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2 - Heavy quarks

Published online by Cambridge University Press:  19 October 2009

Aneesh V. Manohar
Affiliation:
University of California, San Diego
Mark B. Wise
Affiliation:
California Institute of Technology
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Summary

The light u, d, and s quarks have masses mq that are small compared to the scale of nonperturbative strong dynamics. Consequently, it is a good approximation to take the mq → 0 limit of QCD. In this limit QCD has an SU(3)L × SU(3)R chiral symmetry, which can be used to predict some properties of hadrons containing these light quarks. For quarks with masses mQ that are large compared with the scale of nonperturbative strong dynamics, it is a good approximation to take the mQ → ∞ limit of QCD. In this limit QCD has spin-flavor heavy quark symmetry, which has important implications for the properties of hadrons containing a single heavy quark.

Introduction

The QCD Lagrangian in Eq. (1.82) describes the strong interactions of light quarks and gluons. As discussed in Sec. 1.4, there is a nonperturbative scale ΛQCD that is dynamically generated by QCD. A color singlet state, such as a meson made up of a quark–antiquark pair, is bound by the nonperturbative gluon dynamics. If the quarks are light, the typical size of such a system is of the order of Λ−1QCD. Consider a Q meson that contains a heavy quark with mass mQ ≫ ΛQCD, and a light quark with mass mq ≪ ΛQCD. Such a heavy-light meson also has a typical size of the order of Λ−1QCD, as for mesons containing only light quarks. The typical momentum transfer between the heavy and light quarks in the Q meson arising from nonperturbative QCD dynamics is of the order of ΛQCD.

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Publisher: Cambridge University Press
Print publication year: 2000

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  • Heavy quarks
  • Aneesh V. Manohar, University of California, San Diego, Mark B. Wise, California Institute of Technology
  • Book: Heavy Quark Physics
  • Online publication: 19 October 2009
  • Chapter DOI: https://doi.org/10.1017/CBO9780511529351.003
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  • Heavy quarks
  • Aneesh V. Manohar, University of California, San Diego, Mark B. Wise, California Institute of Technology
  • Book: Heavy Quark Physics
  • Online publication: 19 October 2009
  • Chapter DOI: https://doi.org/10.1017/CBO9780511529351.003
Available formats
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Save book to Google Drive

To save content items to your account, please confirm that you agree to abide by our usage policies. If this is the first time you use this feature, you will be asked to authorise Cambridge Core to connect with your account. Find out more about saving content to Google Drive.

  • Heavy quarks
  • Aneesh V. Manohar, University of California, San Diego, Mark B. Wise, California Institute of Technology
  • Book: Heavy Quark Physics
  • Online publication: 19 October 2009
  • Chapter DOI: https://doi.org/10.1017/CBO9780511529351.003
Available formats
×