Recent lattice determinations of the hadronic-vacuum polarization contribution to the muon anomalous magnetic moment $a_{\mu }^{\mathrm{HVP}}$ have confirmed the discrepancy with the data-driven dispersive method. In the meanwhile the CMD-3 Collaboration has reported a result for the $e^{+}{e}^{-}\to {\pi }^{+}{\pi }^{-}$ cross section considerably larger than previous experimental results (and close to the lattice determinations) exacerbating the discordance between different $e^{+}{e}^{-}$ datasets. We explore to what extent these disagreements can be accounted for by some new physics effect altering selectively the individual experimental determinations of $\sigma (e^{+}{e}^{-}\to \mathrm{hadrons})$. We find that specific effects of GeV-scale new particles are able to shift upwards the KLOE and BABAR results in the low and intermediate energy windows, while leaving the CMD-3 energy scan unaffected. Although these new physics effects cannot fully explain all the discrepancies among the different $\sigma (e^{+}{e}^{-}\to \mathrm{hadrons})$ datasets, they succeed in mitigating the overall tension between data-driven and lattice estimates of $a_{\mu }^{\mathrm{HVP}}$. Remarkably, the additional loop corrections involving the new particles concur to solve the residual discrepancy with the experimental value of $(g-2{)}_{\mu }$.

We consider $F$-term hybrid inflation and supersymmetry breaking in the context of a model that largely respects a global $U(1)$ $R$ symmetry. The Kähler potential parametrizes the Kähler manifold with an enhanced $U(1)\times (SU(1,1)/U(1))$ symmetry, where the scalar curvature of the second factor is determined by the achievement of a supersymmetry-breaking de Sitter vacuum without ugly tuning. The magnitude of the emergent soft tadpole term for the inflaton can be adjusted in the range (1.2–460) TeV—increasing with the dimensionality of the representation of the waterfall fields—so that the inflationary observables are in agreement with the observational requirements. The mass scale of the supersymmetric partners turns out to lie in the region (0.09–253) PeV which is compatible with high-scale supersymmetry and the results of LHC on the Higgs boson mass. The $\mu$ parameter can be generated by conveniently applying the Giudice-Masiero mechanism and assures the out-of-equilibrium decay of the $R$ saxion at a low reheat temperature $T_{\mathrm{rh}}\le 163\mathrm{GeV}$.

If dark matter is a light scalar field weakly interacting with elementary particles, such a field induces oscillations of the physical constants, which results in a time-varying force acting on macroscopic objects. In this paper, we report on a search for such a signal in the data of the two LIGO detectors during their third observing run. We focus on the mass of the scalar field in the range of ${10}^{-13}-{10}^{-11}\mathrm{eV}$ for which the signal falls within the detectors’ sensitivity band. We first formulate the cross-correlation statistics that can be readily compared with publicly available data. It is found that inclusion of the anisotropies of the velocity distribution of dark matter caused by the motion of the Solar System in the Milky Way Galaxy enhances the signal by a factor of $\sim 2$ except for the narrow-mass range around $\simeq 3\times {10}^{-13}\mathrm{eV}$ for which the correlation between the interferometer at Livingston and the one at Hanford is suppressed. From the nondetection of the signal, we derive the upper limits on the coupling constants between the elementary particles and the scalar field for five representative cases. For all the cases in which the weak equivalence principle is not satisfied, tests of the violation of the weak equivalence principle provide the tightest upper limit on the coupling constants. Upper limits from the fifth-force experiment are always stronger than the ones from LIGO, but the difference is less than a factor of $\sim 5$ at large-mass range. Our study demonstrates that gravitational-wave experiments are starting to bring us meaningful information about the nature of dark matter. The formulation provided in this paper may be applied to the data of upcoming experiments as well and is expected to probe a much wider parameter range of the model.

In this work, we construct promising model-building routes towards SO(10) grand unified theory inflation and examine their ability to explain the recent pulsar timing arrays (PTAs) results hinting at a stochastic gravitational wave (GW) background at nanohertz frequencies. We consider a supersymmetric framework within which the so-called doublet-triplet splitting problem is solved without introducing fine-tuning. Additionally, realistic fermion masses and mixings, gauge coupling unification, and cosmic inflation are incorporated by utilizing superfields with representations no higher than the adjoint representation. Among the three possible scenarios, two of these cases require a single adjoint Higgs field, and do not lead to cosmic strings. In contrast, the third scenario featuring two adjoints, can lead to a network of metastable cosmic strings that generates a GW background contribution compatible with the recent PTA findings and testable by various ongoing and upcoming GW observatories.

We study the possibility of detecting dark radiation (DR) produced by a combination of interactions with the thermal bath and ultralight primordial black hole (PBH) evaporation in the early Universe. We show that the detection prospects via cosmic microwave background (CMB) measurements of the effective relativistic degrees of freedom $\mathrm{\Delta }{\mathrm{N}}_{\mathrm{eff}}$ get enhanced in some part of the parameter space compared to the purely nonthermal case where DR is produced solely from a PBH. On the other hand, for a certain part of the parameter space, DR that initially decouples from the bath, followed by its production from PBH evaporation, can reenter the thermal bath leading to much tighter constraints on the PBH parameter space. We also discuss the complementary detection prospects via observation of stochastic gravitational waves (GW) sourced by PBH density perturbations. The complementary probes offered by CMB and GW observations keep the detection prospects of such light degrees of freedom very promising in spite of limited discovery prospects at particle physics experiments.

The dileptons and dineutrinos observed in the final states of flavor-changing neutral b decays provide an ideal platform for probing physics beyond the standard model. Although the latest measurements of $R_{K^{(*)}}$ agree well with the standard model prediction, there exists several other observables such as $P_5^{\prime }$, $\mathcal{B}(B_s\to \varphi {\mu }^{+}{\mu }^{-})$ and $\mathcal{B}(B_s\to {\mu }^{+}{\mu }^{-})$ in $b\to s{\ell }^{+}{\ell }^{-}$ transition decays that shows deviation from the standard model prediction. Similarly, very recently Belle II collaboration reported a more precise upper bound of $\mathcal{B}(B\to K^{+}\nu \overline{\nu })<4.1\times {10}^{-5}$ by employing a new inclusive tagging approach and it also deviates from the standard model expectation. The $b\to s{\ell }^{+}{\ell }^{-}$ and $b\to s\nu \overline{\nu }$ transition decays are related not only in the standard model but also in beyond the standard model physics due to $SU(2{)}_L$ gauge symmetry, and can be most effectively investigated using the standard model effective field theory formalism. Additionally, the $b\to s\nu \overline{\nu }$ decay channels are theoretically cleaner than the corresponding $b\to s{\ell }^{+}{\ell }^{-}$ decays, as these processes do not get contributions from nonfactorizable corrections and photonic penguin contributions. In this context, we study ${\mathrm{\Lambda }}_b\to ({\mathrm{\Lambda }}^{*}(\to p{K}^{-}),\mathrm{\Lambda }(\to p\pi ))({\mu }^{+}{\mu }^{-},\nu \overline{\nu })$ baryonic decays undergoing $b\to s{\ell }^{+}{\ell }^{-}$ and $b\to s\nu \overline{\nu }$ quark level transitions in a standard model effective field theory formalism. We give predictions of several observables pertaining to these decay channels in the standard model and in case of several new physics scenarios.

Results from the experiments like LSND, and MiniBooNE hint towards the possible presence of an extra eV-scale sterile neutrino. The addition of such a neutrino will significantly impact the standard three-flavor neutrino oscillations; in particular, it can give rise to additional degeneracies due to new sterile parameters. In our work, we investigate how the sensitivity to determine the octant of the neutrino mixing angle ${\theta }_{23}$ is affected by introducing a sterile neutrino to the standard three generation framework. We compute the oscillation probabilities analytically in the presence of a sterile neutrino, using the approximation that ${\mathrm{\Delta }}_{21}$, the smallest mass squared difference, is zero. We use these probabilities to understand the degeneracies analytically at different baselines. We present our results of the sensitivity to octant of ${\theta }_{23}$ for beam neutrinos using a liquid argon time projection chamber (LArTPC). We also obtain octant sensitivity using atmospheric neutrinos using the same LArTPC detector. For the latter, we present our results assuming (i) no charge identification capability, and (ii) partial charge identification capability using the charge tagging ability of muon capture in argon. In addition, we include the charge tagging capability of muon capture in argon which allows one to differentiate between muon neutrino and antineutrino events. The combined sensitivity of beam and atmospheric neutrinos in a similar experimental setup is also delineated. We observe that by combining simulated data from the beam and atmospheric neutrinos (including charge-id for muons), the sensitivity to the octant of ${\theta }_{23}$ for true values of ${\theta }_{23}=41°(49°)$ exceeds $4\sigma (3\sigma )$ for more than 50% values of true ${\delta }_{13}$.

Recent lattice QCD results for the low-lying odd-parity excitations of the nucleon near the $N^{*}(1535)$ and $N^{*}(1650)$ resonance positions have revealed that the lattice QCD states have magnetic moments consistent with predictions from a constituent quark model. Using Hamiltonian effective field theory (HEFT) to describe pion-nucleon scattering in the $I(J^P)=\frac{1}{2}({\frac{1}{2}}^{-})$ channel, we represent these two quark-model-like states as two single-particle bare basis states, dressed and mixed by meson-baryon scattering channels. By constraining the free parameters of the Hamiltonian with $S_{11}$ pion-nucleon scattering data, we perform the first calculation of the finite-volume spectrum using two bare-baryon basis states. By comparing this spectrum to contemporary lattice QCD results at three lattice volumes, we analyze the eigenvectors of the Hamiltonian to gain insight into the structure and composition of these two low-lying resonances. We find that an interpretation of the two low-lying nucleon resonances as quark-model-like states dressed by meson-baryon interactions is consistent with both the $S_{11}$ scattering data and lattice QCD. We introduce a novel HEFT formalism for estimating scattering-state contaminations in lattice QCD correlation functions constructed with standard three-quark operators. Not only are historical lattice QCD results described with excellent accuracy, but correlation functions with large scattering-state contaminations are identified.

Understanding the dynamics of bound state formation is one of the fundamental questions in confining quantum field theories such as Quantum Chromodynamics (QCD). One hadronization mechanism that has garnered significant attention is the breaking of a string initially connecting a fermion and an antifermion. Deepening our understanding of real-time string-breaking dynamics with simpler, lower dimensional models like the Schwinger model can improve our understanding of the hadronization process in QCD and other confining systems found in condensed matter and statistical systems. In this paper, we consider the string-breaking dynamics within the Schwinger model and investigate its modification inside a thermal medium, treating the Schwinger model as an open quantum system coupled to a thermal environment. Within the regime of weak coupling between the system and environment, the real-time evolution of the system can be described by a Lindblad evolution equation. We analyze the Liouvillian gaps of this Lindblad equation and the time dependence of the system’s von Neumann entropy. We observe that the late-time relaxation rate decreases as the environment correlation length increases. Moreover, when the environment correlation length is infinite, the system exhibits two steady states, one in each of the sectors with definite charge-conjugation-parity ($CP$) quantum numbers. For parameter regimes where an initial string breaks in vacuum, we observe a delay of the string breaking in the medium, due to kinetic dissipation effects. Conversely, in regimes where an initial string remains intact in vacuum time evolution, we observe string breaking (melting) in the thermal medium. We further discuss how the Liouvillian dynamics of the open Schwinger model can be simulated on quantum computers and provide an estimate of the associated Trotter errors.

We present a lattice calculation of the $K\to \pi \pi$ matrix elements and amplitudes with both the $\mathrm{\Delta }I=3/2$ and $1/2$ channels and ${ϵ}^{\prime }$, the measure of direct $CP$ violation. We use periodic boundary conditions (PBC), where the correct kinematics of $K\to \pi \pi$ can be achieved via an excited two-pion final state. To overcome the difficulty associated with the extraction of excited states, our previous work [Z. Bai et al., Standard Model prediction for direct $CP$ violation in $K\to \pi \pi$ decay, Phys. Rev. Lett. 115, 212001 (2015); R. Abbott et al., Direct $CP$ violation and the $\mathrm{\Delta }I=1/2$ rule in $K\to \pi \pi$ decay from the Standard Model, Phys. Rev. D 102, 054509 (2020).] successfully employed G-parity boundary conditions, where pions are forced to have nonzero momentum enabling the $I=0$ two-pion ground state to express the on shell kinematics of the $K\to \pi \pi$ decay. Here instead we overcome the problem using the variational method which allows us to resolve the two-pion spectrum and matrix elements up to the relevant energy where the decay amplitude is on shell. In this paper we report an exploratory calculation of $K\to \pi \pi$ decay amplitudes and ${ϵ}^{\prime }$ using PBC on a coarser lattice size of ${24}^3\times 64$ with inverse lattice spacing $a^{-1}=1.023\mathrm{GeV}$ and the physical pion and kaon masses. The results are promising enough to motivate us to continue our measurements on finer lattice ensembles in order to improve the precision in the near future.

Inspired by the recent observation of $e^{+}{e}^{-}\to \omega X(3872)$ by the BESIII Collaboration, in this work we study the production of the charmonium ${\chi }_{cJ}(2P)$ by $e^{+}{e}^{-}$ annihilation. We find that the $e^{+}{e}^{-}\to \omega {\chi }_{c0}(2P)$ and $e^{+}{e}^{-}\to \omega {\chi }_{c2}(2P)$ have sizable production rates, when taking the cross section data from $e^{+}{e}^{-}\to \omega X(3872)$ as the scaling point and treating the $X(3872)$ as the charmonium ${\chi }_{c1}(2P)$. Considering that the dominant decay modes of ${\chi }_{c0}$ and ${\chi }_{c2}(2P)$ involve $D\overline{D}$ final states, we propose that $e^{+}{e}^{-}\to \omega D\overline{D}$ is an ideal process to identify ${\chi }_{c0}(2P)$ and ${\chi }_{c2}(2P)$, which is similar to the situation that happens in the $D\overline{D}$ invariant mass spectrum of the $\gamma \gamma \to D\overline{D}$ and $B^{+}\to D^{+}{D}^{-}{K}^{+}$ processes. With the continued accumulation of experimental data, these proposed production processes offer a promising avenue for exploration by the BESIII and Belle II collaborations.

Inspired by the recent observation of new ${\mathrm{\Omega }}_c^0$ states by the LHCb Collaboration, we explore the excited ${\mathrm{\Omega }}_c$ states from the pentaquark perspective in the quark delocalization color screening model. Our results indicate that the ${\mathrm{\Omega }}_c(3185)$ can be well interpreted as a molecular $\mathrm{\Xi }D$ predominated resonance state with $J^P=1/2^{-}$. The ${\mathrm{\Omega }}_c(3120)$ can also be interpreted as a molecular ${\mathrm{\Xi }}_c^{*}\overline{K}$ state with $J^P=3/2^{-}$ and a new molecular state ${\mathrm{\Xi }}_c^{*}{\overline{K}}^{*}$ with $J^P=5/2^{-}$ and a mass of 3526 MeV is predicted, which is worth searching in the future. Other reported ${\mathrm{\Omega }}_c$ states cannot be well described in the framework of pentaquark systems in the present work. The three-quark excited state or the unquenched picture may be a good explanation, which is worth further exploration.

We consider electroweak gauge boson corrections to the masses of pseudoscalar mesons to next to leading order in ${\alpha }_s$ and $1/N_C$. The pion mass shift induced by the $Z$ boson is shown to be $m_{{\pi }^{\pm }}-m_{{\pi }^0}=-0.00201(12)\mathrm{MeV}$. While being small compared to the electromagnetic mass shift, the prediction lies about a factor of $\sim 4$ above the precision of the current experimental measurement and a factor $O(10)$ below the precision of current lattice calculations. This motivates future implementations of these electroweak gauge boson effects on the lattice. Finally, we consider beyond standard model contributions to the pion mass difference.

In this study, we investigate the nonleptonic decays of the charmed-baryon ${\mathrm{\Xi }}_c^0$ induced by the $c\to u(d\overline{d})/(s\overline{s})$ transition. Utilizing the factorization assumption, we decompose the decay amplitudes in terms of transition form factors which are then calculated within the light-front quark model. We employ helicity amplitudes to analyze the nonleptonic decay modes of the charmed-baryons ${\mathrm{\Xi }}_c^0$ and derive benchmark results for decay widths and branching fractions. Our calculations suggest that the branching fractions for some of these rare nonleptonic decays are at the order of ${10}^{-5}–{10}^{-4}$, which are likely to be detectable at experiments such as LHCb, Belle-II, etc. The potential data accumulated in the future may help to further our understanding of the decay mechanism in the presence of charm quarks.

This paper reports the study of $D_s^{+}\to {\tau }^{+}\nu$ via ${\tau }^{+}\to {\pi }^{+}{\overline{\nu }}_{\tau }$ using a boosted decision tree method, with $7.33{\mathrm{fb}}^{-1}$ of $e^{+}{e}^{-}$ collision data collected by the BESIII detector at center-of-mass energies between 4.128 and 4.226 GeV. The branching fraction of $D_s^{+}\to {\tau }^{+}{\nu }_{\tau }$ is determined to be $(5.44\pm 0.17_{\mathrm{stat}}\pm 0.13_{\mathrm{syst}})\%$. The product of the $D_s^{+}$ decay constant $f_{D_s^{+}}$ and the Cabibbo-Kobayashi-Maskawa matrix element $|V_{cs}|$ is $f_{D_s^{+}}|V_{cs}|=(248.3\pm {3.9}_{\mathrm{stat}}\pm {3.1}_{\mathrm{syst}}\pm {1.0}_{\text{input}})\mathrm{MeV}$. Combining with the $|V_{cs}|$ value obtained from the Standard Model global fit or the $f_{D_s^{+}}$ from the lattice quantum chromodynamics, we determine $|V_{cs}|=0.993\pm 0.015_{\mathrm{stat}}\pm 0.012_{\mathrm{syst}}\pm 0.004_{\text{input}}$ and $f_{D_s^{+}}=(255.0\pm {4.0}_{\mathrm{stat}}\pm {3.2}_{\mathrm{syst}}\pm {1.0}_{\text{input}})\mathrm{MeV}$. The first uncertainty is statistical, the second one is systematic and the third one is due to the input parameters, mainly the lifetime of $D_s^{+}$. All results obtained in this work supersede the BESIII previous results based on $6.32{\mathrm{fb}}^{-1}$ of $e^{+}{e}^{-}$ collision data taken at center-of-mass energies between 4.178 and 4.226 GeV.

Out-of-time-order correlators are widely used as an indicator of quantum chaos but give false-positive quantum Lyapunov exponents for integrable systems with isolated saddle points. We propose an alternative indicator that fixes this drawback and retains all advantages of out-of-time-order correlators. In particular, the new indicator correctly predicts the average Lyapunov exponent and the Ehrenfest time in the semiclassical limit, can be calculated analytically using the replica trick, and satisfies the bound on chaos.

Motivated by the existence of two-body hadronic molecules composed of $\mathrm{\Omega }\mathrm{\Omega }$, ${\mathrm{\Omega }}_{ccc}{\mathrm{\Omega }}_{ccc}$, and ${\mathrm{\Omega }}_{bbb}{\mathrm{\Omega }}_{bbb}$ predicted by lattice QCD simulations, we use the Gaussian expansion method to investigate whether three-body systems composed of $\mathrm{\Omega }\mathrm{\Omega }\mathrm{\Omega }$, ${\mathrm{\Omega }}_{ccc}{\mathrm{\Omega }}_{ccc}{\mathrm{\Omega }}_{ccc}$, and ${\mathrm{\Omega }}_{bbb}{\mathrm{\Omega }}_{bbb}{\mathrm{\Omega }}_{bbb}$ can bind with the two-body ${}^1{S}_0$ interactions provided by lattice QCD. Our results show that none of the three-body systems bind. On the other hand, we find that with the one-boson exchange potentials the $\mathrm{\Omega }\mathrm{\Omega }\mathrm{\Omega }$ system develops a bound state, for which the ${}^5{S}_2$ interaction plays an important role. Our studies support the existence of the ${\frac{3}{2}}^{+}$ $\mathrm{\Omega }\mathrm{\Omega }\mathrm{\Omega }$ bound state and the nonexistence of the ${\frac{3}{2}}^{+}$ ${\mathrm{\Omega }}_{ccc}{\mathrm{\Omega }}_{ccc}{\mathrm{\Omega }}_{ccc}$ and ${\mathrm{\Omega }}_{bbb}{\mathrm{\Omega }}_{bbb}{\mathrm{\Omega }}_{bbb}$ bound states, due to the suppressed ${}^5{S}_2$ interactions in heavier systems.

We analyze newly expanded and refined data from lattice studies of an $SU(3)$ gauge theory with eight Dirac fermions in the fundamental representation. We focus on the light composite states emerging from these studies, consisting of a set of pseudoscalars and a single light scalar. We first consider the view that this theory is just outside the conformal window. In this case, the pseudoscalars arise from spontaneous breaking of chiral symmetry. Identifying the scalar in this case as an approximate dilaton, we fit the lattice data to a dilaton effective field theory, finding that it yields a good fit even at lowest order. For comparison, we then consider the possibility that the theory is inside the conformal window. The fermion mass provides a deformation, triggering confinement. We employ simple scaling laws to fit the lattice data and find that it is of lesser quality.

An analysis is given of the local phase space of gravity coupled to matter to second order in perturbation theory. Working in local regions with boundaries at finite distance, we identify matter, Coulomb, and additional boundary modes. The boundary modes take the role of reference frames for both diffeomorphisms and internal Lorentz rotations. Passing to the quantum level, we identify the constraints that link the bulk and boundary modes. The constraints take the form of a multifingered Schrödinger equation, which determines the relational evolution of the quantum states in the bulk with respect to the quantum reference fields for the local gravitational symmetries at the boundary. Taking the boundary to infinity, we obtain quantum reference frames for asymptotic symmetries.

The addition of mass terms in general breaks gauge symmetries which can be recovered usually via Stueckelberg fields. The massive BF model describes massive spin-1 particles while preserving the $U(1)$ symmetry without Stueckelberg fields. Replacing the spin-1 curvature (field strength) by the Riemann tensor one can define its spin-2 analog (massive“BR” model). Here we investigate the canonical structure of the free mBR model in terms of gauge invariants in arbitrary dimensions and compare with the massive BF model. We also investigate nonlinear completions of the mBR model in arbitrary dimensions. In $D=3$ we find a nonlinear completion in the form of a bimetric model which is a subcase of a new class of bimetric models whose decoupling limit is ghost free at leading order. Their spectrum consists only of massive spin-2 particles. In arbitrary dimensions $D\ge 3$ we show that the consistency of a possible single metric completion of the mBR model is related with the consistency of a higher rank description of massless spin-1 particles in arbitrary backgrounds.