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DELPHI experiment


DELPHI was a detector for e+e- physics, with special emphasis on powerful particle identification , three-dimensional information, high granularity and precise vertex determination. It was installed at LEP (Large Electron and Positron collider) at CERN where it has operated between August 1989 and November 2000.

The official DELPHI homepage contains information on the detector, the physics goals and  event pictures. 

Activities at the IIHE:

Contributions to detector hardware and software



  • The Belgian laboratories (IIHE(ULB-VUB), UA UMH) have designed, constructed and maintained the 700 Forward Muon Chambers (MUF) of the DELPHI detector. This consisted of the construction of the detector itself, the development of the readout and trigger hardware and software and the development of the offline software for simulation and data reconstruction. There are Photographs of the MUF detector construction, transport and installation in Brussels and in DELPHI.


  • Some engineers in Brussels have taken responsibilities in the Central Trigger of the DELPHI experiment.
  • The DELPHI  raw data reconstruction software DELANA, and the event viewing software were partly designed and maintained by physicists of the IIHE.
  • The IIHE was also involved in the maintenance of the Surround Muon Chambers (MUS) software.

Contributions to data analysis

  • The Brussels group worked on analyses of the e+e- -> W+W- data with the aim of:
    • W mass measurement and study of colour reconnection in the fully hadronic channel (J. D'Hondt)
    • Spin Density Matrix analysis and measurement of CP-violating anomalous Triple Gauge boson Couplings (C. De Clercq, J. Lemonne).
  • the IIHE group was also involved in :
    • analysis of di-muon final states around and below the Z0 peak (Cao Fang,  Catherine De Clercq, Jacques Lemonne, Frederic Stichelbaut)
    • analysis of di-tau  final states around the Z0 peak (Daniel Bertrand, Veronique Lefébure)
    • measurement of charged Triple Gauge boson Couplings in the fully hadronic WW channel (A. Van Lysebetten)


The DELPHI Collaboration operates the experiment as a coherent and structured scientific enterprise with important efforts from institutions around the world. The joint activities of building and designing the detector, the exploitation of the computing infrastructures as well as the long series of data quality, commissioning and calibration activities, result in joint publications. Publications which would not have been possible without this strong collaboration and research from all these institutions. Within these experimental activities which are at the basis of all the scientific publications our institute was very much present. The collaboration has published some key results refereed to below.The full publication record of the DELPHI experiment can be found here

  Our institute has taken the lead in the write-up of several journal publications, of which some recent highlights are mentioned below:

  • Study of W boson polarisations and Triple Gauge boson Couplings in the reaction e^+ e^- -> W^+ W^- at LEP 2 PH-EP 2007-036 ( 6 October 2007) (Eur. Phys. J. C54 (2008) 345-364)
  • Measurement of the Mass and Width of the W Boson in e+e- Collisions at sqrt(s) = 161 - 209 GeV PH-EP 2007-026 ( 12 July 2007) (Eur. Phys. J. C55 (2008) 1-38)  
  • Investigation of Colour Reconnection in WW Events with the DELPHI detector at LEP-2 PH-EP 2006-037 ( 22 November 2006) (Eur. Phys. J. C51 (2007) 249-269)  
  • Bose-Einstein Correlations in W ^ + W ^ - events at LEP2 LEP-PH 2004-072 ( 10 December 2004) (Euro. Phys. J. C44 (2005) 161-174)  
  • Measurement of the W-pair Production Cross-section and W Branching Ratios in e+e- Collisions at sqrt(s) = 161-209 GeV EP 2003-071 ( 4 November 2003) (Eur. Phys. J. C34 (2004) 127-144)  
  • Search for the Standard Model Higgs Boson at LEP  EP 2003-011 ( 25 Avril 2003) (Phys. Lett. B 565(2003)61-75)  
  • Final results from DELPHI on the searches for SM and MSSM Neutral Higgs bosons  EP 2003-008 ( 11 February 2003) (Eur. Phys. J. C32 (2004) 145-183)  
  • Search for the Standard Model Higgs boson at LEP in the year 2000  EP 2001-004 ( 10 January 2001) (Phys.Lett.B499(2001)23)  
  • Measurement of the Mass and Width of the W Boson in e+e- Collisions at sqrt(s) = 189 GeV  EP 2001-029 ( 19 February 2001) Physics Letters B511(2001)159
  • Measurement of Trilinear Gauge Boson Couplings WWV , ( V \equiv Z, gam ) in \ee\ Collisions at 189 GeV EP 2001-006 ( 8 January-2001) (Phys. Lett. B502(2001)9)  
  • W pair production cross-section and W branching fractions in e^+ e^- interactions at 189 GeV EP 2000-035 ( 14 February 2000) Physics Letters B479(2000)89  
  • A Combination of Preliminary Electroweak Measurements and Constraints on the Standard Model EP 2000-016 ( 21 January 2000) hep-ex/061203 and arXiv:0712.0929