity. Visible