We consider the generic possibility that the Universe’s energy budget includes some form of relativistic or semi-relativistic dark radiation (DR) with nongravitational interactions with standard model (SM) particles. Such dark radiation may consist of SM singlets or a nonthermal, energetic component of neutrinos. If such DR is created at a relatively recent epoch, it can carry sufficient energy to leave a detectable imprint in experiments designed to search for very weakly interacting particles: dark matter and underground neutrino experiments. We analyze this possibility in some generality, assuming that the interactive dark radiation is sourced by late decays of an unstable particle, potentially a component of dark matter, and considering a variety of possible interactions between the dark radiation and SM particles. Concentrating on the sub-GeV energy region, we derive constraints on different forms of DR using the results of the most sensitive neutrino and dark matter direct detection experiments. In particular, for interacting dark radiation carrying a typical momentum of $\sim 30\mathrm{MeV}/c$, both types of experiments provide competitive constraints. This study also demonstrates that non-standard sources of neutrino emission (e.g., via dark matter decay) are capable of creating a “neutrino floor” for dark matter direct detection that is closer to current bounds than is expected from standard neutrino sources.

We calculate in the nonrelativistic QCD (NRQCD) factorization framework all leading relativistic corrections to the exclusive production of ${\chi }_{cJ}+\gamma$ in $e^{+}{e}^{-}$ annihilation. In particular, we compute for the first time contributions induced by octet operators with a chromoelectric field. The matching coefficients multiplying production long distance matrix elements (LDMEs) are determined through perturbative matching between QCD and NRQCD at the amplitude level. Technical challenges encountered in the nonrelativistic expansion of the QCD amplitudes are discussed in detail. The main source of uncertainty comes from the not so well known LDMEs. Accounting for it, we provide the following estimates for the production cross sections at $\sqrt{s}=10.6\mathrm{GeV}$: $\sigma (e^{+}{e}^{-}\to {\chi }_{c0}+\gamma )=(1.4\pm 0.3)\mathrm{fb}$, $\sigma (e^{+}{e}^{-}\to {\chi }_{c1}+\gamma )=(15.0\pm 3.3)\mathrm{fb}$, and $\sigma (e^{+}{e}^{-}\to {\chi }_{c2}+\gamma )=(4.5\pm 1.4)\mathrm{fb}$.

Positrons beam dump experiments have unique features to search for very narrow resonances coupled superweakly to $e^{+}{e}^{-}$ pairs. Due to the continued loss of energy from soft photon bremsstrahlung, in the first few radiation lengths of the dump a positron beam can continuously scan for resonant production of new resonances via $e^{+}$ annihilation off an atomic $e^{-}$ in the target. In the case of a dark photon $A^{\prime }$ kinetically mixed with the photon, this production mode is of first order in the electromagnetic coupling $\alpha$, and thus parametrically enhanced with respect to the $O({\alpha }^2)e^{+}{e}^{-}\to \gamma A^{\prime }$ production mode and to the $O({\alpha }^3)A^{\prime }$ bremsstrahlung in $e^{-}$-nucleon scattering so far considered. If the lifetime is sufficiently long to allow the $A^{\prime }$ to exit the dump, $A^{\prime }\to e^{+}{e}^{-}$ decays could be easily detected and distinguished from backgrounds. We explore the foreseeable sensitivity of the Frascati PADME experiment in searching with this technique for the 17 MeV dark photon invoked to explain the ${}^8\mathrm{Be}$ anomaly in nuclear transitions.

The DAMPE $e^{+}{e}^{-}$ excess at around 1.4 TeV could be explained in the type-II seesaw model with a scalar dark mater $D$ which is stabilized by a discrete $Z_2$ symmetry. The simplest scenario is the annihilation $DD\to H^{++}{H}^{--}$ followed by the subsequent decay $H^{\pm \pm }\to e^{\pm }{e}^{\pm }$, with both the DM and triplet scalars roughly 3 TeV with a small mass splitting. In addition to the Drell-Yan process at future 100 TeV hadron colliders, the doubly charged components could also be produced at lepton colliders like ILC and CLIC in the off shell mode and mediate lepton flavor violating processes $e^{+}{e}^{-}\to {\ell }_i^{\pm }{\ell }_j^{\mp }$ (with $i\ne j$). A wide range of parameter space of the type-II seesaw could be probed, which are well below the current stringent lepton flavor constraints.

In this work we study the electrized quark matter under finite temperature and density conditions in the context of the SU(2) and SU(3) Nambu–Jona-Lasinio models. To this end, we evaluate the effective quark masses and the Schwinger quark-antiquark pair production rate. For the SU(3) NJL model we incorporate in the Lagrangian the ’t Hooft determinant and we present a set of analytical expressions more convenient for numerical evaluations. We predict a decrease of the pseudocritical electric field with the increase of the temperature for both models and a more prominent production rate for the SU(3) model when compared to the SU(2).

It is shown that neutrino oscillation processes can be consistently described in the framework of quantum field theory using only the plane wave states of the particles. Namely, the oscillating electron survival probabilities in experiments with neutrino detection by charged-current and neutral-current interactions are calculated in the quantum field–theoretical approach to neutrino oscillations based on a modification of the Feynman propagator in the momentum representation. The approach is most similar to the standard Feynman diagram technique. It is found that the oscillating distance-dependent probabilities of detecting an electron in experiments with neutrino detection by charged-current and neutral-current interactions exactly coincide with the corresponding probabilities calculated in the standard approach.

We identify the $T$-odd structure functions that appear in the description of polarized top quark decays in the sequential decay $t(\uparrow )\to X_b+W^{+}(\to {\ell }^{+}+{\nu }_{\ell })$ (two structure functions) and the quasi-three-body decay $t(\uparrow )\to X_b+{\ell }^{+}+{\nu }_{\ell }$ (one structure function). A convenient measure of the magnitude of the $T$-odd structure functions is the contribution of the imaginary part $\mathrm{Im}{g}_R$ of the right-chiral tensor coupling $g_R$ to the $T$-odd structure functions which we work out. Contrary to the case of QCD, the NLO electroweak corrections to polarized top quark decays admit absorptive one-loop vertex contributions. We analytically calculate the imaginary parts of the relevant four electroweak one-loop triangle vertex diagrams and determine their contributions to the $T$-odd helicity structure functions that appear in the description of polarized top quark decays.

We present an analytic representation of $F_K/F_{\pi }$ as calculated in three-flavor two-loop chiral perturbation theory, which involves expressing three mass scale sunsets in terms of Kampé de Fériet series. We demonstrate how approximations may be made to obtain relatively compact analytic representations. An illustrative set of fits using lattice data is also presented, which shows good agreement with existing fits.

The ${\mathrm{\Lambda }}_c(2590){\mathrm{\Sigma }}_c$ system can exchange a pion near the mass-shell. Owing to the opposite intrinsic parity of the ${\mathrm{\Lambda }}_c(2590)$ and ${\mathrm{\Sigma }}_c$, the pion is exchanged in S-wave. This gives rise to a Coulomb-like force that might be able to bind the system. If one takes into account that the pion is not exactly on the mass shell, there is a shallow S-wave state, which we generically call the $Y_{cc}(5045)$ and $Y_{c\overline{c}}(5045)$ for the ${\mathrm{\Lambda }}_c(2590){\mathrm{\Sigma }}_c$ and ${\mathrm{\Lambda }}_c(2590){\overline{\mathrm{\Sigma }}}_c$ systems respectively. For the baryon-antibaryon case this Coulomb-like force is independent of spin: the $Y_{c\overline{c}}(5045)$ baryonia will appear either in the spin $S=0$ or $S=1$ configurations with G-parities $G=(-1{)}^{L+S+1}$. For the baryon-baryon case the Coulomb-like force is attractive in the spin $S=0$ configuration, for which a doubly charmed molecule is expected to form near the threshold. This type of spectrum might be very well realized in other molecular states composed of two opposite parity hadrons with the same spin and a mass difference close to that of a pseudo-Goldstone boson, of which a few examples include the $\mathrm{\Lambda }(1405)N$, $\mathrm{\Lambda }(1520){\mathrm{\Sigma }}^{*}$, $\mathrm{\Xi }(1690)\mathrm{\Sigma }$, $D_{s0}^{*}(2317)D$ and $D_{s1}^{*}(2460)D^{*}$ molecules.

We consider a nonsupersymmetric USp Yang-Mills Chern-Simons gauge theory coupled to fundamental flavors. The theory is realised in type-IIB string theory via an embedding in a Hanany-Witten brane configuration which includes an orientifold and antibranes. We argue that the theory admits a magnetic Seiberg dual. Using the magnetic dual we identify dynamics in field theory and brane physics that correspond to various phases, obtaining a better understanding of three-dimensional bosonization and dynamical breaking of flavor symmetry in USp ${\mathrm{QCD}}_3$ theory. In field theory both phases correspond to magnetic “squark” condensation. In string theory, they correspond to open string tachyon condensation and brane reconnection. We also discuss other phases where the magnetic ‘squark’ is massive. Finally, we briefly comment on the case of unitary gauge groups.

We consider the coupling of the electromagnetic field to a nonlocal gravity theory comprising of the Einstein-Hilbert action in addition to a nonlocal $R{\square }^{-2}R$ term associated with a mass scale $m$. We demonstrate that in the case of the minimally coupled electromagnetic field, real corrections about the Reissner-Nordström background only exist between the inner Cauchy horizon and the event horizon of the black hole. This motivates us to consider the modified coupling of electromagnetism to this theory via the Kaluza ansatz. The Kaluza reduction introduces nonlocal terms involving the electromagnetic field to the pure gravitational nonlocal theory. An iterative approach is provided to perturbatively solve the equations of motion to arbitrary order in $m^2$ about any known solution of general relativity. We derive the first-order corrections and demonstrate that the higher order corrections are real and perturbative about the external background of a Reissner-Nordström black hole. We also discuss how the Kaluza reduced action, through the inclusion of nonlocal electromagnetic fields, could also be relevant in quantum effects on curved backgrounds with horizons.

The “thin-wall approximation” gives a simple estimate of the decay rate of an unstable quantum field. Unfortunately, the approximation is uncontrolled. In this paper I show that there are actually two different thin-wall approximations and that they bracket the true decay rate: I prove that one is an upper bound and the other a lower bound. In the thin-wall limit, the two approximations converge. In the presence of gravity, a generalization of this lemma provides a simple sufficient condition for nonperturbative vacuum instability.

In classical electrodynamics, an accelerating charged body emits radiation and experiences a corresponding radiation-reaction force, or self-force. We extend to higher order in the total charge a previous rigorous derivation of the electromagnetic self-force in flat spacetime by Gralla, Harte, and Wald. The method introduced by Gralla, Harte, and Wald computes the self-force from the Maxwell field equations and conservation of stress-energy in a limit where the charge, size, and mass of the body go to zero, and it does not require regularization of a singular self-field. For our higher-order computation, an adjustment of the definition of the mass of the body is necessary to avoid including self-energy from the electromagnetic field sourced by the body in the distant past. We derive the evolution equations for the mass, spin, and center-of-mass position of the body through second order. We derive, for the first time, the second-order acceleration dependence of the evolution of the spin (self-torque), as well as a mixing between the extended body effects and the acceleration-dependent effects on the overall body motion.

We study axial quasinormal modes of static neutron stars in the nonminimal derivative coupling sector of Horndeski theory. We focus on the fundamental curvature mode, which we analyze for 10 different equations of state with different matter content. A comparison with the results obtained in pure general relativity reveals that, apart from modifying the spectrum of the frequencies and the damping times of the stars, this theory modifies several universal relations between the modes and physical parameters of the stars that are otherwise matter independent.

The Gleyzes-Langlois-Piazza-Vernizzi (GLPV) theories up to quartic order are the general scheme of scalar-tensor theories allowing the possibility for realizing the tensor propagation speed $c_t$ equivalent to 1 on the isotropic cosmological background. We propose a dark energy model in which the late-time cosmic acceleration occurs by a simple k-essence Lagrangian analogous to the ghost condensate with cubic and quartic Galileons in the framework of GLPV theories. We show that a wide variety of the variation of the dark energy equation of state $w_{\mathrm{DE}}$ including the entry to the region $w_{\mathrm{DE}}<-1$ can be realized without violating conditions for the absence of ghosts and Laplacian instabilities. The approach to the tracker equation of state $w_{\mathrm{DE}}=-2$ during the matter era, which is disfavored by observational data, can be avoided by the existence of a quadratic k-essence Lagrangian $X^2$. We study the evolution of nonrelativistic matter perturbations for the model $c_t^2=1$ and show that the two quantities $\mu$ and $\mathrm{\Sigma }$, which are related to the Newtonian and weak lensing gravitational potentials respectively, are practically equivalent to each other, such that $\mu \simeq \mathrm{\Sigma }>1$. For the case in which the deviation of $w_{\mathrm{DE}}$ from $-1$ is significant at a later cosmological epoch, the values of $\mu$ and $\mathrm{\Sigma }$ tend to be larger at low redshifts. We also find that our dark energy model can be consistent with the bounds on the deviation parameter ${\alpha }_{\mathrm{H}}$ from Horndeski theories arising from the modification of gravitational law inside massive objects.

A thick dark matter disk is predicted in cold dark matter simulations as the outcome of the interaction between accreted satellites and the stellar disk in Milky Way–sized halos. We study the effects of a self-interacting thick dark disk on the energetic neutrino flux from the Sun. We find that for particle masses between 100 GeV and 1 TeV and dark matter annihilation to ${\tau }^{+}{\tau }^{-}$, either the self-interaction may not be strong enough to solve the small-scale structure motivation or a dark disk cannot be present in the Milky Way.

The discovery of dark matter (DM) at XENONnT or LZ would place constraints on DM particle mass and coupling constants. It is interesting to ask when these constraints can be compatible with the DM thermal production mechanism. We address this question within the most general set of renormalizable models that preserve Lorentz and gauge symmetry, and that extend the standard model by one DM candidate of mass $m_{\mathrm{DM}}$ and one particle of mass $M_{\mathrm{med}}$ mediating DM-quark interactions. Our analysis divides into two parts. First, we postulate that XENONnT/LZ has detected ${\mu }_S\sim \mathcal{O}(100)$ signal events, and use this input to calculate the DM relic density, ${\mathrm{\Omega }}_{\mathrm{DM}}{h}^2$. Then, we identify the regions in the $M_{\mathrm{med}}-{\mathrm{\Omega }}_{\mathrm{DM}}{h}^2$ plane which are compatible with the observed signal and with current CMB data. We find that for most of the models considered here, $\mathcal{O}(100)$ signal events at XENONnT/LZ and the DM thermal production are only compatible for resonant DM annihilations, i.e. for $M_{\mathrm{med}}\simeq 2m_{\mathrm{DM}}$. In this case, XENONnT/LZ would be able to simultaneously measure $m_{\mathrm{DM}}$ and $M_{\mathrm{med}}$. We also discuss the dependence of our results on $m_{\mathrm{DM}}$, ${\mu }_S$ and the DM spin, and provide analytic expressions for annihilation cross sections and mediator decay widths for all models considered in this study.

We propose a long-term strategy for detecting thermal neutrinos from the remnant of binary neutron-star mergers with a future M-ton water-Cherenkov detector such as Hyper-Kamiokande. Monitoring $\gtrsim 2500$ mergers within $\lesssim 200\mathrm{Mpc}$, we may be able to detect a single neutrino with a human time-scale operation of $\approx 80\text{Mtyears}$ for the merger rate of $1{\mathrm{Mpc}}^{-3}{\mathrm{Myr}}^{-1}$, which is slightly lower than the median value derived by the LIGO-Virgo Collaboration with GW170817. Although the number of neutrino events is minimal, contamination from other sources of neutrinos can be reduced efficiently to $\approx 0.03$ by analyzing only $\approx 1\mathrm{s}$ after each merger identified with gravitational-wave detectors if gadolinium is dissolved in the water. The contamination may be reduced further to $\approx 0.01$ if we allow the increase of waiting time by a factor of $\approx 1.7$. The detection of even a single neutrino can pin down the energy scale of thermal neutrino emission from binary neutron-star mergers and could strongly support or disfavor formation of remnant massive neutron stars. Because the dispersion relation of gravitational waves is now securely constrained to that of massless particles with a corresponding limit on the graviton mass of $\lesssim {10}^{-22}\mathrm{eV}/c^2$ by binary black-hole mergers, the time delay of a neutrino from gravitational waves can be used to put an upper limit of $\lesssim O(10)\mathrm{meV}/c^2$ on the absolute neutrino mass in the lightest eigenstate. Large neutrino detectors will enhance the detectability, and, in particular, 5 Mt Deep-TITAND and 10 Mt MICA planned in the future will allow us to detect thermal neutrinos every $\approx 16$ and 8 years, respectively, increasing the significance.

Renormalization constants (RCs) of overlap quark bilinear operators on $2+1$-flavor domain wall fermion configurations are calculated by using the RI/MOM and RI/SMOM schemes. The scale independent RC for the axial vector current is computed by using a Ward identity. Then the RCs for the quark field and the vector, tensor, scalar, and pseudoscalar operators are calculated in both the RI/MOM and RI/SMOM schemes. The RCs are converted to the $\overline{\mathrm{MS}}$ scheme and we compare the numerical results from using the two intermediate schemes. The lattice size is $48^3\times 96$ and the inverse spacing $1/a=1.730(4)\mathrm{GeV}$.

We consider maximally supersymmetric $\mathrm{SU}(N)$ Yang-Mills theory in Euclidean signature compactified on a flat two-dimensional torus with antiperiodic (“thermal”) fermion boundary conditions imposed on one cycle. At large $N$, holography predicts that this theory describes certain black hole solutions in type IIA and IIB supergravity, and we use lattice gauge theory to test this. Unlike the one-dimensional quantum mechanics case where there is only the dimensionless temperature to vary, here we emphasize there are two more parameters which determine the shape of the flat torus. While a rectangular Euclidean torus yields a thermal interpretation, allowing for skewed tori modifies the holographic dual black hole predictions and results in another direction to test holography. Our lattice calculations are based on a supersymmetric formulation naturally adapted to a particular skewing. Using this we perform simulations up to $N=16$ with several lattice spacings for both skewed and rectangular tori. We observe the two expected black hole phases with their predicted behavior, with a transition between them that is consistent with the gravity prediction based on the Gregory-Laflamme transition.