The low-energy effective theory ($\sim \mathrm{TeV}$) of the little Higgs model with $SU(6)/Sp(6)$, as proposed by Low, Skiba, and Smith (LSS), exhibits a two-Higgs-doublet model (2HDM) structure. The symmetry dictates interesting Yukawa patterns, translating to nontrivial fermion couplings with both of the Higgs doublets. The couplings of the scalars with the fermions can induce flavor-changing neutral currents (FCNC), which get constraints from flavor physics observables such as $\mathrm{BR}(B\to X_s\gamma )$, $B_s-{\overline{B}}_s$ mixing, etc. The precision measurement of the $Zb\overline{b}$ vertex, the top and Higgs masses along with other Higgs coupling measurements at the Large Hadron Collider (LHC) also enforce severe restrictions on the LSS model. Direct LHC search results of beyond-the-Standard-Model (BSM) particles also impose bounds on the masses. We probe the LSS model in view of the above constraints through a random scan in the multidimensional parameter space. We observe, contrary to the general 2HDM scenario, that the emergent 2HDM from the LSS model is less constrained from the flavor data and the $Zb\overline{b}$ measurement but is severely constrained from the electroweak (EW) searches at the LHC. From the flavor data and $Zb\overline{b}$, we find that the charged Higgs mass is relaxed, with $\tan \beta$ being restricted to 0.5–5, whereas the charged Higgs mass is pushed to larger than 1 TeV along with $\tan \beta$ being further restricted to $<3$ when the LHC bounds are incorporated.

We show that proton storage ring experiments designed to search for proton electric dipole moments can also be used to look for the nearly dc spin precession induced by dark energy and ultralight dark matter. These experiments are sensitive to both axion-like and vector fields. Current technology permits probes of these phenomena up to 3 orders of magnitude beyond astrophysical limits. The relativistic boost of the protons in these rings allows this scheme to have sensitivities comparable to atomic comagnetometer experiments that can also probe similar phenomena. These complementary approaches can be used to extract the microphysics of a signal, allowing us to distinguish between pseudoscalar, magnetic and electric dipole moment interactions.

$CP$ violation beyond the Standard Model (SM) is a crucial missing piece for explaining the observed matter-antimatter asymmetry in the Universe. Recently, the ATLAS experiment at the Large Hadron Collider performed an analysis of electroweak $Zjj$ production, thereby excluding the SM locally at 95% confidence level in the measurement of $CP$-sensitive observables. We take the excess interpretation in terms of anomalous gauge-Higgs interactions at face value and discuss further steps that are required to scrutinize its origin. In particular, we discuss the relevance of multiboson production using adapted angular observables to show how they can be used to directly tension the reported $Zjj$ excess in a more comprehensive analysis. To connect the excess to a concrete UV scenario for which the underlying assumptions of the $Zjj$ analysis are valid, we identify vectorlike leptons as a candidate theory consistent with the observed $CP$-odd Wilson coefficient hierarchy observed by ATLAS. We perform a complete one-loop matching calculation to motivate further model-specific and correlated new physics searches. In parallel, we provide estimates of the sensitivity reach of the LHC’s high luminosity phase for this particular scenario of $CP$ violation in light of electroweak precision and Run-2 Higgs data. These provide strong constraints on the model’s $CP$-even low-energy phenomenology, but also inform the size of the $CP$-odd SM deformation indirectly via our model hypothesis.

We investigate the effect of repulsive interaction between hadrons on the fluctuations of the conserved charges. We calculate the baryon, the electric charge, and the strangeness susceptibilities within the ambit of hadron resonance gas model extended to include the short range repulsive interactions. The repulsive interactions are included through a mean-field approach where the single particle energy gets modified due to mean-field interactions between hadrons proportional to the number density of hadrons. We assume different mean-field interactions for mesons and baryons. It is shown that the repulsive interactions play a very crucial role to describe hadronic matter near transition temperature. We also show that in order to consistently describe higher order conserved charge fluctuations mesonic repulsive interactions cannot be neglected. Further, we demonstrate that the repulsive interaction of baryons is essential to describe the lattice simulation results at finite baryon chemical potential for higher order fluctuations.

Observation of the interference between the atmospheric-scale and solar-scale oscillations is one of the challenging and tantalizing goals of the ongoing and upcoming neutrino experiments. An inevitable first step required for such analyses is to establish the way the oscillation $S$ matrix can be decomposed into the atmospheric and solar waves, the procedure dubbed as the amplitude decomposition. In this paper, with the use of the perturbative framework proposed by Denton et al. (DMP), we establish the prescription for amplitude decomposition which covers the whole kinematical region of the terrestrial neutrino experiments. We analyze the limits to the atmospheric- and solar-resonance regions to argue that the dynamical two modes of the DMP decomposition can be interpreted as the matter-dressed atmospheric and solar oscillations. The expressions of the oscillation probability, which are decomposed into the noninterference and interference terms, are derived for all the relevant flavor oscillation channels. Through construction of the DMP decomposition, we reveal the nature of $\psi$ (${\theta }_{12}$ in matter) symmetry as due to the $S$ matrix rephasing invariance. A new picture of the DMP perturbation theory emerged, a unified perturbative framework for neutrino oscillation in earth matter.

We report branching fraction measurements of four decay modes of the ${\mathrm{\Lambda }}_c^{+}$ baryon, each of which includes an $\eta$ meson and a $\mathrm{\Lambda }$ baryon in the final state, and all of which are measured relative to the ${\mathrm{\Lambda }}_c^{+}\to p{K}^{-}{\pi }^{+}$ decay mode. The results are based on a $980\mathrm{f}{\mathrm{b}}^{-1}$ data sample collected by the Belle detector at the KEKB asymmetric-energy $e^{+}{e}^{-}$ collider. Two decays, ${\mathrm{\Lambda }}_c^{+}\to \eta {\mathrm{\Sigma }}^0{\pi }^{+}$ and $\mathrm{\Lambda }(1670){\pi }^{+}$, are observed for the first time, while the measurements of the other decay modes, ${\mathrm{\Lambda }}_c^{+}\to \eta \mathrm{\Lambda }{\pi }^{+}$ and $\eta \mathrm{\Sigma }(1385{)}^{+}$, are more precise than those made previously. We obtain relative branching fractions of $\mathcal{B}({\mathrm{\Lambda }}_c^{+}\to \eta \mathrm{\Lambda }{\pi }^{+})/\mathcal{B}({\mathrm{\Lambda }}_c^{+}\to p{K}^{-}{\pi }^{+})=0.293\pm 0.003\pm 0.014$, $\mathcal{B}({\mathrm{\Lambda }}_c^{+}\to \eta {\mathrm{\Sigma }}^0{\pi }^{+})/\mathcal{B}({\mathrm{\Lambda }}_c^{+}\to p{K}^{-}{\pi }^{+})=0.120\pm 0.006\pm 0.010$, $\mathcal{B}({\mathrm{\Lambda }}_c^{+}\to \mathrm{\Lambda }(1670){\pi }^{+})\times \mathcal{B}(\mathrm{\Lambda }(1670)\to \eta \mathrm{\Lambda })/\mathcal{B}({\mathrm{\Lambda }}_c^{+}\to p{K}^{-}{\pi }^{+})=(5.54\pm 0.29\pm 0.73)\times {10}^{-2}$, and $\mathcal{B}({\mathrm{\Lambda }}_c^{+}\to \eta \mathrm{\Sigma }(1385{)}^{+})/\mathcal{B}({\mathrm{\Lambda }}_c^{+}\to p{K}^{-}{\pi }^{+})=0.192\pm 0.006\pm 0.016$. The mass and width of the $\mathrm{\Lambda }(1670)$ are also precisely determined to be $1674.3\pm 0.8\pm 4.9\mathrm{MeV}/c^2$ and $36.1\pm 2.4\pm 4.8\mathrm{MeV}$, respectively, where the uncertainties are statistical and systematic, respectively.

Two polarizations of the gravitational waves, the plus and cross modes, are derived from general relativity. However, alternative theories of gravity can yield the gravitational waves with up to six polarizations. Searching for the polarizations beyond plus and cross is an important test of general relativity. In principle, one spaceborne detector, like LISA, could measure the gravitational wave polarizations from a long time observation with its orbital motion. With comparable sensitivities, the joint LISA and TAIJI missions will improve the observations on the polarization predictions of theories beyond general relativity. In this work, a class of parametrized post-Einsteinian waveforms is employed to describe the alternative polarizations, and six parametrized post-Einsteinian parameters quantifying the deviation from the general relativity waveforms are examined by using the LISA-TAIJI network. Our results show that the measurements on amplitudes of alternative polarizations from joint LISA-TAIJI observation could be improved by more than 10 times compared to LISA single mission in an optimal scenario.

In the framework of spatially covariant gravity, it is natural to extend a gravitational theory by putting the lapse function $N$ and the spatial metric $h_{ij}$ on an equal footing. We find two sufficient and necessary conditions for ensuring two physical degrees of freedom (DoF) for the theory with the lapse function being dynamical by Hamiltonian analysis. A class of quadratic actions with only two DoF is constructed. In the case that the coupling functions depend on $N$ only, we find that the spatial curvature term cannot enter the Lagrangian and thus this theory possesses no wave solution and cannot recover general relativity (GR). In the case that the coupling functions depend on the spatial derivatives of $N$, we perform a spatially conformal transformation on a class of quadratic actions with nondynamical lapse function to obtain a class of quadratic actions with $\dot{N}$. We confirm this theory has two DoF by checking the two sufficient and necessary conditions. Besides, we find that a class of quadratic actions with two DoF can be transformed from GR by disformal transformation.

We analyze the causal structure of McVittie spacetime for a classical bouncing cosmological model. In particular, we compute the trapping horizons of the metric and integrate the trajectories of radial null geodesics before, during, and after the bounce takes place. In the contracting phase up to the occurrence of the bounce, a dynamical black hole is present. When the universe reaches a certain minimum scale, the trapping horizons disappear and the black hole ceases to exist. After the bounce, the central weak singularity becomes naked. In the expanding phase, for large positive values of the cosmic time, the behavior of null geodesics indicates that the solution contains a black hole. These results suggest that neither a contracting nor an expanding universe can accommodate a black hole at all times.

Rapidly spinning neutron stars are promising sources of continuous gravitational waves. Detecting such a signal would allow probing of the physical properties of matter under extreme conditions. A significant fraction of the known pulsar population belongs to binary systems. Searching for unknown neutron stars in binary systems requires specialized algorithms to address unknown orbital frequency modulations. We present a search for continuous gravitational waves emitted by neutron stars in binary systems in early data from the third observing run of the Advanced LIGO and Advanced Virgo detectors using the semicoherent, GPU-accelerated, binaryskyhough pipeline. The search analyzes the most sensitive frequency band of the LIGO detectors, 50–300 Hz. Binary orbital parameters are split into four regions, comprising orbital periods of three to 45 days and projected semimajor axes of two to 40 light seconds. No detections are reported. We estimate the sensitivity of the search using simulated continuous wave signals, achieving the most sensitive results to date across the analyzed parameter space.

We propose a simple model based on the assumption that the varying fine structure constant $\alpha$ is an effect of the cosmological expansion to investigate the relation between the varying $\alpha$ and the cosmological components. For a spatially flat, homogeneous, and isotropic universe, the current proportion of cosmological components and age of the universe predicted by the model are consistent with the cosmological observations. Furthermore, the predicted current variation rate of $\alpha$ is also close to the atomic clock measurements. For the early universe, we predict a very strict constraint, which is compatible with the upper limit given by the investigations of cosmic microwave background and big bang nucleosynthesis.

One of the uncertainties in nuclear physics is whether a phase transition between hadronic matter to quark matter exists in supranuclear equations of state. Such a feature can be probed via gravitational-wave signals from binary neutron star inspirals that contain information of the induced tides. The dynamical part of the tides is caused by the resonance of pulsation modes of stars, which causes a shift in the gravitational-wave phase. In this paper, we investigate the dynamical tides of the interfacial mode ($i$-mode) of spherical degree $l=2$, a nonradial mode caused by an interface associated with a quark-hadron phase transition inside a hybrid star. In particular, we focus on hybrid stars with a crystalline quark matter core and a fluid hadronic envelope. We employ a hybrid method which consists of a general relativistic calculation of the stellar structure, together with Newtonian formulations of tidal couplings and mode excitations. We find that the resonant frequency of such $i$-modes typically ranges from 300 Hz to 1500 Hz, and the frequency increases as the shear modulus of the quark core increases. We next estimate the detectability of such a mode with existing and future gravitational-wave events from the inspiral waveform with a Fisher analysis. We find that GW170817 and GW190425 have the potential to detect the $i$-mode if the quark-hadron phase transition occurs at a sufficiently low pressure and the shear modulus of the quark matter phase is large enough. We also find that the third-generation gravitational-wave detectors can further probe the $i$-mode with intermediate transition pressure. Finally, we check our hybrid method against a fully-Newtonian analysis and find that the two results can be off by a factor of a few. Thus, the results presented here should be valid as an order-of-magnitude estimate and provide a new, interesting direction for probing the existence of quark core inside a neutron star using the $i$-mode. A full general relativistic formalism, however, needs to be pursued for further analysis.

Nonlinear QCD evolution equations are essential tools in understanding the saturation of partons at small Bjorken $x_{\mathrm{B}}$, as they are supposed to restore an upper bound of unitarity for the cross section of high-energy scattering. In this paper, we present an analytical solution of the Balitsky-Kovchegov equation using the homogeneous balance method. The obtained analytical solution is similar to the solution of a traveling wave. By matching the gluon distribution in the dilute region which is determined from the global analysis of experimental data (CT14 analysis), we get a definitive solution of the dipole-proton forward scattering amplitude in the momentum space. Based on the acquired scattering amplitude and the behavior of geometric scaling, we present also a new estimated saturation scale $Q_s^2(x)$.

We investigate the effects of non-Hermiticity on interacting fermionic systems. We do this by including non-Hermitian bilinear terms into the $3+1$ dimensional Nambu–Jona-Lasinio (NJL) model. Two possible bilinear modifications give rise to $\mathcal{P}\mathcal{T}$-symmetric theories; this happens when the standard NJL model is extended either by a pseudovector background field $ig\overline{\psi }{\gamma }_5{B}_{\mu }{\gamma }^{\mu }\psi$ or by an antisymmetric-tensor background field $g\overline{\psi }{F}_{\mu \nu }{\gamma }^{\mu }{\gamma }^{\nu }\psi$. The three remaining bilinears are anti-$\mathcal{P}\mathcal{T}$-symmetric in nature, $ig\overline{\psi }{B}_{\mu }{\gamma }^{\mu }\psi ,ig\overline{\psi }{\gamma }_5\psi$ and $ig\overline{\psi }\mathbb{1}\psi$, so that the Hamiltonian then has no overall symmetry. The pseudovector $ig\overline{\psi }{\gamma }_5{B}_{\mu }{\gamma }^{\mu }\psi$ and the vector $ig\overline{\psi }{B}_{\mu }{\gamma }^{\mu }\psi$ combinations, are, in addition, chirally symmetric. Thus, within this framework we are able to examine the effects that the various combinations of non-Hermiticity, $\mathcal{P}\mathcal{T}$ symmetry, chiral symmetry, and the two-body interactions of the NJL model have on the existence and dynamical generation of a real effective fermion mass (a feature which is absent in the corresponding modified massless free Dirac models) as well as on the masses of the composite particles, the pseudoscalar and scalar mesonic modes ($\pi$ and $\sigma$ mesons). Our findings demonstrate that $\mathcal{P}\mathcal{T}$ symmetry is not necessary for real fermion mass solutions to exist; rather, the two-body interactions of the NJL model supersede the non-Hermitian bilinear effects. The effects of chiral symmetry are evident most clearly in the meson modes, the pseudoscalar of which will always be Goldstone in nature if the system is chirally symmetric. Second solutions of the mesonic equations are also discussed.

We discuss a mechanism of neutrinoless double beta decay, where neutrinos of different flavors come into play. This is realized by effective flavor-violating scalar interactions. As one consequence, we find that within the normal mass ordering the neutrino effective mass may no longer vanish due to contributions from other flavors. We evaluate the necessary nuclear matrix elements, consider the interference between the standard diagram and the new scalar one, and analyze a UV-complete model that realizes the scalar interaction. Tests of the complete model are possible at colliders and future neutrino experiments. Our scenario represents an alternative mechanism for neutrinoless double beta decay, where nevertheless lepton number violation resides only in Majorana mass terms of light neutrinos.

We study the pair description of heavy tetraquark systems $|QQ\overline{Q}\overline{Q}⟩$ in the frame of a nonrelativistic potential model. By taking the two heavy quark pairs $(Q\overline{Q})$ as colored clusters, the four-quark Schrödinger equation is reduced to a two-pair equation, when the inner motion inside the pairs can be neglected. Taking into account all the Casimir scaling potentials between two quarks and using the lattice QCD simulated mixing angle between the two color-singlet states for the tetraquark system, we extracted a detailed pair potential between the two heavy quark pairs.

One of the substantial sources of systematic errors in neutrino oscillation experiments that utilize neutrinos from accelerator sources stems from a lack of precision in modeling single-pion production (SPP). Oscillation analyses rely on Monte Carlo event generators (MC), providing theoretical predictions of neutrino interactions on nuclear targets. Pions produced in these processes provide a significant fraction of oscillation signal and background on both elementary scattering and detector simulation levels. Thus, it is of critical importance to develop techniques that will allow us to accommodate state-of-the-art theoretical models describing SPP into MCs. In this work, we investigate various algorithms to implement single-pion production models in Monte Carlo event generators. Based on comparison studies, we propose a novel implementation strategy that combines satisfactory efficiency with high precision in reproducing details of theoretical models predictions, including pion angular distributions. The proposed implementation is model-independent, thereby providing a framework that can include any model for SPP. We have tested the new algorithm with the Ghent low energy model for single-pion production implemented in the NuWro Monte Carlo event generator.

Future large liquid-scintillator (LS) detectors are competitive with and complementary to the water-Cherenkov detectors on the searches for diffuse supernova neutrino background and nucleon decay. In a companion paper, we have performed a systematic calculation of the neutral-current (NC) background induced by atmospheric neutrino interactions on ${}^{12}\mathrm{C}$ nuclei in LS detectors, which are expected to be crucially important for the experimental searches for the diffuse supernova neutrino background and nucleon decay. In this paper, we perform a systematic study on the measurement of the NC background and evaluate the associated uncertainties. We first exploit the characteristics of the NC background, in particular, the multiplicities of neutrons and pions, and the possible association with unstable residual nuclei. It turns out that the neutron multiplicity distribution is very powerful to discriminate among different models. Then, we develop a maximum-likelihood method to allow an in situ measurement of the NC interactions with a triple-coincidence signature. Finally, a data-driven approach is proposed to evaluate the uncertainty of the NC background in the search for the diffuse supernova neutrino background. We conclude that future large LS experiments like the Jiangmen Underground Neutrino Observatory will be able to make a unique contribution to the worldwide dataset to improve the prediction of atmospheric neutrino NC interactions on ${}^{12}\mathrm{C}$.

The experimental searches for diffuse supernova neutrino background and proton decay in next-generation large liquid-scintillator (LS) detectors are competitive with and complementary to those in the water-Cherenkov detectors. In this paper, we carry out a systematic study of the dominant background induced by atmospheric neutrinos via their neutral-current (NC) interactions with the ${}^{12}\mathrm{C}$ nuclei in the LS detectors. The atmospheric neutrino fluxes at the location of Jiangmen Underground Neutrino Observatory (JUNO) are used, as the JUNO detector is obviously a suitable representative for future LS detectors. Then, we implement the sophisticated generators genie and nuwro to simulate the neutrino interactions with the carbon nuclei, and the package talys to deal with the deexcitations of final-state nuclei. Finally, the event rates for the production of additional nucleons, $\gamma$’s, $\alpha$’s, pions, and kaons are obtained and categorized, and the systematic uncertainty of the NC background represented by a variety of data-driven nuclear models is estimated. The implications of the NC background from atmospheric neutrinos for the detection of diffuse supernova neutrino background and proton decay are also discussed.

This paper presents studies of the performance of water-based liquid scintillators (WbLS) in both 1-kt and 50-kt detectors. Performance is evaluated in comparison to both pure water Cherenkov detectors and a nominal model for pure scintillator detectors. Performance metrics include energy, vertex, and angular resolution, along with a metric for the ability to separate the Cherenkov from the scintillation signal as being representative of various particle identification capabilities that depend on the Cherenkov/scintillation ratio. We also modify the time profile of scintillation light to study the same performance metrics as a function of rise and decay time. We go on to interpret these results in terms of their impact on certain physics goals, such as solar neutrinos and the search for Majorana neutrinos. This work supports and validates previous results, and the assumptions made therein, and serves as a significant stepping stone to complete detector design studies by using a more detailed detector model and full reconstruction, with a primarily data-driven optical model, and fewer model assumptions. With this model, a high-coverage 50-kt detector achieves better than 10 (1)% precision on the flux of neutrinos from the Carbon-Nitrogen-Oxygen cycle with a water-based liquid scintillator (pure LS) target in five years of data taking. A 1-kt LS detector, with a conservative 50% fiducial volume of 0.5 kt, can achieve better than 5% detection. A liquid scintillator detector has sensitivity into the normal hierarchy region for Majorana neutrinos with half-life sensitivity of $T_{1/2}^{0\nu \beta \beta }>1.4\times {10}^{28}\mathrm{years}$ at 90% C.L. for 10 years of data taking with a Te-loaded target.