10 - H1 - Desy

Chapter 3
The H1 experiment at HERA
This chapter introduces the experimental apparatus used to collect the data that this
analysis is based on. At first, in section 3.1, an overview of the HERA 1 ep collider is
given. The most important elements of the H1 detector are introduced in section 3.2.
Special care is taken to describe parts particularly relevant for this analysis.
3.1 HERA storage ring
The HERA [84] storage ring in located at the DESY 2 research facility in Hamburg, Germany.
It is an unique electron 3 -proton collider providing an opportunity to study leptonparton
interaction at high energies. Figure 3.1 shows an overview of the HERA facility.
The proton beam preparation starts with the acceleration of negatively charged hydrogen
ions up to 50 MeV in the linear accelerator (H − -linac). In order to obtain the proton beam,
ions are stripped off the electrons before the injection into the DESY III ring. Seventy
bunches with a bunch crossing distance of 96 ns, identical to HERA, are accelerated up
to 7.5 GeV in the DESY III ring. The bunches are then transferred into the PETRA 4
storage ring, where they are accelerated further. The 70 GeV protons are injected to the
HERA ring. The procedure is repeated until HERA is filled with 210 proton bunches. In
the HERA ring, protons are accelerated to their final energies of 920 GeV.
The lepton acceleration starts with the e − -linac (e + -linac in case of positron beam) accelerator,
where they are accelerated to the energies of 450 MeV. A single bunch of electrons
≈ 60 mA is transferred into the DESY II ring, where it is accelerated to the energies of
7 GeV. Seventy electron bunches are injected into the PETRA II ring, where they reach
the energy of 14 GeV. The final energy of 27.6 GeV is achieved at the last stage of the
acceleration in the HERA ring, where 210 electron bunches circle the ring with 96 ns
1 Hadron Electron Ring Anlage.
2 Deutsches Elektronen Synchrotron.
3 Unless otherwise stated, here and in the following the term electron refers to both the electron and
the positron.
4 Positron Elektron Tandem Ring Anlage