The heavy quark expansion for inclusive semileptonic charm decays revisited

• Published in: The journal of high energy physics 2019-12, Vol.2019 (12), p.1-28, Article 67
• Main Authors: Fael, Matteo, Mannel, Thomas, Vos, K. Keri
• Format: Article
• Language: English
• Subjects: ASTRONOMY AND ASTROPHYSICS; Charm (particle physics); Classical and Quantum Gravitation; Elementary Particles; Heavy Quark Physics; High energy physics; Physics; Physics and Astronomy; Quantum Field Theories; Quantum Field Theory; Quantum Physics; Quark Masses and SM Parameters; Regular Article - Theoretical Physics; Relativity Theory; String Theory
• ISSN: 1029-8479; 1029-8479
• DOI: 10.1007/JHEP12(2019)067

A bstract The Heavy Quark Expansion (HQE) has become an extremely powerful tool in flavor physics. For charm decays, where the expansion parameters α s ( m c ) and Λ QCD /m c are bigger than for bottom decays, it remains to be seen if the HQE can be applied with similar success. Nevertheless, to make optimal use of the plethora of data already available and coming in the near future, a better understanding of HQE for charm decays is crucial. This paper discusses in detail how the HQE for charm decays is set up, what is the role of four-quark (weak annihilation) operators and how this compares to the well understood bottom decays. Subtleties concerning radiative corrections and the charm mass scheme are briefly discussed. An experimental study of the relevant HQE hadronic matrix elements will then show if the HQE expansion for charm converges well enough. Besides serving as an important cross check for inclusive B decays, in the end, this study might open the road for inclusive |V cs | and |V cd | extractions.