Advanced predictions for moments of the B{yields}X{sub s}{gamma} photon spectrum
- Institute for High-Energy Phenomenology, Newman Laboratory for Elementary-Particle Physics, Cornell University, Ithaca, New York 14853 (United States)
Based on a new, exact QCD factorization formula for the partial B{yields}X{sub s}{gamma} decay rate with a restriction on large photon energy, improved predictions are presented for the partial moments <E{sub {gamma}}> and <E{sub {gamma}}{sup 2}>-<E{sub {gamma}}>{sup 2} of the photon spectrum defined with a cut E{sub {gamma}}{>=}E{sub 0}. In the region where {delta}=m{sub b}-2E{sub 0} is large compared with {lambda}{sub QCD}, a theoretical description without recourse to shape functions can be obtained. However, for {delta}<<m{sub b} it is important to separate short-distance contributions arising from different scales. The leading terms in the heavy-quark expansion of the moments receive contributions from the scales {delta} and {radical}(m{sub b}{delta}) only, but not from the hard scale m{sub b}. For these terms, a complete scale separation is achieved at next-to-next-to-leading order in renormalization-group improved perturbation theory, including two-loop matching contributions and three-loop running. The results presented here can be used to extract the b-quark mass and the quantity {mu}{sub {pi}}{sup 2} with excellent theoretical precision. A fit to experimental data reported by the Belle Collaboration yields m{sub b}{sup SF}=(4.62{+-}0.10{sub exp}{+-}0.03{sub th}) GeV and {mu}{sub {pi}}{sup 2,SF}=(0.11{+-}0.19{sub exp}{+-}0.08{sub th}) GeV{sup 2} in the shape-function scheme at a scale {mu}{sub f}=1.5 GeV, while m{sub b}{sup kin}=(4.54{+-}0.11{sub exp}{+-}0.04{sub th}) GeV and {mu}{sub {pi}}{sup 2,kin}=(0.49{+-}0.18{sub exp}{+-}0.09{sub th}) GeV{sup 2} in the kinetic scheme at a scale {mu}{sub f}=1 GeV.
- OSTI ID:
- 20713650
- Journal Information:
- Physical Review. D, Particles Fields, Vol. 72, Issue 7; Other Information: DOI: 10.1103/PhysRevD.72.074025; (c) 2005 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA); ISSN 0556-2821
- Country of Publication:
- United States
- Language:
- English
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