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W. J. Metzger

Publications and source records attributed to W. J. Metzger.

14 recordsLinked to original sources
arXiv2018

Interpreting BEC in e+e- annihilation

The usual interpretation of Bose-Einstein correlations (BEC) of identical boson pairs relates the width of the peak in the correlation function at small relative four-momentum to the spatial extent of the source of the bosons. However, in the tau-model, which successfully describes BEC in hadronic Z decay, the width of the peak is related to the temporal extent of boson emission. Some new checks on the validity of both the tau-model and the usual descriptions are presented.

hep-ex↗
arXiv2011

Bose-Einstein Correlations and the Tau-Model

Bose-Einstein correlations of pairs of identical charged pions produced in hadronic Z decays are analyzed in terms of various parametrizations. A good description is achieved using a Lévy stable distribution in conjunction with a model where a particle's momentum is highly correlated with its space-time point of production, the tau model. However, a small but significant elongation of the particle emission region is observed in the Longitudinal Center of Mass frame, which is not accommodated in the tau model. This is investigated using an ad hoc modification of the tau model.

hep-ex↗
arXiv2008

Parametrization of Bose-Einstein Correlations and Reconstruction of the Space-Time Evolution of Pion Production in e+e- Annihilation

A parametrization of the Bose-Einstein correlation function of pairs of identical pions produced in hadronic e+e- annihilation is proposed within the framework of a model (the tau-model) in which space-time and momentum space are very strongly correlated. Using information from the Bose-Einstein correlations as well as from single-pion spectra,it is then possible to reconstruct the space-time evolution of pion production.

hep-ph↗
arXiv2006

Parametrization of Bose-Einstein Correlations and Reconstruction of the Source Function in Hadronic Z-boson Decays using the L3 Detector

Bose-Einstein correlations of pairs of identical charged pions produced in hadronic Z decays are analyzed in terms of various parametrizations. A good description is achieved using a Levy stable distribution in conjunction with a hadronization model having highly correlated configuration and momentum space, the tau-model. Using these results, the source function is reconstructed.

hep-ex↗
arXiv2003

QCD at LEP

Several preliminary QCD results from e+e- interactions at LEP are reported. These include studies of event shape variables, which are used to determine alpha_s and for studies of the validity of power corrections. Further, a study of color reconnection effects in 3-jet Z decays is reported.

hep-ex↗
arXiv2003

Bose-Einstein and Other Correlations in Hadronic Z Decay

In hadronic Z decays, Bose-Einstein correlations in neutral pion pairs are compared to those in identical charged pion pairs. Bose-Einstein correlations are also measured in triplets of identical charged pions, and comparison with those in pairs of pions indicates that pion production is completely incoherent. Further, factorial cumulants are used to compare correlations among like-sign as well as among all particles with those of several Monte Carlo models.

hep-ex↗
arXiv2001

Measurement of the Scaling Property of Factorial Moments in Hadronic Z Decay

Both three- and one-dimensional studies of local multiplicity fluctuations in hadronic Z decay are performed using data of the L3 experiment at LEP. The normalized factorial moments in three dimensions exhibit power-law scaling, indicating that the fluctuations are isotropic, which correspends to a self-similar fractal. A detailed study of the corresponding one-dimensional moments confirms this conclusion. However, two-jet subsamples have anisotropic fluctuations, correspending to a self-affine fractal. These features are, at least qualitatively, reproduced by the Monte Carlo models \JETSET and \HERWIG.

hep-ph↗
arXiv2001

New Bose-Einstein Results from L3

In hadronic Z decays, we compare Bose-Einstein correlations in \Pgpz pairs with those in identical charged pion pairs. We also measure Bose-Einstein correlations in triplets of identical charged pions. From the first study, the source radius is found to be smaller for \Pgpz-\Pgpz than for \Pgppm-\Pgppm, as would be expected, e.g., in a string model. However, the second study shows that the data are consistent with the pion production being completely incoherent. Both studies use data collected by the L3 collaboration at LEP.

hep-ph↗
arXiv1997

Multiplicities, fluctuations and QCD: Interplay between soft and hard physics?

Multiplicity fluctuations are studied both globaly (in terms of high-order moments) and locally (in terms of small phase-space intervals). The ratio of cumulant factorial to factorial moments of the charged-particle multiplicity distribution shows a quasi-oscillatory behaviour similar to that predicted by the NNLLA of perturbative QCD. However, an analysis of the sub-jet multiplicity distribution at perturbative scales shows that these oscillations cannot be related to the NNLLA prediction. We investigate how it is possible to reproduce the oscillations within the framework of Monte-Carlo models. Furthermore, local multiplicity fluctuations in angular phase-space intervals are compared with Monte-Carlo models and with first-order QCD predictions. While JETSET reproduces the experimental data very well, the predictions of the Double Leading Log Approximations and estimates obtained in Modified Leading Log Approximations deviate significantly from the data.

hep-ex↗
arXiv1997

Local properties of local multiplicity distributions in hadronic Z decay

Preliminary results on local multiplicity fluctuations in hadronic Z decays are presented. The data were obtained using the L3 detector at LEP. It is investigated to what extent Monte-Carlo models, which are tuned to reproduce global event-shape variables and single-particle inclusive distributions, can describe the local fluctuations measured by means of bunching parameters.

hep-ex↗