The lensing of gravitational waves (GWs) occurs when GWs experience local gravitational potential. In the weak-lensing regime, it has been reported that a simple consistency relation holds between the variances of the magnification and phase modulation. In this paper, we present two additional consistency relations between the averages and variances of the weakly lensed GW signals in wave optics. We demonstrate that these consistency relations are derived as the weak-lensing limit of the full-order relations for the averages of the amplification factor and its absolute square. These full-order relations appear to originate from energy conservation and the Shapiro time delay, and they are demonstrated to hold irrespective of the matter distribution.

To probe the cosmic particle flux at the highest energies, large volumes of dense material like ice have to be monitored. This can be achieved by exploiting the radio signal. In this work, we provide a macroscopic model to predict the radar echo signatures found when a radio signal is reflected from a cosmic-ray or neutrino-induced particle cascade propagating in a dense medium like ice. Its macroscopic nature allows for an energy independent run-time, taking less than 10 s for simulating a single scatter event. As a first application, we discuss basic signal properties and simulate the expected signal for the T-576 beam-test experiment at the Stanford Linear Accelerator Center. We find good signal strength agreement with the only observed radar echo from a high-energy particle cascade to date.

Stellar energy loss is a sensitive probe of light, weakly coupled dark sectors, including ones containing millicharged particles (MCPs). The emission of MCPs can affect stellar evolution and therefore can alter the observed properties of stellar populations. In this work, we improve upon the accuracy of existing stellar limits on MCPs by self-consistently modeling (1) the MCP emission rate, accounting for all relevant in-medium effects and production channels and (2) the evolution of stellar interiors (including backreactions from MCP emission) using the mesa stellar evolution code. We find MCP emission leads to significant brightening of the tip of the red-giant branch. Based on photometric observations of 15 globular clusters whose bolometric magnitudes are inferred using parallaxes from Gaia astrometry, we obtain robust bounds on the existence of MCPs with masses below 100 keV.

The AMS02 experiment has published the periodic spectra of proton, helium, and helium isotopes across the majority of solar cycle 24. These precise data exhibit temporal structures that correlate with solar modulation. In this study, we utilize these data to probe three analytic solar modulation models, including the force-field approximation, the convection-diffusion model, and the extended force-field approximation with a drift effect. We adopt a method that eliminates the influence of interstellar cosmic ray spectra, and use Earth-observed spectra at time $t_1$ to predict those at time $t_2$. In order to explore the rigidity dependence of solar modulation models, we substitute the conventional potential parameter $\varphi$ with a modified parameter ${\varphi }^{\prime }=\frac{R}{k_2(R)}\varphi$ for our analysis. Combined with the ${\chi }^2$ minimization method, the best-fit modulation parameter ${\varphi }^{\prime }$ can be evaluated. First, we test the validity of a rigidity-independent ${\varphi }^{\prime }$ and find that both the force-field approximation (FFA) and the extended force-field approximation (EFFA) agree well with data near the solar minimum period. However, all models significantly deviate from the data during the solar maximum. Consequently, we assume a constant ${\varphi }^{\prime }(t_1)$ at solar minimum and calculate $\mathrm{\Delta }{\varphi }^{\prime }={\varphi }^{\prime }(t_2)-{\varphi }^{\prime }(t_1)$ for each rigidity bin at time $t_2$. It is found that $\mathrm{\Delta }{\varphi }^{\prime }$ generally adheres to a linear-logarithm relationship with rigidity at any given time. By adopting a linear-logarithm formula of $\mathrm{\Delta }{\varphi }^{\prime }$, we further discover that both the modified FFA and EFFA can reconcile the observations during solar maxima. This suggests that, at solar maximum, the parameter ${\varphi }^{\prime }$, which correlates with the diffusion pattern in the heliospheric magnetic fields, exhibits a rigidity dependence. Moreover, the modified EFFA enhances the concordance with data during periods of pronounced dips, as observed by AMS02. This implies that the drift effect could significantly contribute to these solar transient phenomena.

The next generation of space- and ground-based facilities promise to reveal an entirely new picture of the gravitational wave sky: thousands of galactic and extragalactic binary signals, as well as stochastic gravitational wave backgrounds (SGWBs) of unresolved astrophysical and possibly cosmological signals. These will need to be disentangled to achieve the scientific goals of experiments such as LISA, Einstein Telescope, or Cosmic Explorer. We focus on one particular aspect of this challenge: reconstructing an SGWB from (mock) LISA data. We demonstrate that simulation-based inference (SBI)—specifically truncated marginal neural ratio estimation (TMNRE)—is a promising avenue to overcome some of the technical difficulties and compromises necessary when applying more traditional methods such as Monte Carlo Markov Chains (MCMC). To highlight this, we show that we can reproduce results from traditional methods both for a template-based and agnostic search for an SGWB. Moreover, as a demonstration of the rich potential of SBI, we consider the injection of a population of low signal-to-noise ratio supermassive black hole transient signals into the data. TMNRE can implicitly marginalize over this complicated parameter space, enabling us to directly and accurately reconstruct the stochastic (and instrumental noise) contributions. We publicly release our TMNRE implementation in the form of the code saqqara.

We apply the chiral quark-soliton model, used previously to describe baryons with one heavy quark, to the case of heavy tetraquarks. We argue that the model is insensitive to the nature of the heavy object bound by the soliton, i.e., to its mass and spin. Therefore, a heavy quark can be replaced by an antidiquark without modifying the soliton background. Diquark dynamics is taken into account by means of the nonrelativistic Schrödinger equation with the Cornell potential. We fix the Cornell potential parameters from the charmonia and bottomonia spectra. We first compute $B_c$-meson masses to check our fitting procedure, and then compute diquark masses by appropriately rescaling color factors in the Cornell potential. We then compute tetraquark masses and confirm previous findings that only $bb$ tetraquarks are bound.

Quantum field theory in the presence of strong background fields contains interesting problems where quantum computers may someday provide a valuable computational resource. In the noisy intermediate-scale quantum era it is useful to consider simpler benchmark problems in order to develop feasible approaches, identify critical limitations of current hardware, and build new simulation tools. Here we perform quantum simulations of strong-field QED (SFQED) in $3+1$ dimensions, using real-time nonlinear Breit-Wheeler pair production as a prototypical process. The strong-field QED Hamiltonian is derived and truncated in the Furry-Volkov mode expansion, and the interactions relevant for Breit-Wheeler are transformed into a quantum circuit. Quantum simulations of a “null double slit” experiment are found to agree well with classical simulations following the application of various error mitigation strategies, including an asymmetric depolarization algorithm which we develop and adapt to the case of Trotterization with a time-dependent Hamiltonian. We also discuss longer-term goals for the quantum simulation of SFQED.

We study the $\mu \to e$ conversion process in nuclear targets arising in models of axionlike particles (ALPs) with hadronic and charged lepton flavor violating (CLFV) interactions. Contributions to this process generally fall into two categories: spin-independent (SI) and spin-dependent (SD). While the SI contribution can be generated by a dipole operator through purely leptonic ALP interactions, the SD contribution can also be present through ALP-quark interactions at tree-level. It is naively anticipated that the SI contribution would be dominant due to its coherent enhancement. In this paper, we show that is not generically the case; in particular, for naturally sized ALP couplings to quarks of order $\sim m_q/f_a$, the SD interaction induced by ALP-${\pi }^0$ mixing turns out to be the leading contribution to $\mu \to e$ conversion. Intuitively, this stems from the suppressed dipole contribution by the QED one-loop factor which counters the effect of SI coherent enhancement. Our study highlights the importance of $\mu \to e$ conversion searches in exploring the parameter space of generic ALP models, and demonstrates the competitiveness of these searches in probing the CLFV ALP parameter space in the heavy mass range of $m_a\gtrsim m_{\mu }$.

We discuss the thermal target curves of Majorana, Dirac, scalar, and vector light dark matter (DM) that are associated with the freeze-out mechanism via the annihilation into the $e^{+}{e}^{-}$ pair through the electron-specific spin-0 mediator of dark matter. We also discuss the mechanism to produce the regarded DM mediator in the electron (positron) fixed-target experiments such as NA64e and LDMX. We derive the corresponding experimental reaches of NA64e and LDMX that are complementary to the DM thermal target parameter space.

The Zee-Babu model is a minimal realization of radiative neutrino mass generation mechanism at the two-loop level. We study the phenomenology of this model at future multi-TeV muon colliders. After imposing all theoretical and low-energy experimental constraints on the model parameters, we find that the Zee-Babu states are expected not to reside below the TeV scale, making it challenging to probe them at the LHC. We first analyze the production rates for various channels, including multi singly charged and/or doubly charged scalars at muon colliders. For concreteness, we study several benchmark points that satisfy neutrino oscillation data and other constraints and find that most channels have large production rates. We then analyze the discovery reach of the model using two specific channels: the pair production of singly and doubly charged scalars. For the phenomenologically viable scenarios considered in this study, charged scalars with masses up to $\mathcal{O}(3–4)\mathrm{TeV}$ can be probed for the center-of-mass energy of 10 TeV and total luminosity of $10{\mathrm{ab}}^{-1}$.

The diverse and distinct collider phenomenology of color-sextet scalars motivates a thorough investigation of their effective couplings to the Standard Model at the LHC. Some of the more unique sextet signals involve not only jets but also leptons. In previous work, we proposed an LHC search for color-sextet scalars in a channel with jets and a hard opposite-sign lepton pair, which results from a dimension-six coupling. In this sequel we study the counterpart processes with neutrinos, which produce jets in association with missing transverse energy ($E_{\mathrm{T}}^{\mathrm{miss}}$) in addition to possible leptons. We consider multiple search channels, including both single and pair sextet production, all characterized by significant missing energy and some featuring distinctive kinematic features. Our multifaceted study consists of three reinterpreted existing searches and a joint-likelihood analysis designed by us to maximize HL-LHC sensitivity to single sextet production. We show that our dedicated strategy in the $\mathrm{jets}+\text{lepton}+E_{\mathrm{T}}^{\mathrm{miss}}$ channel can supersede today’s limits from reinterpreted searches, and we make sensitivity projections for the HL-LHC. Altogether, our analysis can exclude sextet scalars lighter than 4.4 TeV or probe effective cutoffs as high as 16.8 TeV.

Supersymmetric models with a strongly interacting superconformal hidden sector (HS) may drive soft supersymmetry (SUSY) breaking scalar masses, bilinear soft term $B\mu$ and Higgs combinations $m_{H_{u,d}}^2+{\mu }^2$ to small values at some intermediate scale, leading to unique sparticle mass spectra along with possibly diminished fine-tuning in spite of a large superpotential $\mu$ parameter. We set up a computer code to calculate such spectra, which are then susceptible to a variety of constraints: (1) possible charge-or-color breaking (CCB) minima in the scalar potential, (2) unbounded from below (UFB) scalar potential, (3) improper electroweak symmetry breaking, (4) a charged or sneutrino lightest SUSY particle (LSP), (5) generating $m_h\sim 125\mathrm{GeV}$, (6) consistency with LHC sparticle mass limits, and (7) naturalness. We find this bevy of constraints leaves little or no viable parameter space for the case where hidden sector dynamics dominates minimal supersymmetric standard model (MSSM) running, even for the case of nonuniversal gaugino masses. For the case with moderate HS running with comparable MSSM running, and with universal gaugino masses, then the fine-tuning is ameliorated, but nonetheless remains high. Viable spectra with moderate HS running and with low fine-tuning and large $\mu$ can be found for nonuniversal gaugino masses.

Soft and collinear radiation in collider processes can be described in a universal way, that is independent of the underlying process. Recent years have seen a number of approaches for probing whether radiation beyond the leading soft approximation can also be systematically classified. In this paper, we study a formula that captures the leading next-to-soft QCD radiation affecting processes with both final- and initial-state partons, by shifting the momenta in the nonradiative squared amplitude. We first examine $\mathrm{W}+\text{jet}$ production, and show that a previously derived formula of this type indeed holds in the case in which massive color singlet particles are present in the final state. Next, we develop a physical understanding of the momentum shifts, showing precisely how they disrupt the well-known angular ordering property of leading soft radiation.

The quartic Higgs-gauge-boson coupling $g_{hhWW}$ is sensitive to the electroweak symmetry breaking mechanism; however, it is challenging to be measured at the Large Hadron Collider. We show that the coupling can be well probed at future lepton colliders through di-Higgs boson production via the vector boson fusion channel. We perform a detailed simulation of ${\ell }^{+}{\ell }^{-}\to \nu \overline{\nu }hh\to 4b+{\cancel{E}}_T$ with parton showering effects at $e^{+}{e}^{-}$, ${\mu }^{+}{\mu }^{-}$ and $e^{-}{\mu }^{+}$ colliders. We find that the regions of $g_{hhWW}/g_{hhWW}^{\mathrm{SM}}<0.86$ and $g_{hhWW}/g_{hhWW}^{\mathrm{SM}}>1.32$ can be discovered at the $5\sigma$ confidence level at the 10 TeV ${\mu }^{+}{\mu }^{-}$ collider with an integrated luminosity of $3{\mathrm{ab}}^{-1}$. We also demonstare that $g_{hhWW}/g_{hhWW}^{\mathrm{SM}}$ is constrained within [0.72, 1.66], [0.72, 1.70], [0.84, 1.32], and [0.88, 1.14] at the 1 TeV $e^{+}{e}^{-}$, $e\mu$ colliders, 2 TeV $e\mu$ collider, and 10 TeV ${\mu }^{+}{\mu }^{-}$ collider, respectively, given null excess observed at the $2\sigma$ confidence level with an integrated luminosity of $3{\mathrm{ab}}^{-1}$.

The Short-Baseline Neutrino program in Fermilab aims to resolve the nature of the low-energy excess events observed in LSND and MiniBooNE, and analyze with unprecedented precision neutrino interactions with argon. These studies require a reliable estimate of neutrino cross sections, in particular for charged current quasielastic scattering (CCQE). Here, we report updates of the nuwro Monte Carlo generator that, most notably, bring the state-of-the-art spectral functions to model the ground state properties of the argon nucleus, and improve the accuracy of the cross sections at low energies by accounting for the effects of the nuclear Coulomb potential. We discuss these developments in the context of electron and neutrino interactions, by comparing updated nuwro predictions to experimental data from Jefferson Laboratory Hall A and MicroBooNE. The MicroBooNE CCQE-dominated data are described with the ${\chi }^2$ per degree of freedom of 0.7, compared with 1.0 in the local Fermi gas model. The largest improvement is observed for the angular distributions of the produced protons, where the ${\chi }^2$ reduces nearly by half. Being obtained using the axial form factor parametrization from MINERvA, our results indicate a consistency between the CCQE measurements in MINERvA and MicroBooNE.

We present a mathematical framework for constructing the most general neutrino mass matrices that yield the observed spectrum of light active neutrino masses in conjunction with arbitrarily many heavy sterile neutrinos, without the need to assume a hierarchy between Dirac and Majorana mass terms. The seesaw mechanism is a byproduct of the formalism, along with many other possibilities for generating tiny neutrino masses. We comment on phenomenological applications of this approach, in particular deriving a mechanism to address the long-standing $(g-2{)}_{\mu }$ anomaly in the context of the left-right symmetric model.

We develop further the investigations by Narayan [de Sitter space, extremal surfaces, and time entanglement, Phys. Rev. D 107, 126004 (2023)] on de Sitter space, extremal surfaces, and time entanglement. We discuss the no-boundary de Sitter extremal surface areas as certain analytic continuations from AdS while also amounting to space-time rotations. The structure of the extremal surfaces suggests a geometric picture of the time-entanglement or pseudo-entanglement wedge. We also study some entropy relations for multiple subregions. The analytic continuation suggests a heuristic Lewkowycz-Maldacena formulation of the extremal surface areas. In the bulk, this is now a replica formulation on the Wavefunction, which suggests interpretation as pseudo-entropy. Finally, we also discuss aspects of future-past entangled states and time evolution.

Recently, an infinite family of one-parameter generalizations of the Veneziano amplitude were bootstrapped using as input assumptions an integer mass spectrum, crossing symmetry, high-energy boundedness, and exchange of finite spins. This new result was dubbed the hypergeometric Veneziano amplitude, with a real-valued deformation parameter r. For concreteness we work in a setup where the lowest-mass state is a tachyon of mass $m_0^2=-1$ and using the partial-wave decomposition and the positivity of said decomposition’s coefficients we are able to bound the deformation parameter to $r\ge 0$ and, also, to obtain an upper bound on the number of spacetime dimensions $D\le 26$, which is the critical dimension of bosonic string theory.

General relativity predicts the existence of only two tensorial gravitational wave polarizations, while a generic metric theory of gravity can possess up to four additional polarizations, including two vectors and two scalar ones. These vector/scalar polarizations are in general generated by the intrinsic new vector/scalar degrees of freedom of the specific theories of gravity. In this paper, we show that, with the violation of the Lorentz symmetry in the framework of the standard model extension, the additional nontensorial polarizations can be directly excited by the two tensorial degrees of freedom. We consider the diffeomorphism invariant standard model extension in the gravity sector with the Lorentz-violating coefficients ${\widehat{\mathit{s}}}^{(d)\mu \rho \nu \sigma }$ of the even mass dimension $d\ge 4$. In addition to the extra polarizations induced by the tensor modes, the gravitational wave in this theory travels at a speed depending on the propagation direction, experiences dispersion if and only if $d\ge 6$, and possesses neither velocity nor amplitude birefringence. The excitement of the extra polarizations is also chiral. The antenna pattern functions of interferometers due to such kinds of gravitational waves are generally linear combinations of those for all polarizations. Detected by pulsar timing arrays and the Gaia satellite, the stochastic gravitational wave background in this model could induce couplings among cross correlations, of the redshifts of photons and the astrometric deflections of the positions of pulsars, for different polarizations. These characteristics enable the use of interferometers, pulsar timing arrays, and Gaia missions to constrain this model.

It is known that the appearance of microscopic objects with distinct topologies and different Euler characteristics, such as instantons and wormholes, at the spacetime-foam level in Euclidean quantum gravity approaches leads to spacetime topology changes. Such changes, in principle, may affect the field equations that arise through the semiclassical variation procedure of gravitational actions. Although in the case of Einstein-Hilbert action the presence of microscopic wormholes does not lead to any nontrivial result, when the Gauss-Bonnet term is added in the gravitational action, the above effective topological variation procedure induces an effective cosmological constant that depends on the Gauss-Bonnet coupling and the wormhole density. Since the latter in a dynamical spacetime is in general time-dependent, one obtains an effective dark energy sector of topological origin.