Searching for leptophilic composite asymmetric dark sector at $e^+e^-$ colliders

Abstract

Composite asymmetric dark matter (ADM) models provide a well-motivated paradigm that simultaneously explains dark matter (DM) relic density and matter-antimatter asymmetry. In these models, the mass of the DM candidate (the lightest dark baryon) is generated through the dark confinement scale dynamics. Although the leptophilic composite ADM model offers a viable framework, comprehensive studies of its collider phenomenology are absent. This work systematically explores novel signatures from the leptophilic composite asymmetric dark sector at both low-energy and high-energy $e^+e^-$ colliders as well as other existing collider constraints. We demonstrate detectability of TeV-scale mediators along with sub-GeV to GeV-scale lightest dark mesons at Belle II and its proposed far detector, GAZELLE, as well as Circular Electron Positron Collider/Future Circular Collider-electron-positron experiments. Moreover, these experiments exhibit complementary coverage of the model parameter space.

Figures (12)

• Figure 1: Diagrams illustrating dark shower production evolving into invisible or emerging lepton jets. Left panel: $e^+ e^-$ annihilation via $t$-channel mediator $X$ producing a dark quark pair ($q_d\overline{q_d}$). Right panel: $q\overline{q}$ annihilation yielding mediator pairs, where each mediator decays to a dark quark and a SM lepton.
• Figure 2: The dark pion proper decay length with respect to $m_{\pi_d}$. Here we fixed the parameters $\kappa = 1.0$, $f_{\pi_d} = m_{\pi_d}$, and $m_X = 1$ TeV.
• Figure 3: Exclusion region for dark pion masses $10\text{ MeV}\leq m_{\pi_d} < 2m_\mu$. The red dashed line separates long-lived (below) and prompt (above) $X^\pm$ decays. The blue and black dashed lines indicate where all $\pi_d$ particles escape detection at the LHC and LEP, respectively. The blue and black shaded regions correspond to slepton search constraints (LHC) ATLAS:2019lff and monophoton search constraints (LEP) Fox:2011fxLiu:2019ogn. The green region represents the parameter space where the proper lifetime of $\pi_d$ exceeds one second, conservatively evaluated at $m_{\pi_d} = 0.2\text{ GeV}$.
• Figure 4: Exclusion region for dark pion masses $2m_\mu < m_{\pi_d} < 2m_\tau$. The blue dashed line indicates where all $\pi_d$ particles escape detection at the LHC, making this region subject to slepton search constraints. The red dashed line retains the same interpretation as in Fig. \ref{['fig:light']}. The green region represents the parameter space where the proper lifetime of $\pi_d$ exceeds one second, conservatively evaluated at $m_{\pi_d} = 3\text{ GeV}$.
• Figure 5: Kinematic distributions for the signal benchmark points BP2 and BP3 at the BaBar. The distributions of the leading $p_T$ and subleading $p_T$ dark pions and their daughter muons are represented by solid and dashed lines, respectively. Top left: transverse momentum $p_T$ of muons from dark pion decays. Top right: invariant mass $m_{\mu^+\mu^-}$ of muon pairs. Bottom left: transverse decay distance $R_{xy}$ of dark pions. Bottom-right: track impact parameter significance $d_0/\sigma_0$.