Fit to b->sg Moments

The fit uses all public moment measurements of the photon energy distribution of b-> s gamma decays where correlation matrices are available. 

It is based on calculations in the Shape Function Scheme (see hep-ph/0504071) and Dressed Gluon Exponentiation (DGE) (see hep-ph/0502159) approach.

Fit Input

The table below lists the moment measurements that form the basis for the combined fit. We used the lowest photon energy moments measured by all the collaborations.

Experiment Photon Moments References
BABAR First Moment and Variance at 1.9 GeV hep-ex/0508004 (Phys.Rev. D72 (2005) 052004)
BABAR First Moment and Variance at 1.9 GeV hep-ex/0507001
Belle First Moment and Variance at 1.8 GeV hep-ex/0403004 (Phys. Rev. Lett 93(2004)061803) hep-ex/0508005
CLEO First Moment and Variance at 2.0 GeV hep-ex/0403052 (Phys.Rev.Lett. 87 (2001) 251807)

Fit Results 

We fit the moments using the SF scheme and the DGE approach. In case of the DGE approach, we have assumed theoretical errors coming from the matching coefficient (between m_b (default) and m_b/2), alphas (0.1176+/-0.002), the 3/2 renormalon residue (C=0.1 and C=10 with C=1 (default)) and nf (3 and 4 (default)).

Theoretical Calculation mb mu_pi^2 Correlation Chi^2/Ndof Plot
SF Scheme mb = 4.56 +- 0.05GeV mu_pi^2 = 0.28 +- 0.08 GeV^2 rho = -0.855 chi2/Ndof = 1.02/6 Delta Chi^2=1 Ellipse
DGE mb = 4.17  +- 0.05 GeV chi2/Ndof = 1.9/5. Overlay of theoretical predictions from fit to the moment

Last update: 2006/03/05 Francesca Di Lodovico