Author : I. Stewart
Publisher :
ISBN 13 :
Total Pages : 68 pages
Book Rating : 4.:/5 (316 download)
Book Synopsis Semileptonic Decays and Sides of the Unitarity Triangle by : I. Stewart
Download or read book Semileptonic Decays and Sides of the Unitarity Triangle written by I. Stewart and published by . This book was released on 2003 with total page 68 pages. Available in PDF, EPUB and Kindle. Book excerpt: The elements of the CKM matrix enter the expressions for the decay rates and mixing amplitudes of hadrons. In some cases, the theoretical expressions are free of strong interaction effects, for example the CP asymmetry in B {yields} J/{psi} K{sub S}{sup 0}, so that measuring the CP asymmetry directly gives the value of sin 2{beta}, with the error in the result given by the experimental error in the measurement. In most cases, however, the experimentally measured quantities depend on strong interactions physics, and it is absolutely essential to have accurate model-free theoretical calculations to compare with experiment. A number of theoretical tools have been developed over the years which now allow us to compute B decays with great accuracy, sometimes at the level of a few percent or better. These calculations are done using effective theory methods applied to QCD, and do not rely on model assumptions. Inclusive decays can be treated using the operator product expansion (OPE). The total decay rate is given by twice the imaginary part of the forward scattering amplitude, using the optical theorem. In heavy hadron decays, the intermediate states in the forward scattering amplitude can be integrated out, so that the decay rate can be written as an expansion in local operators. The expansion parameter is 1/m{sub B}, the mass of the decaying hadron. OPE techniques have been well-studied in the context of deep-inelastic scattering, where the expansion in powers of 1/Q{sup 2} is called the twist expansion. In inclusive B decays, the leading term in the 1/m{sub B} expansion gives the parton decay rate, and nonperturbative effects enter at higher orders in 1/m{sub B}.
