We present DarkELF, a python package to calculate interaction rates of light dark matter in dielectric materials, including screening effects. The full response of the material is parametrized in the terms of the energy loss function (ELF) of material, which DarkELF converts into differential scattering rates for both direct dark matter electron scattering and through the Migdal effect. In addition, DarkELF can calculate the rate to produce phonons from sub-MeV dark matter scattering via the dark photon mediator, as well as the absorption rate for dark matter comprised of dark photons. The package includes precomputed ELFs for Al, <math><mrow><msub><mrow><mi>Al</mi></mrow><mrow><mn>2</mn></mrow></msub><msub><mrow><mi>O</mi></mrow><mrow><mn>3</mn></mrow></msub></mrow></math>, GaAs, GaN, Ge, Si, <math><msub><mi>SiO</mi><mn>2</mn></msub></math>, and ZnS, and allows the user to easily add their own ELF extractions for arbitrary materials.

CERN

Simon Knapen

United States

Jonathan Kozaczuk

Tongyan Lin

python Package for Dark Matter Scattering in Dielectric Targets

Effective field theory arguments suggest that if beyond the standard model (BSM) sectors contain new sources of <math><mrow><mi>C</mi><mi>P</mi></mrow></math> violation that couple to QCD, these sources will renormalize the <math><mi>θ</mi></math> term and frustrate ultraviolet solutions to the strong <math><mrow><mi>C</mi><mi>P</mi></mrow></math> problem. Simultaneously, they will generate distinctive patterns of low-energy electric dipole moments in hadronic, nuclear, atomic, and molecular systems. Observing such patterns thus provides evidence that strong <math><mrow><mi>C</mi><mi>P</mi></mrow></math> is solved by an infrared relaxation mechanism. We illustrate the renormalization of <math><mi>θ</mi></math> and the collections of electric dipole moments generated in several models of BSM physics, confirming effective field theory expectations, and demonstrate that measurements of ratios of electric dipole moments at planned experiments can provide valuable input on the resolution of the strong <math><mrow><mi>C</mi><mi>P</mi></mrow></math> problem.

Netherlands

Jordy de Vries

Patrick Draper

Kaori Fuyuto

Benjamin Lillard

Uncovering an axion mechanism with the EDM portfolio

When a nucleus in an atom undergoes a collision, there is a small probability of an electron being excited inelastically as a result of the Migdal effect. In this Letter, we present the first complete derivation of the Migdal effect from dark matter-nucleus scattering in semiconductors, which also accounts for multiphonon production. The rate of the Migdal effect can be expressed in terms of the energy loss function of the material, which we calculate with density functional theory methods. Because of the smaller gap for electron excitations, we find that the rate for the Migdal effect is much higher in semiconductors than in atomic targets. Accounting for the Migdal effect in semiconductors can therefore significantly improve the sensitivity of experiments such as DAMIC, SENSEI, and SuperCDMS to sub-GeV dark matter.

Migdal Effect in Semiconductors

A number of direct detection experiments are searching for electron excitations created by the scattering of sub-GeV dark matter. We present an alternate formulation of dark matter-electron scattering in terms of the dielectric response of a material. For dark matter which couples to electrons, this approach automatically accounts for in-medium screening effects, which were not included in previous rate calculations for semiconductor targets. We show that the screening effects appear for both scalar and vector mediators. The result is a non-negligible reduction of reach for direct detection experiments which use dielectric materials as targets. We also explore different determinations of the dielectric response, including first-principles density functional theory (DFT) calculations and a data-driven analytic approximation using a Mermin oscillator model.

Dark matter-electron scattering in dielectrics

A primary goal of a future e + e  −  collider program will be the precision measurement of Higgs boson properties. For practical reasons it is of interest to determine the minimal set of detector specifications required to reach this and other scientific goals. Here we investigate the precision obtainable for the e + e  −  → Zh → μ + μ  −  X inclusive cross section and the Higgs boson mass using the di-muon recoil method, considering a detector that has only an inner tracking system within a solenoidal magnetic field, surrounded by many nuclear interaction lengths of absorbing material, and an outer muon identification system. We find that the sensitivity achievable in these measurements with such a tracking detector is only marginally reduced compared to that expected for a general purpose detector with additional electromagnetic and hadronic calorimeter systems. The difference results mainly from multi-photon backgrounds that are not as easily rejected with tracking detectors. We also comment on the prospects for an analogous measurement of the e + e  −  → Zh → e + e  −  X inclusive cross section. Finally, we study searches for light scalars utilizing the di-muon recoil method, estimating the projected reach with a tracking or general purpose detector.

Scott Thomas

Precision inclusive Higgs physics at e + e  −  colliders with tracking detectors and without calorimetry

Light new physics weakly coupled to the Higgs can induce a strong first-order electroweak phase transition (EWPT). Here, we argue that scenarios in which the EWPT is driven first-order by a light scalar with mass between <math><mrow><mo>∼</mo><mn>10</mn><mtext> </mtext><mtext> </mtext><mi>GeV</mi><mo>−</mo><msub><mrow><mi>m</mi></mrow><mrow><mi>h</mi></mrow></msub><mo>/</mo><mn>2</mn></mrow></math> and small mixing with the Higgs will be conclusively probed by the high-luminosity LHC and future Higgs factories. Our arguments are based on analytic and numerical studies of the finite-temperature effective potential and provide a well-motivated target for exotic Higgs decay searches at the LHC and future lepton colliders.

China

Michael J. Ramsey-Musolf

Jessie Shelton

Exotic Higgs boson decays and the electroweak phase transition

We present a first calculation of the rate for plasmon production in semiconductors from nuclei recoiling against dark matter. The process is analogous to bremsstrahlung of transverse photon modes, but with a longitudinal plasmon mode emitted instead. For dark matter in the 10 MeV—1 GeV mass range, we find that the plasmon bremsstrahlung rate is 4–5 orders of magnitude smaller than that for elastic scattering, but 4–5 orders of magnitude larger than the transverse bremsstrahlung rate. Because the plasmon can decay into electronic excitations and has characteristic energy given by the plasma frequency <math><msub><mi>ω</mi><mi>p</mi></msub></math>, with <math><msub><mi>ω</mi><mi>p</mi></msub><mo>≈</mo><mn>16</mn><mtext> </mtext><mtext> </mtext><mi>eV</mi></math> in Si crystals, plasmon production provides a new signature and method to detect nuclear recoils from sub-GeV dark matter.

Plasmon production from dark matter scattering

We present the first end-to-end nonperturbative analysis of the gravitational wave power spectrum from a thermal first-order electroweak phase transition (EWPT), using the framework of dimensionally reduced effective field theory and preexisting nonperturbative simulation results. We are able to show that a first-order EWPT in any beyond the Standard Model (BSM) scenario that can be described by a Standard Model-like effective theory at long distances will produce gravitational wave signatures too weak to be observed at existing and planned detectors. This implies that colliders are likely to provide the best chance of exploring the phase structure of such theories, while transitions strong enough to be detected at gravitational wave experiments require either previously neglected higher-dimension operators or light BSM fields to be included in the dimensionally reduced effective theory and therefore necessitate dedicated nonperturbative studies. As a concrete application, we analyze the real singlet-extended Standard Model and identify regions of parameter space with single-step first-order transitions, comparing our findings to those obtained using a fully perturbative method. We discuss the prospects for exploring the electroweak phase diagram in this model at collider and gravitational wave experiments in light of our nonperturbative results.

Finland

Oliver Gould

Lauri Niemi

Switzerland

Tuomas V. I. Tenkanen

United Kingdom

David J. Weir

Nonperturbative analysis of the gravitational waves from a first-order electroweak phase transition

Many existing and proposed experiments targeting QCD axion dark matter (DM) can also search for a broad class of axionlike particles (ALPs). We analyze the experimental sensitivities to electromagnetically coupled ALP DM in different cosmological scenarios with the relic abundance set by the misalignment mechanism. We obtain benchmark DM targets for the standard thermal cosmology, a pre-nucleosynthesis period of early matter domination, and a period of kination. These targets are theoretically simple and assume <math><mi>O</mi><mo>(</mo><mn>1</mn><mo>)</mo></math> misalignment angles, avoiding fine-tuning of the initial conditions. We find that some experiments will have sensitivity to these ALP DM targets before they are sensitive to the QCD axion, and others can potentially reach interesting targets below the QCD band. The ALP DM abundance also depends on the origin of the ALP mass. Temperature-dependent masses that are generated by strong dynamics (as for the QCD axion) correspond to DM candidates with smaller decay constants, resulting in even better detection prospects.

Nikita Blinov

Australia

Matthew J. Dolan

Dark matter targets for axionlike particle searches

In the standard model, the renormalization of the QCD vacuum angle <math><mrow><mi>θ</mi></mrow></math> is extremely tiny, and small <math><mi>θ</mi></math> is technically natural. In the general standard model effective field theory (SMEFT), however, <math><mi>Δ</mi><mi>θ</mi></math> is quadratically divergent, reflecting the fact that new sources of hadronic <math><mi>C</mi><mi>P</mi></math>-violation typically produce <math><mi>O</mi><mo>(</mo><mn>1</mn><mo>)</mo></math> threshold corrections to <math><mi>θ</mi></math>. The observation of such <math><mi>C</mi><mi>P</mi></math>-violating interactions would therefore be in tension with solutions to the strong <math><mi>C</mi><mi>P</mi></math> problem in which <math><mi>θ</mi><mo>=</mo><mn>0</mn></math> is an ultraviolet boundary condition, pointing to the Peccei-Quinn mechanism as the explanation for why <math><mi>θ</mi></math> is small in the infrared. We study the quadratic divergences in <math><mi>θ</mi></math> arising from dimension-6 SMEFT operators and discuss the discovery prospects for these operators at electric dipole moment experiments, the LHC, and future proton-proton colliders.