Inclusive Measurement of the Photon Energy Spectrum in b → s γ Decays

We compute the differentialB → X s γ decay width in the Standard Model as a function of the photon energy using Dressed Gluon Exponentiation (DGE). The resummed spectrum is matched with the fixed-order expansion, making use of the next-to-next-toleading order (NNLO) results for the matrix element of the magnetic dipole interaction O 7 and NLO ones for other operators in the effective Weak Hamiltonian. We develop a new technique to implement constraints on the analytic structure of the Sudakov factor in moment space. This improves the behavior of the resummed spectrum away from the Sudakov region. We also derive an analytic expression for the Borel transform of the perturbative series for the O 7 spectrum in the large-β 0 limit. Using this example we demonstrate that exponentiation in moment space is necessary for the calculation of the spectrum for E γ > ∼ 2 GeV. Finally, we investigate numerically the relation between renormalons, power corrections and support properties. We present predictions for the branching fraction and the first few spectral moments as a function of a cut E γ > E 0 and estimate the theoretical uncertainty.

Section: Introductionsupporting

confidence: 68%

Section: The Total Bfmentioning

confidence: 99%

Radiative B decay spectrum: DGE at NNLO

Andersen¹,

Gardi²

2007

“…Once one has integrated out the SUSY particles, the charged Higgs interaction becomes 28) where S + = H + , G + and the 3 × 3 matrices coupling C S + L,R are given by 30) where y S + (1) = cos β, sin β and y S + (2) = sin β, − cos β. The neutral Higgs and Goldstone boson interact with the down quarks in the following way…”

Section: Jhep08(2005)094mentioning

confidence: 99%

Probing the flavour structure of supersymmetry breaking with rare B-processes — a beyond leading order analysis

Foster

Okumura

Roszkowski

2005

In the framework of minimal supersymmetry with general flavour mixing in the squark sector we consider dominant beyond leading order (BLO) effects in the rare processes B → X s γ, Bs → µ + µ − and Bs − B s mixing. We present analytic expressions for corrected vertices, which are applicable in general, and provide a recipe for the inclusion of the dominant and subdominant BLO effects in existing LO calculations. We also derive similar expressions in the mass insertion approximation. We investigate in more detail the focusing effect pointed out in our earlier work, which, at large tan β and µ > 0, leads to a reduced supersymmetric contribution to the above processes. We also find that, in some cases, flavour dependence, that accidentally cancels at leading order, can reappear at BLO. We further include electroweak corrections, which, while generally subdominant, in some cases may have a substantial effect. For example, their contribution to the charged Higgs vertex in B → X s γ can be of the order of 20% at BLO. They can also reduce the contribution of LL insertions to Bs → µ + µ − and Bs − B s mixing by up to 20%, even at the LO. We also analyse radiative generation of CKM elements and find the possibility that the CKM matrix elements K ts and K cb can be generated entirely by LR insertions. This work constitutes the first complete analysis of dominant BLO effects in the GFM scenario.

“…This process has also been recently measured with good accuracy at the B factories, by Babar [59] and by Belle [60]. The strategy to be followed in this process would be very similar to that of the present work, since the experimental information has the same form.…”

Section: Discussionmentioning

confidence: 69%

Neural network parametrization of the lepton energy spectrum in semileptonic B meson decays

Rojo

2006

We construct a parametrization of the lepton energy spectrum in inclusive semileptonic decays of B mesons, based on the available experimental information: moments of the spectrum with cuts, their errors and their correlations, together with kinematical constraints. The result is obtained in the form of a Monte Carlo sample of neural networks trained on replicas of the experimental data, which represents the probability density in the space of lepton energy spectra. This parametrization is then used to extract the b quark mass m 1S b in a way that theoretical uncertainties are minimized, for which the value m 1S b = 4.84 ± 0.14 exp ± 0.05 th GeV is obtained.