In this work, we show that ultralight dark photons, which couple to the Standard Model photon through kinetic mixing, can potentially source galactic scale magnetic fields. Although these magnetic fields would be too weak to detect at present in galaxies due to plasma screening effects, we show that dark photons can provide the seed magnetic field strength (<math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mn>10</mn><mrow><mo>−</mo><mn>20</mn></mrow></msup><mtext> </mtext><mtext> </mtext><mi mathvariant="normal">G</mi></math>) required for dynamo amplification in galaxies. Such dynamo-amplified magnetic fields are consistent with observations of <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi mathvariant="normal">μ</mi><mi mathvariant="normal">G</mi></math> strength galactic magnetic fields.

United States

Joshua Berger

Amit Bhoonah

Canada

Joseph Bramante

J. Leo Kim

China

Ningqiang Song

Lawrence M. Widrow

Galactic magnetic fields seeded by ultralight dark photons

High-energy muon beam dump experiments are powerful probes of new physics models beyond the Standard Model, particularly those involving flavor-dependent interactions. We demonstrate the potential of muon beam dump by placing strong constraints on three new physics models utilizing data from the recent <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mi>NA</mi><mrow><mn>64</mn><mi>μ</mi></mrow></mrow></math> experiment: (1) axions coupling to photons, (2) axions coupling to muons, and (3) a dark sector mediated by a massless <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>U</mi><mo stretchy="false">(</mo><mn>1</mn><msub><mo stretchy="false">)</mo><mrow><msub><mi>L</mi><mi>μ</mi></msub><mo>−</mo><msub><mi>L</mi><mi>τ</mi></msub></mrow></msub></math> gauge boson. The new particles can be identified from the significant missing energy as the invisible channel, or the distinct energy deposition signature as the visible channel. We find that the current <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mi>NA</mi><mrow><mn>64</mn><mi>μ</mi></mrow></mrow></math> data do not yet probe new parameter region on axion-photon coupling, while excluding new parameter space for the axion-muon coupling <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>g</mi><mrow><mi>a</mi><mi>μ</mi><mi>μ</mi></mrow></msub><mo>≳</mo><mn>4</mn><mo>×</mo><msup><mn>10</mn><mrow><mo>−</mo><mn>3</mn></mrow></msup><mtext> </mtext><mtext> </mtext><mrow><msup><mrow><mi>GeV</mi></mrow><mrow><mo>−</mo><mn>1</mn></mrow></msup></mrow></math> and the axion mass <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>m</mi><mi>a</mi></msub><mo>≲</mo><mn>0.2</mn><mtext> </mtext><mtext> </mtext><mi>GeV</mi></math>. For the dark sector, the current data provide stringent constraints that surpass existing ones by nearly one order of magnitude. The data from the 2023 <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mi>NA</mi><mrow><mn>64</mn><mi>μ</mi></mrow></mrow></math> run, once available, will be capable of excluding new axion-photon coupling parameter space and probing the flavor structure of new physics, with more sensitivity advancement expected in near future runs.

Haotian Li

Zuowei Liu

Probing axion and flavored new physics with the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mi>NA</mi><mrow><mn>64</mn><mi>μ</mi></mrow></mrow></math> experiment

The decay of asymmetric dark matter (ADM) can lead to distinct neutrino signatures characterized by an asymmetry between neutrinos and antineutrinos. In the high-energy regime, the Glashow resonant interaction <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><msub><mrow><mover accent="true"><mrow><mi>ν</mi></mrow><mrow><mo stretchy="false">¯</mo></mrow></mover></mrow><mrow><mi>e</mi></mrow></msub><mo>+</mo><msup><mrow><mi>e</mi></mrow><mrow><mo>−</mo></mrow></msup><mo stretchy="false">→</mo><msup><mrow><mi>W</mi></mrow><mrow><mo>−</mo></mrow></msup></mrow></math> yields an increase in sensitivity to the neutrino flux, and stands out as the only way of discerning the antineutrino component in the diffuse high-energy astrophysical neutrino flux. This offers a unique opportunity in the search for dark matter with masses above the PeV scale. We examine the neutrino signal stemming from ADM decay and set the first stringent constraints on ADM lifetime <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>τ</mi><mi>X</mi></msub></math>. For ADM with mass <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>m</mi><mi>X</mi></msub><mo>≳</mo><mn>10</mn><mtext> </mtext><mtext> </mtext><mi>PeV</mi></math>, we exclude <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>τ</mi><mi>X</mi></msub><mo>≲</mo><msup><mn>10</mn><mn>29</mn></msup><mtext> </mtext><mtext> </mtext><mi mathvariant="normal">s</mi></math> using the data from the recent IceCube search for Glashow resonance events. Our projections further show that sensitivities at the forthcoming IceCube-Gen2 could approach <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mn>10</mn><mn>30</mn></msup><mtext> </mtext><mtext> </mtext><mi mathvariant="normal">s</mi></math>, depending on the decay channel. The current constraints on symmetric dark matter decay to neutrinos are also improved by up to a factor of 3 thanks to the Glashow resonance.

Qinrui Liu

Aaron C. Vincent

Constraints on heavy asymmetric and symmetric dark matter from the Glashow resonance

Neutron stars provide ideal astrophysical laboratories for probing new physics beyond the Standard Model. If axions exist, then photons can develop linear polarization during photon-axion conversion in the magnetic field of a neutron star. We find that the plasma in the neutron star magnetosphere could dramatically enhance the polarization through the resonant conversion effect. With the polarization measurements from PSR <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mi mathvariant="normal">B</mi><mn>0656</mn><mo>+</mo><mn>14</mn></mrow></math>, 4U <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mn>0142</mn><mo>+</mo><mn>61</mn></mrow></math>, and the benchmark polarization measurement in the midinfrared band, we demonstrate that optical and infrared polarization from neutron stars can provide strong constraints on the axion-photon coupling over a broad axion mass range <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mn>10</mn><mrow><mo>−</mo><mn>11</mn></mrow></msup><mo>≲</mo><msub><mi>m</mi><mi>a</mi></msub><mo>≲</mo><msup><mn>10</mn><mrow><mo>−</mo><mn>3</mn></mrow></msup><mtext> </mtext><mtext> </mtext><mi>eV</mi></math>.

Liangliang Su

Lei Wu

Polarization signals from axion-photon resonant conversion in a neutron star magnetosphere

If millicharged particles (MCPs) exist they can be created in the atmosphere when high energy cosmic rays collide with nuclei and could subsequently be detected at neutrino experiments. We extend previous work, which considered MCPs from decays of light mesons and proton bremsstrahlung, by including production from <math><mi>ϒ</mi></math> meson decays and the Drell-Yan process. MCPs with masses below a GeV primarily arise from proton bremsstrahlung, while heavier MCPs predominantly originate from heavy meson decays and Drell-Yan. We analyze the resulting single scatter and multiple scatter signals at SuperK and JUNO. Searches for low energy coincident signals at JUNO will be sensitive to MCPs with millicharges up to an order of magnitude beyond current constraints for MCP masses between 2 and 10 GeV.

Han Wu

United Kingdom

Edward Hardy

Searching for heavy millicharged particles from the atmosphere

We consider the effect of isospin-violating dark matter-nucleon interactions on direct detection constraints in the regime of small dark matter mass and large scattering cross section. Isospin-violation can lead to both reductions in sensitivity (due to a reduced cross section for scattering with nuclei in the detector) and enhancements in sensitivity (due to a reduced cross section for scattering in the overburden). Isospin-violating effects can thus open up some closed regions of parameter space, while closing off other regions.

Jason Kumar

Danny Marfatia

Opening windows with isospin-violating dark matter

If the temperature of the hot thermal plasma in the early Universe was within a few orders of magnitude of the Planck scale <math><mrow><msub><mrow><mi>M</mi></mrow><mrow><mi>Pl</mi></mrow></msub></mrow></math>, then the hoop conjecture predicts the formation of microscopic black holes from particle collisions in the plasma. Although these evaporated instantly, they would have left behind a relic abundance of all stable degrees of freedom which couple to gravity. Here we show that, upon minimal assumptions of a high reheat temperature and semiclassical black hole dynamics, this process could have produced the relic abundance of dark matter observed today for a particle mass anywhere in the range of <math><mrow><mn>100</mn><mtext> </mtext><mtext> </mtext><mi>keV</mi><mo>≲</mo><msub><mrow><mi>m</mi></mrow><mrow><mi>dm</mi></mrow></msub><mo>&lt;</mo><msub><mrow><mi>M</mi></mrow><mrow><mi>Pl</mi></mrow></msub></mrow></math>, though it could be subdominant to graviton-mediated freeze-in above <math><mrow><msub><mrow><mi>m</mi></mrow><mrow><mi>dm</mi></mrow></msub><mo>∼</mo><mi>MeV</mi></mrow></math>. The production mechanism does not rely on any additional assumptions about nongravitational dark matter-Standard Model interaction.

Avi Friedlander

Dark matter from hot big bang black holes

We present, for the first time, a complete treatment of strongly interacting dark matter capture in planets, taking Earth as an example. We focus on light dark matter and the heating of Earth by dark matter annihilation, addressing a number of crucial dynamical processes which have been overlooked, such as the “ping-pong effect” during dark matter capture. We perform full Monte Carlo simulations and obtain improved bounds on strongly-interacting dark matter from Earth heating and direct detection experiments for both spin-independent and spin-dependent interactions, while also allowing for the interacting species to make up a subcomponent of the cosmological dark matter.

Gopolang Mohlabeng

India

Nirmal Raj

Light dark matter accumulating in planets: Nuclear scattering

The evaporation of primordial black holes provides a promising dark matter production mechanism without relying on any nongravitational interactions between the dark sector and the Standard Model. In theories of “large” extra dimensions (LEDs), the true scale of quantum gravity, <math><msub><mi>M</mi><mo>*</mo></msub></math>, could be well below the Planck scale, thus allowing for energetic particle collisions to produce microscopic black holes in the primordial plasma at temperatures as low as <math><mi>T</mi><mo>≳</mo><mn>100</mn><mtext> </mtext><mtext> </mtext><mi>GeV</mi></math>. Additionally, LEDs modify the relationship between black hole mass, radius, and temperature, allowing microscopic black holes to grow to macroscopic sizes in the early Universe. In this work we study three scenarios for the production of dark matter via LED black holes: (1) delayed evaporating black holes (DEBHs) which grow to macroscopic sizes before ultimately evaporating, (2) instantly evaporating black holes (IEBHs) which immediately evaporate, and (3) stable black hole relics with a mass <math><msub><mi>M</mi><mo>*</mo></msub></math> known as Planckeons. For a given reheating temperature, <math><msub><mi>T</mi><mi>RH</mi></msub></math>, we show that DEBHs produce significantly less dark matter than both IEBHs and Planckeons. IEBHs are able to produce the observed relic abundance of dark matter so long as the reheating scale is in the range <math><msup><mn>10</mn><mrow><mo>−</mo><mn>2</mn></mrow></msup><mo>≤</mo><msub><mi>T</mi><mi>RH</mi></msub><mo>/</mo><msub><mi>M</mi><mo>*</mo></msub><mo>≤</mo><msup><mn>10</mn><mrow><mo>−</mo><mn>1</mn></mrow></msup></math>. We calculate the average speed for the resulting dark matter and show that it would be sufficiently cold for all dark matter masses <math><msub><mi>m</mi><mrow><mi>d</mi><mi>m</mi></mrow></msub><mo>≳</mo><msup><mn>10</mn><mrow><mo>−</mo><mn>4</mn></mrow></msup><mtext> </mtext><mtext> </mtext><mi>GeV</mi></math>. This mechanism is viable for any scale of quantum gravity in the range <math><msup><mn>10</mn><mn>4</mn></msup><mtext> </mtext><mtext> </mtext><mi>GeV</mi><mo>≤</mo><msub><mi>M</mi><mo>*</mo></msub><mo>≤</mo><msub><mi>M</mi><mi>Pl</mi></msub></math> and for any number of LEDs.

Dark matter from higher-dimensional primordial black holes

Dark photon dark matter that has a kinetic mixing with the Standard Model photon can resonantly convert in environments where its mass <math><msub><mi>m</mi><msup><mi>A</mi><mo>′</mo></msup></msub></math> coincides with the plasma frequency. We show that such conversion in neutron stars or accreting white dwarfs in the Galactic Center can lead to detectable radio signals. Depending on the dark matter spatial distribution, future radio telescopes could be sensitive to values of the kinetic mixing parameter that exceed current constraints by orders of magnitude for <math><msub><mi>m</mi><msup><mi>A</mi><mo>′</mo></msup></msub><mo>∈</mo><mrow><mo>(</mo><mn>6</mn><mo>×</mo><msup><mn>10</mn><mrow><mo>−</mo><mn>6</mn></mrow></msup><mo>,</mo><mn>7</mn><mo>×</mo><msup><mn>10</mn><mrow><mo>−</mo><mn>4</mn></mrow></msup><mo>)</mo></mrow><mtext> </mtext><mtext> </mtext><mi>eV</mi></math>.