If $X(3872)$ is a weakly bound charm-meson molecule, it can be produced in $e^{+}{e}^{-}$ annihilation by the creation of $D^{*0}{\overline{D}}^{*0}$ from a virtual photon followed by the rescattering of the $P$-wave charm-meson pair into the $X$ and a photon. A triangle singularity produces a narrow peak in the cross section for $e^{+}{e}^{-}\to X\gamma$ about 2.2 MeV above the $D^{*0}{\overline{D}}^{*0}$ threshold. We predict the normalized cross section in the region of the peak. We show that the absorptive contribution to the cross section for $e^{+}{e}^{-}\to D^{*0}{\overline{D}}^{*0}\to X\gamma$, which was calculated previously by Dubynskiy and Voloshin, does not give a good approximation to the peak from the triangle singularity.

In this work, we show how the knowledge of the first few terms of the Euler-Heisenberg Lagrangian’s weak-field expansion in a magnetic field background is enough to reconstruct the pair-production rate in a strong electric field background. To this end, we study its associated truncated Borel sum using Padé approximants, as advocated in a recent work by Costin and Dunne [10].

We obtain the ratio of semiclassical partition functions for the extension under mixed flux of the minimal surfaces subtending a circumference and a line in Euclidean ${\mathrm{AdS}}_3\times {\mathrm{S}}^3\times {\mathrm{T}}^4$. We reduce the problem to the computation of a set of functional determinants. If the Ramond-Ramond flux does not vanish, we find that the contribution of the $B$-field is comprised in the conformal anomaly. In this case, we successively apply the Gel’fand-Yaglom method and the Abel-Plana formula to the flat-measure determinants. To cancel the resultant infrared divergences, we shift the regularization of the sum over half-integers depending on whether it corresponds to massive or massless fermionic modes. We show that the result is compatible with the zeta-function regularization approach. In the limit of pure Neveu-Schwarz-Neveu-Schwarz flux we argue that the computation trivializes. We extend the reasoning to other surfaces with the same behavior in this regime.

We study the implications of a change of coordinatization of momentum space for theories with curved momentum space. We of course find that after a passive diffeomorphism the theory yields the same physical predictions, as one would expect considering that a simple reparametrization should not change physics. However, it appears that general momentum-space covariance (invariance under active diffeomorphisms of momentum space) cannot be enforced, and within a given set of prescriptions on how the theory should encode momentum-space metric and affine connection the physical predictions do depend on the momentum space background. These conclusions find support in some general arguments and in our quantitative analysis of a much-studied toy model with maximally symmetric (curved) momentum space.

We present a consistent canonical formulation of the flat Oppenheimer-Snyder model, including the Schwarzschild exterior. The switching between comoving and stationary observers is realized by promoting the coordinate transformation between dust proper time and Schwarzschild-Killing time to a canonical one. This leads to two different forms of the Hamiltonian constraint, both (almost) deparametrizable with regard to one of these times. A preliminary quantization of these constraints reveals a consistent picture for both observers: the singularity is avoided by a bounce.

We present a new method to measure neutrino masses using the dark matter-neutrino relative velocity. The relative motion between dark matter and neutrinos results in a parity-odd bispectrum which can be measured from cross-correlation of different cosmic fields. This new method is not affected by most systematics which are parity even and not limited by the knowledge of optical depth to the cosmic microwave background. We estimate the detectability of the relative velocity effect and find that the minimal sum of neutrino masses could be detected at high significance with upcoming surveys.

We revisit the stochastic effects in the model of anisotropic inflation containing a $U(1)$ gauge field. We obtain the Langevin equations for the inflaton and gauge fields perturbations and solve them analytically. We show that if the initial value of the electric field is larger than its classical attractor value, then the random stochastic forces associated with the gauge field is balanced by the frictional damping (classical) force and the electric field falls into an equilibrium (stationary) regime. As a result, the classical attractor value of the electric field is replaced by its stationary value. We show that the probability of generating quadrupolar statistical anisotropy consistent with cosmic microwave background constraints can be significant.

A weakly interacting dark matter candidate is difficult to detect at high-energy colliders like the LHC, if its mass is close to or higher than a TeV. On the other hand, pair annihilation of such particles may give rise to $e^{+}{e}^{-}$ pairs in dwarf spheroidal galaxies (dSph), which in turn can lead to radio synchrotron signals that are detectable at the upcoming Square Kilometre Array (SKA) telescope within a moderate observation time. We investigate the circumstances under which this complementarity between collider and radio signals of dark matter can be useful in probing physics beyond the standard model of elementary particles. Both particle physics issues and the roles of diffusion and electromagnetic energy loss of the $e^{\pm }$ are taken into account. First, the criteria for detectability of trans-TeV dark matter are analyzed independently of the particle physics model(s) involved. We thereafter use some benchmarks based on a popular scenario, namely, the minimal supersymmetric standard model. It is thus shown that the radio flux from a dSph like Draco should be observable in about 100 h at the SKA, for dark matter masses up to 4–8 TeV. In addition, the regions in the space spanned by astrophysical parameters, for which such signals should be detectable at the SKA, are marked out.

The Galactic Center excess (GCE) of GeV gamma rays can be explained as a signal of annihilating dark matter or of emission from unresolved astrophysical sources, such as millisecond pulsars. Evidence for the latter is provided by a statistical procedure—referred to as non-Poissonian template fitting (NPTF)—that distinguishes the smooth distribution of photons expected for dark matter annihilation from a “clumpy” photon distribution expected for point sources. In this paper, we perform an extensive study of the NPTF on simulated data, exploring its ability to recover the flux and luminosity function of unresolved sources at the Galactic Center. When astrophysical background emission is perfectly modeled, we find that the NPTF successfully distinguishes between the dark matter and point source hypotheses when either component makes up the entirety of the GCE. When the GCE is a mixture of dark matter and point sources, the NPTF may fail to reconstruct the correct contribution of each component. These results are related to the fact that in the ultrafaint limit, a population of unresolved point sources is exactly degenerate with Poissonian emission. We further study the impact of mismodeling the Galactic diffuse backgrounds, finding that while a dark matter signal could be attributed to point sources in some outlying cases for the scenarios we consider, the significance of a true point source signal remains robust. Our work enables us to comment on a recent study by Leane and Slatyer (2019) that questions prior NPTF conclusions because the method does not recover an artificial dark matter signal injected on actual Fermi data. We demonstrate that the failure of the NPTF to extract an artificial dark matter signal can be natural when point sources are present in the data—with the effect further exacerbated by the presence of diffuse mismodeling—and does not on its own invalidate the conclusions of the NPTF analysis in the Inner Galaxy.

In this work, we analyze the three-body $B_{(s)}\to {\eta }_c(1S,2S)K\pi$ decays within the framework of the perturbative QCD approach (PQCD) under the quasi-two-body approximation, where the kaon-pion invariant mass spectra are dominated by the $K_0^{*}(1430{)}^0$, $K_0^{*}(1950{)}^0$, $K^{*}(892{)}^0$, $K^{*}(1410{)}^0$, $K^{*}(1680{)}^0$, and $K_2^{*}(1430{)}^0$ resonances. The time-like form factors are adopted to parametrize the corresponding $S$, $P$, $D$-wave kaon-pion distribution amplitudes for the concerned decay modes, which describe the final-state interactions between the kaon and pion in the resonant region. The $K\pi S$-wave component at low $K\pi$ mass is described by the LASS line shape, while the time-like form factors of other resonances are modeled by the relativistic Breit-Wigner function. We find the following main points: (a) the PQCD predictions of the branching ratios for most considered $B\to {\eta }_c(1S)(K^{*0}\to )K^{+}{\pi }^{-}$ decays agree well with the currently available data within errors; (b) for $\mathcal{B}(B^0\to {\eta }_c(K_0^{*}(1430)\to )K^{+}{\pi }^{-})$ and $\mathcal{B}(B^0\to {\eta }_c{K}^{+}{\pi }^{-}(\mathrm{NR}))$ (where NR means nonresonant), our predictions of the branching ratios are a bit smaller than the measured ones; and (c) the PQCD results for the $D$-wave contributions considered in this work can be tested once precise data from the future LHCb and Belle-II experiments become available.

We analyze the allowed region of the muon anomalous magnetic moment (muon $g-2$) satisfying lepton flavor violations, $Z$ boson decays, and collider physics, in a framework of multicharged particles. Then we explore the typical size of the muon $g-2$ and discuss which mode dominantly affects the muon $g-2$.

It is known that limits on baryon-number-violating nucleon decays do not, in general, imply corresponding suppression of $n-\overline{n}$ transitions. Indeed, it has been shown, using a model with fermions propagating in higher dimensions, that even with nucleon decays suppressed far below observable levels, $n-\overline{n}$ oscillations can occur at a rate comparable to existing experimental limits, motivating new searches for such oscillations. In the context of this model we investigate a related question, namely the implications of limits on $\mathrm{\Delta }L=-1$ proton and bound neutron decays mediated by four-fermion operators for rates of nucleon decays mediated by $k$-fermion operators with $k=6$ and $k=8$. These include a variety of nucleon and dinucleon decays to dilepton and trilepton final states with $\mathrm{\Delta }L=-3,-2,1$, and 2. We carry out a low-energy effective field theory analysis of relevant operators for these decays and show that, in this extra-dimensional model, the rates for these decays are strongly suppressed and hence are in accord with experimental limits.

We propose a novel realization of spontaneous supersymmetry breaking in de Sitter vacuum by $F$- and $D$-terms in $N=1$ four-dimensional supergravity coupled to a chiral superfield with $SU(1,1)/U(1)$ target space. Our construction features gauged $U(1{)}_R$ symmetry rotating the chiral scalar field by a phase. Both supersymmetry and $R$-symmetry can be spontaneously broken, and for two particular parameter choices we obtain no-scale supergravity with positive tunable cosmological constant.

Extra $CP$-violating source for electroweak baryogenesis can dynamically appear at finite temperature in the complex two-Higgs doublet model, which might help to alleviate the strong constraints from the electric dipole moment experiments. In this scenario, we study the detailed phase transition dynamics and the corresponding gravitational wave signals in synergy with the collider signals at future lepton colliders. For some parameter spaces, various phase transition patterns can occur, such as the multistep phase transition and supercooling. Gravitational waves complementary to collider signals can help to pin down the underlying phase transition dynamics or different phase transition patterns.

$P_c(4312)$ observed by the LHCb collaboration is confirmed as a pentaquark and its structure, production, and decay behaviors attract great attention from theorists and experimentalists. Since its mass is very close to sum of ${\mathrm{\Sigma }}_c$ and $\overline{D}$ masses, it is naturally tempted to be considered as a molecular state composed of ${\mathrm{\Sigma }}_c$ and $\overline{D}$. Moreover, $P_c(4312)$ is observed in the channel with $J/\psi p$ final state, requiring that isospin conservation $P_c(4312)$ is an isospin-$1/2$ eigenstate. In the literature, several groups used various models to estimate its spectrum. We systematically study the pentaquarks within the framework of the Bethe-Salpeter equation; thus $P_c(4312)$ is an excellent target because of the available data. We calculate the spectrum of $P_c(4312)$ in terms of the Bethe-Salpter equations and further study its decay modes. Some predictions on other possible pentaquark states that can be tested in future experiments are made.

The bottomonium spectrum is far from being established. The structures of higher vector states, including the $\mathrm{\Upsilon }(10580)$, $\mathrm{\Upsilon }(10860)$, and $\mathrm{\Upsilon }(11020)$ states, are still in dispute. In addition, whether the $\mathrm{\Upsilon }(10750)$ signal which was recently observed by the Belle Collaboration is a normal $b\overline{b}$ state or not should be examined. Faced with such a situation, we carried out a systematic investigation of the bottomonium spectrum in the scheme of the relativistic flux tube (RFT) model. A Chew-Frautschi-like formula was derived analytically for the spin average mass of bottomonium states. We further incorporated the spin-dependent interactions and obtained a complete bottomonium spectrum. We found that the most established bottomonium states can be explained in the RFT scheme. The $\mathrm{\Upsilon }(10750)$, $\mathrm{\Upsilon }(10860)$, and $\mathrm{\Upsilon }(11020)$ could be predominantly the $3^3{D}_1$, $5^3{S}_1$, and $4^3{D}_1$ states, respectively. Our predicted masses of $1F$ and $1G$ $b\overline{b}$ states are in agreement with the results given by the method of lattice QCD, which can be tested by experiments in future. We also compared the RFT model with the quark potential model in detail. The differences of these two kinds of models were discussed.

Tremendous efforts are required to scale the summit of observing neutrinoless double beta decay ($0\nu \beta \beta$). This article quantitatively explores the interplay between exposure (target $\mathrm{mass}\times \mathrm{data}$ taking time) and background levels in $0\nu \beta \beta$ experiments. In particular, background reduction can substantially alleviate the necessity of unrealistic large exposure as the normal mass hierarchy (NH) is probed. The nondegenerate (ND)-NH can be covered with an exposure of $\mathcal{O}(100)$ ton-year, which is only an order of magnitude larger than those planned for next-generation projects—provided that the background could be reduced by $\mathcal{O}({10}^{-6})$ relative to the current best levels. It follows that background suppression will be playing increasingly important and investment-effective, if not determining, roles in future $0\nu \beta \beta$ experiments with sensitivity goals of approaching and covering ND-NH.

Compactification of M-string theory on manifolds with $G_2$ structure yields a wide variety of 4D and 3D physical theories. We analyze the local geometry of such compactifications as captured by a gauge theory obtained from a three-manifold of ADE singularities. Generic gauge theory solutions include a nontrivial gauge field flux as well as normal deformations to the three-manifold captured by noncommuting matrix coordinates, a signal of T-brane phenomena. Solutions of the 3D gauge theory on a three-manifold are given by a deformation of the Hitchin system on a marked Riemann surface which is fibered over an interval. We present explicit examples of such backgrounds as well as the profile of the corresponding zero modes for localized chiral matter. We also provide a purely algebraic prescription for characterizing localized matter for such T-brane configurations. The geometric interpretation of this gauge theory description provides a generalization of twisted connected sums with codimension seven singularities at localized regions of the geometry. It also indicates that geometric codimension six singularities can sometimes support 4D chiral matter due to physical structure “hidden” in T-branes.

The null results in dark matter direct detection experiments imply the present scalar dark matter (DM) annihilation cross section to bottom quark pairs through the Higgs boson exchange is smaller than about ${10}^{-31}{\mathrm{cm}}^3/\mathrm{s}$ for a wide DM mass range, which is much smaller than the required annihilation cross section for thermal relic DM. We propose models of a thermal relic DM with the present annihilation cross section being very suppressed. This property can be realized in an extra $U(1)$ gauge interacting complex scalar DM, where the thermal DM abundance is determined by coannihilation through the gauge interaction while the present annihilation is governed by Higgs bosons exchange processes. An interaction between DM and the extra $U(1)$ breaking Higgs field generates a small mass splitting between DM and its coannihilating partner so that coannihilation becomes possible and also the $Z^{\prime }$-mediated scattering off with a nucleon in direct DM search becomes inelastic. We consider scalar dark matter in $U(1{)}_{B-L}$, $U(1{)}_{(B-L{)}_3}$ and $U(1{)}_{L_{\mu }-L_{\tau }}$ extended models and identify viable parameter regions. We also discuss various implications to future DM detection experiments, the DM interpretation of the gamma-ray excess in the globular cluster 47 Tucanae, the muon anomalous magnetic moment, the Hubble tension and others.