2020 Impact factor 4.590
Particles and Fields
Eur. Phys. J. C 4, 453-461
DOI 10.1007/s100529800783

The hadronic recoil mass spectrum in semileptonic B decays
and extracting |Vub| in a model-insensitive way

I. Bigi1 - R.D. Dikeman2 - N. Uraltsev2,3

1 Department of Physics, University of Notre Dame du Lac, Notre Dame, IN 46556, USA
2 Theoretical Physics Institute, University of Minnesota, Minneapolis, MN 55455
3 St.Petersburg Nuclear Physics Institute, Gatchina, St.Petersburg 188350, Russia

Received: 30 July 1997 / Published online: 23 February 1998

We present an extended discussion of the previously noted possibility to extract |Vub| from an analysis of the hadronic recoil mass spectrum in $B\rightarrow X_u\,\ell \nu$ decays. Invariant mass spectra containing perturbative as well as nonperturbative corrections are given; their shape is manifestly sensitive to the three basic quantities $\mu _\pi ^2$, mb and $\alpha_s$, whereas the total integrated rate is much less so. Only a small fraction of $b\rightarrow u$transitions generates a recoil mass MX of at least MD. Moreover we find that the fraction of events with $M_X \leq 1.5\,\mbox{GeV}$ (to reject leakage from $b \rightarrow c$ due to measurement errors) exhibits fairly little dependence on $\mu _\pi ^2$, mb and $\alpha_s$;|Vub| can then be extracted in a largely model-insensitive way. This conclusion is based on the applicability of the OPE to actual semileptonic B decays. A direct cross-check of this assumption and a determination of the required basic parameters of the heavy quark expansion will be possible in the future with more experimental data.

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