The paper presents joint analysis of the characteristics of the electron-photon and Cherenkov components, and muons with a threshold ${ϵ}_{\mathrm{thr}}\ge 1\mathrm{GeV}$ and zenith angles less than 60°. The analysis is based on complex data of air shower registration. A quantitative estimation of muons at different distances from the shower axis and the ratio of muons and charged particles at a distance of 600 m are obtained. The empirical relationship found between ${\rho }_{\mu }(600)/{\rho }_{\mu +e}(600)$ and the depth of the maximum $X_{\max }$ estimated by Cherenkov light data. It allowed to estimate $X_{\max }$ in individual showers by fraction of muons ${\rho }_{\mu }(600)/{\rho }_{\mu +e}(600)$. From the set of such showers, the dependence of $X_{\max }$ on the energy $E_0$ was found. Mass composition of cosmic rays with highest energies is estimated by comparison of the experimental $X_{\max }$ and QGSJetII-04 simulation $X_{\max }$ for different primary nuclei. The composition of cosmic rays determined from the muon component of air showers, mainly consists of protons and helium nuclei in the energy range 5–10 EeV. At energies greater than 30 EeV the mass composition is becoming heavier due to CNO and iron nuclei.

We study the lepton-induced resonant production of color-adjoint leptons (leptogluons) at the LHC, employing the lepton parton density function of the proton. We demonstrate that this production mechanism can be useful to extend the LHC ability to search for leptogluons beyond purely quark/gluon-initiated production processes up to $\sim 3.5\mathrm{TeV}$ leptogluon masses and $\mathcal{O}(1)\mathrm{TeV}$ compositeness scales. Discerning leptogluons from scalar and vector leptoquarks is also possible in this channel, given a data sample containing the order of 100 signal events. We argue that the resonant channel can be combined with leptogluon pair and associated leptogluon-lepton productions to boost exclusion limits and discovery prospects at the LHC.

Electromagnetically neutral dark sector particles may feebly interact with photons through higher dimensional effective operators, such as mass-dimension-five magnetic and electric dipole moment, and a mass- dimension-six anapole moment and charge radius operators. In this work, we use hypercharge gauge field form factors to treat dark states, which will induce not only electromagnetic form factors but also the corresponding $Z$ boson operators. Taking a Dirac fermion $\chi$ as an example, we investigate the probes of searching for such dark states at current and future $e^{+}{e}^{-}$ collider experiments including BESIII, STCF, Belle II, and CEPC via monophoton searches. Compared with current experiments, we find that electron colliders including BESIII, STCF, and Belle II, which operate with the center of mass at several GeV, have leading sensitivity on the corresponding electromagnetic form factors for the mass-dimension-five operators with dark states lighter than several GeV, while they cannot provide competitive upper limits for the mass-dimension-six operators. Future CEPC operated with the center of mass on and beyond the mass of $Z$ boson with competitive luminosity can probe the unexplored parameter space for dark states with mass-dimension-five (six) operators in the mass region of $m\lesssim 100\mathrm{GeV}$ ($10\mathrm{MeV}\lesssim m\lesssim 100\mathrm{GeV}$).

We present three-loop helicity amplitudes for the production of a single photon in association with one jet in quantum chromodynamics, a final state which provides a standard candle of the Standard Model at the Large Hadron Collider. We employ a recently proposed variation of the so-called tensor projection method in the ’t Hooft-Veltman scheme (tHV) which avoids the computation of contributions due to unphysical ($-2\epsilon$)-dimensional polarizations of the external states. We obtain compact analytic results expressed in terms of harmonic polylogarithms.

In $\mathrm{AdS}/\mathrm{CFT}$ corresponding, the UV divergence of generating functional on the field theory can be removed as the IR divergence in the gravity. This geometric process is well known as holographic renormalization. The standard method of holographic renormalization is based on the Fefferman-Graham expansion, which is strict and universal but technically cumbersome. To improve the technique, different methods have been proposed. Here we develop an alternative approach to holographic renormalization based on the Hamilton-Jacobi formulation of gravity. Compared to previous approaches, its distinguishing feature is the generation of exact ansatz of counterterms. We apply this approach to several typical holographic models, which consistently performs well.

The scattering of Dirac fermions in the background fields of topological solitons of the ($2+1$)-dimensional ${\mathbb{CP}}^{N-1}$ model is studied using analytical and numerical methods. It is shown that the exact solutions for fermionic wave functions can be expressed in terms of the confluent Heun functions. The question of the existence of bound states for the fermion-soliton system is then investigated. General formulas describing fermion scattering are obtained, and a symmetry property for the partial phase shifts is derived. The amplitudes and cross sections of the fermion-soliton scattering are obtained in an analytical form within the framework of the Born approximation, and the symmetry properties and asymptotic forms of the Born amplitudes are investigated. The dependences of the first few partial phase shifts on the fermion momentum are obtained by numerical methods, and some of their properties are investigated and discussed.

The spatial variation and temporal variation in surface potential are important error sources in various precision experiments and deserved to be considered carefully. In the former case, the theoretical analysis shows that this effect depends on the surface potentials through their spatial autocorrelation functions. By making some modification to the quasilocal correlation model, we obtain a rigorous formula for the patch force, where the magnitude is proportional to $\frac{1}{a^2}{(\frac{a}{w})}^{\beta (a/w)+2}$ with $a$ the distance between two parallel plates, $w$ the mean patch size, and $\beta$ the scaling coefficient from $-2$ to $-4$. A torsion balance experiment is then conducted, and we obtain a 0.4 mm effective patch size and 20 mV potential variance. In the latter case, we apply an adatom diffusion model to describe this mechanism and predicts a $f^{-3/4}$ frequency dependence above 0.01 mHz. This prediction meets well with a typical experimental results. Finally, we apply these models to analyze the patch effect for two typical experiments. Our analysis will help to investigate the properties of surface potentials.

We propose a new scenario of early dark energy (EDE) with a dark Higgs field trapped at the origin. To keep this dark Higgs trapped until around the matter-radiation equality, we use dark photons produced nonthermally by coherent oscillations of axions, which have a much stronger trapping effect than thermal mass. When the trapping ends, the dark Higgs quickly decays into dark photons, which are then redshifted as radiation. In fact, dark photons are self-interacting dark radiation, and the dark Higgs field can also be in thermal equilibrium if its self-coupling is small enough. In some cases, these particles can act as the Wess-Zumino dark radiation. The dark Higgs EDE scenario works well for an ordinary Mexican-hat potential, and the dark Higgs naturally sits at the origin from the beginning, since it is the symmetry-enhanced point. Thus, unlike the axion EDE, there is no need for elaborate potentials or fine-tuning with respect to the initial condition. Interestingly, the axion not only produces dark photons, but also explains dark matter. We find the viable parameter region of the axion decay constant and the axion mass where dark matter and the $H_0$ tension can be simultaneously explained. We also discuss the detectability of the axion in the presence of axion-photon coupling, and show that the axion can be the QCD axion.

We present here results from the first-ever search for dark-photon dark matter that could have coupled to baryons in LISA Pathfinder, the technology demonstrator for a space-based gravitational-wave antenna. After analyzing approximately three months of data taken by LISA Pathfinder in the frequency range $[2\times {10}^{-5},5]\mathrm{Hz}$, corresponding to dark-photon masses of $[8\times {10}^{-20},2\times {10}^{-14}]\mathrm{eV}/c^2$, we find no evidence of a dark-matter signal and set upper limits on the strength of the dark-photon/baryon coupling. To perform this search, we leveraged methods that search for quasimonochromatic gravitational-wave signals in ground-based interferometers and are robust against non-Gaussianities and gaps in the data. Our work therefore represents a proof-of-concept test of search methods in LISA to find persistent, quasimonochromatic signals and shows our ability to handle non-Gaussian artifacts and gaps while maintaining good sensitivity compared to the optimal matched filter. The results also indicate that these methods can be powerful tools in LISA to not only find dark matter, but also look for other persistent signals from, e.g., intermediate-mass black hole inspirals and galactic white dwarf binaries.

Hydrodynamical instabilities, such as the standing accretion shock instability (SASI), play an essential role in the dynamics of core-collapse supernovae, with observable imprints in the neutrino and gravitational wave signals. Yet, the impact of stellar rotation on the development of SASI is poorly explored. We investigate the conditions favoring the growth of SASI in the presence of rotation through a perturbative analysis. The properties of SASI are compared in two stationary configurations, cylindrical and spherical equatorial, which mainly differ by their advection timescales from the shock to the proto-neutron star surface. Without rotation, the mode $m=1$, corresponding to a one-armed spiral SASI deformation, can be significantly more unstable in the spherical equatorial configuration. In fact, the shorter advection time in the spherical equatorial geometry allows for a larger contribution of the entropic-acoustic coupling from the region of adiabatic compression near the surface of the proto-neutron star. The angular momentum of the collapsing core favors the growth of prograde spiral modes $m=1$ and $m=2$ in both geometries. Although the growth rate of the spiral instability is systematically faster in spherical geometry, its oscillation frequency is remarkably insensitive to the geometry. Such a contrast with nonrotating flows calls for a deeper understanding of the role of advection in the mechanism of spiral SASI. Our findings suggest that the resonant coupling of acoustic waves with their corotation radius may play a major role in the instability mechanism of collapsing cores with rotation. Elucidating this physical mechanism is essential to interpret the signal from future multimessenger supernova observations.

Two simple ways by which the standard signals of the Standard Model Higgs boson can be depleted are its couplings to fermions and gauge bosons can be suppressed by a universal factor, and part of its branching fraction can be drained into invisible final states. A large class of theories can impose one or both of these depletion factors, even if mild, by way of additional scalar bosons that are singlets under the Standard Model but mix with the Higgs boson. We perform a comprehensive survey of the present status of the depleted Higgs boson, and discuss future prospects for detecting the presence of either depletion factor. We also survey the constraints status and future detection prospects for the generic case of extra mixed-in scalars which generically lead to these depletion factors for the Higgs boson. We find, for example, that precision study of the Higgs boson in many cases is more powerful than searches for the extra scalar states, given the slate of next-generation experiments that are on the horizon.

The detection of neutron-antineutron oscillation will be a discovery of fundamental importance in particle physics and cosmology. In models discussed widely in literature, the process is generated through heavy new physics with weak, perturbative coupling at the scale of the experiment. Acknowledging the fact that nature has been quite evasive regarding the strength and scale of new physics, we discuss a new mechanism, generated by confining new physics, at $\sim 2\mathrm{GeV}$, resulting in low-energy baryon number violating effects. The mechanism predicts baryon number violating processes like neutron disappearance, neutron-neutron annihilation and neutron-antineutron oscillation generated through the condensation of the linear moose.

We study a class of models in which the Standard Model (SM) and dark matter (DM) belong to a conformal/scale-invariant theory at high energies. Scale invariance is spontaneously broken at scale $f$, giving rise to a dilaton as the corresponding Goldstone boson. In the low-energy theory, we assume that DM interacts with the SM solely through the dilaton portal, which is suppressed by the conformal breaking scale $f$. For $f\gg \mathrm{TeV}$, the portal interactions are extremely weak, resulting in DM not being in thermal equilibrium with the SM. Thus, ultraviolet freeze-in production of DM occurs through the dilaton portal, being most effective at the maximum temperature of the SM bath. The temperature evolution is greatly impacted by the reheating dynamics, which we parametrize using a general equation of state $w$ and temperature at the end of reheating $T_{\mathrm{rh}}$. We analyze the implications of the reheating dynamics for DM production in this framework and identify regions of parameter space that result in the observed DM relic abundance for a wide range of DM masses and reheating temperatures for scalar, vector, or fermion DM.

We study the statistical significances for exclusion and discovery of proton decay at current and future neutrino detectors. Various counterintuitive flaws associated with frequentist and modified frequentist statistical measures of significance for multichannel counting experiments are discussed in a general context and illustrated with examples. We argue in favor of conservative Bayesian-motivated statistical æmeasures, and as an application we employ these measures to obtain the current lower limits on proton partial lifetime at various confidence levels, based on Super-Kamiokande’s data, generalizing the 90% C.L. published limits. Finally, we present projections for exclusion and discovery reaches for proton partial lifetimes in $p\to \overline{\nu }{K}^{+}$ and $p\to e^{+}{\pi }^0$ decay channels at Hyper-Kamiokande, DUNE, JUNO, and THEIA.

We analyze the neutral meson mixing by directly solving the dispersion relation obeyed by the mass and width differences of the two meson mass eigenstates. We solve for the parameters $x$ and $y$, proportional to the mass and width differences in the charm mixing, respectively, taking the box-diagram contributions to $x(s)$ and $y(s)$ at large mass squared $s$ of a fictitious $D$ meson as inputs. The SU(3) symmetry breaking is introduced through physical thresholds of different $D$ meson decay channels for $y(s)$. These threshold-dependent effects, acting like nonperturbative power corrections in QCD sum rules, stabilize the solutions of $y(s=m_D^2)$ with the $D$ meson mass $m_D$. We then calculate $x(s)$ through the dispersive integration of $y(s)$, and show that our predictions $x(m_D^2)\approx 0.21\%$ and $y(m_D^2)\approx 0.52\%$ are close to the data in both $CP$-conserving and $CP$-violating cases. It is observed that the channel containing dikaon states provides the major source of SU(3) breaking, which enhances $x(m_D^2)$ and $y(m_D^2)$ by four orders of magnitude relative to the perturbative results. We also predict the coefficient ratio $q/p$ involved in the charm mixing with $|q/p|-1\approx 2\times {10}^{-4}$ and $Arg(q/p)\approx 6\times {10}^{-3}$ degrees, which can be scrutinized by precise future measurements. The formalism is extended to studies of the $B_{s(d)}$ meson mixing and the kaon mixing, and the small deviations of the obtained width differences from the perturbative inputs explain why the above mixing can be understood via short-distance dynamics. We claim that the puzzling charm mixing is attributed to the strong Glashow-Iliopoulos-Maiani suppression on perturbative contributions, instead of to breakdown of the quark-hadron duality, which occurs only at 15% level.

Borrowing the structures of the hydrogen atom, molecular ion, and diatomic molecule, we predict the nature of a new type of hydrogenlike charm-pion or charm-kaon matter that could be obtained by replacing the proton and electron in hydrogen matter with a charmed meson and a pion or a kaon, respectively. We find that the spectra of the atom, molecular ion, and diatomic molecule can be obtained simultaneously with the Coulomb potential for the hydrogen, the charm-pion, and the charm-kaon systems. The predicted charm-pion matter also allows us to explore the mass shift mediated by the strong interaction. For the charm-pion and charm-kaon systems, the strong interactions could lead to binding energy shifts. Our calculations suggests that the binding energy shifts in charm-pion systems are in the order of several to tens of eV. For the charm-kaon systems, the results are in the order of tens to hundreds of eV. Exploring hydrogenlike charm-pion matter must lead to new demands for high-precision experiments.

Starting from a reanalysis of previous work, we construct the proper low-energy quantum field theory (QFT) limit of a full quantum gravity theory in the Born-Oppenheimer approach. We separate the gravitational sector into a classical background, given by a vacuum diagonal Bianchi I cosmology, and its quantum perturbations represented by the two graviton degrees of freedom; we further include quantum matter in the form of a test scalar field. We then implement a Born-Oppenheimer separation, where the gravitons and matter play the roles of “slow” and “fast” quantum components, respectively, and perform a WKB expansion in a Planckian parameter. The functional Schrödinger evolution for matter is recovered after averaging over quantum-gravitational effects, provided that a condition is imposed on the gravitons’ wave functional. Such a condition fixes the graviton dynamics and is equivalent to the purely gravitational Wheeler-DeWitt constraint imposed in previous approaches. The main accomplishment of the present work is to clarify that QFT in curved spacetime can be recovered in the low-energy limit of quantum gravity only after averaging over the graviton degrees of freedom, in the spirit of effective field theory. Furthermore, it justifies a posteriori the implementation of the gravitational Wheeler-DeWitt equation on the “slow” gravitons’ wave functional rather than assuming its validity a priori.

Local flatness is a property shared by all the spin foam models. It ensures that the theory’s fundamental building blocks are flat by requiring locally-trivial parallel transport. In the context of simplicial Lorentzian spin foam theory, we show that local flatness is the main responsible for the emergence of geometry independently of the details of the spin foam model. We discuss the asymptotic analysis of the Engle-Pereira-Rovelli-Livine spin foam amplitudes in the large quantum number regime, highlighting the interplay with local flatness.

We extend our holographic analysis of the emission of photons by a strongly coupled plasma subject to a very intense external magnetic field. We previously showed that in a particular model, any photon produced by the plasma had to be in its only polarization state parallel to the reaction plane. In this paper we consider a construction that relaxes a formerly imposed constraint, permitting the emission of photons with either out-plane or in-plane polarization. This constitutes a completion of our former study because the fully back-reacted equations decouple for these two polarization states in such a manner that those involving the in-plane are identical to the ones we explored previously. In view of the above, part of the details concerning the calculations and of the numerical results for the differential rate of emitted photons that we present here correspond exactly to those omitted in our preceding letter. One of our main results is that the production of photons is increased by the introduction of a nonvanishing magnetic field with an intensity up to a value $B_{\vartheta }$, above which the effect is reversed and said production becomes lower than the $B=0$ case. The characteristic intensity $B_{\vartheta }$ depends on the propagation direction and tends to zero as the photon momentum becomes aligned with the magnetic field. Additionally, we also show that the magnetic field has the effect of increasing the value of the elliptic flow, providing a possible explanation for the excess measured in collision experiments. The holographic model is constructed using an effective five-dimensional action that includes a scalar field in addition to the constant magnetic field.

In this paper, we derive a soft gluon theorem in the near horizon region of the Schwarzschild black hole from the Ward identity of the near horizon large gauge transformation. The flat spacetime soft gluon theorem can be recovered as a limiting case of the curved spacetime.