The physics of hadronic tau decays
- Laboratoire de l'Accelerateur Lineaire, IN2P3/CNRS and Universite de Paris-Sud 11, BP34, F-91898 Orsay (France)
Hadronic {tau} decays provide a clean laboratory for the precise study of quantum chromodynamics (QCD). Observables based on the spectral functions of hadronic {tau} decays can be related to QCD quark-level calculations to determine fundamental quantities like the strong-coupling constant, parameters of the chiral Lagrangian |V{sub us}|, the mass of the strange quark, and to simultaneously test the concept of quark-hadron duality. Using the best available measurements and a revisited analysis of the theoretical framework, the value {alpha}{sub s}(m{sub {tau}}{sup 2})=0.345{+-}0.004{sub exp}{+-}0.009{sub th} is obtained. Taken together with the determination of {alpha}{sub s}(M{sub Z}{sup 2}) from the global electroweak fit, this result leads to the most accurate test of asymptotic freedom: the value of the logarithmic slope of {alpha}{sub s}{sup -1}(s) is found to agree with QCD at a precision of 4%. The {tau} spectral functions can also be used to determine hadronic quantities that, due to the nonperturbative nature of long-distance QCD, cannot be computed from first principles. An example for this is the contribution from hadronic vacuum polarization to loop-dominated processes like the anomalous magnetic moment of the muon. This article reviews the measurements of nonstrange and strange {tau} spectral functions and their phenomenological applications.
- OSTI ID:
- 21013699
- Journal Information:
- Reviews of Modern Physics, Vol. 78, Issue 4; Other Information: DOI: 10.1103/RevModPhys.78.1043; (c) 2006 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA); ISSN 0034-6861
- Country of Publication:
- United States
- Language:
- English
Similar Records
Energy-energy correlations in e sup + e sup minus annihilation measured at E sub cm = 29 GeV and M sub z
Test of the running of {bold {alpha}}{sub {ital s}} in {bold {tau}} decays
Related Subjects
CHIRAL SYMMETRY
CHIRALITY
COUPLING CONSTANTS
HADRONS
LAGRANGIAN FUNCTION
MAGNETIC MOMENTS
MASS
MUONS
PARTICLE DECAY
QUANTUM CHROMODYNAMICS
QUANTUM ELECTRODYNAMICS
QUARK-HADRON INTERACTIONS
S QUARKS
SPECTRAL FUNCTIONS
STRONG-COUPLING MODEL
TAU PARTICLES
VACUUM POLARIZATION