Displays of Aleph events

Events observed with the Aleph detector at LEP are visualised with the event display program DALI.

In this page we have selected pictures of several basic types of Z decay events. The displays are X-Y projections, i.e. you look at them parallel to the beam axis. The central part of ALEPH consists of several different tracking detectors. The points where charged particles interact with the tracking detectors (hits) are shown as squares and the tracks fitted to the hits are drawn as thin lines. The outer part of ALEPH consists of calorimeters, i.e. detector components that measure the energy of the particles. The total energy deposited per calorimeter cell is drawn as a histogram. For penetrating particles (muons) one can see the hits in tracking chambers of the outermost calorimeter (hadron calorimeter) and muon detectors. There are also some blue hits. These originate from particles for which the trajectory does not point back to the vertex or which have low momentum.

For each event there is a choice from two colour sets.

A decay into e+ and e-: red or yellow version.
A decay into + and -: red or yellow version.
A decay into tau+ and tau-: red version
(one tau has decayed into an electron while the other tau has decayed into 3 pions).
A decay into two muons and two gammas: red or yellow version.
A 2-jet event resulting from the Z decaying into two quarks: red or yellow version.
A 3-jet event coming from a Z decaying into two quarks and one gluon: red or yellow version.
A 4-jet event: red or yellow version.
The postscript files of these pictures can be found in the picture database (see below) by entering the string "cal" as search string and selecting the directory "high-quality".

The LEP running at the Z peak came to an end in September 1995. The first events at higher energies were announced in on 6th November 1995 in CERN Press Release PR 09.95

We give here a selection of the first events observed in Aleph at 130 GeV, 140 GeV and 161 GeV


You can search the full list of available DALI pictures using the picture database query form (you also can save or print these pictures).

webmaster@alephwww.cern.ch, 9th July 1996