No. 32 (00120)

Family name : Sokolov
Given name : Anatoly
Affiliation : Institute for High Energy Physics
Abbreviation : IHEP
E-mail address : sokolov_a@mx.ihep.su
Title : Jet reconstruction in a digital hadronic calorimeter
Authors : Anatoly Sokolov
Abstract : 
The physics program for an electron-positron linear collider with the
center mass energy ranging from 90 GeV to 1 TeV, is largely dominated by
events with final state containing many jets. For an experiment on such
an accelerator the calorimeter should reconstruct well the multi-jet
events. This could be done through a so-called energy-flow algorithm
which employs not only the calorimeter but also the tracker. The
energy-flow algorithm is based on the idea to replace, for the charged
fraction of the event, the energy and angle information as derived by
the calorimeter by the much more accurate particle momentum as measured
in the powerful tracker device.

The optimal application of this method requires establishement of
sufficient spatial and energy resolution for all individual tracks to
allow efficient shower separation in the boosted jets. Thus the
calorimeter has to have good energy resolution and to be highly
granular. High granularity of ECAL and a digital HCAL gives a great
ability for particle separation.

To realize this ability it is necessary to  develop  sofisticated
algorithms of hadronic shower separation. Fuzzy clustering algorithms
for a shower separation and neural networks for an energy reconstruction
was used for jet reconstruction in this calorimeter.  These algorithms
was tested using a full simulation of the calorimeter based on GEANT4.

Digital hadronic calorimeter with a granularity of a few cubic cm has a
spatial and energy resolution enough to reach a jet energy resolution of
Delta Ejet ~ 30%*sqrt(Ejet) which seemed mandatory for the very rich
physics program on the linear collider.