<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

Upcoming space-based gravitational-wave detectors will be sensitive to millions and resolve tens of thousands of stellar-mass binary systems at mHz frequencies. The vast majority of these will be double white dwarfs in our Galaxy. The greatest part will remain unresolved, forming an incoherent stochastic foreground signal. Using state-of-the-art galactic models for the formation and evolution of binary white dwarfs and accurate LISA simulated signals, we introduce a test for foreground Gaussianity and stationarity, building on methods available for ground-based detectors. We explain the observed non-stationarity with a new analytical modulation induced by the LISA constellation motion and the intrinsic anisotropy of the source distribution. By demodulating the foreground signal, we reveal a deviation from Gaussianity in the 2–10 mHz frequency band. Our finding is crucial to design faithful data models: the proposed method serves as a diagnostic and estimation tool to flag and model deviations, respectively. Neglecting them would introduce systematic biases on individual sources and astrophysical foregrounds parameter estimation, ultimately leading to inaccurate interpretation of the LISA data.

Italy

United Kingdom

Riccardo Buscicchio

Antoine Klein

Germany

Valeriya Korol

France

Francesco Renzo

Christopher Moore

Davide Gerosa

Alessandro Carzaniga

Test for LISA foreground Gaussianity and stationarity: galactic white-dwarf binaries

<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

The production of three Higgs bosons could be a stretch goal for the LHC and a strategic case for future colliders. In this work, we analyse the phenomenological prospects of (neutral) triple Higgs compared to di-Higgs boson production, for a range of Higgs-sector extensions from a strong first-order electroweak phase transition perspective. In parallel, we include constraints from existing exotics and Higgs boson measurements that further limit the parameter space of such models. Resonance contributions offer large modifications in particular for triple Higgs production, albeit starting from a small SM expectation. With enhancements of order 40 over the SM, however, experimental efforts to obtain limits at the HL-LHC are well motivated and well placed. This is further highlighted by the potential of these processes to inform the investigation of the thermal history of our Universe.

Lisa Biermann

Christoph Borschensky

Christoph Englert

Margarete Mühlleitner

Wrishik Naskar

Double and triple Higgs boson production to probe the electroweak phase transition

The Higgs potentials of extended Higgs sectors exhibit a complex and interesting vacuum structure. When travelling back in time, i.e. going to higher temperatures, the structure may change and exhibit interesting phase patterns and sequences of phases related to the respective minima of the potential. The investigation of the vacuum structure can give us indirect insights in beyond-Standard-Model physics and the evolution of the Universe. In this paper, we investigate the possibility of an intermediate charge-breaking (CB) phase in the 2-Higgs-Doublet Model (2HDM) type I. The existence has been reported previously by using a simple potential setup. We here confirm that the intermediate CB phase can still exist when using the one-loop corrected effective potential including thermal masses. We discuss its features and the relation with SU(2) symmetry (non-)restoration as well as its consistency with the current experimental data. Lastly, we show for some selected benchmark points the rich and interesting phase patterns and sequences that the 2HDM can undergo during its evolution from the early Universe to today’s electroweak vacuum.

Japan

Mayumi Aoki

Igor Ivanov

Hiroto Shibuya

Intermediate charge-breaking phases and symmetry non-restoration in the 2-Higgs-Doublet Model

The top quark as the heaviest particle in the Standard Model (SM) defines an important mass scale for Higgs physics and the electroweak scale itself. It is therefore a well-motivated degree of freedom which could reveal the presence of new interactions beyond the SM. Correlating modifications of the top-Higgs interactions in the 2-Higgs-Doublet Model (2HDM), we analyse effective field theory deformations of these interactions from the point of view of a strong first-order electroweak phase transition (SFOEWPT). We show that such modifications are compatible with current Higgs data and that an SFOEWPT can be tantamount to a current overestimate of exotic Higgs searches’ sensitivity at the LHC in   <math> <mi>t</mi> <mover> <mi>t</mi> <mo>¯</mo> </mover> </math>  $$ t\overline{t} $$  and four top quark final states. We argue that these searches remain robust from the point of accidental signal-background interference so that the current experimental strategy might well lead to 2HDM-like discoveries in the near future.

 Anisha

Duarte Azevedo

Effective 2HDM Yukawa interactions and a strong first-order electroweak phase transition

We note the possibility to perform a parametrically improved search for gauged baryon (B) and baryon minus lepton (<math><mi>B</mi><mo>−</mo><mi>L</mi></math>) Dark Photon Dark Matter (DPDM) using auxiliary channel data from LISA Pathfinder. In particular we use the measurement of the differential movement between the test masses (TMs) and the space craft (SC) which is nearly as sensitive as the tracking between the two TMs. TMs and SC are made from different materials and therefore have different charge-to-mass ratios for both <math><mi>B</mi><mo>−</mo><mi>L</mi></math> and B. Thus, the surrounding DPDM field induces a relative acceleration of nearly constant frequency. For the case of <math><mi>B</mi><mo>−</mo><mi>L</mi></math>, we find that LISA Pathfinder can constrain previously unexplored parameter space, providing the world leading limits in the mass range <math><mn>4</mn><mo>⋅</mo><msup><mrow><mn>10</mn></mrow><mrow><mo>−</mo><mn>19</mn></mrow></msup><mspace width="0.25em"></mspace><mtext>eV</mtext><mo>&lt;</mo><mi>m</mi><mo>&lt;</mo><mn>3</mn><mo>⋅</mo><msup><mrow><mn>10</mn></mrow><mrow><mo>−</mo><mn>17</mn></mrow></msup><mspace width="0.25em"></mspace><mtext>eV</mtext></math>. This limit can easily be recast also for dark photons that arise from gauging other global symmetries of the SM.

Jonas Frerick

Joerg Jaeckel

Felix Kahlhoefer

Kai Schmidt-Hoberg

Riding the dark matter wave: Novel limits on general dark photons from LISA Pathfinder

As one of the detection targets of all gravitational wave detectors today, the stochastic gravitational wave background (SGWB) provides an important means of understanding the evolution of our universe. In this paper, we explore the feasibility of detecting the SGWB generated by the loops arising throughout the cosmological evolution of the cosmic string network, using both individual space detectors (LISA and TAIJI) and joint space detectors (LISA-TAIJI). For the joint detectors, we choose three different configurations of TAIJI, namely TAIJIm, TAIJIp, and TAIJIc, to form the LISA-TAIJI networks, and we investigate their ability to detect the SGWB. By comparing the power-law sensitivity (PLS) curves of individual space detectors and joint detectors with the energy density spectrum of SGWB, we find that LISA-TAIJIc has the best sensitivity for detecting the SGWB from cosmic string loops. It thus holds promise for further constraining the tension of cosmic strings  $$G\mu =O(10^{-17})$$  <math> <mrow> <mi>G</mi> <mi>μ</mi> <mo>=</mo> <mi>O</mi> <mo>(</mo> <msup> <mn>10</mn> <mrow> <mo>-</mo> <mn>17</mn> </mrow> </msup> <mo>)</mo> </mrow> </math>  .

Bo-Rui Wang

Jin Li

He Wang

Probing the gravitational wave background from cosmic strings with the alternative LISA-TAIJI network

In this paper, we investigate the possibility of a strong first-order electroweak phase transition (SFOEWPT) in the model ‘CP in the Dark’. The Higgs sector of the model consists of two scalar doublets and one scalar singlet with a specific discrete symmetry. After spontaneous symmetry breaking the model has a Standard-Model-like phenomenology and a hidden scalar sector with a viable Dark Matter candidate supplemented by explicit CP violation that solely occurs in the hidden sector. The model ‘CP in the Dark’ has been implemented in the C++ code BSMPT v2.3 which performs a global minimisation of the finite-temperature one-loop corrected effective potential and searches for SFOEWPTs. An SFOEWPT is found to be allowed in a broad range of the parameter space. Furthermore, there are parameter scenarios where spontaneous CP violation is generated at finite temperature. The in addition spontaneously broken  $${\mathbb {Z}}_2$$  <math> <msub> <mi>Z</mi> <mn>2</mn> </msub> </math>   symmetry then leads to mixing between the dark and the visible sector so that CP violation in the dark is promoted at finite temperature to the visible sector and thereby provides additional sources of CP violation that are not restricted by the electric dipole moment measurements at zero temperature. Thus, ‘CP in the Dark’ provides a promising candidate for the generation of the baryon asymmetry of the universe through electroweak baryogenesis.

Jonas Müller

Electroweak phase transition in a dark sector with CP violation

Recently we presented the upgrade of our code BSMPT for the calculation of the electroweak phase transition (EWPT) to BSMPT v2 which now includes the computation of the baryon asymmetry of the universe (BAU) in the CP-violating 2-Higgs-Doublet Model (C2HDM). In this paper we use BSMPT v2 to investigate the size of the BAU that is obtained in the C2HDM with the two implemented approaches FH and VIA to derive the transport equations, by taking into account all relevant theoretical and experimental constraints. We identify similarities and differences in the results computed with the two methods. In particular, we analyse the dependence of the obtained BAU on the parameters relevant for successful baryogenesis. Our investigations allow us to pinpoint future directions for improvements both in the computation of the BAU and in possible avenues taken for model building. Recently, it was argued that the source term in the VIA method vanishes at leading order which would have consequences for the derived BAU in this method.

Philipp Basler

Electroweak baryogenesis in the CP-violating two-Higgs doublet model