Experimental study of the triple gluon vertex

The DELPHI collaboration Abreu, P. ; Adam, W. ; Adami, F. ; et al.
Phys.Lett.B 255 (1991) 466-476, 1991.
Inspire Record 301659 DOI 10.17182/hepdata.48514

In four-jet events from e + e − →Z 0 →multihadrons one can separate the three principal contributions from the triple-gluon vertex, double gluon-bremsstrahlung and the secondary quark-antiquark production, using the shape of the two-dimensional angular distributions in the generalized Nachtmann-Reiter angle θ NR ∗ and the opening angle of the secondary jets. Thus one can identify directly the contribution from the triple-gluon vertex without comparison with a specific non-QCD model. Applying this new method to events taken with the DELPHI-detector we get for the ratio of the colour factor N c to the fermionic Casimir operator C F : N c C F = 2.55 ± 0.55 ( stat. ) ± 0.4 ( fragm. + models ) ± 0.2 ( error in bias ) in agreement with the value 2.25 expected in QCD from N c =3 and C F = 4 3 .

1 data table

NC, CF, and TR are the color factors for SU(3) group.


Search for anomalous production of single photons at s**(1/2) = 130-GeV and 136-GeV

The DELPHI collaboration Adam, W. ; Abreu, P. ; Adye, T. ; et al.
Phys.Lett.B 380 (1996) 471-479, 1996.
Inspire Record 418937 DOI 10.17182/hepdata.47517

This letter reports the results of the measurement of single photon production in the reaction e + e − → γ + invisible particles at centre-of-mass energies s =130 and 136 GeV and an integrated luminosity of 5.83 pb −1 , collected with the DELPHI detector at LEP. The signal is compatible with the prediction of the Standard Model for the process e + e − → ν ν γ , and the number of neutrino families has been determined to be N ν = 3.1 ± 0.6. Limits have been derived on anomalous neutral gauge boson couplings and on compositeness in the framework of a specific model.

1 data table

SIG with C=HPC and C=FEMC correpond to the events in the barrel and forwardregion, respectively.