We explore the supernova neutrino-boosted dark matter (<math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mi>SN</mi><mi>ν</mi><mi>BDM</mi></mrow></math>) and its direct detection. During core-collapse supernova, an abundance of neutrinos are emitted. These supernova neutrinos can transfer their kinetic energy to the light dark matter via their interactions, and thus are detected in the neutrino and dark matter experiments. Because of the exponential suppression of the high-energy neutrino flux, the kinetic energy carried by a large portion of <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mi>SN</mi><mi>ν</mi><mi>BDM</mi></mrow></math> falls within the MeV range. We consider a simplified model where dark matter interacts with both electrons and neutrinos through a light mediator. In this case, the enhancement in the scattering rate from the light mediator combined with the excitation of the plasmon resonance in silicon significantly enhances the sensitivity in experiments using low-threshold detectors, such as skipper CCDs, in contrast to conventional neutrino and dark matter direct-detection experiments. We calculate the total scattering rate induced by <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mi>SN</mi><mi>ν</mi><mi>BDM</mi></mrow></math> and derive exclusion limits from Super-K, XENON1T, SENSEI, and DAMIC-M.

China

Jun-Wei Sun

Lei Wu

Yan-Hao Xu

Bin Zhu

Probing supernova neutrino boosted dark matter with collective excitations

We study the transverse momentum ( $p_T$ ) differential anisotropic flow and flow fluctuation in Pb+Pb collisions at $\sqrt{s_{_{NN}}}$ =5.02 TeV at the LHC. A (3+1)-dimensional CLVisc hydrodynamics framework with fluctuating TRENTO (or AMPT) initial conditions is utilized to simulate the space-time evolution of the quark-gluon plasma (QGP) medium. The effects of shear viscosity and the sub-nucleon structure on anisotropic flow and flow fluctuation are analyzed. Our result shows that shear viscosity tends to suppress both flow coefficients ( ${v_2\{2}\}$ , ${v_2\{4\}}$ , and ${\langle v_2\rangle}$ ) and flow fluctuation ( ${\sigma_{v_2}}$ ) owing to its smearing effect on local density fluctuation. The flow coefficients appear to be insensitive to the sub-nucleon structure, whereas the flow fluctuation ${\sigma_{v_2}}$ tends to be suppressed by the sub-nucleon structure in central collisions but enhanced in peripheral collisions. After taking into account the sub-nucleon structure effect, our numerical result can qualitatively describe the relative flow fluctuations ( ${v_2\{4\}/v_2\{2\}}$ , $F({v_2})$ ) measured by the ALICE Collaboration at the LHC. We further investigate the effects of shear viscosity, sub-nucleon structure, and initial condition model on the flow angle and flow magnitude decorrelations ( ${A_2^f}$ , ${M_2^f}$ ) using the four-particle correlation method. We find that the flow decorrelation effect is typically stronger in central collisions than in peripheral collisions. The flow angle decorrelation is found to be insensitive to the shear viscosity and sub-nucleon structure, whereas the flow magnitude decorrelation shows quite different behaviors when using the TRENTO and AMPT initial condition models. Our study sheds light on the anisotropic flow, transport properties, and initial structure of the QGP created in high-energy nuclear collisions.

Germany

Jie Zhu

Canada

Xiang-Yu Wu

Guang-You Qin

Anisotropic flow, flow fluctuation, and flow decorrelation in relativistic heavy-ion collisions: the roles of sub-nucleon structure and shear viscosity * Supported in part by the Natural Science Foundation of China (12225503, 11890710, 11890711, 11935007). Zhu Jie is supported in part by the China Scholarship Council (202306770009). Wu Xiang-Yu is supported in part by the National Science Foundation within the framework of the JETSCAPE collaboration (OAC-2004571) and in part by the Natural Sciences and Engineering Research Council of Canada. Some of the calculations were performed in the Nuclear Science Computing Center at Central China Normal University (NSC$^{3}$), Wuhan, Hubei, China.

A plasmon, a collective mode of electronic excitation in solid-state detectors, provides a novel way to detect light dark matter (DM). In this work, we present the conditions of DM to produce a plasmon resonance, requiring relativistic velocities for light DM, and generalize the collective excitation framework to account for relativistic DM. As a demonstration, we consider the cosmic ray boosted DM and find that the plasmon resonance can be significantly enhanced in the scenario with a light mediator. Utilizing the first data from the SENSEI experiment with the skipper CCDs at SNOLAB, we obtain a new strong limit on the sub-MeV DM-electron scattering cross section.

Zheng-Liang Liang

Liangliang Su

Plasmon-Enhanced Direct-Detection Method for Boosted Sub-MeV Dark Matter

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>.

Ningqiang Song

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

We investigate the Klein-Gordon (KG) oscillators in a global monopole (GM) spacetime in Eddington-inspired Born-Infeld (EiBI) gravity and a Wu-Yang magnetic monopole (WYMM). We discuss the gravitational effects in the presence of Ricci scalar curvature <math altimg='si1.svg'><mi>R</mi><mo linebreak='goodbreak' linebreakstyle='after'>=</mo><msubsup><mrow><mi>R</mi></mrow><mrow><mi>&#965;</mi></mrow><mrow><mi>&#965;</mi></mrow></msubsup></math>. It is observed that the presence of the Ricci scalar curvature, effectively and manifestly, introduces a force field that makes the corresponding quantum mechanical repulsive core more repulsive. Similar effect is also observed for the EiBI-gravitational field. We reiterate and report that the corresponding bosonic KG-oscillator quantum mechanical system admits a solution in the form of confluent Heun functions, the truncation of which into a physically admissible polynomial is shown to be associated with some parametric correlations/conditions. The use of such conditions/correlations is mandatory and yields a set of allowed/restricted quantum mechanical orbital <italic>&#8467;</italic>-excitations, for all radial quantum numbers <math altimg='si2.svg'><msub><mrow><mi>n</mi></mrow><mrow><mi>r</mi></mrow></msub><mo>&#8805;</mo><mn>0</mn></math>. Our procedure is shown to be quite handy, in the sense that it allows one to retrieve results for KG-oscillators in GM-spacetime in different EiBI-gravity and Ricci scalar curvature settings.

Türkiye

Omar Mustafa

KG-oscillators in Eddington-inspired Born-Infeld gravity: Wu-Yang magnetic monopole and Ricci scalar curvature effects

Because of the dense environment, neutron stars (NSs) can serve as an ideal laboratory for studying the interactions between dark matter (DM) and ordinary matter. In the process of DM capture, deep inelastic scattering may dominate over elastic scattering, especially for the DM with a large momentum transfer. In this work, we calculate DM-nucleon deep inelastic scattering via a vector mediator and estimate its contribution to the capture rate. Using the surface temperature of the NSs, we derive the exclusion limits for the DM-nucleon scattering cross section in the mass range <math><mrow><mn>1</mn><mtext> </mtext><mtext> </mtext><mi>GeV</mi><mo>&lt;</mo><msub><mrow><mi>m</mi></mrow><mrow><mi>χ</mi></mrow></msub><mo>&lt;</mo><msup><mrow><mn>10</mn></mrow><mrow><mn>5</mn></mrow></msup><mtext> </mtext><mtext> </mtext><mi>GeV</mi></mrow></math>. We find the bounds for DM with the mass <math><mo>≳</mo><mn>1</mn><mtext> </mtext><mtext> </mtext><mi>GeV</mi></math> can be changed several times after including the deep inelastic scattering contribution.

Meiwen Yang

Deep inelastic scattering in the capture of dark matter by neutron stars

Light feebly interacting dark matter is widely predicted in a plethora of new physics models. However, due to very feeble couplings with the standard-model particles, its relic density produced via the relativistic thermal freeze-out process easily exceeds the observed value. The entropy dilution in an early matter-dominated era provides an attractive mechanism for solving such an overabundance problem. In this work, we note that this dark matter dilution mechanism will lead to two distinctive kinks in the primordial GW spectrum, whose frequencies strongly correlate with the DM mass. We show that the GW detectors, such as Cosmic Explorer (CE) and Big Bang Observer (BBO), can measure the kinks in the primordial GW spectrum and will offer a new avenue to probe light feebly interacting dark matter.

Yuchao Gu

Yongcheng Wu

Gravitational wave as a probe of light feebly interacting dark matter

Several pulsar timing array collaborations recently reported evidence of a stochastic gravitational wave background (SGWB) at nHz frequencies. While the SGWB could originate from the merger of supermassive black holes, it could be a signature of new physics near the 100 MeV scale. Supercooled first-order phase transitions (FOPTs) that end at the 100 MeV scale are intriguing explanations, because they could connect the nHz signal to new physics at the electroweak scale or beyond. Here, however, we provide a clear demonstration that it is not simple to create a nHz signal from a supercooled phase transition, due to two crucial issues that could rule out many proposed supercooled explanations and should be checked. As an example, we use a model based on nonlinearly realized electroweak symmetry that has been cited as evidence for a supercooled explanation. First, we show that a FOPT cannot complete for the required transition temperature of around 100 MeV. Such supercooling implies a period of vacuum domination that hinders bubble percolation and transition completion. Second, we show that even if completion is not required or if this constraint is evaded, the Universe typically reheats to the scale of any physics driving the FOPT. The hierarchy between the transition and reheating temperature makes it challenging to compute the spectrum of the SGWB.

Peter Athron

Andrew Fowlie

Chih-Ting Lu

Australia

Lachlan Morris

Zhongxiu Xu

Can Supercooled Phase Transitions Explain the Gravitational Wave Background Observed by Pulsar Timing Arrays?

This study explores a minimal renormalizable dark matter (DM) model, incorporating a sub-GeV Majorana DM and a singlet scalar particle ϕ. Using scalar and pseudo-scalar interactions (couplings c  s  and c  p ), we investigate implications for DM detection, considering s-wave, p-wave, and combined (s+p wave) contributions in DM annihilation cross-section, as well as loop-correction contributions to DM-nucleon elastic scattering. Identifying a broad parameter space (10 MeV &lt; m  χ  ≲ m  ϕ ) within the 2σ allowed region, we explore scenarios (|c  s | ≫ |c  p |, |c  s | ≪ |c  p |, and |c  s | ≈ |c  p |). We find that (i) a non-zero pseudo-scalar coupling alleviates direct detection constraints as a comparison with the previous pure scalar coupling case; (ii) CMB observations set stringent limits on pseudo-scalar interaction dominant cases, making s-wave annihilation viable only for m  χ  &gt; 1 GeV; (iii) the preferred ϕ-resonance region can be tested in the future indirect detection experiments, such as e-ASTROGAM.

Yu-Tong Chen

Japan

Shigeki Matsumoto

Tian-Peng Tang

Yue-Lin Tsai

Light thermal dark matter beyond p-wave annihilation in minimal Higgs portal model

We consider Klein–Gordon (KG) particles in a global monopole (GM) spacetime within Eddington-inspired Born–Infeld gravity (EiBI-gravity) and in a Wu–Yang magnetic monopole (WYMM). We discuss a set of KG-oscillators in such spacetime settings. We propose a textbook power series expansion for the KG radial wave function that allows us to retrieve the exact energy levels for KG-oscillators in a GM spacetime and a WYMM without EiBI-gravity. We, moreover, report some conditionally exact, closed form, energy levels (through some parametric correlations) for KG-oscillators in a GM spacetime and a WYMM within EiBI-gravity, and for massless KG-oscillators in a GM spacetime and a WYMM within EiBI-gravity under the influence of a Coulomb plus linear Lorentz scalar potential. We report the effects of the Eddington parameter $$\kappa $$ <math> <mi>κ</mi> </math> , GM-parameter $$\alpha $$ <math> <mi>α</mi> </math> , WYMM strength $$\sigma $$ <math> <mi>σ</mi> </math> , KG-oscillators’ frequency $$\Omega $$ <math> <mi>Ω</mi> </math> , and the coupling parameters of the Coulomb plus linear Lorentz scalar potential, on the spectroscopic structure of the KG-oscillators at hand. Such effects are studied over a vast range of the radial quantum number $$n_r\ge 0$$ <math> <mrow> <msub> <mi>n</mi> <mi>r</mi> </msub> <mo>≥</mo> <mn>0</mn> </mrow> </math> and include energy levels clustering at $$\kappa&gt;&gt;1$$ <math> <mrow> <mi>κ</mi> <mo>&gt;</mo> <mo>&gt;</mo> <mn>1</mn> </mrow> </math> (i.e., extreme EiBI-gravity), and at $$|\sigma |&gt;&gt;1$$ <math> <mrow> <mo>|</mo> <mi>σ</mi> <mo>|</mo> <mo>&gt;</mo> <mo>&gt;</mo> <mn>1</mn> </mrow> </math> (i.e., extreme WYMM strength).

Brazil

A. Soares

C. Pereira

R. Vitória

On the Klein–Gordon oscillators in Eddington-inspired Born-Infeld gravity global monopole spacetime and a Wu–Yang magnetic monopole