We analyze the sensitivity of fixed-target experiments to sub-GeV thermal relic dark matter models, accounting for variations in both mediator and dark matter mass, and including dark matter production through both on- and off-shell mediators. It is commonly thought that the sensitivity of such experiments is predicated on the existence of an on-shell mediator that is produced and then decays to dark matter. While accelerators do provide a unique opportunity to probe the mediator directly, our analysis demonstrates that their sensitivity extends beyond this commonly discussed regime. In particular, we provide sensitivity calculations that extend into both the effective field theory regime where the mediator is much heavier than the dark matter and the regime of an off-shell mediator lighter than a dark matter particle-antiparticle pair. Our calculations also elucidate the resonance regime, making it clear that all but a fine-tuned region of thermal freeze-out parameter space for a range of simple models is well covered.

We study the possibility to directly detect the boosted dark matter generated from the scatterings with high energetic cosmic particles, such as protons and electrons. As a concrete example, we consider the sub-GeV dark matter mediated by a $\mathrm{U}(1{)}_D$ gauge boson, which has a mixing with a $U(1{)}_Y$ gauge boson in the Standard Model. The enhanced kinetic energy of the light dark matter from the collision with the cosmic rays can recoil the target nucleus and electron in the underground direct detection experiments, transferring enough energy to them to be detectable. We show the impact of boosted dark matter with existing direct detection experiments as well as collider and beam-dump experiments.

I consider contributions to the neutron electric dipole moment within two-Higgs-doublet models which allow for small flavor changing neutral Higgs couplings. In a previous paper, I considered flavor changing interactions for the Standard Model Higgs boson to first order in the flavor changing coupling. In that paper I found that the obtained value of the neutron electric dipole moment was below the present experimental limit, given previous restrictions on such couplings. Because this was an effective theory, the result depended on an ultraviolet cut off $\mathrm{\Lambda }$, parametrized as $\ln ({\mathrm{\Lambda }}^2)$. In the present paper I demonstrate that, when going to two-Higgs-doublet models, the result stays the same as in the previous paper, up to $M_{\mathrm{SM}}^2/M_H^2$ corrections, where $M_{\mathrm{SM}}$ is the mass of the top quark or the $W$ boson. $M_H$ is the mass of the heavy neutral scalar Higgs boson $H$ which is much heavier than the light neutral Higgs boson $h$ with mass $M_h$. In the limit $M_H^2\gg M_h^2$, the $\ln ({\mathrm{\Lambda }}^2)$ behavior in the previous paper is replaced by $\ln ({\widetilde{M_H}}^2)$, where $\widetilde{M_H}$ is of order $M_H$. I also explain how some divergences due to exchange of the pseudoscalar Higgs $A$ are canceled by similar contributions from the scalar heavy Higgs $H$, and that these contributions, and finite contributions from $A$ exchange, are suppressed.

We present two-loop results for the quark condensate in an external magnetic field within chiral perturbation theory using coordinate-space techniques. At finite temperature, we explore the impact of the magnetic field on the pion-pion interaction in the quark condensate for arbitrary pion masses and derive the correct weak magnetic field expansion in the chiral limit. At zero temperature, we provide the complete two-loop representation for the vacuum energy density and the quark condensate.

A study of the lineshape of the ${\chi }_{c1}(3872)$ state is made using a data sample corresponding to an integrated luminosity of $3{\mathrm{fb}}^{-1}$ collected in $pp$ collisions at center-of-mass energies of 7 and 8 TeV with the LHCb detector. Candidate ${\chi }_{c1}(3872)$ and $\psi (2S)$ mesons from $b$-hadron decays are selected in the $J/\psi {\pi }^{+}{\pi }^{-}$ decay mode. Describing the lineshape with a Breit-Wigner function, the mass splitting between the ${\chi }_{c1}(3872)$ and $\psi (2S)$ states, $\mathrm{\Delta }m$, and the width of the ${\chi }_{c1}(3872)$ state, ${\mathrm{\Gamma }}_{\mathrm{BW}}$, are determined to be $\genfrac{}{}{0ex}{}{\mathrm{\Delta }m=185.598\pm 0.067\pm 0.068\mathrm{MeV},}{{\mathrm{\Gamma }}_{\mathrm{BW}}=1.39\pm 0.24\pm 0.10\mathrm{MeV},}$ where the first uncertainty is statistical and the second systematic. Using a Flatté-inspired model, the mode and full width at half maximum of the lineshape are determined to be $\genfrac{}{}{0ex}{}{\mathrm{mode}=3871.69_{-0.04-0.13}^{+0.00+0.05}\mathrm{MeV},}{\mathrm{FWHM}=0.22_{-0.06-0.13}^{+0.07+0.11}\mathrm{MeV}.}$ An investigation of the analytic structure of the Flatté amplitude reveals a pole structure, which is compatible with a quasibound $D^0{\overline{D}}^{*0}$ state but a quasivirtual state is still allowed at the level of 2 standard deviations.

We evaluate the correlators for the vector potential and for the field strength tensor of the electromagnetic field in the geometry of two parallel planar plates in AdS spacetime. Two types of boundary conditions are considered on the plates. The first one is a generalization of the perfect conductor boundary condition and the second one corresponds to the confining boundary conditions. By using the expressions for the correlators, the vacuum expectation values (VEVs) of the photon condensate and of the electric and magnetic fields squared are investigated. As another important local characteristic of the vacuum state we consider the VEV of the energy-momentum tensor. The Casimir forces acting on the plates are decomposed into the self-action and interaction parts. It is shown that the interaction forces are attractive for both types of boundary conditions. At separations between the plates larger than the curvature radius of the background geometry they decay exponentially as functions of the proper distance. The self-action force per unit surface of a single plate does not depend on its location and depending on the boundary condition and on the number of spatial dimensions can be either attractive or repulsive with respect to the AdS boundary. By using the generalized zeta function technique we also evaluate the total Casimir energy. Applications are given in $Z_2$-symmetric braneworld models of the Randall-Sundrum type for vector fields with even and odd parities.

In this paper we study the shadow of rotating Kaluza-Klein (KK) black holes and the connection between the shadow radius and the real part of quasinormal modes (QNMs) in the eiokonal limit. In addition we have explored the quasiperiodic oscillations (QPOs) in the rotating KK black hole.

One of the important parameters in cosmology is the parameter characterizing the equation of state (EOS) of the sources driving the cosmic expansion. Epochs that are dominated by radiation, matter or scalar fields, whether they are probed either directly or indirectly, can be characterised by a unique value of this parameter. However, the EOS parameter during reheating—a phase succeeding inflation which is supposed to rapidly defrost our Universe—remains to be understood satisfactorily. In order to circumvent the complexity of defining an instantaneous EOS parameter during reheating, an effective parameter $w_{\mathrm{eff}}$, which is an average of the EOS parameter over the duration of reheating, is usually considered. The value of $w_{\mathrm{eff}}$ is often chosen arbitrarily to lie in the range $-1/3\le w_{\mathrm{eff}}\le 1$. In this work, we consider the time evolution of the EOS parameter during reheating and relate it to inflationary potentials $V(\varphi )$ that behave as ${\varphi }^p$ around the minimum, a proposal which can be applied to a wide class of inflationary models. We find that, given the index $p$, the effective EOS parameter $w_{\mathrm{eff}}$ is determined uniquely. We discuss the corresponding effects on the reheating temperature and its implications.

In this paper, we present the first study that compares different models of Bayesian neural networks (BNNs) to predict the posterior distribution of the cosmological parameters directly from the cosmic microwave background (CMB) temperature and polarization maps. We focus our analysis on four different methods to sample the weights of the network during training: Dropout, DropConnect, Reparameterization Trick (RT), and Flipout. We find that Flipout outperforms all other methods regardless of the architecture used, and provides tighter constraints for the cosmological parameters. Moreover, we compare our results with a Markov chain Monte Carlo (MCMC) posterior analysis and obtain comparable error correlations among parameters, with BNNs that are orders of magnitude faster in inference, albeit less accurate. Thanks to the speed of the inference process with BNNs, the posterior distribution—the outcome of the neural network—can be used as the initial proposal for the Markov chain. We show that this combined approach increases the acceptance rate in the Metropolis-Hasting algorithm and accelerates the convergence of the MCMC, while reaching the same final accuracy. In the second part of the paper, we present a guide to the training and calibration of a successful multichannel BNN for the CMB temperature and polarization map. We show how tuning the regularization parameter for the standard deviation of the approximate posterior on the weights in Flipout and RT can produce unbiased and reliable uncertainty estimates, i.e., the regularizer acts like a hyperparameter analogous to the dropout rate in Dropout. The best performances are nevertheless achieved with a more convenient method, in which the network parameters are kept free during training to achieve the best uncalibrated performances, and the confidence intervals are calibrated in a subsequent phase. Additionally, we describe existing strategies for calibrating the networks and propose new ones. Finally, we show how polarization, when combined with the temperature in a unique multichannel tensor fed to a single BNN, helps to break degeneracies among parameters and provides stringent constraints. The results reported in this paper can be extended to other cosmological data sets in order to capture features that can be extracted directly from the raw data, such as non-Gaussianity or foreground emissions.

We present an analysis of more than 11 years of Fermi-GBM data in which 217 gamma-ray bursts (GRBs) are found for which their main burst is preceded by a precursor flash. We find that short GRBs ($<2\mathrm{s}$) are $\sim 10$ times less likely to produce a precursor than long GRBs. The quiescent time profile, given by the time between the precursor and the main burst, is well described by a double Gaussian distribution, indicating that the observed precursors have two distinct physical progenitors. The light curves of the identified precursor GRBs are publicly available in an online catalog (https://icecube.wisc.edu/~grbweb_public/Precursors.html).

The center of the Milky Way is offering one of the most striking mysteries in astroparticle physics. An excess of $\gamma$ rays (GCE) has been measured by several groups in the data collected by the Fermi Large Area Telescope (LAT) toward the Galactic center region. The spectrum and spatial morphology of the GCE have been claimed by some groups to be compatible with a signal from the galactic halo of dark matter (DM). Instead, other analyses have demonstrated that the GCE properties, e.g., its energy spectrum, highly depend on the choice of the galactic interstellar emission (IEM) model source catalogs and analysis techniques. In this paper, we investigate the sensitivity of Fermi LAT to detect the characteristics of the GCE. In particular, we simulate the GCE as given by DM, and we verify that, with a perfect knowledge of the background components, its energy spectrum, position, spatial morphology, and symmetry is properly measured. We also inspect two more realist cases for which there are imperfections in the IEM model. In the first, we have an unmodeled $\gamma$-ray source, constituted by the low-latitude component of the Fermi bubbles. In the second, we simulate the data with one IEM template and analyze the data with another. We verify that a mismodeling of the IEM introduces a systematics of about 10–15% in the GCE energy spectrum between 1–10 GeV and about 5% in the value of the slope for a Navarro-Frenk-White DM density profile, which is used to fit the GCE spatial morphology. Finally, we show how the GCE would be detected in case of alternative processes such as $\gamma$-ray emission from a bulge population of pulsars or from electrons and positrons or protons injected from the Galactic center. We demonstrate that for each of these cases, there is a distinctive smoking gun signature that would help to identify the real mechanism behind the origin of the GCE.

The strongly interacting partonic medium created post ultrarelativistic heavy ion collision experiments exhibits a significant temperature-gradient between the central and peripheral regions of the collisions, which in turn, is capable of inducing an electric field in the medium; a phenomenon known as Seebeck effect. The effect is quantified by the magnitude of the induced electric field per unit temperature gradient—the Seebeck coefficient ($S$). We study the coefficient, $S$, with the help of the relativistic Boltzmann transport equation in relaxation-time approximation as a function of temperature ($T$) and chemical potential ($\mu$), wherein we find that, with current quark masses, the magnitude of $S$ for individual quark flavors as well as that for the partonic medium decreases with $T$ and increases with $\mu$, with the electric charge of the flavor deciding the sign of $S$. The emergence of a strong magnetic field ($B$) in the noncentral collisions at heavy-ion collider experiments motivates us to study the effect of $B$ on the Seebeck effect. The strong $B$ affects $S$ in multifold ways via (i) modification of phase-space due to the dimensional reduction, (ii) dispersion relation in lowest Landau level (occupation probability), and (iii) relaxation time. We find that a strong $B$ not only decreases the magnitudes of $S\mathrm{s}$ of individual species, it also flips their signs. This leads to a faster reduction of the magnitude of $S$ of the medium than its counterpart at $B=0$. We then explore how the interactions among partons described in perturbative thermal QCD in the quasiparticle framework affect the Seebeck effect. The interactions indeed affect the coefficient drastically. For example, even in strong $B$, there is no more a flip of the sign of $S$ for individual species and the magnitudes of $S$ of individual species as well as that of the medium get enhanced in comparison with the current quark mass description at either $B=0$ or $B\ne 0$.

We model clusters of axions with spherically symmetric momentum but arbitrary spatial distributions and study the directional profile of photos produced in their evolution through spontaneous and stimulated decay of axions via the process $a\to \gamma +\gamma$. Several specific examples are presented.

A recent preliminary investigation based on Durgut’s report at the American Physical Society site shows a structure at 18.4 GeV exists in the invariant mass distribution of $\mathrm{\Upsilon }{l}^{+}{l}^{-}(l=e,\mu )$ at the LHC center-of-mass energy of 7 and 8 TeV. Its appearance attracts attention of theorists and experimentalists of high energy physics, because it might be a Higgs-like boson of 18.4 GeV which would serve as a signal of the new physics beyond the Standard Model. We have carried out computations on the corresponding quantities (production and decay rates) based on quantum field theory and compared the results with experimental data. Our numerical results do not support the assertion that the 18.4 GeV peak corresponds to a neutral $0^{++}$ boson which decays into $\mathrm{\Upsilon }{l}^{+}{l}^{-}$. Much further works (both experimental and theoretical) are badly needed.

In this article, we investigate the ${\mu }^{-}\to e^{-}X$ process in a muonic atom, where $X$ is a light neutral boson. By calculating the spectrum of the emitted electron for several cases, we discuss the model-discriminating power of the process. We report the strong model dependence of the spectrum near a high-energy end point. Our findings show that future experiments using muonic atoms are helpful to identify the properties of exotic bosons.

A new set of the next-to-leading order (NLO) and the next-to-next-to-leading order (NNLO) low-energy constants $L_i^r$ and $C_i^r$ in chiral perturbation theory is obtained. These values are computed using the new experimental data with a new calculation method. This method combines the traditional global fit and Monte Carlo method together. The higher order contributions are estimated with this method. The theoretical values of the observables provide good convergence at each chiral dimension, except for the NNLO values of the $\pi K$ scattering lengths $a_0^{3/2}$ and $a_0^{1/2}$. The fitted values for $L_i^r$ at NLO are close to their results with the new method at NNLO; i.e., these $L_i^r$ are nearly order-independent in this method. The estimated ranges for $C_i^r$ are consistent with those in the literature, and their possible upper or/and lower boundaries are given. The values of some linear combinations of $C_i^r$ are also given, and they are more reliable. If one knows a more exact value of $C_i^r$, another $C_i^r$ can be obtained by these values.

We present a study of electroexcitation of nucleon resonances with higher spins, in a soft-wall AdS/QCD model, comparing our results with existing data from the CLAS Collaboration at JLab, from MAMI, and other experiments.

Finite energy QCD sum rules involving nucleon current correlators are used to determine several QCD and hadronic parameters in the presence of an external, uniform, large magnetic field. The continuum hadronic threshold $s_0$, nucleon mass $m_N$, current-nucleon coupling ${\lambda }_N$, transverse velocity $v_{\perp }$, the spin polarization condensate $⟨\overline{q}{\sigma }_{12}q⟩$, and the magnetic susceptibility of the quark condensate ${\chi }_q$, are obtained for the case of protons and neutrons. Due to the magnetic field, and charge asymmetry of light quarks up and down, all the obtained quantities evolve differently with the magnetic field, for each nucleon or quark flavor. With this approach it is possible to obtain the evolution of the above parameters up to a magnetic field strength $eB<1.4{\mathrm{GeV}}^2$.

Quantum-reduced loop gravity is a model of loop quantum gravity, which—from the technical point of view—is characterized by the remarkably simple form of its basic operators. In this article we examine the operators of the quantum-reduced model from the perspective of full loop quantum gravity. We show that, in spite of their simplicity, the operators of the quantum-reduced model are simply the operators of the full theory acting on states in the Hilbert space of the quantum-reduced model. The passage from the full theory operators to the “reduced” operators simply consists of noting that the states of the quantum-reduced model are assumed to carry large spin quantum numbers, and discarding terms which are of lower than leading order in $j$. Our findings clarify the relation between the quantum-reduced model and full loop quantum gravity, and strengthen the technical foundations on which the kinematical structure of the quantum-reduced model is based.

Quasinormal modes of usual, four-dimensional, Kerr black holes are described by certain solutions of a confluent Heun differential equation. In this work, we express these solutions in terms of the connection matrices for a Riemann-Hilbert problem, which was recently solved in terms of the Painlevé V transcendent. We use this formulation to generate small-frequency expansions for the angular spheroidal harmonic eigenvalue and derive conditions on the monodromy properties for the radial modes. Using exponentiation, we relate the accessory parameter to a semiclassical conformal description and discuss the properties of the operators involved. For the radial equation, while the operators at the horizons have Liouville momenta proportional to the entropy intake, we find that spatial infinity is described by a Whittaker operator.