Physics – High Energy Physics – High Energy Physics - Phenomenology
Scientific paper
2003-08-15
Phys.Lett. B579 (2004) 340-346
Physics
High Energy Physics
High Energy Physics - Phenomenology
8 pages, LaTeX, two figure. Contributed to the Lepton-Photon Conference, 2003, FNAL
Scientific paper
10.1016/j.physletb.2003.10.115
We point out that applying the photon energy cut significantly modifies the moments of energy spectrum in B->X_s+gamma decays, with a certain class of effects not accounted for in the mostly used OPE expressions. This leads to a systematic bias in the extracted values of the b quark mass and other heavy quark parameters. The apparent b quark mass increases typically by 70MeV or more, together with an even more dramatic downward shift in the kinetic expectation value. Accounting for these cut-related shifts brings different measurements into a good agreement, when the OPE-based theory employs the robust approach. These nonperturbative effects are exponential in the effective hardness severely lowered by high cuts, and do not signify a breakdown of the 1/m_b expansion itself. Similar effects in semileptonic b->c decays are briefly addressed. We stress the utility of the second moment of E_gamma once these effects are incorporated.
Bigi Ikaros I.
Uraltsev Nikolai
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