Constraints on exclusive branching fractions $B{F}_i(B^{+}\to X_c^i{l}^{+}\nu )$ from moment measurements in inclusive $B\to X_{c}l\nu$ decays

Abstract

As an alternative to direct measurements, we extract exclusive branching fractions of semileptonic B-meson decays to charmed mesons, $B{F}_i(B\to X_c^{i}l\nu )$ with $X_c^i=D,D^{\ast },D_0,D_1^{\prime },D_1,D_2,D^{\prime },D^{\prime \ast }$ and non-resonant final states $(D^{(\ast )}\pi {)}_{nr}$, from a fit to electron energy, hadronic mass and combined hadronic mass-energy moments measured in inclusive $B\to X_{c}l\nu$ decays. The fit is performed by constraining the sum of exclusive branching fractions to the measured value of $BF(B\to X_{c}l\nu )$, and with different sets of additional constraining terms for the directly measured branching fractions. There is no fit scenario in which a single branching fraction alone is enhanced to close the gap between $BF(B\to X_{c}l\nu )$ and the sum of known branching fractions $B{F}_i(B\to X_c^{i}l\nu )$. The fitted $BF(B\to D^{\ast }l\nu )$ is 5% to 10% larger than the direct measurement depending on whether or not $BF(B\to D^{\ast }l\nu )$ is constrained to its direct measurement. $BF(B\to Dl\nu )$ values are in good agreement with the direct measurement unless $BF(B\to D^{\ast }l\nu )$ is constrained, which results in a higher $BF(B\to Dl\nu )$ value. Within large uncertainties, $BF(B\to D_1^{\prime }l\nu )$ agrees with direct measurements. Depending on the fit scenario, $BF(B\to D_{0}l\nu )$ is consistent with or larger than its direct measurement. The fit is not able to easily disentangle $B\to D_{1}l\nu$ and $B\to D_{2}l\nu$, and tends to increase the sum of these two branching fractions. $BF(B\to (D^{(\ast )}\pi {)}_{nr}l\nu )$ with non-resonant $(D^{(\ast )}\pi {)}_{nr}$ final states is found to be 0.2-0.4%, consistent with $B\to D^{(\ast )}\pi l\nu$ and $B\to D^{\ast \ast }(D^{(\ast )}\pi )l\nu$ measurements. No indication is found for significant contributions from so far unmeasured $B\to D^{\prime (\ast )}l\nu$ decays assuming that the $D^{\prime }$ and $D^{\prime \ast }$ can be identified with the observed $D(2550)$, respectively, $D^{\ast }(2600)$ state.

Comments: 57 pages, 28 figures, 23 tables