The tidal deformability and the radius of neutron stars are observables, which have been used to constrain the neutron star equation of state and explore the composition in neutron stars. We investigated the radius and tidal deformability of dark matter admixed neutron stars (DANSs) by utilizing the two-fluid TOV (Tolman-Oppenheimer-Volkoff) equation. Assuming that the dark matter modeled as fermions (with or without self-interaction) or self-interacting bosons, for a series of DANSs at a fixed mass, it is shown that there exists the DANSs with smaller normal matter radii but larger tidal deformabilities. This negative correlation does not exist in the normal neutron stars. In other words, if the observation finds that the neutron stars with a fixed mass exists such a situation, that is, having a smaller observed radius but a larger tidal deformability, it will indicate the existence of dark matter in neutron stars. In addition, the relevant neutron star observations can also be used to constrain the dark matter parameters.

With about a hundred binary black hole (BBH) mergers detected by LIGO-Virgo-KAGRA, and with several hundreds expected in the current O4 run, gravitational waves (GWs) are revolutionizing our understanding of the Universe. Some BBH sources are too faint to be individually detected, but collectively they may give rise to a stochastic GW background (SGWB). In this paper, we calculate the SGWB associated with BBH mergers dynamically assembled in dense star clusters, using state-of-the-art numerical models. We discuss the role of modeling the evolution of the mass distribution of BBH mergers, which has significant implications for model selection and parameter estimation, and could be used to distinguish between different channels of BBH formation. We demonstrate how the birth properties of star clusters affect the amplitude and frequency spectrum of the SGWB, and show that upcoming observation runs of ground-based GW detectors may be sensitive enough to detect it. Even in the case of a nondetection, we find that GW data can be used to constrain the highly uncertain cluster birth properties, which can complement direct observations of young massive clusters and protostar clusters in the early Universe by The James Webb Space Telescope.

Scenarios such as the QCD axion with the Peccei-Quinn symmetry broken after inflation predict an enhanced matter power spectrum on subparsec scales. These theories lead to the formation of dense dark matter structures known as minihalos, which provide insights into early Universe dynamics and have implications for direct detection experiments. We examine the mass loss of minihalos during stellar encounters, building on previous studies that derived formulas for mass loss and performed $N$-body simulations. We propose a new formula for the mass loss that accounts for changes in the minihalo profile after disruption by a passing star. We also investigate the mass loss for multiple stellar encounters. We demonstrate that accurately assessing the mass loss in minihalos due to multiple stellar encounters necessitates considering the alterations in the minihalo’s binding energy after each encounter, as overlooking this aspect results in a substantial underestimation of the mass loss.

The excesses in the electron and positron spectra observed by many experiments, such as PAMELA and AMS-02, have sparked significant theoretical investigation. It is not easy to distinguish the two primary hypotheses dark matter annihilation/decay and pulsars from the spectral features. Should pulsars be the source of this excess, the expected variability in their distribution may introduce distinct irregularities in the positron energy spectrum. In this study, we use an irregularity estimator to detect these potential features in the positron energy spectrum of AMS-02. Our analysis of the current AMS-02 data reveals these spectral irregularities with a statistical significance of $1.75\sigma$. However, our projection indicates that, with AMS-02 data collected over a period of 20 years, such irregularities could be identified with a confidence level of $3\sigma$ level in 71% of our simulations.

Observations of accreting neutron stars are widely used to constrain the microphysical properties of superdense matter. A key ingredient in this analysis is the heating associated with nuclear reactions in the outer layers of the neutron star (crust), as well as the equation of state and composition of these layers. As recently shown, the neutron hydrostatic/diffusion (nHD) condition is valid in the inner part of the crust, where some of the neutrons are not bound to the nuclei, and this condition should be properly incorporated into crustal models. Here we construct models of the accreted crust of a neutron star, taking into account the nHD condition and proton shell effects in nuclei. For numerical illustration, we employ the recently proposed compressible liquid drop model, which incorporates shell effects. However, our approach is general and can also be used in future studies relying on more sophisticated nuclear physics models.

Coalescing massive black hole binaries (MBHBs) are one of primary sources for space-based gravitational wave (GW) observations. The mergers of these binaries are expected to give rise to detectable electromagnetic (EM) emissions with a narrow time window. The premerger detection of GW signals is vital for follow-up EM observations. The conventional approach for searching GW signals involves high computational costs. In this study, we present a deep learning model to search for GW signals from MBHBs. Our model is able to process 4.7 days of simulated data within 0.01 seconds and detect GW signals several hours to days before the final merger. The model provides the possibility of the coincident GW and EM detection of MBHBs.

An important mechanism for production of the Higgs boson at the prospective Large Hadron-electron Collider (LHeC) is via neutral current (NC) weak boson fusion (WBF) processes. Aside from its role in measurements of Higgs couplings within the standard model, this production mode is particularly useful in searchings of Higgs decays into invisible particles in various models for the Higg portal dark matter. In this work we compute the electroweak corrections for the NC WBF at the LHeC up to the one-loop level. For a center-of-mass energy of 1.98 TeV, the magnitudes of the relative corrections for the total cross section at next-to-leading (NLO) order are respectively 8% and 17%, in the two renormalization schemes we use. The NLO terms also distort various distributions (notably, those for Higgs and electron observables) computed at the leading order. Along with our previous treatment of the charge current processes, this paper completes the calculation of the NLO electroweak effects for the dominant Higgs production modes at the LHeC.

We investigate the potential to detect Higgs boson decays to four bottom quarks through a pair of pseudoscalars, a final state that is predicted by many theories beyond the Standard Model. For the first time, the signal sensitivity is evaluated for the final state using the vector boson fusion (VBF) production with and without an associated photon, for the Higgs at $m_H=125\mathrm{GeV}$, at hadron colliders. The signal significance is $0.5\sigma$ to $6\sigma$, depending on the pseudoscalar mass $m_a$, when setting the Higgs decay branching ratio to unity, using an integrated luminosity of $150{\mathrm{fb}}^{-1}$ at $\sqrt{s}=13\mathrm{TeV}$. This corresponds to an upper limit of 0.3, on the Higgs branching ratio to four bottom quarks, with a nonobservation of the decay. We also consider several variations of selection requirements—input variables for the VBF tagging and the kinematic variables for the photon—that could help guide the design of new triggers for the Run-3 period of the LHC and for the HL-LHC.

Vector boson fusion is arguably the most direct collider probe of electroweak symmetry breaking. Typically, the signature includes two forward/backward jets with low transverse momenta with a scale that is set by the mass of the vector boson. For this reason, an upper cut is used when searching for vector boson fusion processes in the Standard Model. Alternatively, the upper cut on the forward jets can be removed and the high-momentum exchange region of vector boson fusion can be studied. This phase space region has sensitivity to new physics via higher dimensional operators and form factors. In this work, we study the high-momentum region of the vector boson fusion channel where the Higgs decays to $b\overline{b}$. We show that, depending on the form of new physics, the limits on the new physics scale range from 0.5 to 1.8 TeV.

Although axionlike particles (ALPs) are popular dark matter candidates, their mass generation mechanisms as well as cosmic thermal evolutions are unclear. In this paper, we propose a new mass generation mechanism of an ALP during the electroweak phase transition in the presence of the type-II seesaw mechanism. In this scenario, the ALP gets mass uniquely at the electroweak scale, so there is a cutoff scale on the ALP oscillation temperature that is irrelevant to the specific mass of the ALP, serving as a distinctive feature of this scenario. Interactions of the ALP have been systematically studied, which shows that the ALP does not couple to diphotons. Instead, it couples to active neutrinos as well as the electron. Therefore, it can be boosted by cosmic rays and can be tested in proposed direct detection experiments with various condensed matter materials as targets.

Third-generation dark matter detectors will be fully sensitive to the ${}^8\mathrm{B}$ solar neutrino flux. Because of this, the characterization of such a background has been the subject of extensive analyses over the last few years. In contrast, little is known about the impact of reactor neutrinos. In this paper, we report on the implications of such a flux for dark matter direct-detection searches. We consider five potential detector deployment sites envisioned by the recently established XLZD Consortium: SURF, SNOLAB, Kamioka, LNGS, and Boulby. By using public reactor data, we construct five reactor clusters—involving about 100 currently operating commercial nuclear reactors each—and determine the net neutrino flux at each detector site. Assuming a xenon-based detector and a 50 ton-year exposure, we show that in all cases the neutrino event rate may be sizable, depending on energy recoil thresholds. Of all possible detector sites, SURF and LNGS are those with the smallest reactor neutrino background. On the contrary, SNOLAB and Boulby are subject to the strongest reactor neutrino fluxes, with Kamioka being subject to a more moderate background. Our findings demonstrate that reactor neutrino fluxes should be taken into account in the next round of dark matter searches. We argue that this background may be particularly relevant for directional detectors, provided they meet the requirements we have employed in this analysis.

The self-interacting dark matter (SIDM) paradigm offers a potential solution to the small-scale structure problems faced by collisionless cold dark matter. This framework incorporates self-interactions among dark matter particles, typically mediated by a particle with a MeV-scale mass. Recent evidences of nano-Hertz gravitational waves from pulsar timing arrays (PTAs) such as NANOGrav, CPTA, EPTA, and PPTA suggest the occurrence of a first-order phase transition (FOPT) at a MeV-scale temperature. Considering the close proximity between these two scales, we propose that the mediator mass in the SIDM model originates from the spontaneous breaking of a $U(1{)}^{\prime }$ symmetry, which is driven by the FOPT indicated by PTA data. Consequently, the alignment of these two scales is believed to be deeply connected by the same underlying physics. By extensively exploring the parameter space, remarkably, we find that the parameter space favored by SIDM just provides an explanation for the PTA data.

We determine the masses of the sequential fourth generation quarks $b^{\prime }$ and $t^{\prime }$ in the extension of the Standard Model by solving the dispersion relations associated with the mixing between the neutral states $Q\overline{q}$ and $\overline{Q}q$, with $Q$ ($q$) being a heavy (light) quark. The box diagrams responsible for the mixing, which provide the perturbative inputs to the dispersion relations, involve multiple intermediate channels, i.e., the $ut$ and $ct$ channels, $u$ ($c$, $t$) being an up (charm, top) quark, in the $b^{\prime }$ case, and the $d{b}^{\prime }$, $s{b}^{\prime }$, and $b{b}^{\prime }$ ones, $d$ ($s$, $b$) being a down (strange, bottom) quark, in the $t^{\prime }$ case. The common solutions for the above channels lead to the masses $m_{b^{\prime }}=(2.7\pm 0.1)$ and $m_{t^{\prime }}\approx 200\mathrm{TeV}$ unambiguously. We show that these superheavy quarks, forming bound states in a Yukawa potential, barely contribute to Higgs boson production via gluon fusion and decay to photon pairs and bypass current experimental constraints. The mass of the ${\overline{b}}^{\prime }{b}^{\prime }$ ground state is estimated to be about 3.2 TeV. It is thus worthwhile to continue the search for $b^{\prime }$ quarks or ${\overline{b}}^{\prime }{b}^{\prime }$ resonances at the (high-luminosity) Large Hadron Collider.

The Large Hadron Collider provides a unique opportunity to study quantum entanglement and violation of Bell inequalities at the highest energy available today. In this paper, we will investigate these quantum correlations with top quark pair production, which represents a system of two-qubits. The semileptonic top pair channel has a factor of 6 increase in statistics and easier reconstruction with respect to the dileptonic channel. Although measuring the spin polarization of the hadronic top quark is known to be challenging, our study indicates that it is feasible to reconstruct the spin density matrix of the two-qubit system using an optimal hadronic polarimeter. This is achieved with the aid of jet substructure techniques and NN-inspired reconstruction methods, which improve the mapping between subjets and quarks. We find that entanglement can already be observed at more than the $5\sigma$ level with existing data, and violation of Bell inequalities may be probed above the $4\sigma$ level at the HL-LHC with $3{\mathrm{ab}}^{-1}$ of data.

The flavor structure of quarks and leptons is not yet fully understood, but it hints a more fundamental theory of nonuniversal generations. We therefore propose a simple extension of the Standard Model by flipping (i.e., enlarging) the hypercharge $U(1{)}_Y$ to $U(1{)}_X\otimes U(1{)}_N$ for which both $X$ and $N$ depend on generations of both quark and lepton. By anomaly cancellation, this extension not only explains the existence of just three fermion generations as observed but also requires the presence of a right-handed neutrino per generation, which motivates seesaw neutrino mass generation. Furthermore, in its minimal version with a scalar doublet and two scalar singlets, the model naturally generates the measured fermion-mixing matrices while it successfully accommodates several flavor anomalies observed in the neutral meson mixings, $B$-meson decays, lepton-flavor-violating processes of charged leptons, as well as satisfying constraints from particle colliders.

We apply the Grabowska-Kaplan framework, originally proposed for lattice chiral gauge theories, to QCD. We show that the resulting theory contains a conserved and gauge invariant singlet axial current, both on the lattice and in the continuum limit. This must give rise to a difference with QCD, with the simplest possibility being a superfluous Nambu-Goldstone boson in the physical spectrum not present in QCD. We find a similar unwanted conserved current in the recent “disk” formalism, this time limiting ourselves to the continuum formulation. A similar problem is expected when either of these formalisms is used for its original goal of constructing lattice chiral gauge theories. Finally we discuss a conjecture about the possible dynamics that might be associated with the unwanted conserved current and the fate of ‘t Hooft vertices.

At its critical point, the three-dimensional lattice Ising model is described by a conformal field theory (CFT), the 3D Ising CFT. Instead of carrying out simulations on Euclidean lattices, we use the quantum finite elements method to implement radially quantized critical ${\varphi }^4$ theory on simplicial lattices approaching $\mathbb{R}\times S^2$. Computing the four-point function of identical scalars, we demonstrate the power of radial quantization by the accurate determination of the scaling dimensions ${\mathrm{\Delta }}_{\epsilon }$ and ${\mathrm{\Delta }}_T$ as well as ratios of the operator product expansion coefficients $f_{\sigma \sigma \epsilon }$ and $f_{\sigma \sigma T}$ of the first spin-0 and spin-2 primary operators $\epsilon$ and $T$ of the 3D Ising CFT.

The paper calculates the helicity-dependent dihadron fragmentation function by extending the dihadron spectator model and examine the single longitudinal spin asymmetry $A_{UL}^{\sin (2{\varphi }_h)}$ from dihadron in semi-inclusive inelastic scattering. This function elucidates the relationship between the longitudinal polarization of the fragmented quark and the transverse momentum of the resulting hadron pairs. A study by the COMPASS collaboration detected a minimal signal in their experimental search for this azimuthal asymmetry in semi-inclusive inelastic scattering. Here, we use the spectator model to calculate the unknown T-odd dihadron fragmentation function $H_1^{\perp }$. Adopting collinear factorization to describe the data, avoiding the transverse momentum dependent factorization and the associated resummation effects, helping us understand the asymmetry and explaining why the signal is so weak. We involve the approach of transverse momentum dependence in the model calculations, in order to formulate the differential cross sections and the spin asymmetries in terms of the collinear parton distributions and the collinear dihadron fragmentation functions. A transverse momentum factor analysis method was used, in which the transverse momentum of the final hadron pairs was not integrated. The asymmetry of $\sin (2{\varphi }_h)$ in COMPASS kinematics was calculated and compared with experimental data. In addition, predictions for the same asymmetry are also presented for HERMES and the Electron Ion Collider.

Inspired by the recently observed resonance states $P_{\psi s}^{\mathrm{\Lambda }}(4338{)}^0$ and $P_{cs}(4459{)}^0$ by LHCb Collaboration in $J/\psi \mathrm{\Lambda }$ decay channel, we perform a systematical study of all possible hidden-heavy pentaquarks with strangeness $S=0,-1,-2,-3$, in unified framework of MIT bag model. The color-spin wave functions in terms of Young-Yamanouchi bases and transformed into baryon-meson couplings are utilized to calculate masses, magnetic moments, and relative partial widths of the hidden-heavy pentaquarks, suggesting that the observed $P_{\psi s}^{\mathrm{\Lambda }}(4338{)}^0$ is likely to be a $1/2^{-}$ compact $P_{cs}$ pentaquark, and the $P_{cs}(4459{)}^0$ favors two-peak structure of $3/2^{-}$ and $1/2^{-}$ $P_{cs}$ states. Our computation indicates that hidden-heavy pentaquarks have the masses around 4.35–4.90 GeV for the $P_{cs}$, 11.21–11.67 GeV for the $P_{bs}$, 4.73–5.02 GeV for the $P_{css}$, and 11.54–11.77 GeV for the $P_{bss}$.

We present the analytic calculation of the leading-order three-point energy correlator (EEEC) in hadronic Higgs decays, including both the gluon-initiated channel $H\to gg+X$ and quark-initiated channel $H\to q\overline{q}+X$. The phase-space integration is evaluated directly using Mandelstam variables $s_{ij}=(p_i+p_j{)}^2$, and the appearing square roots can be rationalized by either conformal ratios or celestial coordinate variables. Throughout the calculation, we observe the same transcendental function space as in $\mathcal{N}=4$ super–Yang-Mills theory and $e^{+}{e}^{-}\to \text{hadrons}$. Different infrared limits are also explored using the full analytic result, offering the fixed-order data for EEEC factorization and resummation. Given its nontrivial shape dependence, the EEEC presents an excellent opportunity to explore the dynamics of gluon jets originating from the $H\to gg$ decay channel at future lepton colliders.