Moments of the hadronic invariant mass spectrum in $B\to X_{c}l$$\nu$ decays at Belle

We present a measurement of the hadronic invariant mass squared ($M_X^2$) spectrum in charmed semileptonic $B$ meson decays $B\to X_c\ell \nu$ based on $140{\mathrm{fb}}^{-1}$ of Belle data collected near the ${\rm Y}(4S)$ resonance. We determine the first, the second central, and the second noncentral moments of this spectrum for lepton energy thresholds ranging between 0.7 and 1.9 GeV. Full correlations between these measurements are evaluated.

Figure 1

$M_{\mathrm{bc}}$ distributions for charged and neutral $B_{\mathrm{tag}}$ candidates after requiring $|\Delta E|<0.05\mathrm{GeV}$. No constraints are made on the signal side. The points with error bars are on-resonance data after subtraction of the scaled off-resonance data. The combinatorial background (cross-hatched histogram) is estimated using MC simulation.

Figure 2

Measured hadronic mass spectrum for different lepton energy thresholds. The points with error bars are the experimental data after subtraction of the continuum background. The histograms show the $B\to X_c\ell \nu$ signal and the different background components, explained in more detail in the text.

Figure 3

Graphical representation of the results in Table 2. The error bars indicate the statistical and total experimental errors.