Search for the Familon via $B^{\pm}\to π^{\pm}X^{0}$, $B^{\pm}\to K^{\pm}X^{0}$, and $B^{0}\to K_{S}^{0} X^{0}$ Decays

TL;DR

The two-body decay of the B meson to a light pseudoscalar meson h = pi(+/-),K+/-,K(0)(S) and a massless neutral feebly interacting particle X(0) such as the familon, the Nambu-Goldstone boson associated with a spontaneously broken global family symmetry is searched for.

Abstract

We have searched for the two-body decay of the B meson to a light pseudoscalar meson $h = π^+, K^+, K^0_S$ and a massless neutral weakly-interacting particle $X^0$ such as the familon, the Nambu-Goldstone boson associated with a spontaneously broken global family symmetry. We find no significant signal by analyzing a data sample containing 9.7 million $B\bar{B}$ mesons collected with the CLEO detector at the Cornell Electron Storage Ring, and set a 90% C.L. upper limit of $4.9 \times 10^{-5}$ and $5.3 \times 10^{-5}$ on the branching fraction for the decays $B^+ \to h^+ X^0$ and $B^0 \to K^0_S X^0$, respectively. These upper limits correspond to a lower bound of about $10^{8}$ GeV on the family symmetry breaking scale involving the third generation of quarks.

Figures (2)

• Figure 1: Distribution of the Fisher discriminant used in the $B^{\pm}\to h^{\pm}X^0$ analysis for simulated signal (solid) and continuum (dashed) as well as off-resonance data (points) samples. The histograms are normalized to the statistics of the off-resonance data. The signal histogram is plotted assuming a branching ratio of $50 \times 10^{-5}$. The vertical line represents the optimum selection value below which events were accepted.
• Figure 2: Momentum distribution of the meson candidates. Filled and empty dots represent the on-resonance and the normalized off-resonance data, respectively. Solid histogram shows the prediction from $e^+ e^- \to q{\bar{q}}$ plus $b\to c$ simulations while the dashed histogram shows the distribution from $e^+ e^- \to q{\bar{q}}$ only. These histograms are normalized to the statistics of our data sample. Simulated signal events are shown by the dotted histogram assuming that ${\cal B}(B^{\pm}\to h^{\pm}X^0)\approx 30\times 10^{-5}$ and ${\cal B}(B^{0}\to K_{S}^{0}X^0)\approx 12\times 10^{-5}$. The accepted signal region is indicated by the arrows.