skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: Multiplicity Difference between Heavy and Light Quark Jets Revisited

Abstract

A peculiar prediction of perturbative QCD, obtained within the Local Parton Hadron Duality (LPHD) framework, is that the multiplicity difference {delta}Ql between heavy and light quark jets produced in e+e- annihilation is energy independent. In the Modified Leading Logarithmic Approximation (MLLA) the corresponding constant is derived in terms of a few experimentally measurable quantities. While the energy independence of {delta}Ql has been successfully verified experimentally for b-quarks up to the highest LEP2 energy, its numerical prediction ({delta}{sub bl}{sup MLLA} = 5.5 {+-} 0.8) overestimates the experimental results. The work presented in this talk, done in collaboration with Yuri L. Dokshitzer, Valery A. Khoze and Wolfgang Ochs, shows that in the light of new experimental results and the improvement in the understanding of the experimental data, this prediction needs indeed a revision. We now find {delta}bl = 4.4 {+-} 0.4, in better agreement with experiment, and we shaw that the remaining difference can be attributed largely to next-to-MLLA contributions, an important subset of which are identified and evaluated. The situation with charmed quarks is also reviewed.

Authors:
 [1]
  1. INFN e Dipartimento di Fisica dell' Universita, viale Berti Pichat 6/2, 40127 Bologna (Italy)
Publication Date:
OSTI Identifier:
20800115
Resource Type:
Journal Article
Resource Relation:
Journal Name: AIP Conference Proceedings; Journal Volume: 828; Journal Issue: 1; Conference: 35. internationals symposium on multiparticle dynamics; Workshop on particle correlations and femtoscopy, Kromeriz (Czech Republic), 9-17 Aug 2005; Other Information: DOI: 10.1063/1.2197393; (c) 2006 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS; ANNIHILATION; APPROXIMATIONS; B QUARKS; C QUARKS; D QUARKS; DUALITY; ELECTRON-ELECTRON INTERACTIONS; GLUONS; HADRONS; JET MODEL; MULTIPLICITY; QUANTUM CHROMODYNAMICS; U QUARKS

Citation Formats

Fabbri, Fabrizio. Multiplicity Difference between Heavy and Light Quark Jets Revisited. United States: N. p., 2006. Web. doi:10.1063/1.2197393.
Fabbri, Fabrizio. Multiplicity Difference between Heavy and Light Quark Jets Revisited. United States. doi:10.1063/1.2197393.
Fabbri, Fabrizio. Tue . "Multiplicity Difference between Heavy and Light Quark Jets Revisited". United States. doi:10.1063/1.2197393.
@article{osti_20800115,
title = {Multiplicity Difference between Heavy and Light Quark Jets Revisited},
author = {Fabbri, Fabrizio},
abstractNote = {A peculiar prediction of perturbative QCD, obtained within the Local Parton Hadron Duality (LPHD) framework, is that the multiplicity difference {delta}Ql between heavy and light quark jets produced in e+e- annihilation is energy independent. In the Modified Leading Logarithmic Approximation (MLLA) the corresponding constant is derived in terms of a few experimentally measurable quantities. While the energy independence of {delta}Ql has been successfully verified experimentally for b-quarks up to the highest LEP2 energy, its numerical prediction ({delta}{sub bl}{sup MLLA} = 5.5 {+-} 0.8) overestimates the experimental results. The work presented in this talk, done in collaboration with Yuri L. Dokshitzer, Valery A. Khoze and Wolfgang Ochs, shows that in the light of new experimental results and the improvement in the understanding of the experimental data, this prediction needs indeed a revision. We now find {delta}bl = 4.4 {+-} 0.4, in better agreement with experiment, and we shaw that the remaining difference can be attributed largely to next-to-MLLA contributions, an important subset of which are identified and evaluated. The situation with charmed quarks is also reviewed.},
doi = {10.1063/1.2197393},
journal = {AIP Conference Proceedings},
number = 1,
volume = 828,
place = {United States},
year = {Tue Apr 11 00:00:00 EDT 2006},
month = {Tue Apr 11 00:00:00 EDT 2006}
}
  • We examine the experimental results which have been obtained so far on the ratio of the mean multiplicity between quark and gluon jets, [l angle][ital n][r angle][sub gluon]/[l angle][ital n][r angle][sub quark]. We point out that none of the results yet obtained provide a quantitative test of the QCD prediction for this ratio, because of differences between the experimental and theoretical definitions of the jets or event samples. We propose a technique accessible to the CERN LEP experiments in which the experimental jet definitions correspond to the theoretical ones, allowing a direct test of the QCD result. Using the HERWIGmore » Monte Carlo program, we demonstrate the viability of our proposed technique.« less
  • The charged-particle multiplicities of hadronic events deriving from produced bottom or charm quarks have been measured in the Mark II detector at PEP in e/sup +/e/sup -/ annihilation at 29 GeV. For events containing one semileptonic and one hadronic weak decay, we find multiplicities of 15.2 +- 0.5 +- 0.7 for bottom and 13.0 +- 0.5 +- 0.8 for charm. The corresponding multiplicities of charged particles accompanying the pair heavy hadrons are 5.2 +- 0.5 +- 0.9 for bottom, and 8.1 +- 0.5 +- 0.9 for charm.
  • No abstract prepared.
  • Here, the study of heavy-light meson masses should provide a way to determine renormalized quark masses and other properties of heavy-light mesons. In the context of lattice QCD, for example, it is possible to calculate hadronic quantities for arbitrary values of the quark masses. In this paper, we address two aspects relating heavy-light meson masses to the quark masses. First, we introduce a definition of the renormalized quark mass that is free of both scale dependence and renormalon ambiguities, and discuss its relation to more familiar definitions of the quark mass. We then show how this definition enters a mergermore » of the descriptions of heavy-light masses in heavy-quark effective theory and in chiral perturbation theory (χPT). For practical implementations of this merger, we extend the one-loop χPT corrections to lattice gauge theory with heavy-light mesons composed of staggered fermions for both quarks. Putting everything together, we obtain a practical formula to describe all-staggered heavy-light meson masses in terms of quark masses as well as some lattice artifacts related to staggered fermions. In a companion paper, we use this function to analyze lattice-QCD data and extract quark masses and some matrix elements defined in heavy-quark effective theory.« less