Probing a Secluded U(1) at B-factories

Abstract

A secluded U(1) gauge field, kinetically mixed with Standard Model hypercharge, provides a `portal' mediating interactions with a hidden sector at the renormalizable level, as recently exploited in the context of WIMP dark matter. The secluded U(1) symmetry-breaking scale may naturally be suppressed relative to the weak scale, and so this sector is efficiently probed by medium energy electron-positron colliders. We study the collider signatures of the minimal secluded U(1) model, focusing on the reach of B-factory experiments such as BaBar and BELLE. In particular, we show that Higgs-strahlung in the secluded sector can lead to multi-lepton signatures which probe the natural range for the kinetic mixing angle of 10^(-2)-10^(-3) over a large portion of the kinematically accessible parameter space.

Figures (3)

• Figure 1: Total width $\Gamma_{V}$ (GeV) and branching ratios for $V$: $V\rightarrow e^+ e^-$ (dashed), $V\rightarrow \mu^+ \mu^-$ (dotted), and $V\rightarrow \tau^+ \tau^-$ (dot-dashed), and $V\rightarrow {\rm hadrons}$ (solid) for the choice of $\kappa=10^{-2}$ and $\alpha'=\alpha$.
• Figure 2: Total width $\Gamma_{h'}$ (GeV) and branching ratios for $h'$ for the case $m_V=2$ GeV: $h'\rightarrow e^+ e^-$ (dashed), $h'\rightarrow \mu^+ \mu^-$ (dotted), $h'\rightarrow \tau^+ \tau^-$ (dot-dashed), and $h'\rightarrow V V$ (solid) for the choice of $\kappa=10^{-2}$ and $\alpha'=\alpha$. On the left panel, the vertical line delineates the boundary separating two- and four-particle final states, while the grey band defines the mass range where the decay distance varies from 1 mm to 1 m leading to displaced vertices in the detector.
• Figure 3: Sensitivity of the $B$-factory experiments for $\kappa = 10^{-2}$ (left) and $\kappa = 10^{-3}$ (right), with $\alpha'=\alpha$. The discovery modes are $l^+l^-$ plus missing energy (light), $6e$ (medium), and $6\mu$ (dark). In the region $m_{h'} > 2 m_V \, (m_{h'} > m_V)$, above the dotted (dashed) line the signal contains $3\,(2)$ leptons pairs with invariant mass $m_{l^+l^-}\simeq m_V$.