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.Comment: 11 pages, 11 eps figures, Presented at the XXVII Symposium on Multiparticle Dynamics, September 8-12, 1997 Frascati-Rome, Ital

Genuine Correlations of Like-Sign Particles in Hadronic Z0 Decays

Correlations among hadrons with the same electric charge produced in Z0 decays are studied using the high statistics data collected from 1991 through 1995 with the OPAL detector at LEP. Normalized factorial cumulants up to fourth order are used to measure genuine particle correlations as a function of the size of phase space domains in rapidity, azimuthal angle and transverse momentum. Both all-charge and like-sign particle combinations show strong positive genuine correlations. One-dimensional cumulants initially increase rapidly with decreasing size of the phase space cells but saturate quickly. In contrast, cumulants in two- and three-dimensional domains continue to increase. The strong rise of the cumulants for all-charge multiplets is increasingly driven by that of like-sign multiplets. This points to the likely influence of Bose-Einstein correlations. Some of the recently proposed algorithms to simulate Bose-Einstein effects, implemented in the Monte Carlo model PYTHIA, are found to reproduce reasonably well the measured second- and higher-order correlations between particles with the same charge as well as those in all-charge particle multiplets.Comment: 26 pages, 6 figures, Submitted to Phys. Lett.

Multiparticle production in QCD jets.

We briefly summarize the main results presented at the IPPP workshop on Multiparticle Production in QCD Jets, held in Durham in December 2001. (From the workshop 'Multiparticle Production in QCD Jets', 12–15 December 2001

Editorial. Migration and Education

This Special Edition of Power and Education on the subject of Migration and Education could not come at a more critical time. There is no ‘agreed’ definition for migration (International Organisation for Migration, 2005); however, it is commonly held that migration is the physical movement from one place to another. This may be in small or large groups. Education, which has been used synonymously to schooling, is similarly problematic to define, and has been suggested by Gregory (2002) to be concerned primarily with equipping minds to makes sense of the physical, social and cultural worlds. From these definitions, a close relationship between migration and education can be seen, which is being bolstered by the increased pace of globalisation. The relationship between these two concepts – education and migration – one can deduce, is as interrelated as they are dynamic. Nevertheless, interrelatedness is perhaps most noticeable in terms of world trade, although less noticeable forms of interrelatedness such as government policies and written and spoken communication skills are at play. The resulting interplay is a plethora of opportunities and challenges, often premised on a shifting borderland narrative and manifested in discourses around curricula and qualifications comparability, educational accreditation, social justice and identity trajectories