We present a theoretical study of the ${\mathrm{\Xi }}^{*}(1690)$ resonance in the ${\mathrm{\Lambda }}_c^{+}\to \mathrm{\Lambda }{K}^{+}{\overline{K}}^0$ decay, where the weak-interaction part proceeds through the Cabibbo-favored process $c\to s+u\overline{d}$. Next, the intermediate two mesons and one-baryon state can be constructed with a pair of $q\overline{q}$ with the vacuum quantum numbers. Finally, the ${\mathrm{\Xi }}^{*}(1690)$ is mainly produced from the final-state interactions of $\overline{K}\mathrm{\Lambda }$ in coupled channels, and this is shown in the $\overline{K}\mathrm{\Lambda }$ invariant mass distribution. The scalar meson $a_0(980)$ and nucleon excited state $N^{*}(1535)$ are also taken into account in the decaying channels $K^{+}{\overline{K}}^0$ and $K^{+}\mathrm{\Lambda }$, respectively. Within model parameters, the $K^{+}{\overline{K}}^0$, ${\overline{K}}^0\mathrm{\Lambda }$, and $K^{+}\mathrm{\Lambda }$ invariant mass distributions are calculated, and it is found that our theoretical results can well reproduce the experimental measurements, especially for the clear peak around 1690 MeV in the $\overline{K}\mathrm{\Lambda }$ spectrum. The proposed weak decay process ${\mathrm{\Lambda }}_c^{+}\to \mathrm{\Lambda }{K}^{+}{\overline{K}}^0$ and the interaction mechanism can provide valuable information on the nature of the ${\mathrm{\Xi }}^{*}(1690)$ resonance.

Applying the developed Bethe-Salpeter theory for dealing with resonance, we investigate the time evolution of molecular state composed of two vector mesons as determined by the total Hamiltonian. Then exotic meson resonance ${\chi }_{c0}(3915)$ is considered as a mixed state of two unstable molecular states $D^{*0}{\overline{D}}^{*0}$ and $D^{*+}{D}^{*-}$, and the mass and width for physical resonance ${\chi }_{c0}(3915)$ are calculated in the framework of relativistic quantum field theory. In this actual calculation, we minutely show how to obtain the correction for energy level of resonance and to exhibit the key features of dispersion relation in an extended Feynman diagram. The numerical results are consistent with the experimental values.

We investigate the process ${\eta }_c\to {\overline{K}}^0{K}^{+}{\pi }^{-}$ by taking into account the $S$-wave $K^{*}{\overline{K}}^{*}$ and $\rho \omega$ interactions within the unitary coupled-channel approach, where the scalar meson $a_0(1710)$ is dynamically generated. In addition, the contributions from the intermediate resonances $K_0^{*}(1430{)}^{-}\to {\overline{K}}^0{\pi }^{-}$ and $K_0^{*}(1430{)}^0\to K^{+}{\pi }^{-}$ are also considered. We find a significant dip structure around 1.8 GeV, associated to the $a_0(1710)$, in the ${\overline{K}}^0{K}^{+}$ invariant mass distribution, and the clear peaks of the $K_0^{*}(1430)$ in the ${\overline{K}}^0{\pi }^{-}$ and $K^{+}{\pi }^{-}$ invariant mass distributions, consistent with the BABAR measurements. We further estimate the branching fractions $\mathcal{B}({\eta }_c\to {\overline{K}}^{*0}{K}^{*+}{\pi }^{-})=5.5\times {10}^{-3}$ and $\mathcal{B}({\eta }_c\to \omega {\rho }^{+}{\pi }^{-})=7.9\times {10}^{-3}$. Our predictions can be tested by the BESIII and Belle II experiments in the future.

In this article we clear up misconceptions concerning the dark bubble model as a realization of dark energy in string theory. In particular we point out important differences with Randall-Sundrum, and explain why gravity neither is, nor need be, localized on the dark bubble.

In the present work, we theoretically investigate gravitational lensing in the spacetime of a holonomy corrected Schwarzschild black hole. Analytical expressions for the light deflection angle are obtained in both the weak field limit and the strong field limit. Furthermore, we analyze observables, such as relativistic images and magnifications, and compare the results with those expected in a Schwarzschild spacetime. We discuss the possibilities and difficulties of investigating such a solution in practice.

In Einstein-Gauss-Bonnet gravity, we study the quasinormal modes (QNMs) of the tensor perturbations for the so-called Maeda-Dadhich black hole which locally has a topology ${ℳ}^n\simeq M^4\times {𝒦}^{n-4}$. Our discussion is based on the tensor perturbation equation [L.-M. Cao and L.-B. Wu, Phys. Rev. D 103, 064054 (2021).], where the Kodama-Ishibashi gauge-invariant formalism for Einstein gravity theory has been generalized to the Einstein-Gauss-Bonnet gravity theory. With the help of characteristic tensors for the constant curvature space ${𝒦}^{n-4}$, we investigate the effect of extra dimensions and obtain the scalar equation in four-dimensional spacetime, which is quite different from the Klein-Gordon equation. Using the asymptotic iteration method and the numerical integration method with the Kumaresan-Tufts frequency extraction method, we numerically calculate the QNM frequencies. In our setups, characteristic frequencies depend on six distinct factors. They are the spacetime dimension $n$, the Gauss-Bonnet coupling constant $\alpha$, the black hole mass parameter $\mu$, the black hole charge parameter $q$, and two “quantum numbers” $l$, $\gamma$. Without loss of generality, the impact of each parameter on the characteristic frequencies is investigated while fixing the other five parameters. Interestingly, the dimension of the compactification part has no significant impact on the lifetime of QNMs.

Axions and axionlike particles are a prominent dark matter candidate, drawing motivation in part from the axiverse of string theory. Axionlike particles can also arise as composite degrees of freedom of a dark sector, for example, as dark pions in dark quantum chromodynamics. In a dark Standard Model (SM) wherein all six quark flavors are light while the photon is massive, one finds a rich low-energy spectrum of stable and ultralight particles, in the form of neutral and charged dark scalars, and complex neutral scalars analogous to the SM kaon, with mass splittings determined by the mass and charge of the dark quarks. The model finds a natural portal to the visible sector via kinetic coupling of the dark and visible photons and consequent millicharges for dark matter. The dark matter can be a mixture of all these ultralight bosonic degrees of freedom and exhibits both parity-even and parity-odd interactions, making the theory testable at a wide variety of experiments. In context of dark QCD with $N_f$ flavors of light quarks, this scenario predicts $N_f^2-1$ ultralight axionlike particles—effectively an axiverse from dark QCD. This “$\pi$-axiverse” is consistent with but makes no recourse to string theory and is complementary to the conventional string theory axiverse.

Mega electron volt (MeV) gamma-ray observations are promising diagnostic tools for observing the Universe. However, the sensitivity of MeV gamma-ray telescopes is limited by peculiar backgrounds, restricting the applicability of MeV gamma-ray observations. Thus, background identification is crucial in the design of next-generation telescopes. Here, we assessed the background contributions of the electron-tracking Compton camera (ETCC) onboard SMILE-$2+$ in balloon experiments. This assessment was performed using Monte Carlo simulations. The results revealed that a background below 400 keV existed due to the atmospheric gamma-ray background, cosmic-ray/secondary-particle background, and accidental background. Moreover, an unresolved background component that was not related to direct Compton-scattering events in the ETCC was confirmed above 400 keV. Overall, this study demonstrated that the Compton-kinematics test is a powerful tool for removing backgrounds and principally improves the signal-to-noise ratio at 400 keV by an order of magnitude.

We investigate the impact of a mean field model for the $\alpha \mathrm{\Omega }$ dynamo potentially active in the postmerger phase of a binary neutron star coalescence. We do so by deriving equations for ideal general relativistic magnetohydrodynamics with an additional $\alpha$ term, which closely resemble their Newtonian counterpart, but remain compatible with standard numerical relativity simulations. We propose a heuristic dynamo closure relation for the magnetorotational instability-driven turbulent dynamo in the outer layers of a differentially rotating magnetar remnant and its accretion disk. As a first demonstration, we apply this framework to the early stages of post-merger evolution ($\lesssim 50\mathrm{ms}$). We demonstrate that depending on the efficacy of the dynamo action, magnetically driven outflows can be present with their amount of baryon loading correlating with the magnetic field amplification. These outflows can also contain precursor flaring episodes before settling into a quasisteady state. For the dynamo parameters explored in this work, we observe electromagnetic energy fluxes of up to ${10}^{50}\mathrm{erg}/\mathrm{s}$, although larger amplification parameters will likely lead to stronger fluxes. Our results are consistent with the expectation that substantial dynamo amplification (either during or after the merger) may be necessary for neutron-star remnants to power short gamma-ray bursts or precursors thereof.

We calculate, in a systematic way, the general structure of the self-energy of light massive fermions and the effective propagator in a thermomagnetic medium with the inclusion of anomalous magnetic moment (AMM) of the fermion in the weak field approximation. It is found that the self-energy of a massive fermion in this case consists of five nontrivial structure factors in contrast to the massless case where the self-energy contains only four. We employ the real time formalism (RTF) of thermal field theory within the ambit of hard thermal loop (HTL) approximation in the evaluation of the structure factors. The collective modes are obtained from the poles of the effective propagator of the fermion. The investigation of the dispersion relations for nondegenerate ground state shows that the effect of the magnetic field is more for up quark than the down quark because of the larger charge of the former. The important observation is that in the first excited state the degeneracy, which exists for nonzero magnetic field is lifted due to the inclusion of the AMM. It is also observed that the first excited state becomes less dispersive compared to the case when AMM is not considered, whereas the second excited state becomes more dispersive when both the magnetic field and the AMM are nonzero in comparison to the case with vanishing AMM. These effects are observed in both particle and holelike excitations. Qualitatively similar behavior is also seen in the case of down quarks.

We analyze six classes of $t$-channel dark matter simplified models in which the Standard Model field content is extended by a colored mediator and a dark matter state. The two new states are enforced to be odd under a new parity, while all Standard Model fields are taken even so that dark matter stability is guaranteed. We study several possibilities for the spin of the new particles and the self-conjugate property of the dark matter, and we focus on model configurations in which the dark matter couples to the right-handed up quark for simplicity. We investigate how the parameter spaces of the six models can be constrained by current and future cosmological, astrophysical and collider searches, and we highlight the strong complementary between those probes. Our results demonstrate that scenarios featuring a complex (non self-conjugate) dark matter field are excluded by cosmology and astrophysics alone, the only possibility to avoid these bounds being to invoke very weak couplings and mechanisms such as conversion-driven freeze-out. For models with self-conjugate dark matter, mediator and dark matter masses are pushed deep into the TeV regime, with the lower limits on the mediator mass reaching 3 to 4 TeV and those on the dark matter mass 1 to 2 TeV. In large parts of the parameter space these strong bounds are driven by same-sign mediator pair production, a channel so far not considered in the experimental analyses embedding $t$-channel dark matter model interpretations.

Searches for additional sources of $CP$ violation at the Large Hadron Collider are a central part of the Higgs physics program beyond the Standard Model. Studies employing so-called signed observables that track $CP$ violation through purpose-built asymmetries bolster efforts based on Higgs boson rate analyses under clear assumptions. A possibility which is, so far, unexplored at the LHC, is a significant nonlinear realization of $CP$ violation, which is naturally described in nonlinear Higgs effective field theory (HEFT). We perform an analysis of the HL-LHC potential to constrain such interactions considering a large range of single and double Higgs production processes, including differential information where this is statistically and theoretically possible. A particular emphasis of our work is distinguishing expected correlations in the Standard Model effective field theory from those attainable in HEFT.

We test a novel idea of using a ${\pi }^{-}$ beam in the fixed-target experiments to search for new physics in the events with missing energy. Bounds for invisible vector $\rho$ meson decay were derived, analyzed, and compared with the current limits on searching dark matter in the accelerator based experiments. We demonstrate that the new approach can be effective tool to probe sub-GeV dark matter parameter space.

Gapped fermion theories with gapless boundary fermions can exist in any number of dimensions. When the boundary has even space-time dimensions and hosts chiral fermions, a quantum Hall current flows from the bulk to the boundary in a background electric field. This current compensates for the boundary chiral anomaly. Such a current inflow picture is absent when the boundary theory is odd dimensional. However, in recent work, the idea of quantum Hall current has been generalized to describe odd dimensional boundary theories in the continuous Euclidean space-time dimension of infinite volume. In this paper, we extend this idea to a lattice regulated finite volume theory of $1+1$ dimensional Wilson-Dirac fermions. This fermion theory with a domain wall in fermion mass can host gapless modes on the wall. The number of gapless fermions is equal to the integral of the divergence of the lattice generalized Hall current.

We study the consequences of mode-collapse of normalizing flows in the context of lattice field theory. Normalizing flows allow for independent sampling. For this reason, it is hoped that they can avoid the tunneling problem of local-update Markov Chain Monte Carlo algorithms for multimodal distributions. In this work, we first point out that the tunneling problem is also present for normalizing flows but is shifted from the sampling to the algorithm’s training phase. Specifically, normalizing flows often suffer from mode-collapse for which the training process assigns vanishingly low probability mass to relevant modes of the physical distribution. This may result in a significant bias when the flow is used as a sampler in a Markov-Chain or with importance sampling. We propose a metric to quantify the degree of mode-collapse and derive a bound on the resulting bias. Furthermore, we propose various mitigation strategies in particular in the context of estimating thermodynamic observables, such as the free energy.

Nearly ten years ago, Kang, Ma, Qiu, and Sterman derived an evolution equation for a $Q\overline{Q}$ pair fragmenting into a quarkonium. In this study we explore the consequence of this evolution for the color-evaporation model, focusing on $J/\psi$ transverse-momentum ($p_t$) distributions in proton-proton collisions. We show that, as expected, it softens the spectrum obtained by fixed-order calculations. While next-to-leading-order calculations strongly overestimate data at large $p_t$, ours, including the (approximate) $Q\overline{Q}$ evolution and next-to-leading-order cross sections computed with Madgraph, are in good agreement with experiments. Since our study with the color-evaporation model shows a significant effect of the $Q\overline{Q}$ evolution at large $p_t$, a new determination of long-distance-matrix elements of non-relativistic QCD could be necessary. To describe data at small and intermediate $p_t$, we use the $k_t$-factorization approach, and we argue that quarkonia data could help constrain this formalism.

The contribution of hadronic scattering of light by light to the hyperfine structure of muonium is calculated using experimental data on the transition form factors of two photons into a hadron. The amplitudes of interaction between a muon and an electron with horizontal and vertical exchange are constructed. The contributions due to the exchange of pseudoscalar, axial vector, scalar, and tensor mesons are taken into account.

The production cross sections of ${\mathrm{D}}^0$ and ${\mathrm{\Lambda }}_{\mathrm{c}}^{+}$ hadrons originating from beauty-hadron decays (i.e., nonprompt) were measured for the first time at midrapidity ($|y|<0.5$) by the ALICE Collaboration in proton-proton collisions at a center-of-mass energy $\sqrt{s}=13\mathrm{TeV}$. They are described within uncertainties by perturbative QCD calculations employing the fragmentation fractions of beauty quarks to baryons measured at forward rapidity by the LHCb Collaboration. The $\mathrm{b}\overline{\mathrm{b}}$ production cross section per unit of rapidity at midrapidity, estimated from these measurements, is $\mathrm{d}{\sigma }_{\mathrm{b}\overline{\mathrm{b}}}/\mathrm{d}y{|}_{|y|<0.5}=83.1\pm 3.5(\mathrm{stat})\pm 5.4(\mathrm{syst}{)}_{-3.2}^{+12.3}(\text{extrap})\mathrm{\mu }\mathrm{b}$. The baryon-to-meson ratios are computed to investigate the hadronization mechanism of beauty quarks. The nonprompt ${\mathrm{\Lambda }}_{\mathrm{c}}^{+}/{\mathrm{D}}^0$ production ratio has a similar trend to the one measured for the promptly produced charmed particles and to the $\mathrm{p}/{\pi }^{+}$ and $\mathrm{\Lambda }/{\mathrm{K}}_{\mathrm{S}}^0$ ratios, suggesting a similar baryon-formation mechanism among light, strange, charm, and beauty hadrons. The $p_{\mathrm{T}}$ -integrated nonprompt ${\mathrm{\Lambda }}_{\mathrm{c}}^{+}/{\mathrm{D}}^0$ ratio is found to be significantly higher than the one measured in ${\mathrm{e}}^{+}{\mathrm{e}}^{-}$ collisions.

We consider an accelerated relativistic fluid in four-dimensional (anti–)de Sitter space-time. Analyzing only hydrodynamic equations, we construct the equilibrium stress-energy tensor. We confirm that (A)dS vacuum corresponds to a thermal bath in the accelerated frame with a temperature, depending on the acceleration in a flat higher-dimensional (namely, five-dimensional) space, in which curved space-times are embedded. We develop the duality between hydrodynamics and gravity finding a direct relationship between the transport coefficients in flat and curved space-times.