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Universality and m_X cut effects in B -> Xs l+ l-

Keith S. M. Lee·Zoltan Ligeti·Iain W. Stewart·Frank J. Tackmann
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Abstract

The most precise comparison between theory and experiment for the B -> Xs l+ l- rate is in the low q^2 region, but the hadronic uncertainties associated with an experimentally required cut on m_X potentially spoil the search for new physics in these decays. We show that a 10-30% reduction of dΓ(B -> Xs l+ l-) / dq^2 due to the m_X cut can be accurately computed using the B -> X_s gamma shape function. The effect is universal for all short distance contributions in the limit m_X^2 << m_B^2, and this universality is spoiled neither by realistic values of the m_X cut nor by alpha_s corrections. Both the differential decay rate and forward-backward asymmetry with an m_X cut are computed.

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Keith S. M. Lee, Zoltan Ligeti, Iain W. Stewart, Frank J. Tackmann. 2006-07-09. Universality and m_X cut effects in B -> Xs l+ l-. https://doi.org/10.1103/physrevd.74.011501

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