Sensitivity of the ${\eta }^{(\prime )}\to {\pi }^0\gamma \gamma$ and ${\eta }^{\prime }\to \eta \gamma \gamma$ decays to a sub-GeV leptophobic $U(1{)}_B$ boson

Abstract

The sensitivity of the rare decays ${\eta }^{(\prime )}\to {\pi }^0\gamma \gamma$ and ${\eta }^{\prime }\to \eta \gamma \gamma$ to signatures of a leptophobic $B$ boson in the MeV-GeV mass range is analyzed in this work. By adding an explicit $B$-boson resonance exchange, $\eta \to B\gamma \to {\pi }^0\gamma \gamma$, to the Standard Model contributions from vector and scalar meson exchanges, and employing experimental data for the associated branching ratios, it allows us to improve the current constraints on the $B$-boson mass $m_B$ and coupling to Standard Model particles ${\alpha }_B$. From these constraints and the analysis of the available experimental $\gamma \gamma$ invariant mass distribution, we show that a $B$-boson signature in the resonant mass range $m_{{\pi }^0}\lesssim m_B\lesssim m_{\eta }$ is strongly suppressed and would be very difficult to experimentally identify, assuming that the leptophobic $B$ boson only decays to Standard Model particles. In contrast, the limits outside this mass window are less stringent and the corresponding $t$- and $u$-channel signatures may still be observable in the data, as it occurs with the nonresonant Standard Model $\rho$, $\omega$ and $\varphi$ meson exchanges. In addition, we make use of experimental data from the ${\eta }^{\prime }\to {\pi }^0\gamma \gamma$ and ${\eta }^{\prime }\to \eta \gamma \gamma$ decays to explore larger $B$-boson masses. Our results are relevant for the $B$-boson search programs at existing and forthcoming light-meson facilities, such as KLOE(-II) and Jefferson Lab Eta Factory experiments.

15 pages, 12 figures, 1 table; v2 includes a discussion of the uncertainty of the Standard Model estimate and an improvement in the overall presentation

References in corpus (14)

• Search for a dark photon in e+e- collisions at BABAR
• Search for $A^{\prime }\to {\mu }^{+}{\mu }^{-}$ decays
• Search for light massive gauge bosons as an explanation of the $(g-2{)}_{\mu }$ anomaly at MAMI
• Neutron scattering and extra short range interactions
• New weakly-coupled forces hidden in low-energy QCD
• Leptophobic Dark Matter at Neutrino Factories
• Hidden GeV-scale interactions of quarks
• Precision tests of fundamental physics with $\eta$ and ${\eta }^{\prime }$ mesons
• A new measurement of the rare decay eta -> pi^0 gamma gamma with the Crystal Ball/TAPS detectors at the Mainz Microtron
• Theoretical analysis of the $\gamma \gamma \to {\pi }^0\eta$ process
• $\eta \to {\pi }^0\gamma \gamma$ decay within a chiral unitary approach revisited
• Scalar and vector meson exchange in V->P0P0gamma decays
• A theoretical analysis of the semileptonic decays ${\eta }^{(\prime )}\to {\pi }^0{l}^{+}{l}^{-}$ and ${\eta }^{\prime }\to \eta l^{+}{l}^{-}$
• Search for a dark vector gauge boson decaying to ${\pi }^{+}{\pi }^{-}$ using $\eta \to {\pi }^{+}{\pi }^{-}\gamma$ decays