B→Xulbar nul decay distributions to order αs

We present "state-of-the-art" theoretical expressions for the triple differentialB → X u l −ν decay rate and for theB → X s γ photon spectrum, which incorporate all known contributions and smoothly interpolate between the "shape-function region" of large hadronic energy and small invariant mass, and the "OPE region" in which all hadronic kinematical variables scale with M B . The differential rates are given in a form which has no explicit reference to the mass of the b quark, avoiding the associated uncertainties. Dependence on m b enters indirectly through the properties of the leading shape function, which can be determined by fitting theB → X s γ photon spectrum. This eliminates the dominant theoretical uncertainties from predictions forB → X u l −ν decay distributions, allowing for a precise determination of |V ub |. In the shape-function region, short-distance and long-distance contributions are factorized at next-to-leading order in renormalization-group improved perturbation theory. Higher-order power corrections include effects from subleading shape functions where they are known. When integrated over sufficiently large portions in phase space, our results reduce to standard OPE expressions up to yet unknown O(α 2 s ) terms. Predictions are presented for partial B → X u l −ν decay rates with various experimental cuts. An elaborate error analysis is performed that contains all significant theoretical uncertainties, including weak annihilation effects. We suggest that the latter can be eliminated by imposing a cut on high lepton invariant mass.

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“…where the star distributions have the following effect on a function f when integrated over a domain Q 2 [21]:…”

Section: Leading-power Factorization Formulamentioning

confidence: 99%

Theory of charmless inclusiveBdecays and the extraction ofVub

2005

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“…We include the contributions from dimension-3 operators at O(α s ) and those from dimension-5 operators (whose matrix elements are proportional to the heavy-quark effective theory parameters λ 1,2 ) at tree level, using [10,11]. If thep + spectrum is integrated without a weight function, the tree-level power corrections from dimension-5 operators vanish.…”

Section: Calculation Of the Event Fractionmentioning

confidence: 99%

Proposal for a Precision Measurement of|Vub|

et al. 2004

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“…At the level of physical observables, but not of structure functions, semileptonic b → u decays can be obtained as the m c → 0 limit of our results. In this case the expressions simplify considerably, and the complete structure functions are known since a few years [19].…”

Section: Introductionmentioning

confidence: 99%