We study experimentally observable signals for nonlinear QCD dynamics in deep inelastic scattering (DIS) at small Bjorken variable $x$ and moderate virtuality $Q^2$, by quantifying differences between the linear Dokshitzer-Gribov-Lipatov-Altarelli-Parisi evolution and nonlinear evolution with the Balitsky-Kovchegov equation. To remove the effect of the parametrization freedom in the initial conditions of both equations, we first match the predictions for the DIS structure functions $F_2$ and $F_{\mathrm{L}}$ from both frameworks in a region in $x$, $Q^2$ where both frameworks should provide an accurate description of the relevant physics. The differences in the dynamics are then quantified by the deviations when one moves away from this matching region. For free protons we find that the differences in $F_2$ remain at a few-percent level, while in $F_{\mathrm{L}}$ the deviations are larger, up to 10% at the Electron Ion Collider (EIC) and 40% at the Large Hadron-electron Collider (LHeC) kinematics. With a heavy nucleus the differences are up to 10% in $F_2$, and can reach 20% and 60% in $F_{\mathrm{L}}$ for the EIC and the LHeC, respectively.

We study hidden-flavor pentaquarks, $Q\overline{Q}qqq$, based on a constituent quark-model with a standard quark-quark interaction that reproduces the low-energy meson and baryon spectra. We make use of dynamical correlations between the heavy quarks arising from the Coulomb-like nature of the short-range interaction. A detailed comparison is made with other results in the literature and with experimental data. Our results show a different pattern for open-flavor and hidden-flavor pentaquarks, as suggested by the data. Further implications about the existence of quarkonia bound to nuclei are discussed.

Stimulated by the newly observed $a_0(1817)$ by the BESIII Collaboration, we find a perfect Regge trajectory composed of the $a_0(980)$, $a_0(1450)$, and $a_0(1817)$, which leads us to categorize the $a_0(980)$, $a_0(1450)$, and $a_0(1817)$ into the isovector scalar meson family. This scenario is supported by their two-body Okubo-Zweig-Iizuka allowed strong decay behaviors. In this scheme, we also predict the third radial excitation of the $a_0(980)$, which is denoted as the $a_0(2115)$, accessible at future experiment as a direct test of this assignment. We find another Regge trajectory which contains three isoscalar scalar states $f_0(980)$, $X(1812)$, and $f_0(2100)$. We investigate their two-body Okubo-Zweig-Iizuka allowed strong decay patterns, which are roughly consistent with the experimental data. The $f_0(980)$, $X(1812)$, and $f_0(2100)$ can be well grouped into the isoscalar scalar meson family. We want to emphasize that these two Regge trajectories have a similar slope. In summary, the present work provides a scheme of constructing the scalar meson family based on these reported scalar states. The possibility of the $f_0(1710)$ as the candidate of the scalar glueball cannot be excluded by the observation of the $a_0(1817)$ since the $a_0(1817)$ is more suitable as the isovector partner of the $X(1812)$.

We consider the experimental data on yields of protons, strange ${\mathrm{\Lambda }}^{\prime }\mathrm{s}$, and multistrange baryons ($\mathrm{\Xi }$, $\mathrm{\Omega }$), and antibaryons production on nuclear targets, and the experimental ratios of multistrange to strange antibaryon production, at the energy region from SPS up to LHC, and compare them to the results of the quark-gluon string model calculations. In the case of heavy nucleus collisions, the experimental dependence of the ${\overline{\mathrm{\Xi }}}^{+}/\overline{\mathrm{\Lambda }}$, and, in particular, of the ${\overline{\mathrm{\Omega }}}^{+}/\overline{\mathrm{\Lambda }}$ ratios, on the centrality of the collision, shows a manifest violation of quark combinatorial rules.

We introduce a method for the separation of soft and collinear logarithms in QCD parton evolution at $\mathcal{O}({\alpha }_s^2)$ and at leading color. Using an implementation of the technique in the dire parton shower, we analyze the numerical impact of genuine triple-collinear corrections from quark pair emission in $e^{+}{e}^{-}\to$ hadrons.

Vector boson fusion established itself as a highly reliable channel to probe the Higgs boson and an avenue to uncover new physics at the Large Hadron Collider. This channel provides the most stringent bound on Higgs’s invisible decay branching ratio, where the current upper limits are significantly higher than the one expected in the Standard Model. It is remarkable that merely low-level calorimeter data from this characteristically simple process can improve this limit substantially by employing sophisticated deep learning techniques. The construction of such neural networks seems to comprehend the event kinematics and radiation pattern exceptionally well. However, the full potential of this outstanding capability also warrants a precise theoretical projection of QCD parton showering and corresponding radiation pattern. This work demonstrates the relation using different recoil schemes in the parton shower with leading-order and higher-order computation.

Generation of arbitrarily spin polarized muon pairs is investigated via polarized $e^{-}{e}^{+}$ collision. We calculate the completely polarized cross section $\mathrm{d}{\sigma }_{e^{-}{e}^{+}\to {\mu }^{-}{\mu }^{+}}$ and construct the fully spin-resolved Monte Carlo simulation method to explicitly describe the production of polarized muon pairs. We find that, due to the flip of mixed helicities along the scattering angle, arbitrarily polarized muon pairs with both of the longitudinal and transverse spin components can be produced. Moreover, we also find that the transverse polarization of the muon pairs depends on the directions of transverse spins of initial electrons and positrons. The collision of tightly collimated electron and positron beams with highly longitudinal polarization and nanocoulomb charge can generate about 40% muon pairs with longitudinal polarization and about 60% muon pairs with transverse polarization. The compact high-flux $e^{-}{e}^{+}\to {\mu }^{-}{\mu }^{+}$ muon source could be implemented through the next-generation laser-plasma linear collider and would be essential to facilitate the investigation of fundamental physics and the measurement technology in broad areas.

An inclusive search for nonresonant signatures of beyond the standard model (SM) phenomena in events with three or more charged leptons, including hadronically decaying $\tau$ leptons, is presented. The analysis is based on a data sample corresponding to an integrated luminosity of $138{\mathrm{fb}}^{-1}$ of proton-proton collisions at $\sqrt{s}=13\mathrm{TeV}$, collected by the CMS experiment at the LHC in 2016–2018. Events are categorized based on the lepton and $b$-tagged jet multiplicities and various kinematic variables. Three scenarios of physics beyond the SM are probed, and signal-specific boosted decision trees are used for enhancing sensitivity. No significant deviations from the background expectations are observed. Lower limits are set at 95% confidence level on the mass of type-III seesaw heavy fermions in the range 845–1065 GeV for various decay branching fraction combinations to SM leptons. Doublet and singlet vectorlike $\tau$ lepton extensions of the SM are excluded for masses below 1045 GeV and in the mass range 125–150 GeV, respectively. Scalar leptoquarks decaying exclusively to a top quark and a lepton are excluded below 1.12–1.42 TeV, depending on the lepton flavor. For the type-III seesaw as well as the vectorlike doublet model, these constraints are the most stringent to date. For the vectorlike singlet model, these are the first constraints from the LHC experiments. Detailed results are also presented to facilitate alternative theoretical interpretations.

We present a systematic quantum algorithm, which integrates both the hadronic state preparation and the evaluation of real-time light-front correlators, to study parton distribution functions (PDFs). As a proof of concept, we demonstrate the first direct simulation of the PDFs in the $1+1$ dimensional Nambu-Jona-Lasinio model. We show the results obtained by exact diagonalization and by quantum computation using classical hardware. The agreement between these two distinct methods and the qualitative consistency with QCD PDFs validate the proposed quantum algorithm. Our work suggests the encouraging prospects of calculating QCD PDFs on current and near-term quantum devices. The presented quantum algorithm is expected to have many applications in high energy particle and nuclear physics.

After the phase transition of a grand unified theory (GUT), its single coupling splits into the couplings of the basic interactions. On the other side, the measurement of the Weinberg mixing angle in the electroweak theory determines that the couplings associated to the SU(2) and U(1) symmetries were already distinct in its symmetric phase, before the electroweak breaking. This picture is consistent as we understand that such couplings evolve independently with the energy scale, meeting a common point together with the strong interaction coupling at the GUT scale. From a BRST symmetry point of view, this implies that each independent coupling should be associated to independent cocycles defined on a cohomological basis. The problem is that, before the GUT symmetry breaking, the BRST operator associated to this symmetric phase predicts a single Yang-Mills coupling. This sets the question of what should be the BRST operator of the asymmetric phase, that would allow for the splitting of this coupling but at the same time, remain compatible with the BRST operator of the symmetric phase. In this work, we proceed to answer this question.

We present a quantum description of electrically charged spherically symmetric black holes given by coherent states of gravitons in which both the central singularity and the Cauchy horizon are not realized.

In the model of a fermion field coupled to loop quantum gravity, we consider the Gauss and the Hamiltonian constraints. According to the explicit solutions to the Gauss constraint, the fermion spins and the gravitational spin networks intertwine with each other so that the fermion spins contribute to the volume of the spin network vertices. For the Hamiltonian constraint, the regularization and quantization procedures are presented in detail. By introducing an adapted vertex Hilbert space to remove the regulator, we propose a diffeomorphism covariant graph-changing Hamiltonian constraint operator of the fermion field. This operator shows how fermions move in the loop quantum gravity spacetime and simultaneously influences the background quantum geometry. Moreover, as an innovation of our work, introducing the vertex Hilbert space also fixes issues so that a densely defined symmetric Hamiltonian constraint operator can be obtained.

The quark nugget (QN) model of dark matter suggests that the dark matter may consist of compact composite objects of quark matter. Although such composite particles can strongly interact with visible matter, they may remain undetected because of a small cross section to mass ratio. We focus on anti-QNs made of antiquarks since they are heated by annihilation with visible matter and radiate. We study the radiation spectrum and power from anti-QNs in our Galaxy and compare them with satellite observations. Thermal radiation from anti-QN is produced by fluctuations of the positron density. We calculate the thermal radiation of anti-QNs with the use of the Mie theory and found its ratio to the black-body radiation. This allows us to find the equilibrium temperature of anti-QNs in the interstellar medium and determine their contribution to the observed diffuse background radiation in our Galaxy in different frequency intervals, from radio to UV. We also consider nonthermal radiations from anti-QNs, which are produced by products of annihilations of particles of the interstellar gas with anti-QNs. Such radiations include photons from decays of ${\pi }^0$ mesons, synchrotron, bremsstrahlung, and transition radiations from ${\pi }^{\pm }$ mesons, electrons, and positrons. Synchrotron radiation in MHz frequency range and flux of photons from ${\pi }^0$ decays may be above the detection threshold in such detectors as Fermi-LAT.

The tidal properties of a neutron star are measurable in the gravitational waves emitted from inspiraling binary neutron stars, and they have been used to constrain the neutron star equation of state. In the same spirit, we study the dimensionless tidal deformability of dark-matter-admixed neutron stars. The tidal Love number is computed in a two-fluid framework. The dimensionless tidal Love number and dimensionless tidal deformability are computed for dark-matter-admixed stars with the dark matter modeled as ideal Fermi gas or self-interactive bosons. The dimensionless tidal deformability shows a sharp change from being similar to that of a pure normal matter star to that of a pure dark matter star, within a narrow range of intermediate dark matter mass fraction. Based on this result, we illustrate an approach to study the dark matter parameters through the tidal properties of massive compact stars, making use of the self-similarity of the dimensionless tidal deformability–mass relations when the dark matter mass fraction is high.

Asteroid-mass primordial black holes (PBHs) can explain the observed dark matter abundance while being consistent with the current indirect detection constraints. These PBHs can produce gamma-ray signals from Hawking radiation that are within the sensitivity of future measurements by the AMEGO and e-ASTROGAM experiments. PBHs which give rise to such observable gamma-ray signals have a cosmic origin from large primordial curvature fluctuations. There must then be a companion, stochastic gravitational wave (GW) background produced by the same curvature fluctuations. We demonstrate that the resulting GW signals will be well within the sensitivity of future detectors such as LISA, DECIGO, BBO, and the Einstein Telescope. The multimessenger signal from the observed gamma-rays and GWs will allow a precise measurement of the primordial curvature perturbation that produces the PBH. Indeed, we argue that the resulting correlation between the two types of observations can provide a smoking-gun signal of PBHs.

We study the complementary tests of lepton number violation in $0\nu \beta \beta$-decay experiments, long-lived particle (LLP) searches at the LHC main detectors ATLAS/CMS, and a proposed far detector MATHUSLA. In the context of a simplified model with a scalar doublet $S$ and a Majorana fermion $F$, we show that while the $0\nu \beta \beta$-decay experiments can probe a larger portion of parameter space, the LLP searches can uniquely probe the region of smaller couplings and masses if $S$ is at TeV scale while $F$ is at or below the electroweak scale. We also investigate constraints on the parameter space from the existing searches that are insensitive to lepton number violation.

We investigate the sensitivity of future proton-proton colliders to a contact interaction of the form $1/{\mathrm{\Lambda }}^2({\overline{b}}_L{\gamma }_{\mu }{s}_L)({\overline{\mu }}_L{\gamma }^{\mu }{\mu }_L)$ as indicated by the longstanding rare $B$-decay anomalies. We include next to leading order (NLO) QCD and electroweak effects and employ an optimized binning scheme, and carefully validate our background calculation against ATLAS and CMS data. We find that the FCC-hh with $40{\mathrm{ab}}^{-1}$ of luminosity is able to exclude scales $\mathrm{\Lambda }$ up to 26 TeV at 95% CL, and discover $\mathrm{\Lambda }$ up to 20 TeV. While this is not quite enough to exclude or discover the current best-fit value of 39 TeV, this can in principle be achieved with more luminosity and/or higher energy, as we study quantitatively. Our analysis is conservative in that it assumes only a $\overline{b}s\mu \mu$ contact interaction.