The determination of whether the ground state of baryon matter in Quantum Chromodynamics (QCD) is the ordinary nucleus or a quark matter state remains a long-standing question in physics. A critical parameter in this investigation is the bag parameter B, which quantifies the QCD vacuum energy and can be computed using nonperturbative methods such as Lattice QCD (LQCD). By combining the equation of state derived from perturbative QCD (pQCD) with the bag parameter to fit the LQCD-simulated data for isospin-dense matter, we address the stability of quark matter within the LQCD+pQCD framework. Our findings suggest that the current data imposes an upper bound on B^1/4≲ 160 MeV, approaching a conclusive statement on quark matter stability. Given the lower bound on B from the quark condensate contribution to the vacuum energy, the stable 2-flavor quark matter remains possible, whereas the stable 2+1-flavor quark matter is excluded, assuming complete deconfinement and chiral-symmetry restoration and the reliability of pQCD at baryon chemical potentials around the proton mass. Additionally, we derive more general thermodynamic bounds on the quark matter energy-per-baryon and B, which, while weaker, provide complementary insights.

Heterogeneous nucleation is central to many familiar first-order phase transitions such as the freezing of water and the solidification of metals, and it can also play a crucial role in cosmology. We examine nucleation seeded by preexisting domain walls and demonstrate its strong impact on the dynamics of cosmological phase transitions. The bubble solutions take the form of spherical caps, and the contact angle is fixed by the ratio of the domain-wall tension to the bubble-wall tension. A larger domain-wall tension, or equivalently a smaller contact angle, reduces the wall-seeded bubble volume and lowers the critical nucleation action. For theories with Zn >= 3 symmetry, domain-wall junctions naturally appear and we find that they seed nucleation even more efficiently than the walls themselves. Using a two-scalar-field model as an illustration, we compute nucleation temperatures for both homogeneous and heterogeneous channels and show that junction-seeded nucleation occurs at a higher temperature and is the dominant mechanism that completes the first-order cosmological phase transition.

A bstract The hint of a pseudoscalar toponium state at the Large Hadron Collider (LHC) opens a new avenue for studying a novel class of QCD (quasi-)bound states with comparable formation and decay times. Compared with charmonium and bottomonium, toponium is a quasi-bound state, resembling a hydrogen atom of the strong interaction, although it appears as a broader resonance. We compute the masses and annihilation decay widths of the lowest S -wave ( η t , ψ t ) and P -wave ( χ t 0 , χ t 1 ) toponium states, and assess their discovery prospects at the High-Luminosity LHC (HL-LHC) and future lepton colliders, such as the e + e − stage of the Future Circular Collider (FCC-ee). Detecting the vector ψ t state at the HL-LHC is hindered by the Landau-Yang theorem and the gluon-dominated production environment of the collider, whereas lepton colliders offer promising sensitivity through both constituent and two-body decays. A more precise measurement of the η t mass-approximately equal to that of ψ t -at the LHC could help determine the optimal $$ t\overline{t} $$ t t ¯ threshold center-of-mass energy for FCC-ee. The P -wave states remain challenging to observe at both the HL-LHC and future lepton colliders. We also discuss how toponium measurements can be used to probe top-quark properties and to conduct indirect searches for new physics, including light scalars that couple to the top quark.

In this work, we employ both theoretical and data-driven methods to derive the QCD vacuum energy, utilizing the GMOR relation, the low-energy theorem, and the equation of state from lattice QCD. The QCD vacuum energy is determined to be between around ( 163 MeV ) 4 and ( 190 MeV ) 4 . With the assumptions of complete deconfinement, vanishing gluon condensate, full chiral-symmetry restoration, and the validity of perturbative QCD at baryon chemical potentials of order of the proton mass, a very specific kind of quark nugget is found to be less stable than ordinary nuclei.

We propose a novel mechanism for electroweak baryogenesis in which collapsing domain walls formed by an axion-like field replace the bubble walls in a strong first-order electroweak phase transition. The axion-like particle coupling to the Higgs mass term allows domain walls to separate regions with distinct electroweak phases, while the electroweak crossover induces a potential-energy bias that triggers their collapse. The directed wall motion, through the axion-like particle coupling to the electroweak topological term, acts as an effective baryon chemical potential and generates an asymmetry via electroweak sphaleron processes. We show that the observed baryon asymmetry can be obtained from either late-time entropy injection or sphaleron suppression in a weakly broken electroweak domain. The wall collapse also produces a stochastic gravitational-wave background with features distinct from standard electroweak-scale first-order-transition spectra.

We present a complete Lagrangian describing axion interactions with pseudoscalar and (axial-)vector mesons within the three light-flavor quark framework. This formulation incorporates both the standard chiral Lagrangian and the full Wess-Zumino-Witten (WZW) term. By including instanton effects associated with the anomalous U(1)_A symmetry, we demonstrate that physical observables remain invariant under arbitrary chiral phase rotations of the quark fields. This comprehensive Lagrangian provides a robust and consistent framework for exploring axion phenomenology through its interactions with mesons and gauge bosons. As a demonstration, we compute the decay widths of GeV-scale axions into various mesonic final states for several benchmark axion models.

The process e^+e^-→K_S^0K_S^0ψ (3686) is studied by analyzing e+e− collision data samples collected at eight center-of-mass energies ranging from 4.682 to 4.951 GeV with the BESIII detector operating at the BEPCII collider, corresponding to an integrated luminosity of 4.1 fb−1. Observation of the e^+e^-→K_S^0K_S^0ψ (3686) process is found for the first time with a statistical significance of 6.3σ, and the cross sections at each center-of-mass energy are measured. The ratio of cross sections of e^+e^-→K_S^0K_S^0ψ (3686) relative to e+e− → K+K−ψ(3686) is determined to be σ(e^+e^-→K_S^0K_S^0ψ (3686))/σ(e^+e^-→K^+K^-ψ (3686))=0.45± 0.25 , which is consistent with the prediction based on isospin symmetry. The uncertainty includes both statistical and systematic contributions. Additionally, the K_S^0ψ (3686) invariant mass distribution is found to be consistent with three-body phase space. The significance of a contribution beyond three-body phase space is only 0.8σ.

Based on a sample of (2712.4 ± 14.3) × 106 ψ(3686) events collected with the BESIII detector, a partial wave analysis of the decay ψ (3686)→ΛΣ^0π^0 + c.c. is performed to investigate Λ* and Σ* resonances in the π^0Σ^0 and π0Λ invariant mass distributions. Significant contributions are found from the Λ(1405), Λ(1520), Λ(1600), Λ(1670), Λ(1690), Λ(1800), Λ(1890), Λ(2325), Σ(1385), Σ(1660), Σ(1670), Σ(1750), and Σ(1910). The masses, widths, and production branching fractions for each component are determined. In addition, the branching fraction of ψ (3686)→ΛΣ^0π^0 + c.c. is measured to be (1.544 ± 0.013 ± 0.071) × 10−4 for the first time, where the first uncertainty is statistical and the second systematic.

We propose using current and future large-volume neutrino telescopes as “Large Neutrino Colliders" (LνCs) to explore TeV-scale physics beyond the Standard Model. Cosmic neutrinos with energies above 100 PeV colliding with nucleons in the detector reach center-of-mass energies beyond the 14 TeV limit of the Large Hadron Collider (LHC). Using recently predicted and measured high-energy and ultra-high-energy neutrino fluxes from IceCube and KM3NeT, we estimate mass-scale sensitivities for representative new physics scenarios at 1–30 km^3 LνCs. Our results demonstrate that LνCs provide a novel avenue to probe multi-TeV particles with sensitivities comparable to, or even surpassing, those of the LHC.

We measure the Born cross section for the reaction e+e−→ηhc from s=4.129 to 4.600 GeV using datasets collected by the BESIII detector running at the BEPCII collider. A resonant structure in the cross-section line shape near 4.200 GeV is observed with a statistical significance of 7σ. The parameters of this resonance are measured to be M=4188.8±4.7±8.0 MeV/c2 and Γ=49±16±19 MeV, where the first uncertainties are statistical and the second systematic. Published by the American Physical Society 2025

We present a consistent derivation of the complete Wess-Zumino-Witten interactions of axions, including the counter-term necessary to guarantee the gauge invariance of the standard model. By treating the derivative of the axion field as a background gauge field and incorporating auxiliary chiral rotation phases, we ensure consistency in the axion-interaction Lagrangian. This approach allows us to derive basis-independent physical interactions of axions with gauge bosons and vector mesons. These interactions have broad applications in axion phenomenology for both light and heavy axion particles.

We investigate the phases of a strongly coupled QCD-like theory at finite baryon chemical potential using s-confining supersymmetric QCD deformed by anomaly-mediated supersymmetry breaking. Focusing on the case of three colors and four flavors, we identify novel phases including spontaneous breaking of baryon number and/or parity. Both first-order and second-order phase transitions are observed as the baryon chemical potential is varied. These findings may offer insights into possible phases of real QCD at intermediate baryon densities.

We perform the first amplitude analysis of D_{s}^{+}→π^{+}π^{+}π^{-}π^{0} decays based on data samples of electron-positron collisions recorded with the BESIII detector at center-of-mass energies between 4.128 and 4.226 GeV, corresponding to an integrated luminosity of 7.33  fb^{-1}. We report the observation of D_{s}^{+}→f_{0}(980)ρ(770)^{+} with a statistical significance greater than 10σ and determine the branching fractions B(D_{s}^{+}→π^{+}π^{+}π^{-}π^{0}|_{non-η})=(2.04±0.08_{stat}±0.05_{syst})% and B(D_{s}^{+}→ηπ^{+})=(1.56±0.09_{stat}±0.04_{syst})%. Moreover, we measure the relative branching fraction between ϕ→π^{+}π^{-}π^{0} and ϕ→K^{+}K^{-} to be [B(ϕ(1020)→π^{+}π^{-}π^{0})/B(ϕ(1020)→K^{+}K^{-})]=0.230±0.014_{stat}±0.010_{syst}., which deviates from the world average value by more than 4σ.

Dark matter may form bound states in a dark sector with an attractive force between two dark matter particles. Searches for dark matter at colliders can differ dramatically from routine searches if bound states, dubbed darkonia, are produced and decay into visible Standard-Model particles. In this work, we use three representative models with scalar, pseudo-scalar, and vector force carriers to map out the darkonium signatures at both high-energy and low-energy colliders. Some of the bound states can be stable due to generalized parity and charge-conjugation symmetries, while others decay into light dark-force carriers, which subsequently can decay at a displaced vertex. New signatures with a mix of missing energy and multiple di-lepton or di-jet vertices reconstructing intermediate darkonium resonances are within reach at the LHC and Belle II.

Quark nuggets _Z^AQ , as Fermionic non-topological solitons, could have their mass per baryon smaller than ordinary nuclei and behave as exotic nuclei with different relations of atomic number and atomic mass number. Using both the degenerate Fermi gas model and the Friedberg-Lee shell model, we calculate the properties of quark nuggets made of up and down quarks. Similar to ordinary nuclei, quark nuggets could exhibit their own radioactivity, including gamma decay, beta decay, and (explosive) spontaneous fission, with the qualitative properties presented here. These quark nugget properties may provide guidance for searching for quark nuggets in situ from binary neutron star or quark star mergers.

Utilizing a dataset of 6.7 fb(-1) from electron-positron collisions recorded by the BESIII detector at the BEPCII storage ring, a search is conducted for the processes e(+)e(-) -> phi chi(c0) and phi eta(c2)(1D) across centerof-mass energies from 4.47 to 4.95 GeV. In the absence of any significant signals, upper limits are set. These include limits on the dressed cross sections for e(+)e(-) -> phi chi(c0), as well as the product of the dressed cross section for e(+)e(-) -> phi eta(c2)(1D) and a sum of five branching fractions. Furthermore, the product of the electronic width of Y(4660) and the branching fraction of the Y(4660) ->phi chi(c0), denoted as Gamma Y-e+e-((4660)) B-Y(4660)->phi chi(c0), is determined to be <0.35 eV at the 90% confidence level.

We report a search for a lepton-portal dark matter model, where dark matter couples to a charged lepton in the standard model. This simplifified model naturally leads to photon-mediated dark matter interactions with nuclei, making it suitable for direct dark matter detection experiments. Matching to the framework of non-relativistic effective field theory for dark matter, we report the first sensitive search for this model using data from the PandaX-4T commissioning run. Our results yield strong constraints on Dirac fermion dark matter but relatively weaker constraints on Majorana dark matter due to the suppression of effective photon interactions. These constraints complement those obtained from the collider and indirect detection experiments.

This paper calculates the stochastic gravitational wave background from dark binaries with finite-range attractive dark forces, complementing previous works which consider long-range dark forces. The finiteness of the dark force range can dramatically modify both the initial distributions and evolution histories of the binaries. The generated gravitational wave spectrum is enhanced in the intermediate frequency regime and exhibits interesting "knee" and "ankle" features, the most common of which is related to the turn on of the dark force mediator radiation. Other such spectral features are related to changes in the binary merger lifetime and the probability distribution for the initial binary separation. The stochastic gravitational wave background from sub-solar-mass dark binaries is detectable by both space- and ground-based gravitational wave observatories.

Using e+e− collision data collected with the BESIII detector at the BEPCII collider at center-of-mass energies between 3.510 and 4.914 GeV, corresponding to an integrated luminosity of 25 fb−1, we measure the Born cross sections for the process e^+e^-→K^-Ξ^+Λ /Σ^0 at thirty-five energy points with a partial-reconstruction strategy. By fitting the dressed cross sections of e^+e^-→K^-Ξ^+Λ /Σ^0 , evidence for ψ (4160)→K^-Ξ^+Λ is found for the first time with a significance of 4.4σ, including systematic uncertainties. No evidence for other possible resonances is found. In addition, the products of electronic partial width and branching fraction for all assumed resonances decaying into K^-Ξ^+Λ /Σ^0 are determined.

Using $e^+ e^-$ collision data collected at the BESIII detector at center-of-mass energies between 4.128 and 4.226 GeV, corresponding to an integrated luminosity of $7.33~{\rm fb}^{-1}$, we determine the absolute branching fractions of fifteen hadronic $D_s^{+}$ decays with a double-tag technique. In particular, we make precise measurements of the branching fractions $\mathcal{B}(D_s^+ \to K^+ K^- \pi^+)=(5.49 \pm 0.04 \pm 0.07)\%$, $\mathcal{B}(D_s^+ \to K_S^0 K^+)=(1.50 \pm 0.01 \pm 0.01)\%$ and $\mathcal{B}(D_s^+ \to K^+ K^- \pi^+ \pi^0)=(5.50 \pm 0.05 \pm 0.11)\%$, where the first uncertainties are statistical and the second ones are systematic. The \emph{CP} asymmetries in these decays are also measured and all are found to be compatible with zero.