Guy Wilkinson

Abstract:

The hadronic structure of the decay of the τ lepton to three charged particles, τ → 3πντ, is studied using data collected by the DELPHI detector at LEP between 1992 and 1995. The invariant mass of the 3π system, m3π, is fitted using the models of Kühn and Santamaria, Isgur Morningstar and Reader, and Feindt. The 3π and π⁺π^- mass spectra are compared with each model. Below m²3π = 2.3 GeV², all are in good qualitative agreement. Above m²3π = 2.3 GeV², anomalous behaviour is observed, consistent with the existence of a hitherto unseen decay mode of the τ through a radial excitation of the a1 meson. © 1998 Published by Elsevier Science B.V. All rights reserved.

Abstract:

Using D *+ mesons exclusively reconstructed in the DELPHI detector at LEP, an excess of 66 ± 14(stat.) events is observed in the D *+π+ π- final state with a mass of 2637 ± 2(stat.) ± 6(syst.) MeV/c2 and a full width smaller than 15 MeV/c2 (95% C.L.). This signal is compatible with the expected decay of a radially excited D *′ (JP = 1-) meson. © 1998 Published by Elsevier Science B.V. All rights reserved.

Abstract:

The DELPHI experiment at LEP has measured the inclusive charmless B hadron decay branching ratio, the B branching ratio into two charmed particles, and the total number of charmed particles per B decay, using the hadronic Z data taken between 1992 and 1995. The results are extracted from a fit to the b-tagging probability distribution based on the precise impact parameter measurements made using the microvertex detector. The inclusive charmless B branching ratio, including B decays into hidden charm (cc̄), is measured to be 0.033 ± 0.021. The B branching ratio into two open charmed particles is 0.136 ± 0.042. The mean number of charmed particles per B decay (including hidden charm) is 1.147 ± 0.041. After subtracting the B decay branching ratio into hidden charm, the charmless B branching ratio is found to be 0.007 ± 0.021, compatible with the Standard Model expectation. Models that predict an additional contribution to the charmless B branching ratio of 0.037 or higher are excluded with at least 95% confidence. © 1998 Elsevier Science B.V. All rights reserved.

Abstract:

From the Z decays recorded in 1994 and 1995 by the DELPHI detector at LEP, the charged particle multiplicity of weakly decaying B hadrons was measured to be: 4.97 ± 0.03 ± 0.06 excluding the K o and A decay products. © 1998 Published by Elsevier Science B.V. All rights reserved.

Abstract:

Trilinear gauge boson couplings are measured using data taken by DELPHI at 161 GeV and 172 GeV. Values for WWV couplings (V = Z,γ) are determined from a study of the reactions e⁺e^-→ W⁺W^- and e⁺e^- → Wev, using differential distributions from the WW final state in which one W decays hadronically and the other leptonically, and total cross-section data from other channels. Limits are also derived on neutral ZVγ couplings from an analysis of the reaction e⁺e^-→ y + invisible particles. © 1998 Elsevier Science B.V.