<p>Ultralight dark matter (ULDM) is an attractive candidate for cold dark matter, one of the main mysterious components of the Universe. Recent studies suggest that gravitational wave (GW) laser interferometers can also detect bosonic ULDM fields, which would produce monochromatic signals resembling those from GWs. Distinguishing between these potential origins therefore would be essential. In this work, we develop a method to address this challenge for space-based GW interferometers (such as LISA and Taiji) by utilizing the null-response channel (NRC) in interferometric combinations, a channel constructed to have zero response to a specific type of source from a given direction. We find that while the GW NRC remains blind to GWs from a specific direction, it still responds to ULDM, particularly at frequencies above the interferometer’s critical frequency. The ULDM NRC exhibits similar behavior. Based on these observations, we outline a test procedure to discriminate between signal origins. Our method provides a new diagnostic tool for analyzing monochromatic signals in space-based GW interferometers, potentially expanding the scientific scope of future missions.</p>

China

Heng-Tao Xu

Yue-Hui Yao

Yong Tang

Yue-Liang Wu

Distinguishing monochromatic signals in LISA and Taiji: Ultralight dark matter versus gravitational waves

<p>Axion or axionlike particles are one of the leading candidates for dark matter. Because of its tiny coupling with photons, axion dark matter in the background can induce distinct phase velocities for light with different parity, an effect known as birefringence. Here, we propose a modification to the polarization state of the interspacecraft laser link in Laser Interferometer Space Antenna (LISA)-like interferometers to make them sensitive to this birefringence effect. We discuss the prospects of using the Sagnac combinations to search for axion dark matter and derive the corresponding sensitivity. With this setup, we show that next-generation laser interferometers in space would have promising sensitivities on the axion-photon coupling with axion mass around <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><msup><mrow><mn>10</mn></mrow><mrow><mo>−</mo><mn>19</mn></mrow></msup><mo>−</mo><msup><mrow><mn>10</mn></mrow><mrow><mo>−</mo><mn>14</mn></mrow></msup><mtext> </mtext><mtext> </mtext><mi>eV</mi></mrow></math>.</p>

Tingyuan Jiang

Prospects for axion dark matter searches at LISA-like interferometers

Ultralight particles are theoretically well-motivated dark matter candidates. In the vicinity of the Solar System, these ultralight particles can be described as a superposition of plane waves, resulting in a stochastic field with sizable amplitude fluctuations on scales determined by the velocity dispersion of dark matter. In this work, we systematically investigate the sensitivity of space-based gravitational-wave interferometers to the stochastic ultralight dark matter field within the frequentist framework. We derive the projected sensitivity of a single detector using the time-delay interferometry. Our results show that space-based gravitational-wave interferometers have the potential to probe unconstrained regions in parameter space and improve the current limit on coupling strengths. Furthermore, we explore the sensitivity of a detector network and investigate the optimal configuration for ultralight dark matter detection. We introduce the overlap reduction function for ultralight dark matter, which quantifies the degree of correlation between the signals observed by different detectors. We find that the configuration, where the signals observed by two detectors are uncorrelated, is the optimal choice for ultralight dark matter detection due to a smaller chance of missing signals. This contrasts with the detection of stochastic gravitational-wave background, where the correlated configuration is preferred. Our results may provide useful insights for potential joint observations involving space-based gravitational-wave detectors like LISA and Taiji, as well as other ultralight dark matter detection networks operating in the coherence limit.

Probing stochastic ultralight dark matter with space-based gravitational-wave interferometers

Particle decays are always accompanied by the emission of graviton quanta of gravity through bremsstrahlung processes. However, the corresponding branching ratio is suppressed by the square of the ratio of particle's mass to the Planck scale. The resulting present abundance of gravitational waves (GWs), composed of gravitons, is analogously suppressed. We show that superheavy particles, as heavy as the Planck scale, can be naturally produced during the post-inflationary reheating stage in the early Universe and their decays yield dramatic amounts of GWs over broad frequency range. GW observations could hence directly probe Planck-scale physics, notoriously challenging to explore.

Wei-Yu Hu

Japan

Kazunori Nakayama

Volodymyr Takhistov

Gravitational wave probe of Planck-scale physics after inflation

Ultralight dark matter (ULDM) is one of the leading well-motivated dark matter candidates, predicted in many theories beyond the standard model of particle physics and cosmology. There has been increasing interest in searching for ULDM in physical and astronomical experiments, mostly assuming there are additional interactions other than gravity between ULDM and normal matter. Here we demonstrate that even if ULDM has only gravitational interaction, it shall induce gravitational perturbations in solar system that may be large enough to cause detectable signals in future gravitational-wave (GW) laser interferometers in space. We investigate the sensitivities of Michelson time-delay interferometer to ULDM of various spins, and show vector ULDM with mass <math><mi>m</mi><mo>≲</mo><msup><mn>10</mn><mrow><mo>−</mo><mn>18</mn></mrow></msup><mtext> </mtext><mtext> </mtext><mi>eV</mi></math> can be probed by space-based GW detectors aiming at <math><mi>μ</mi><mi>Hz</mi></math> frequencies. Our findings exhibit that GW detectors may directly probe ULDM in some mass ranges that otherwise are challenging to examine.

Jiang-Chuan Yu

Yan Cao

Detecting ultralight dark matter gravitationally with laser interferometers in space

We present the full next-to-leading order (NLO) prediction for the jet-gap-jet cross section at the LHC within the BFKL approach. We implement, for the first time, the NLO impact factors in the calculation of the cross section. We provide results for differential cross sections as a function of the difference in rapidity and azimuthal angle betwen the two jets and the second leading jet transverse momentum. The NLO corrections of the impact factors induce an overall reduction of the cross section with respect to the corresponding predictions with only LO impact factors.

Italy

Dimitri Colferai

United States

Federico Deganutti

Timothy Raben

Christophe Royon

First computation of Mueller Tang processes using a full NLL BFKL approach

We examine contributions to the muon dipole moment g − 2 from a 3-form field Ω, which naturally arises from many fundamental theories, such as the string theory and the hyperunified field theory. In particular, by calculating the one-loop Feynman diagram, we have obtained the leading-order Ω-induced contribution to the muon g − 2, which is found to be finite. Then we investigate the theoretical constraints from perturbativity and unitarity. Especially, the unitarity bounds are yielded by computing the tree-level μ + μ  −  scattering amplitudes of various initial and final helicity configurations. As a result, despite the strong unitarity bounds imposed on this model of Ω, we have still found a substantial parameter space which can accommodates the muon g − 2 data.

Da Huang

Contributions to the muon g − 2 from a three-form field

Dark matter and inflation are two key elements to understand the origin of cosmic structures in modern cosmology, and yet their exact physical models remain largely uncertain. The Weyl scaling invariant theory of gravity may provide a feasible scheme to solve these two puzzles jointly, which contains a massive gauge boson playing the role of dark matter candidate and allows the quadratic scalar curvature term, namely <math><msup><mi>R</mi><mn>2</mn></msup></math>, to realize a viable inflationary mechanism in agreement with current observations. We ponder on the production of dark matter in the Weyl <math><msup><mi>R</mi><mn>2</mn></msup></math> model, including the contribution from the nonperturbative production due to the quantum fluctuations from inflationary vacuum and perturbative ones from scattering. We demonstrate that there are generally three parameter regions for viable dark matter production: (1) If the reheating temperature is larger than <math><msup><mn>10</mn><mn>3</mn></msup><mtext> </mtext><mtext> </mtext><mi>GeV</mi></math>, then the Weyl gauge boson as dark matter can be produced abundantly with mass larger than the inflation scale <math><mo>∼</mo><msup><mn>10</mn><mn>13</mn></msup><mtext> </mtext><mtext> </mtext><mi>GeV</mi></math>. (2) Small mass region with <math><mn>3</mn><mo>×</mo><msup><mn>10</mn><mrow><mo>−</mo><mn>13</mn></mrow></msup><mtext> </mtext><mtext> </mtext><mi>GeV</mi></math> for a higher reheating temperature. (3) Annihilation channel becomes important in the case of higher reheating temperature, which enables the Weyl gauge boson with a mass up to <math><mn>4</mn><mo>×</mo><msup><mn>10</mn><mn>16</mn></msup><mtext> </mtext><mtext> </mtext><mi>GeV</mi></math> to be produced through freeze-in.

Qing-Yang Wang

Dark matter production in Weyl <math><msup><mi>R</mi><mn>2</mn></msup></math> inflation

The recently reported result from XENON1T experiment indicates that there is an excess with 3.5σ significance in the electronic recoil events. Interpreted as new physics, new sources are needed to account for the electronic scattering. We show that a dark fermion ψ with mass about <math><mi>O</mi><mrow><mo>(</mo><mn>10</mn><mo>)</mo></mrow></math> MeV from semi-annihilation of <math><msub><mrow><mi>Z</mi></mrow><mrow><mn>3</mn></mrow></msub></math> dark matter X and subsequent decay of a dark gauge boson <math><msub><mrow><mi>V</mi></mrow><mrow><mi>μ</mi></mrow></msub></math> may be responsible for the excess. The relevant semi-annihilation process is <math><mi>X</mi><mo>+</mo><mi>X</mi><mo>→</mo><mover><mrow><mi>X</mi></mrow><mo>‾</mo></mover><mo>+</mo><msub><mrow><mi>V</mi></mrow><mrow><mi>μ</mi></mrow></msub><mo>(</mo><mo>→</mo><mi>ψ</mi><mo>+</mo><mover><mrow><mi>ψ</mi></mrow><mo>‾</mo></mover><mo>)</mo></math>, in which the final ψ has a box-shape energy spectrum. The fast-moving ψ can scatter with electron through an additional gauge boson that mixes with photon kinetically. The shape of the signals in this model can be consistent with the observed excess. The additional interaction with proton makes this model testable in future searches for nucleus recoil as well. Because of the lightness of invisible particle introduced, this scenario requires non-standard cosmology to accommodate the additional radiation component.

South Korea

P. Ko

Semi-annihilating dark matter for XENON1T excess

Recently, the XENON1T experiment has reported an excess in the electronic recoil events. The excess is consistent with the interpretation of absorption of 3 keV bosonic dark matter, for example, hidden photon dark matter with kinetic mixing of the order of <math><msup><mrow><mn>10</mn></mrow><mrow><mo>−</mo><mn>15</mn></mrow></msup></math>. We point out that the minimally gravitational production provides a viable mechanism for obtaining a correct relic hidden photon abundance. We present parameter dependence of the hidden photon dark matter abundance on the inflationary scale <math><msub><mrow><mi>H</mi></mrow><mrow><mi>inf</mi></mrow></msub></math> and also the reheating temperature <math><msub><mrow><mi>T</mi></mrow><mrow><mi>R</mi></mrow></msub></math>. We show that the inflationary Hubble scale and reheating temperature are both bounded from below, <math><msub><mrow><mi>H</mi></mrow><mrow><mtext>inf</mtext></mrow></msub><mo>≳</mo><mn>7</mn><mo>×</mo><msup><mrow><mn>10</mn></mrow><mrow><mn>11</mn></mrow></msup><mtext> GeV</mtext><mo>,</mo><mspace width="0.25em"></mspace><msub><mrow><mi>T</mi></mrow><mrow><mi>R</mi></mrow></msub><mo>≳</mo><msup><mrow><mn>10</mn></mrow><mrow><mn>2</mn></mrow></msup><mtext> GeV</mtext></math>. In particular, the high-scale inflation is consistent with 3 keV hidden photon dark matter.