ARC Centre of Excellence for Dark Matter Particle Physics

The dark photon is a massive hypothetical particle that interacts with the Standard Model by kinetically mixing with the visible photon. For small values of the mixing parameter, dark photons can evade cosmological bounds to be a viable dark matter candidate. Due to the similarities with the electromagnetic signals generated by axions, several bounds on dark photon signals are simply reinterpretations of historical bounds set by axion haloscopes. However, the dark photon has a property that the axion does not: an intrinsic polarization. Due to the rotation of the Earth, accurately accounting for this polarization is nontrivial, highly experiment dependent, and depends upon assumptions about the dark photon's production mechanism. We show that if one does account for the dark photon polarization, and the rotation of the Earth, an experiment's discovery reach can be enhanced by over an order of magnitude. We detail the strategies that would need to be taken to properly optimize a dark photon search. These include judiciously choosing the location and orientation of the experiment, as well as strategically timing any repeated measurements. Experiments located at $\ifmmode\pm\else\textpm\fi{}35\ifmmode^\circ\else\textdegree\fi{}$ or $\ifmmode\pm\else\textpm\fi{}55\ifmmode^\circ\else\textdegree\fi{}$ latitude, making three observations at different times of the sidereal day, can achieve a sensitivity that is fully optimized and insensitive to the dark photon's polarization state, and hence its production mechanism. We also point out that several well-known searches for axions employ techniques for testing signals that preclude their ability to set exclusion limits on dark photons, and hence should not be reinterpreted as such.

High energy collisions at the High-Luminosity Large Hadron Collider (LHC) produce a large number of particles along the beam collision axis, outside of the acceptance of existing LHC experiments. The proposed Forward Physics Facility (FPF), to be located several hundred meters from the ATLAS interaction point and shielded by concrete and rock, will host a suite of experiments to probe standard model (SM) processes and search for physics beyond the standard model (BSM). In this report, we review the status of the civil engineering plans and the experiments to explore the diverse physics signals that can be uniquely probed in the forward region. FPF experiments will be sensitive to a broad range of BSM physics through searches for new particle scattering or decay signatures and deviations from SM expectations in high statistics analyses with TeV neutrinos in this low-background environment. High statistics neutrino detection will also provide valuable data for fundamental topics in perturbative and non-perturbative QCD and in weak interactions. Experiments at the FPF will enable synergies between forward particle production at the LHC and astroparticle physics to be exploited. We report here on these physics topics, on infrastructure, detector, and simulation studies, and on future directions to realize the FPF’s physics potential.

The neutrino floor is a theoretical lower limit on WIMP-like dark matter models that are discoverable in direct detection experiments. It is commonly interpreted as the point at which dark matter signals become hidden underneath a remarkably similar-looking background from neutrinos. However, it has been known for some time that the neutrino floor is not a hard limit, but can be pushed past with sufficient statistics. As a consequence, some have recently advocated for calling it the "neutrino fog" instead. The downside of current methods of deriving the neutrino floor are that they rely on arbitrary choices of experimental exposure and energy threshold. Here we propose to define the neutrino floor as the boundary of the neutrino fog, and develop a calculation free from these assumptions. The technique is based on the derivative of a hypothetical experimental discovery limit as a function of exposure, and leads to a neutrino floor that is only influenced by the systematic uncertainties on the neutrino flux normalizations. Our floor is broadly similar to those found in the literature, but differs by almost an order of magnitude in the sub-GeV range, and above 20 GeV.

Abstract The nature of dark matter and properties of neutrinos are among the most pressing issues in contemporary particle physics. The dual-phase xenon time-projection chamber is the leading technology to cover the available parameter space for weakly interacting massive particles, while featuring extensive sensitivity to many alternative dark matter candidates. These detectors can also study neutrinos through neutrinoless double-beta decay and through a variety of astrophysical sources. A next-generation xenon-based detector will therefore be a true multi-purpose observatory to significantly advance particle physics, nuclear physics, astrophysics, solar physics, and cosmology. This review article presents the science cases for such a detector.

Neutron stars provide a cosmic laboratory to study the nature of dark matter particles and their interactions. Dark matter can be captured by neutron stars via scattering, where kinetic energy is transferred to the star. This can have a number of observational consequences, such as the heating of old neutron stars to infra-red temperatures. Previous treatments of the capture process have employed various approximation or simplifications. We present here an improved treatment of dark matter capture, valid for a wide dark matter mass range, that correctly incorporates all relevant physical effects. These include gravitational focusing, a fully relativistic scattering treatment, Pauli blocking, neutron star opacity and multi-scattering effects. We provide general expressions that enable the exact capture rate to be calculated numerically, and derive simplified expressions that are valid for particular interaction types or mass regimes and that greatly increase the computational efficiency. Our formalism is applicable to the scattering of dark matter from any neutron star constituents, or to the capture of dark matter in other compact objects.

The standard model axion seesaw Higgs portal inflation (SMASH) model is a well-motivated, self-contained description of particle physics that predicts axion dark matter particles to exist within the mass range of 50 to 200 micro–electron volts. Scanning these masses requires an axion haloscope to operate under a constant magnetic field between 12 and 48 gigahertz. The ORGAN (Oscillating Resonant Group AxioN) experiment (in Perth, Australia) is a microwave cavity axion haloscope that aims to search the majority of the mass range predicted by the SMASH model. Our initial phase 1a scan sets an upper limit on the coupling of axions to two photons of ∣ g aγγ ∣ ≤ 3 × 10 −12 per giga–electron volts over the mass range of 63.2 to 67.1 micro–electron volts with 95% confidence interval. This highly sensitive result is sufficient to exclude the well-motivated axion-like particle cogenesis model for dark matter in the searched region.

We outline two important effects that are missing from most evaluations of the dark matter capture rate in neutron stars. As dark matter scattering with nucleons in the star involves large momentum transfer, nucleon structure must be taken into account via a momentum dependence of the hadronic form factors. In addition, due to the high density of neutron star matter, we should account for nucleon interactions rather than modeling the nucleons as an ideal Fermi gas. Properly incorporating these effects is found to suppress the dark matter capture rate by up to 3 orders of magnitude for the heaviest stars.

We study the discovery potential of the non-Standard Model (SM) heavy Higgs bosons in the Two-Higgs-Doublet Models (2HDMs) at a multi-TeV muon collider and explore the discrimination power among different types of 2HDMs. We find that the pair production of the non-SM Higgs bosons via the universal gauge interactions is the dominant mechanism once above the kinematic threshold. Single Higgs boson production associated with a pair of heavy fermions could be important in the parameter region with enhanced Yukawa couplings. For both signal final states, ${\ensuremath{\mu}}^{+}{\ensuremath{\mu}}^{\ensuremath{-}}$ annihilation channels dominate over the vector boson fusion (VBF) processes, except at high center of mass energies where the VBF processes receive large logarithmic enhancement with the increase of energies. Single Higgs boson $s$-channel production in ${\ensuremath{\mu}}^{+}{\ensuremath{\mu}}^{\ensuremath{-}}$-annihilation via the radiative return can also be important for the Type-L 2HDM in the very large $\mathrm{tan}\ensuremath{\beta}$ region, extending the kinematic reach of the heavy Higgs boson mass to the collider energy. Considering both the production and decay of non-SM Higgs bosons, signals can be identified over the Standard Model backgrounds. With the pair production channels via annihilation, 95% C.L. exclusion reaches in the Higgs mass up to the production mass threshold of $\sqrt{s}/2$ are possible when channels with different final states are combined. Including single production modes can extended the reach further. Different types of 2HDMs can be distinguishable for moderate and large values of $\mathrm{tan}\ensuremath{\beta}$.

An ultra-thin indium tin oxide interlayer design was developed for interfacing perovskite solar cells with Si solar cells thereby minimising shunting effects for large area monolithic tandem devices.

This paper presents the specification, design, and development of the Visible Camera (VIS) on the European Space Agency’s Euclid mission. VIS is a large optical-band imager with a field of view of 0.54 deg 2 sampled at 0″.1 with an array of 609 Megapixels and a spatial resolution of 0″.18. It will be used to survey approximately 14 000 deg 2 of extragalactic sky to measure the distortion of galaxies in the redshift range z = 0.1–1.5 resulting from weak gravitational lensing, one of the two principal cosmology probes leveraged by Euclid . With photometric redshifts, the distribution of dark matter can be mapped in three dimensions, and the extent to which this has changed with look-back time can be used to constrain the nature of dark energy and theories of gravity. The entire VIS focal plane will be transmitted to provide the largest images of the Universe from space to date, specified to reach m AB ≥ 24.5 with a signal-to-noise ratio S/N ≥ 10 in a single broad I E ≃ ( r + i + z ) band over a six-year survey. The particularly challenging aspects of the instrument are the control and calibration of observational biases, which lead to stringent performance requirements and calibration regimes. With its combination of spatial resolution, calibration knowledge, depth, and area covering most of the extra-Galactic sky, VIS will also provide a legacy data set for many other fields. This paper discusses the rationale behind the conception of VIS and describes the instrument design and development, before reporting the prelaunch performance derived from ground calibrations and brief results from the inorbit commissioning. VIS should reach fainter than m AB = 25 with S/N ≥ 10 for galaxies with a full width at half maximum of 0″. 3 in a 1″.3 diameter aperture over the Wide Survey, and m AB ≥ 26.4 for a Deep Survey that will cover more than 50 deg 2 . The paper also describes how the instrument works with the Euclid telescope and survey, and with the science data processing, to extract the cosmological information.

Abstract Neutron stars harbour matter under extreme conditions, providing a unique testing ground for fundamental interactions. We recently developed an improved treatment of dark matter (DM) capture in neutron stars that properly incorporates many of the important physical effects, and outlined useful analytic approximations that are valid when the scattering amplitude is independent of the centre of mass energy. We now extend that analysis to all interaction types. We also discuss the effect of going beyond the zero-temperature approximation, which provides a boost to the capture rate of low mass dark matter, and give approximations for the dark matter up-scattering rate and evaporation mass. We apply these results to scattering of dark matter from leptonic targets, for which a correct relativistic description is essential. We find that the potential neutron star sensitivity to DM-lepton scattering cross sections greatly exceeds electron-recoil experiments, particularly in the sub-GeV regime, with a sensitivity to sub-MeV DM well beyond the reach of future terrestrial experiments.

We show that the excess in electron recoil events seen by the XENON1T experiment can be explained by a relatively low-mass luminous dark matter candidate. The dark matter scatters inelastically in the detector (or the surrounding rock) to produce a heavier dark state with a ∼2-3 keV mass splitting. This heavier state then decays within the detector, producing a peak in the electron recoil spectrum that is a good fit to the observed excess. We comment on the ability of future direct detection experiments to differentiate this model from other "beyond the standard model" scenarios and from possible tritium backgrounds, including the use of diurnal modulation, multichannel signals, etc., as possible distinguishing features of this scenario.

We present a way to search for light scalar dark matter (DM), seeking to exploit putative coupling between dark matter scalar fields and fundamental constants, by searching for frequency modulations in direct comparisons between frequency stable oscillators. Specifically we compare a cryogenic sapphire oscillator (CSO), hydrogen maser (HM) atomic oscillator, and a bulk acoustic wave quartz oscillator (OCXO). This work includes the first calculation of the dependence of acoustic oscillators on variations of the fundamental constants, and demonstration that they can be a sensitive tool for scalar DM experiments. Results are presented based on 16 days of data in comparisons between the HM and OCXO, and 2 days of comparison between the OCXO and CSO. No evidence of oscillating fundamental constants consistent with a coupling to scalar dark matter is found, and instead limits on the strength of these couplings as a function of the dark matter mass are determined. We constrain the dimensionless coupling constant ${d}_{e}$ and combination $|{d}_{{m}_{e}}\ensuremath{-}{d}_{g}|$ across the mass band $4.4\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}19}\ensuremath{\lesssim}{m}_{\ensuremath{\varphi}}\ensuremath{\lesssim}6.8\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}14}\text{ }\text{ }\mathrm{eV}\text{ }{c}^{\ensuremath{-}2}$, with most sensitive limits ${d}_{e}\ensuremath{\gtrsim}1.59\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}1}$, $|{d}_{{m}_{e}}\ensuremath{-}dg|\ensuremath{\gtrsim}6.97\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}1}$. Notably, these limits do not rely on maximum reach analysis (MRA), instead employing the more general coefficient separation technique. This experiment paves the way for future, highly sensitive experiments based on state-of-the-art acoustic oscillators, and we show that these limits can be competitive with the best current MRA-based exclusion limits.

This work describes the operation of a high frequency gravitational wave detector based on a cryogenic bulk acoustic wave cavity and reports observation of rare events during 153 days of operation over two separate experimental runs (run 1 and run 2). In both run 1 and run 2, two modes were simultaneously monitored. Across both runs, the third overtone of the fast shear mode (3B) operating at 5.506 MHz was monitored; whereas in run 1, the second mode was chosen to be the fifth overtone of the slow shear mode (5C) operating at 8.392 MHz. However, in run 2, the second mode was selected to be closer in frequency to the first mode; and it was chosen to be the third overtone of the slow shear mode (3C) operating at 4.993 MHz. Two strong events were observed as transients responding to energy deposition within acoustic modes of the cavity. The first event occurred during run 1 on 12 May 2019 (UTC), and it was observed in the 5.506 MHz mode; whereas the second mode at 8.392 MHz observed no event. During run 2, a second event occurred on 27 November 2019 (UTC) and was observed by both modes. Timings of the events were checked against available environmental observations as well as data from other detectors. Various possibilities explaining the origins of the events are discussed.

We show that XENON1T and future liquid xenon (LXe) direct detection experiments are sensitive to axions through the standard g_{aγ}aFF[over ˜] operators due to inverse-Primakoff scattering. This previously neglected channel significantly improves the sensitivity to the axion-photon coupling, with a reach extending to g_{aγ}∼10^{-10} GeV^{-1} for axion masses up to a keV, thereby extending into the region of heavier QCD axion models. This result modifies the couplings required to explain the XENON1T excess in terms of solar axions, opening a large region of g_{aγ}-m_{a} parameter space that is not ruled out by the CAST helioscope experiment and reducing the tension with the astrophysical constraints. We explore the sensitivity to solar axions for future generations of LXe detectors that can exceed future helioscope experiments, such as IAXO, for a large region of parameter space.

Abstract We present the Cosmic Evolution Early Release Science (CEERS) Survey, a 77.2 hr Director’s Discretionary Early Release Science Program. CEERS demonstrates, tests, and validates efficient extragalactic surveys using coordinated, overlapping parallel observations with the JWST instrument suite, including NIRCam and MIRI imaging, NIRSpec low- ( R ∼ 100) and medium- ( R ∼ 1000) resolution spectroscopy, and NIRCam slitless grism ( R ∼ 1500) spectroscopy. CEERS targets the Hubble Space Telescope–observed region of the Extended Groth Strip field, supported by a rich set of multiwavelength data. CEERS facilitated immediate community science in both of the extragalactic core JWST science drivers “First Light” and “Galaxy Assembly,” including: (1) the discovery and characterization of large samples of galaxies at z ≳ 10 from ∼90 arcmin 2 of NIRCam imaging, constraining their abundance and physical nature; (2) deep spectra of >1000 galaxies, including dozens of galaxies at 6 < z < 10, enabling redshift measurements and constraints on the physical conditions of star formation and black hole growth via line diagnostics; (3) quantifying the first bulge, bar, and disk structures at z > 3; and (4) characterizing galaxy mid-IR emission with MIRI to study dust-obscured star formation and supermassive black hole growth at z ∼ 1–3. As a legacy product for the community, the CEERS team has provided several data releases, accompanied by detailed notes on the data reduction procedures and notebooks to aid in reproducibility. In addition to an overview of the survey and the quality of the data, we provide science highlights from the first two years with CEERS data.

Searches for dark matter–induced recoils have made impressive advances in the last few years. Yet the field is confronted by several outstanding problems. First, the inevitable background of solar neutrinos will soon inhibit the conclusive identification of many dark matter models. Second, and more fundamentally, current experiments have no practical way of confirming a detected signal's Galactic origin. The concept of directional detection addresses both of these issues while offering opportunities to study novel dark matter– and neutrino-related physics. The concept remains experimentally challenging, but gas time projection chambers are an increasingly attractive option and, when properly configured, would allow directional measurements of both nuclear and electron recoils. In this review, we reassess the required detector performance and survey relevant technologies. Fortuitously, the highly segmented detectors required to achieve good directionality also enable several fundamental and applied physics measurements. We comment on near-term challenges and how the field could be advanced.

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Light nonrelativistic components of the galactic dark matter halo elude direct detection constraints because they lack the kinetic energy to create an observable recoil. However, cosmic rays can upscatter dark matter to significant energies, giving direct detection experiments access to previously unreachable regions of parameter space at very low dark matter mass. In this work we extend the cosmic-ray dark matter formalism to models of inelastic dark matter and show that previously inaccessible regions of the mass-splitting p arameter space can be probed. Conventional direct detection of nonrelativistic halo dark matter is limited to mass splittings of $\ensuremath{\delta}\ensuremath{\sim}10\text{ }\text{ }\mathrm{keV}$ and is highly mass dependent. We find that including the effect of cosmic-ray upscattering can extend the reach to mass splittings of $\ensuremath{\delta}\ensuremath{\sim}100\text{ }\text{ }\mathrm{MeV}$ and maintain that reach at much lower dark matter mass.

White dwarfs, the most abundant stellar remnants, provide a promising means of probing dark matter interactions, complimentary to terrestrial searches. The scattering of dark matter from stellar constituents leads to gravitational capture, with important observational consequences. In particular, white dwarf heating occurs due to the energy transfer in the dark matter capture and thermalisation processes, and the subsequent annihilation of captured dark matter. We consider the capture of dark matter by scattering on either the ion or the degenerate electron component of white dwarfs. For ions, we account for the stellar structure, the star opacity, realistic nuclear form factors that go beyond the simple Helm approach, and finite temperature effects pertinent to sub-GeV dark matter. Electrons are treated as relativistic, degenerate targets, with Pauli blocking, finite temperature and multiple scattering effects all taken into account. We also estimate the dark matter evaporation rate. The dark matter-nucleon/electron scattering cross sections can be constrained by comparing the heating rate due to dark matter capture with observations of cold white dwarfs in dark matter-rich environments. We apply this technique to observations of old white dwarfs in the globular cluster Messier 4, which we assume to be located in a DM subhalo. For dark matter-nucleon scattering, we find that white dwarfs can probe the sub-GeV mass range inaccessible to direct detection searches, with the low mass reach limited only by either evaporation or dominant DM annihilation to neutrinos, and can be competitive with direct detection in the 1–104 GeV range. White dwarf limits on dark matter-electron scattering are found to outperform current electron recoil experiments over the full mass range considered, and extend well beyond the ∼ 10 GeV mass regime where the sensitivity of electron recoil experiments is reduced.