[Paper Review] Hidden Photons in beam dump experiments and in connection with Dark Matter

Sarah Andreas|arXiv (Cornell University)|Dec 18, 2012

Dark Matter and Cosmic Phenomena3 citations

TL;DR

This paper presents new experimental limits on hidden photons from past electron beam dump experiments at KEK and Orsay, extending constraints in the MeV–GeV mass range. It further explores hidden sector models with a hidden photon and dark matter, showing that Dirac fermion dark matter can yield spin-independent scattering consistent with direct detection signals, while Majorana fermions exhibit spin-dependent interactions less constrained by current experiments.

ABSTRACT

Hidden sectors with light extra U(1) gauge bosons, so-called hidden photons, recently received much interest as natural feature of beyond standard model scenarios like string theory and SUSY and because of their possible connection to dark matter. This paper presents limits on hidden photons from past electron beam dump experiments including two new limits from experiments at KEK and Orsay. Additionally, various hidden sector models containing both a hidden photon and a dark matter candidate are discussed with respect to their viability and potential signatures in direct detection.

Motivation & Objective

• To derive updated experimental constraints on hidden photons from past electron beam dump experiments, including new limits from KEK and Orsay.
• To assess the viability of hidden sector models containing a hidden photon and a dark matter candidate in light of cosmological and astrophysical observations.
• To investigate the direct detection phenomenology of dark matter in models with a hidden photon, particularly focusing on spin-independent and spin-dependent scattering cross sections.
• To explore how supersymmetric hidden sector models with different symmetry-breaking mechanisms can yield viable dark matter candidates with observable signatures.
• To determine whether such models can reconcile the anomalous muon magnetic moment and direct detection signals like those reported by CoGeNT.

Proposed method

• Utilizes kinetic mixing between the hidden photon and the ordinary photon as the primary portal to the visible sector, parameterized by a small mixing parameter χ.
• Applies Monte Carlo simulations (e.g., MadGraph) to model hidden photon emission in electron beam dumps, accounting for energy loss and angular distribution.
• Estimates observable event rates using a cross-section formula involving beam energy, electron mass, and form factors, with suppression from exponential decay lengths.
• Incorporates detector acceptance and branching ratios (e.g., e⁺e⁻, μ⁺μ⁻) to compute detectable signal rates.
• Constructs a toy model and supersymmetric models with chiral superfields and a hidden U(1) gauge symmetry, analyzing relic density and direct detection via Higgs-portal and gauge-portal interactions.
• Performs parameter scans over DM mass and coupling parameter κ to identify regions consistent with correct relic abundance and direct detection constraints.

Experimental results

Research questions

• RQ1 What are the updated experimental limits on hidden photon mass and kinetic mixing from electron beam dump experiments at KEK and Orsay?
• RQ2 Can hidden sector models with a hidden photon and a dark matter candidate reproduce the correct relic abundance and explain direct detection signals like those from CoGeNT?
• RQ3 How do different mechanisms for hidden gauge symmetry breaking (Fayet-Iliopoulos term vs. radiative breaking) affect the dark matter phenomenology and direct detection cross sections?
• RQ4 What is the role of spin-independent vs. spin-dependent scattering in determining the viability of Dirac and Majorana fermion dark matter candidates?
• RQ5 To what extent can supersymmetric hidden sector models with gravity mediation provide viable dark matter candidates with observable signatures in direct detection?

Key findings

• New limits on the kinetic mixing parameter χ are established for hidden photons in the MeV–GeV mass range, based on data from KEK and Orsay beam dump experiments.
• A Dirac fermion dark matter candidate in a toy model achieves the correct relic abundance and exhibits spin-independent scattering cross sections consistent with the CoGeNT direct detection signal.
• In supersymmetric models with visible-sector-induced symmetry breaking, a Dirac fermion DM candidate also shows spin-independent scattering and can explain direct detection anomalies.
• Majorana fermion DM candidates, while having mostly spin-dependent scattering, remain viable and consistent with current direct detection limits, especially in radiatively broken hidden sectors.
• The Higgs-portal coupling enables spin-independent scattering for Majorana fermions, but cross sections are several orders of magnitude below current experimental limits.
• Scatter plots from parameter scans show that viable regions exist in the DM mass–coupling parameter space that satisfy relic density and direct detection constraints, particularly in models with gravity mediation.