We study the $\mathrm{SU}(N)$ gauge fields coupled with the inflaton through the Chern-Simons coupling and propose a general procedure for constructing homogeneous, isotropic, and attractor solutions of the gauge fields during inflation. Gauge fields develop various vacuum expectation values corresponding to different spontaneous symmetry-breaking patterns of $\mathrm{SU}(N)$, where embedded SU(2) subgroups are broken with the spatial rotation SO(3) symmetry. As specific examples, we construct the stable solutions for $N=3$ and 4. We numerically solve the gauge field dynamics and confirm that our analytic solutions are complete and act as attractors. Notably, the proposed approach is applicable to the other simple Lie groups.

Weak and continuous gravitational-wave (GW) radiation can be produced by newborn magnetars with deformed structure and is expected to be detected by the Einstein telescope in the near future. In this work we assume that the deformed structure of a nascent magnetar is not caused by a single mechanism but by multiple time-varying quadrupole moments such as those present in magnetically induced deformation, starquake-induced ellipticity, and accretion column-induced deformation. The magnetar loses its angular momentum through accretion, magnetic dipole radiation, and GW radiation. Within this scenario, we calculate the evolution of GWs from a newborn magnetar by considering the above three deformations. We find that the GW evolution depends on the physical parameters of the magnetar (e.g., period and surface magnetic field), the adiabatic index, and the fraction of poloidal magnetic energy to the total magnetic energy. In general the GW radiation from a magnetically induced deformation is dominant if the surface magnetic field of the magnetar is large, but the GW radiation from magnetar starquakes is more efficient when there is a larger adiabatic index if all other magnetar parameters remain the same. We also find that the GW radiation is not very sensitive to different magnetar equations of state.

A major challenge for gravitational-wave (GW) detection in the $\mu \mathrm{Hz}$ band is engineering a test mass (TM) with sufficiently low acceleration noise. We propose a GW detection concept using asteroids located in the inner Solar System as TMs. Our main purpose is to evaluate the acceleration noise of asteroids in the $\mu \mathrm{Hz}$ band. We show that a wide variety of environmental perturbations are small enough to enable an appropriate class of $\sim 10\mathrm{km}$-diameter asteroids to be employed as TMs. This would allow a sensitive GW detector in the band $(\mathrm{few})\times {10}^{-7}\mathrm{Hz}\lesssim f_{\mathrm{GW}}\lesssim (\mathrm{few})\times {10}^{-5}\mathrm{Hz}$, reaching strain $h_c\sim {10}^{-19}$ around $f_{\mathrm{GW}}\sim 10\mu \mathrm{Hz}$, sufficient to detect a wide variety of sources. To exploit these asteroid TMs, human-engineered base stations could be deployed on multiple asteroids, each equipped with an electromagnetic transmitter/receiver to permit measurement of variations in the distance between them. We discuss a potential conceptual design with two base stations, each with a space-qualified optical atomic clock measuring the round-trip electromagnetic pulse travel time via laser ranging. Trade space exists to optimize multiple aspects of this mission: for example, using a radio-ranging or interferometric link system instead of laser ranging. This motivates future dedicated technical design study. This mission concept holds exceptional promise for accessing this GW frequency band.

In this work we analyze the $CP$-averaged branching ratios and direct $CP$-violating asymmetries of the four-body decays $B_S\to \pi \pi \pi \pi$ decay from the $S$-wave resonances, $f_0(980)$ and $f_0(500)$ and $P$-wave resonances, $\rho (770)$ by introducing the $S$-wave and $P$-wave $\pi \pi$ distribution amplitudes within the framework of the perturbative QCD approach. We also calculate branching ratios of the two-body decays $B_S^0\to {\rho }^0{\rho }^0$, $B_S^0\to {\rho }^{+}{\rho }^{-}$ from the corresponding quasi-two-body decays models and compare our results with those obtained previously using the perturbative QCD approach, the QCD factorization approach, and the factorization-assisted topological amplitude approach. It is found that the predictions are consistent with present data within errors. The branching ratios of our calculations for the four-body decays $B_S\to \pi \pi \pi \pi$ are at the order of the ${10}^{-7}$. For the $CP$-violating asymmetries, we found that $CP$-violating asymmetry can be enhanced, largely by the $\rho -\omega$ mixing resonances, when $\pi \pi$ pairs masses are in the vicinity of $\omega$ resonance.

We study the transverse momentum dependent (TMD) evolution of the three leading twist dipole type T-odd gluon TMDs inside a transversely polarized nucleon, all of which at small $x$ dynamically originate from the spin dependent odderon. Their energy dependence presents a unique opportunity to study the polarization dependent TMD evolution in the small-$x$ region, where the distributions are identical up to a normalization constant at tree level. We further propose to study their evolution via azimuthal asymmetries in virtual photon-jet production in polarized proton-proton collisions at RHIC. We present model predictions for the asymmetries as functions of the large jet or photon transverse momentum and $Q^2$ which set the hard scales in this process.

In this work, we systematically study the $D{\overline{D}}^{*}/B{\overline{B}}^{*}$ and $D{D}^{*}/\overline{B}{\overline{B}}^{*}$ systems with the Bethe-Salpeter equation in the ladder and instantaneous approximations for the kernel. By solving the Bethe-Salpeter equation numerically with the kernel containing the direct and crossed one-particle exchange diagrams and introducing three different form factors (monopole, dipole, and exponential form factors) at the vertices, we find only the isoscalar $D{\overline{D}}^{*}/B{\overline{B}}^{*}$ and $D{D}^{*}/\overline{B}{\overline{B}}^{*}$ systems can exist as bound states. This indicate that the $X(3872)$ and $T_{cc}^{+}$ could be accommodated as $I^G(J^{PC})=0^{+}(1^{++})$ $D{\overline{D}}^{*}$ and $(I)J^P=(0)1^{+}D{D}^{*}$ bound states while the bound-state explanations for $Z_b(10610)$ and $Z_c(3900)$ are excluded.

In recent years, dark matter direct detection experiments have spurred interest in the Migdal effect, where it is employed to extend their sensitivity to lower dark matter masses. Given the lack of observation of the Migdal effect, the calculation of the signal is subject to large theoretical uncertainties. It is therefore desirable to attempt a first measurement of the Migdal effect, and to test the theoretical predictions of the Migdal effect for the calibration of the experimental response to a potential dark matter signal. In this work, we explore the feasibility of observing the Migdal effect in xenon and argon. We carry out proof-of-concept calculations for low-energy neutrons from a filtered source, and using a reactor, the Spallation Neutron Source, or ${}^{51}\mathrm{Cr}$ as potential neutrino sources. We perform a detector simulation for the xenon target and find that, with available technology, the low-energy neutron source is the most promising, requiring only a modest neutron flux, detector size, and exposure period.

Light-front time-ordered amplitudes are investigated in the virtual scalar meson production process in ($1+1$) dimensions using the scalar field model extended from the conventional Wick-Cutkosky model. There is only one Compton form factor (CFF) in the ($1+1$)-dimensional computation of the virtual meson production process, and we compute both the real and imaginary parts of the CFF for the entire kinematic regions of $Q^2>0$ and $t<0$. We then analyze the contribution of each and every light-front time-ordered amplitude to the CFF as a function of $Q^2$ and $t$. In particular, we discuss the significance of the “cat’s ears” contributions for gauge invariance and the validity of the “handbag dominance” in the formulation of the generalized parton distribution (GPD) function used typically in the analysis of deeply virtual meson production processes. We explicitly derive the GPD from the “handbag” light-front time-ordered amplitudes in the $-t/Q^2\ll 1$ limit and verify that the integrations of the GPD over the light-front longitudinal momentum fraction for the Dokshitzer-Gribov-Lipatov-Altarelli-Parisi and Efremov-Radyushkin-Brodsky-Lepage regions correspond to the valence and nonvalence contributions of the electromagnetic form factor that we have recently reported [Phys. Rev. D 103, 076002 (2021)]. We also discuss the correspondence of the GPD to the parton distribution function for the analysis of the deep inelastic lepton-hadron scattering process and the utility of the new light-front longitudinal spatial variable $\tilde{z}$.

We revisit a two-component dark matter model in which the dark matter particles are a singlet fermion ($\psi$) and a singlet scalar ($S$), both stabilized by a single $Z_4$ symmetry. The model—proposed by Cai and Spray—is remarkably simple, with its phenomenology determined by just five parameters: the two dark matter masses and three dimensionless couplings. In fact, $S$ interacts with the Standard Model particles via the usual Higgs portal, whereas $\psi$ only interacts directly with $S$, via the Yukawa terms $\overline{{\psi }^c}(y_s+y_p{\gamma }^5)\psi S$. We consider the two possible mass hierarchies among the dark matter particles, $M_S<M_{\psi }$ and $M_{\psi }<M_S$, and numerically investigate the consistency of the model with current bounds. The main novelties of our analysis are the inclusion of the $y_p$ coupling, the update of the direct-detection limits, and a more detailed characterization of the viable parameter space. For dark matter masses below 1.3 TeV or so, we find that not only is the model compatible with all known constraints, but it also gives rise to observable signals in future dark matter experiments. Our results show that both dark matter particles may be observed in direct-detection experiments and that the most relevant indirect-detection channel is due to the annihilation of $\psi$. We also argue that this setup can be extended to other $Z_N$ symmetries and additional dark matter particles.

Sterile neutrinos at the GeV scale can resolve several outstanding problems of the Standard Model (SM), such as the source of neutrino masses and the origin of the baryon asymmetry through freeze-in leptogenesis. However, they can be challenging to detect experimentally due to their small couplings to SM particles. In extensions of the SM with new interactions of the sterile neutrinos, they can be produced copiously at accelerators and colliders. We systematically investigate the impact of such novel interactions on the asymmetry from freeze-in leptogenesis. We find that the interactions tend to bring the sterile neutrinos into equilibrium at early times, leading to a significant reduction in the generated asymmetry. We also show that observable rates of several hidden-sector neutrino signatures, such as SM Higgs decays to pairs of sterile neutrinos, can be inconsistent with the observed baryon asymmetry and provide an opportunity to falsify freeze-in leptogenesis.

In this paper, we investigate the quantum coherence for two flavor neutrinos propagating in a Schwarzschild metric. In fact, this issue is explored both qualitatively via calculating the parameter $K_3$ in Leggett-Garg inequality and also quantitatively by evaluating the $l_1$-norm, $\mathcal{C}(\rho )$. Using the weak field approximations, we show that the gravitational effects decrease the maximum value of $K_3$ for some intervals of energy in such a way that there is no violation, while it leaves the maximum amount of the quantum coherence, $\mathcal{C}(\rho )$, unchanged.

We investigate the invisible decay of positronium to probe the fermionic light dark matter mediated by the dark $Z$ boson. The invisible decay rate of positronium through weak interaction in the standard model is too small to be detected in the experiment. We show that it can be enhanced to be observed in the future if the dark matter is lighter than the electron in the dark $Z$ model. We also compute the relic abundance of such light dark matter and discuss the big bang nucleosynthesis constraint with an alternative thermal history scenario.

The triplet or type-II seesaw mechanism is the simplest way to endow neutrinos with mass in the Standard Model (SM). Here we review its associated theory and phenomenology, including restrictions from $S$, $T$, $U$ parameters, neutrino experiments, charged lepton flavor violation as well as collider searches. We also examine restrictions coming from requiring consistency of electroweak symmetry breaking, i.e., perturbative unitarity and stability of the vacuum. Finally, we discuss novel effects associated to the scalar mediator of neutrino mass generation namely, (i) rare processes, e.g., $l_{\alpha }\to l_{\beta }\gamma$ decays, at the intensity frontier, and also (ii) four-lepton signatures in colliders at the high-energy frontier. These can be used to probe neutrino properties in an important way, providing a test of the absolute neutrino mass and mass-ordering, as well as of the atmospheric octant. They may also provide the first evidence for charged lepton flavor violation in nature. In contrast, neutrino nonstandard interaction strengths are found to lie below current detectability.

We study the electromagnetic field effect on charmonium gluon dissociation in quark-gluon plasma. With the effective Hamiltonian derived from QCD multipole expansion under an external electromagnetic field, we first solve the two-body Schrödinger equation for a pair of charm quarks with mean field potentials for color and electromagnetic interactions and obtain the charmonium binding energies and wave functions, and then calculate the gluon dissociation cross section and decay width by taking the color electric and magnetic dipole interactions as perturbations above the mean field and employing Fermi’s golden rule. Considering the charmonium deformation in a magnetic field, the discrete Landau energy levels make the dissociation cross section grow hair, and the electric dipole channel is significantly changed, especially for the $P$-wave states ${\chi }_{c0}$ and ${\chi }_{c\pm }$. From our numerical calculation, the magnetic field strength $eB=5m_{\pi }^2$ already changes the gluon dissociation strongly, which may indicate measurable effects in high-energy nuclear collisions.

We introduce a new family of generalized parton distribution models able to fulfill by construction all the theoretical properties imposed by QCD. These models are built on standard parton distribution functions and extended to off-forward kinematics through a well-defined procedure. We apply this strategy on the pion, first handling a simple but insightful algebraic model, and then exploiting state-of-the-art computations obtained in continuum QCD. We compare these models with a more standard one relying on an xFitter extraction of the pion parton distribution functions. The results for both quark and gluon generalized parton distributions are presented and exploited for calculation of electromagnetic, gravitational, and Compton form factors. Results on the latter highlight the relevance of next-to-leading-order corrections, even in the so-called valence region.

We study the quasi-two-body $D\to TP$ decays and the three-body $D$ decays proceeding through intermediate tensor resonances, where $T$ and $P$ denote tensor and pseudoscalar mesons, respectively. We employ the $D\to T$ transition form factors based upon light cone sum rules and the covariant light-front quark model to evaluate the decay rates, with the former giving a better agreement with current data. Though the tree amplitudes with the emitted meson being a tensor meson vanish under factorization approximation, contributions proportional to the tensor decay constant $f_T$ can be produced from vertex and hard spectator-scattering corrections. We also investigate the finite-width effects of the tensor mesons and find that, contrary to three-body $B$ decays, the tensor-mediated $D$ decays are more seriously affected and the narrow width approximation has to be corrected. More experimental data are required in order to extract information topological amplitudes associated with quasi-two-body $D\to TP$ decays. Among the data, the $D^{+}\to f_2{\pi }^{+}$ and $D^{+}\to {\overline{K}}_2^{*0}{\pi }^{+}$ branching fractions are not self-consistent and further clarification is called for.

We present the first observation of the ${\mathrm{\Omega }}_c^0\to {\mathrm{\Omega }}^{-}{\mu }^{+}{\nu }_{\mu }$ decay and present measurements of the branching fraction ratios of the ${\mathrm{\Omega }}_c^0\to {\mathrm{\Omega }}^{-}{\ell }^{+}{\nu }_{\ell }$ decays compared to the reference mode ${\mathrm{\Omega }}_c^0\to {\mathrm{\Omega }}^{-}{\pi }^{+}$, ($\ell =e$ or $\mu$). This analysis is based on $89.5{\mathrm{fb}}^{-1}$, $711{\mathrm{fb}}^{-1}$, and $121.1{\mathrm{fb}}^{-1}$ data samples collected with the Belle detector at the KEKB asymmetric-energy $e^{+}{e}^{-}$ collider at the center-of-mass energies of 10.52 GeV, 10.58 GeV, and 10.86 GeV, respectively. The ${\mathrm{\Omega }}_c^0$ signal yields are extracted by fitting $M_{\mathrm{\Omega }\ell }$ and $M_{\mathrm{\Omega }\pi }$ spectra. The branching fraction ratios $\mathcal{B}({\mathrm{\Omega }}_c^0\to {\mathrm{\Omega }}^{-}{e}^{+}{\nu }_e)/\mathcal{B}({\mathrm{\Omega }}_c^0\to {\mathrm{\Omega }}^{-}{\pi }^{+})$ and $\mathcal{B}({\mathrm{\Omega }}_c^0\to {\mathrm{\Omega }}^{-}{\mu }^{+}{\nu }_{\mu })/\mathcal{B}({\mathrm{\Omega }}_c^0\to {\mathrm{\Omega }}^{-}{\pi }^{+})$ are measured to be $1.98\pm 0.13(\text{stat})\pm 0.08(\text{syst})$ and $1.94\pm 0.18(\text{stat})\pm 0.10(\text{syst})$, respectively. The ratio of $\mathcal{B}({\mathrm{\Omega }}_c^0\to {\mathrm{\Omega }}^{-}{e}^{+}{\nu }_e)/\mathcal{B}({\mathrm{\Omega }}_c^0\to {\mathrm{\Omega }}^{-}{\mu }^{+}{\nu }_{\mu })$ is measured to be $1.02\pm 0.10(\text{stat})\pm 0.02(\text{syst})$, which is consistent with the expectation of lepton flavor universality.

We explore the role of the dilaton field on higher-derivative supergravity within the framework of double field theory and use it to fix the Lorentz-noncovariant field redefinitions connecting the metric and dilaton fields with the duality multiplets.

The thermodynamic Euler equation for high-energy states of large-$N$ gauge theories is derived from the dependence of the extensive quantities on the number of colors $N$. This Euler equation relates the energy of the state to the temperature, entropy, number of degrees of freedom and its chemical potential, but not to the volume or pressure. In the context of the gauge/gravity duality we show that the Euler equation is dual to the generalized Smarr formula for black holes in the presence of a negative cosmological constant. We also match the fundamental variational equation of thermodynamics to the first law of black hole mechanics, when extended to include variations of the cosmological constant and Newton’s constant.

We consider a gauge theory on the 5D $\kappa$-Minkowski which can be viewed as the noncommutative analog of a $U(1)$ gauge theory. We show that the Hermiticity condition obeyed by the gauge potential $A_{\mu }$ is necessarily twisted. Performing a Becchi-Rouet-Stora-Tyutin gauge-fixing with a Lorentz-type gauge, we carry out a first exploration of the one loop quantum properties of this gauge theory. We find that the gauge-fixed theory gives rise to a nonvanishing tadpole for the time component of the gauge potential, while there is no nonvanishing tadpole 1-point function for the spatial components of $A_{\mu }$. This signals that the classical vacuum of the theory is not stable against quantum fluctuations. Possible consequences regarding the symmetries of the gauge model and the fate of the tadpole in other gauges of noncovariant type are discussed.