Measurement of partial branching fractions of inclusive charmless $B$ meson decays to $K^{+}$, $K^0$, and ${\pi }^{+}$

We present measurements of partial branching fractions of $B\to K^{+}X$, $B\to K^{0}X$, and $B\to {\pi }^{+}X$, where $X$ denotes any accessible final state above the endpoint for $B$ decays to charmed mesons, specifically for momenta of the candidate hadron greater than 2.34 (2.36) GeV for kaons (pions) in the $B$ rest frame. These measurements are sensitive to potential new-physics particles which could enter the $b\to s(d)$ loop transitions. The analysis is performed on a data sample consisting of $383\times {10}^{6}B\overline{B}$ pairs collected with the BABAR detector at the PEP-II $e^{+}{e}^{-}$ asymmetric energy collider. We observe the inclusive $B\to {\pi }^{+}X$ process, and we set upper limits for $B\to K^{+}X$ and $B\to K^{0}X$. Our results for these inclusive branching fractions are consistent with those of known exclusive modes, and exclude large enhancements due to sources of new physics.

Figure 1

Projection of the $m_{\mathrm{ES}}$ variable for the $B_{\mathrm{reco}}$ sample; the dashed line represents the $B\overline{B}$ component, the dot-dashed is the continuum background, and the solid line is the sum of the two components.

Figure 2

Projection plots for the whole $p^{*}$ range for the (a) $K^{+}$, (b) $K_S^0$, and (c) ${\pi }^{+}$ samples. The solid curves are the total fit functions, the (red) dashed lines are the signal components (which are kept fixed at this stage), the (blue) long dashed lines are the $b\to c$ background and the magenta dotted lines are $q\overline{q}$. The scale on the upper border of the plots indicates the mass of the system recoiling against the light hadron.

Figure 3

Projection plots for $p^{*}>2.34(2.36)\mathrm{GeV}$ for the (a) $K^{+}$, (b) $K_S^0$, and (c) ${\pi }^{+}$ samples. The solid curves are the total fit function, the (red) dashed lines are the signal component, the (blue) long dashed are the $b\to c$ background and the magenta dotted are $q\overline{q}$. In order to enhance the signal component we apply cuts on the likelihood (computed excluding the $p^{*}$ variable) which retain 82–88% of signal events while suppressing most of the $q\overline{q}$ background. The scale on the upper border of the plots indicates the mass of the system recoiling against the light hadron.