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Long-lived Light Mediators in a Higgs Portal Model at the FCC-ee

Biplob Bhattacherjee, Camellia Bose, Herbi K. Dreiner, Nivedita Ghosh, Shigeki Matsumoto, Rhitaja Sengupta

Abstract

In the search for beyond the Standard Model (SM) physics, long-lived particles (LLPs) have emerged as potential candidates and are being explored in various ongoing experiments. Future lepton colliders, such as the FCC-ee, shall provide an excellent opportunity to probe LLPs, owing to their clean environment and improved particle identification. This study investigates the potential of the proposed \textbf{I}nnovative \textbf{D}etector for an \textbf{E}lectron-Positron \textbf{A}ccelerator (IDEA) detector at FCC-ee in the detection of LLPs produced from $B$-meson and Higgs boson decays. We explore benchmark scenarios for different final states resulting from LLP decays, including a detailed analysis of the SM long-lived hadronic background. Additionally, we propose dedicated LLP detectors with different configurations, dimensions, and locations with respect to the IDEA detector. DELIGHT B, originally proposed as a dedicated LLP detector for the FCC-hh, stands out as the detector with the maximum efficiency for detecting LLPs produced at FCC-ee. We find that cylindrical detector configurations, if feasible to construct around the IDEA detector, would also enhance sensitivity for LLPs mostly decaying outside it.

Long-lived Light Mediators in a Higgs Portal Model at the FCC-ee

Abstract

In the search for beyond the Standard Model (SM) physics, long-lived particles (LLPs) have emerged as potential candidates and are being explored in various ongoing experiments. Future lepton colliders, such as the FCC-ee, shall provide an excellent opportunity to probe LLPs, owing to their clean environment and improved particle identification. This study investigates the potential of the proposed \textbf{I}nnovative \textbf{D}etector for an \textbf{E}lectron-Positron \textbf{A}ccelerator (IDEA) detector at FCC-ee in the detection of LLPs produced from -meson and Higgs boson decays. We explore benchmark scenarios for different final states resulting from LLP decays, including a detailed analysis of the SM long-lived hadronic background. Additionally, we propose dedicated LLP detectors with different configurations, dimensions, and locations with respect to the IDEA detector. DELIGHT B, originally proposed as a dedicated LLP detector for the FCC-hh, stands out as the detector with the maximum efficiency for detecting LLPs produced at FCC-ee. We find that cylindrical detector configurations, if feasible to construct around the IDEA detector, would also enhance sensitivity for LLPs mostly decaying outside it.

Paper Structure

This paper contains 22 sections, 8 equations, 51 figures, 35 tables.

Table of Contents

  1. Introduction
  2. Scalar LLPs in the Higgs portal
  3. Current status and benchmark choice
  4. Role of $e^+e^-$ Colliders in exploring the Benchmarks
  5. The IDEA Detector
  6. Backgrounds
  7. Analysis Strategy
  8. LLPs with Negligible Trilinear Coupling
  9. Analysis in the Di-muon Final State
  10. Analysis in the Di-pion and Di-kaon Final States
  11. Analysis in the $c\bar{c}$ Final State
  12. Summary for Case A
  13. Production via $Z\to Z^*\phi$
  14. LLPs with large Trilinear Coupling
  15. Analysis in the Di-pion and Di-kaon Final States
  16. ...and 7 more sections

Figures (51)

  • Figure 1: Variation of the $\sin^2\theta\times c\tau$ as a function of the dark Higgs boson mass in the minimal model.
  • Figure 2: Current status (in gray) and future projected sensitivities of proposed experiments (in dashed lines) for the dark Higgs boson model when produced from meson decays and the trilinear coupling is negligible. Benchmark points for the present study are marked with red stars.
  • Figure 3: Current status (in gray) and future projected sensitivities of proposed experiments (in dashed lines) for the dark Higgs boson model when produced from $h$ boson decays in the process, $h\rightarrow \phi\phi$. The gray triangles show the upper limit on the Br($h\to\phi\phi$) for two values of $c\tau$ from the CMS scouting dataset. Benchmark points for the present study are marked as red stars.
  • Figure 4: Fraction of LLP decays in % within each detector component for benchmarks in Case A$(left)$ and Case B$(right)$. The $x$-axis represents the radial direction $R$ of the IDEA detector.
  • Figure 5: Number of events as a function of the transverse decay length in the lab frame, $d_T$, for various SM long-lived mesons and baryons.
  • ...and 46 more figures