Constraining ultralight scalar dark matter couplings with the European Pulsar Timing Array second data release

TL;DR

This paper uses European Pulsar Timing Array data to set new limits on ultralight scalar dark matter couplings, improving constraints over previous PTA and atomic clock experiments by analyzing both gravitational and direct coupling effects.

Contribution

It provides the first combined constraints on ULDM couplings considering both gravitational and direct effects using PTA data.

Findings

EPTA data constrains ULDM coupling coefficients more tightly than previous PTA results.

Constraints are comparable or tighter than those from atomic clock experiments.

ULDM in the specified mass range cannot account for all dark matter based on these constraints.

Abstract

Pulsar Timing Arrays (PTAs) offer an independent method for searching for ultralight dark matter (ULDM), whose wavelike nature induces periodic oscillations in the arrival times of radio pulses. In addition to this gravitational effect, the direct coupling between ULDM and ordinary matter results in pulsar spin fluctuations and reference clock shifts, leading to observable effects in PTAs. The second data release from the European PTA (EPTA) indicates that ULDM cannot account for all dark matter in the mass range $m_{\phi} \in [10^{-24.0}, 10^{-23.3}] \text{ eV}$ based solely on gravitational effects. In this work, we derive constraints on the coupling coefficients by considering both gravitational and coupling effects. Our results demonstrate that EPTA provides stronger constraints on these couplings than previous PTA experiments, and it establishes similar or even tighter constraints compared to other precise experiments, such as atomic clock experiments.