By representing each collider event as a point cloud, we adopt the graphic convolutional network (GCN) with focal loss to reconstruct the Higgs jet in it. This method provides higher Higgs tagging efficiency and better reconstruction accuracy than the traditional methods, which use jet substructure information. The GCN, which is trained on events of the $H+\text{jets}$ process, is capable of detecting a Higgs jet in events of several different processes, even though the performance degrades when there are boosted heavy particles other than the Higgs boson in the event. We also demonstrate the signal and background discrimination capacity of the GCN by applying it to the $t\overline{t}$ process. Taking the outputs of the network as new features to complement the traditional jet substructure variables, the $t\overline{t}$ events can be separated further from the $H+\text{jets}$ events.

We study the experimental constraints on $CP$ violation originating in a dark sector that communicates with the Standard Model through a Higgs portal coupling $H^{†}H{Z}_{\mu \nu }^{\prime }{\tilde{Z}}^{\prime \mu \nu }$, where the $Z^{\prime }$ is from a new $U(1)$ gauge symmetry which is assumed to couple to lepton number. We compute explicitly the leading two-loop contribution of this effective operator to the electron electric dipole moment (EDM) and show that the resulting constraints are comparable to those from direct $Z^{\prime }$ searches at electron-positron colliders when the effective operator is generated at tree level. We also examine an explicit UV completion for this effective operator that was first introduced to achieve electroweak baryogenesis and show that collider constraints from $B$ factories already exclude viable baryogenesis for $Z^{\prime }$ masses below 10 GeV, and that future electron-positron Higgs factories will exclude viable baryogenesis for $Z^{\prime }$ masses up to the $e^{+}{e}^{-}$ center-of-mass energy if anticipated luminosities are achieved. For higher $Z^{\prime }$ masses, the full viable baryogenesis parameter space lies within 6 orders of magnitude of the current upper bound on the electron EDM.

The nucleon-pion-state contribution to QCD two-point and three-point functions relevant for lattice calculations of the nucleon electromagnetic form factors are studied in chiral perturbation theory. To leading order, the results depend on a few experimentally known low-energy constants only, and the nucleon-pion-state contribution to the form factors can be estimated. The nucleon-pion-state contribution to the electric form factor $G_{\mathrm{E}}(Q^2)$ is at the $+5\%$ level for a source-sink separation of 2 fm, and it increases with increasing momentum transfer $Q^2$. For the magnetic form factor, the nucleon-pion-state contribution leads to an underestimation of $G_{\mathrm{M}}(Q^2)$ by about 5% that decreases with increasing $Q^2$. For smaller source-sink separations that are accessible in present-day lattice simulations, the impact is larger, although the chiral perturbation theory results may not be applicable for such small time separations. Still, a comparison with lattice data at $t\approx 1.6\mathrm{fm}$ works reasonably well.

The BABAR Collaboration data of the $D^0\to K_S^0{K}^{+}{K}^{-}$ process are analyzed within a quasi-two-body factorization framework. Starting from the weak effective Hamiltonian, one has to evaluate matrix elements of $D^0$ transitions to two kaons for the tree amplitudes and the transitions between one kaon and two kaons for the annihilation ones ($W$-exchange). In earlier studies, assuming these transitions to proceed through the dominant intermediate resonances, we approximated them as being proportional to the kaon form factors. Here, to obtain a good fit, one has to multiply the scalar-kaon form factors, derived from unitary relativistic coupled-channel models or in a dispersion relation approach, by phenomenological energy-dependent functions. The final state kaon-kaon interactions in the $S$-, $P$-, and $D$- waves are taken into account. All $S$-wave channels are treated in a unitary way. In other respects, it is shown in a model-independent manner that the $K^{+}{K}^{-}$ and ${\overline{K}}^0{K}^{+}S$-wave effective mass squared distributions, corrected for phase space, are significantly different. At variance with the BABAR analysis, it means that the $f_0(980)$ resonance must be included in the phenomenological analysis of the $D^0\to K_S^0{K}^{+}{K}^{-}$ data. The best fit described in the main text has 19 free parameters and indicates (i) the dominance of annihilation amplitudes, (ii) a large dominance of the $f_0(980)$ meson in the near threshold $K^{+}{K}^{-}$ invariant mass distribution, and (iii) a sizable branching fraction to the $[\rho (770{)}^{+}+\rho (1450{)}^{+}+\rho (1700{)}^{+}]K_S^0$ final states. A first Appendix provides an update of the determination of the isoscalar-scalar meson-meson amplitudes based on an enlarged set of data embodying new precise low energy $\pi \pi$ data. A second Appendix proposes two alternative fits using the scalar-kaon form factors calculated from the Muskhelishvili-Omnès dispersion relation approach. These fits have ${\chi }^2$ quite close to that of the best fit but they show important contributions from both the $f_0$ and $a_0^0$ mesons and a weaker role of the ${\rho }^{+}$ mesons.

Relaxation and correlation times are two parameters used frequently in approximate descriptions of the time development of hadronizing system from some initial state toward distributions observed experimentally. Chosen to reproduce the experimental results they represent, in a sense, the history of the hadronization process. The analysis of their changes with energy is the subject of our work.

The first attempt is made to provide a quantitative theoretical interpretation of the WASA-at-COSY experimental data on the basic double-pion production reactions $pn\to d{\pi }^0{\pi }^0$ and $pn\to d{\pi }^{+}{\pi }^{-}$ in the energy region $T_p=1–1.3\mathrm{GeV}$ [Adlarson et al., Phys. Lett. B 721, 229 (2013)]. The data are analyzed within a model based on the production and decay of an intermediate $I(J^P)=0(3^{+})$ dibaryon resonance ${\mathcal{D}}_{03}$ [also denoted as $d^{*}(2380)$]. The observed decrease of the near-threshold enhancement (the so-called ABC effect) in the reaction $pn\to d{\pi }^{+}{\pi }^{-}$ in comparison to that in the reaction $pn\to d{\pi }^0{\pi }^0$ is explained (at least partially) to be due to isospin symmetry violation in the two-pion decay of an intermediate near-threshold scalar $\sigma$ meson emitted from the ${\mathcal{D}}_{03}$ dibaryon resonance under conditions of partial chiral symmetry restoration.

Our improved calculation of the nuclear spin-independent parity violating electric dipole transition amplitude ($E{1}_{\mathrm{PV}}$) for $6s{{}^{2}S}_{1/2}-7s{{}^{2}S}_{1/2}$ in ${}^{133}\mathrm{Cs}$ in combination with the most accurate (0.3%) measurement of this quantity yields a new value for the nuclear weak charge $Q_W=-73.71(26{)}_{ex}(23{)}_{th}$ against the Standard Model (SM) prediction $Q_W^{\mathrm{SM}}=-73.23(1)$. The advances in our calculation of $E{1}_{\mathrm{PV}}$ have been achieved by using a variant of the perturbed relativistic coupled-cluster theory, which treats the contributions of the core, valence, and excited states to $E{1}_{\mathrm{PV}}$ on the same footing unlike the previous high precision calculations. Furthermore, this approach resolves the controversy regarding the sign of the core correlation effects. We discuss the implications of the deviation of our result for $Q_W$ from the SM value by considering different scenarios of new physics.

In this paper we correct previous work on magnetic charge plus a photon mass. We show that contrary to previous claims this system has a very simple, closed form solution which is the Dirac string potential multiplied by a exponential decaying part. Interesting features of this solution are discussed, namely, (i) the Dirac string becomes a real feature of the solution, (ii) the breaking of gauge symmetry via the photon mass leads to a breaking of the rotational symmetry of the monopole’s magnetic field, (iii) the Dirac quantization condition is potentially altered.

It is possible to implement a certain form of modified gravity inspired by loop quantization through nonbijective canonical transformations. The canonical nature might suggest that such modifications are guaranteed to preserve general covariance. Here, however, we show that a dedicated space-time analysis is still required, even in the case of a bijective canonical transformation. In addition, a complete global analysis is presented for a recent proposal of a nonbijective transformation, showing that it does not preserve general covariance and that the only novel physical effect introduced by the modification is the presence of certain time-reversal hypersurfaces between classical space-time regions. These results provide further insights into the physical interpretation of modified dynamics in models of loop quantum gravity.

As the interaction between the black holes and highly energetic infalling charged matter receives quantum corrections, the basic laws of black hole mechanics have to be carefully rederived. Using the covariant phase space formalism, we generalize the first law of black hole mechanics, both “equilibrium state” and “physical process” versions, in the presence of nonlinear electrodynamics fields, defined by Lagrangians depending on both quadratic electromagnetic invariants, $F_{ab}{F}^{ab}$ and $F_{ab}\star F^{ab}$. Derivation of this law demands a specific treatment of the Lagrangian parameters, similar to embedding of the cosmological constant into thermodynamic context. Furthermore, we discuss the validity of energy conditions, several complementing proofs of the zeroth law of black hole electrodynamics, and some aspects of the recently generalized Smarr formula, its (non-)linearity and relation to the first law.

We extend a recently developed numerical code to obtain stationary, axisymmetric solutions that describe rotating black hole spacetimes in a wide class of modified theories of gravity. The code utilizes a relaxed Newton-Raphson method to solve the full nonlinear modified Einstein’s equations on a two-dimensional grid with a Newton polynomial finite difference scheme. We validate this code by considering static and axisymmetric black holes in general relativity. We obtain rotating black hole solutions in scalar–Gauss-Bonnet gravity with a linear (linear scalar–Gauss-Bonnet) and an exponential (Einstein-dilaton–Gauss-Bonnet) coupling and compare them to analytical and numerical perturbative solutions. From these numerical solutions, we construct a fitted analytical model and study observable properties calculated from the numerical results.

We investigate the inflationary consequences of the oscillating dark energy model proposed by Tián [Phys. Rev. D 101, 063531 (2020), which aims to solve the cosmological coincidence problem with a multiaccelerating universe (MAU). We point out that the inflationary dynamics belong to slow-roll inflation. The spectral index of scalar perturbations and the tensor-to-scalar ratio $r$ are shown to be consistent with current Planck measurements. Especially, this model predicts $r\sim {10}^{-7}$, which is far below the observation limits. This result motivates us to explore the smallness of $r$ in the general MAU. We propose a quintessential generalization of the original model and prove $r<0.01$ in general. The null detection to date of primordial gravitational waves provides circumstantial evidence for the MAU. After the end of inflation, the scalar field rolls toward infinity instead of a local minimum, and meanwhile its equation of state is oscillating with an average value larger than $1/3$. In this framework, we show that gravitational particle creation at the end of inflation is capable of reheating the Universe.

We derive all contributions to the dispersion measure (DM) of electromagnetic pulses to linear order in cosmological perturbations, including both density fluctuations and relativistic effects. We then use this result to calculate the power spectrum of DM-based cosmological observables to linear order in perturbations. In particular we study two cases: maps of the dispersion measure from a set of localized sources (including the effects of source clustering), and fluctuations in the density of DM-selected sources. The impact of most relativistic effects is limited to large angular scales, and is negligible for all practical applications in the context of ongoing and envisaged observational programs targeting fast radio bursts. We compare the leading contributions to DM-space clustering, including the effects of gravitational lensing, and find that the signal is dominated by the fluctuations in the free electron column density, rather than the local source clustering or lensing contributions. To compensate for the disappointing irrelevance of relativistic effects, we rederive them in terms of the geodesic equation for massive particles in a perturbed Friedmann-Robertson-Walker metric.

It is nontrivial to recognize phase transitions and track dynamics inside a stochastic process because of its intrinsic stochasticity. In this paper, we employ the deep learning method to classify the phase orders and predict the damping coefficient of fluctuating systems under Langevin description. As a concrete setup, we demonstrate this paradigm for the scalar condensation in QCD matter near the critical point, in which the order parameter of the chiral phase transition can be characterized in a $1+1$-dimensional Langevin equation for the $\sigma$ field. In a supervised learning manner, convolutional neural networks accurately classify the first-order phase transition and crossover based on $\sigma$ field configurations with fluctuations. Noise in the stochastic process does not significantly hinder the performance of the well-trained neural network for phase order recognition. For mixed dynamics with diverse dynamical parameters, we further devise and train the machine to predict the damping coefficients $\eta$ in a broad range. The results show that it is robust to extract the dynamics from the bumpy field configurations.

We discuss several aspects of a generalization of the Chern-Simons action containing the pseudodifferential operator $\sqrt{-\square }$, which we shall call pseudo-Chern-Simons (PCS). First, we derive the PCS from the bosonization of free massive Dirac particles in $(2+1)\mathrm{D}$ in the limit when $m^2\ll p^2$, where $m$ is the fermion mass and $p$ is its momentum. In this regime, the whole bosonized action also has a modified Maxwell term, involving the same pseudodifferential operator. Furthermore, the large-mass $m^2\gg p^2$ regime is also considered. We also investigate the main effects of the PCS term into the pseudo-quantum electrodynamics (PQED), which describes the electromagnetic interactions between charged particles in $(2+1)\mathrm{D}$. We show that the massless gauge field of PQED becomes massive in the presence of a PCS term, without the need of a Higgs mechanism. In the nonrelativistic limit, we show that the static potential has a repulsive term (given by the Coulomb potential) and an attractive part (given by a sum of special functions), whose competition generates bound states of particles with the same charge. Having in mind two-dimensional materials, we also conclude that the presence of a PCS term does not affect the renormalization either of the Fermi velocity or of the band gap in a Dirac-like material.

We use the framework of asymptotic safety above the Planck scale to constrain the parameter space of simple models of new physics that can accommodate the measured value of the anomalous magnetic moment of the muon and the relic density of dark matter. We couple parametrically to the trans-Planckian quantum physics a set of ${\mathrm{SU}(2)}_L\times U(1{)}_Y$ invariant extensions of the Standard Model, each comprising an inert scalar field and one pair of colorless fermions that communicate to the muons through Yukawa-type interactions. The presence of an interactive UV fixed point in the system of gauge and Yukawa couplings imposes a set of boundary conditions at the Planck scale, which allow one to derive unique phenomenological predictions in each case and distinguish the different representations of the gauge group from one another. We apply to the models constraints from the $h\to \mu \mu$ signal strength at ATLAS and CMS, direct LHC searches for electroweak production with leptons and missing energy in the final state, and the dark matter relic density. We find that they further restrict the available parameter space.

Dark sector particles with small electric charge, or millicharge, (mCPs) may lead to a variety of diverse phenomena in particle physics, astrophysics, and cosmology. Assuming their possible existence, we investigate the accumulation and propagation of mCPs in matter, specifically inside the Earth. Even small values of millicharge lead to sizeable scattering cross sections on atoms, resulting in complete thermalization, and as a consequence, considerable build-up of number densities of mCPs, especially for the values of masses of GeV and higher when the evaporation becomes inhibited. Enhancement of mCP densities compared to their galactic abundance, that can be as big as ${10}^{14}$, leads to the possibility of new experimental probes for this model. The annihilation of pairs of mCPs will result in new signatures for the large volume detectors (such as Super-Kamiokande). Formation of bound states of negatively charged mCPs with nuclei can be observed by direct dark matter detection experiments. A unique probe of mCP can be developed using underground electrostatic accelerators that can directly accelerate mCPs above the experimental thresholds of direct dark matter detection experiments.

We study the possibility that dark radiation, sourced through the decay of dark matter in the late Universe, carries electromagnetic interactions. The relativistic flux of particles induces recoil signals in direct detection and neutrino experiments through its interaction with millicharge, electric/magnetic dipole moments, or anapole moment/charge radius. Taking the DM lifetime as 35 times the age of the Universe, as currently cosmologically allowed, we show that direct detection (neutrino) experiments have complementary sensitivity down to $\epsilon \sim {10}^{-11}$ $({10}^{-12})$, $d_{\chi }/{\mu }_{\chi }\sim {10}^{-9}{\mu }_B$ $({10}^{-13}{\mu }_B)$, and $a_{\chi }/b_{\chi }\sim {10}^{-2}{\mathrm{GeV}}^{-2}$ $({10}^{-8}{\mathrm{GeV}}^{-2})$ on the respective couplings. Finally, we show that such dark radiation can lead to a satisfactory explanation of the recently observed XENON1T excess in the electron recoil signal without being in conflict with other bounds.

We make a detailed study of the $D_s$-meson leading-twist light-cone distribution amplitude ${\varphi }_{2;D_s}$ by using the QCD sum rules within the framework of the background field theory. To improve the precision, its moments $⟨{\xi }^n{⟩}_{2;D_s}$ are calculated up to dimension-six condensates. At the scale $\mu =2\mathrm{GeV}$, we obtain $⟨{\xi }^1{⟩}_{2;D_s}=-{0.261}_{-0.020}^{+0.020}$, $⟨{\xi }^2{⟩}_{2;D_s}={0.184}_{-0.012}^{+0.012}$, $⟨{\xi }^3{⟩}_{2;D_s}={-0.111}_{-0.012}^{+0.007}$, and $⟨{\xi }^4{⟩}_{2;D_s}={0.075}_{-0.005}^{+0.005}$. Using those moments, the ${\varphi }_{2;D_s}$ is then constructed by using the light-cone harmonic oscillator model. As an application, we calculate the transition form factor $f_{+}^{B_s\to D_s}(q^2)$ within the light-cone sum rules (LCSR) approach by using a right-handed chiral current, in which the terms involving ${\varphi }_{2;D_s}$ dominate the LCSR. It is noted that the extrapolated $f_{+}^{B_s\to D_s}(q^2)$ agrees with the lattice QCD prediction. After extrapolating the transition form factor to the physically allowable $q^2$ region, we calculate the branching ratio and the CKM matrix element, which give $\mathcal{B}({\overline{B}}_s^0\to D_s^{+}\ell {\nu }_{\ell })=({2.03}_{-0.49}^{+0.35})\times {10}^{-2}$ and $|V_{cb}|=({40.00}_{-4.08}^{+4.93})\times {10}^{-3}$.