Welcome to 
8m Tagger Home Page
The 8m Tagger: Motivation
Main purpose of the detector is to tag photoproduction
events at HERA at high photon-proton center-of-mass
energies (about 290 GeV). It is important for studies
photoproduction processes at highest possible energies
as well as for determination of the photoproduction
backgrounds in the deep-inelastic scattering measurements.
Note: High energy photoproduction at HERA occurs when an incident
electron radiates off a high energy photon which collides with a
proton. Therefore, the outgoing electron flies in a
direction of electron beam and carries away only a small fraction of the primary
electron energy.
Here one can see the (measured) photon energy ranges
tagged in the 8m (yellow), 35m (blue) and 44m (green) ZEUS taggers.
The 8m Tagger: Detector 
So-called 8m tagger is a small detector measuring backward
produced electrons in a 1-3 GeV energy range. It consists
of a small tungsten/scintillator sampling calorimeter
for electron energy measurement with a position
detector made of scintillator fibers. Additionally, in front
of the calorimeter there
is a preshower detector vetoing events when the incident
electron showered before reaching the tagger, and behind it
a scintillator veto counter which allows
for rejecting proton beam related background for example.
The 8m Tagger: Irradiation
1997 doses
The 8m Tagger: Publications
The 8m Tagger: Analysis
The energy and position reconstruction (as well as calibration procedures)
was developed by
Urlike Wollmer . Energy and position measured in the 8m tagger
are available in ZES and the code
can be found in /zow/userd/wollmer/tag8/zes_t8.for.
Last update: 9. August 1998
KP