Higgs-boson production from decays of the fourth-generationb′quark

In a scenario in which the fourth-generation $b^{\prime }$ quark is lighter than $m_t+M_W$, flavor-changing neutral-current $b^{\prime }\to b$ transitions could be substantial. In particular, the decay $b^{\prime }\to \mathrm{bH}$ could be dominant or comparable to the processes $b^{\prime }\to \mathrm{ce}\overline{\nu }$ and/or $b^{\prime }\to \mathrm{bZ}$ for a wide range of the parameters $m_{b^{\prime }}$, $m_t$, $m_{t^{\prime }}$, $M_H$, $V_{c{b}^{\prime }}$, and $V_{t{b}^{\prime }}$. For $b^{\prime }{\overline{b}}^{\prime }$ pairs the latter decays could provide valuable leptonic tags for Higgs-boson production that is especially useful in hadronic colliders for a Higgs boson in the intermediate-mass range $M_Z<M_H<2\mathrm{}{M}_W$. If $b^{\prime }\to b\gamma$ is observed then the strict limit $M_H>m_{b^{\prime }}-m_b$ is implied for $m_{b^{\prime }}<M_Z$. We study the singularities exhibited by the effective flavor-changing neutral-current vertex $b^{\prime }\mathrm{bH}$ and identify them as anomalous thresholds. Experimental prospects are discussed.