Erratum : b-tagging in DELPHI at LEP Abdallah, J.; Abreu, P.; Adam, W. ...
The European physical journal. C, Particles and fields,
2004, Letnik:
32
Journal Article
W+W-gamma production at LEP2 is studied using data collected with the DELPHI detector at centre-of-mass energies between 189 GeV and 209 GeV, corresponding to an integrated luminosity of about 600 ...pb^-1. Cross-sections are measured for the production of W+W- with a hard, central and isolated photon in the final state, and are found to be compatible with the Standard Model prediction. The photon energy spectra are used to derive limits on anomalous contributions to the W+W-Z0gamma and W+W-gammagamma vertices.
The production fractions of charged and neutral b-hadrons in b-quark events from Z0 decays have been measured with the DELPHI detector at LEP. An algorithm has been developed, based on a neural ...network, to estimate the charge of the weakly-decaying b-hadron by distinguishing its decay products from particles produced at the primary vertex. From the data taken in the years 1994 and 1995, the fraction of bbar-quarks fragmenting into positively charged weakly-decaying b-hadrons has been measured to be: f^+ = (42.09 +/- 0.82 (stat.) +/- 0.89 (syst.))%. Subtracting the rates for charged Xibar_b^+ and Omegabar_b^+ baryons gives the production fraction of B^+ mesons: f_Bu = (40.99 +/- 0.82 (stat.) +/- 1.11 (syst.))%.
2+1-dimensional Yang–Mills theory is reinterpreted in terms of metrics on 3-manifolds. The dual gluons are related to diffeomorphisms of the 3-manifolds. Monopoles are identified with points where ...the Ricci tensor has triply degenerate eigenvalues. The dual gluons have the desired interaction with these monopoles. This would give a mass for the dual gluons resulting in confinement.
Searches for resonant sneutrino production in e+e- collisions under the assumption that R-parity is not conserved and that the dominant R-parity violating coupling is lambda_{121} or lambda_{131} ...used data recorded by DELPHI in 1997 to 2000 at centre-of-mass energies of 183 to 208 GeV. No deviation from the Standard Model was observed. Upper limits are given for the lambda_{121} and lambda_{131} couplings as a function of the sneutrino mass and total width. The limits are especially stringent for sneutrino masses equal to the centre-of-mass energies with the highest integrated luminosities recorded.
Observation is made of rapidity-alignment of \KK and \pp pairs which results from their asymmetric orientation in rapidity, with respect to the direction from primary quark to antiquark. The \KK and ...\pp data are consistent with predictions from the fragmentation string model. However, the \pp data strongly disagree with the conventional implementation of the cluster model. The non-perturbative process of `gluon splitting to diquarks' has to be incorporated into the cluster model for it to agree with the data. Local conservation of \pT between particles nearby in rapidity (i.e., \pT compensation) is analysed with respect to the thrust direction for \pipix, \KKx, and \pp pairs. In this case, the string model provides fair agreement with the data. The cluster model is incompatible with the data for all three particle pairs. The model with its central premiss of isotropically-decaying clusters predicts a \pT correlation not seen in the data.
The rapidity-rank structure of \ppb pairs is used to analyze the mechanism of baryon production in hadronic \zz decay. The relative occurrence of the rapidity-ordered configuration \pmpb, where $M$ ...is a meson, and that of \ppb adjacent pairs is compared. The data are found to be consistent with predictions from a mechanism producing adjacent-rank \ppb pairs, without requiring `string-ordered' \pmpb configurations. An upper limit of 15\% at 90\% confidence is determined for the \pmpb contribution.
The study of the directional dependence of two-particle correlations in the hadronic decays of the $Z^0$ boson is performed using the data collected by the DELPHI experiment in the 1992--1995 running ...periods. The comparison between the transverse, $R_{\perp}$, and longitudinal, $R_{\parallel}$, correlation radii confirms the string model prediction that the transverse correlation length is smaller than the longitudinal one, with the measured values of $R_{\perp}=0.53\pm 0.08\,\mathrm{fm}$ and $R_{\parallel}=0.85\pm 0.08\,\mathrm{fm}$, for selected $Z^0\rightarrow q\bar{q}$ events.
PDF
