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Quantum Chromodynamics predicts a phase transition from hadronic matter to quark-gluon plasma (QGP) at high temperatures and energy densities, where quarks and gluons (partons) are no longer confined within hadrons. The QGP forms in ultrarelativistic heavy-ion collisions. Anisotropic flow coefficients, quantifying the azimuthal expansion of produced matter, probe QGP properties. Flow measurements in high-energy heavy-ion collisions show a distinctive grouping of anisotropic flow for baryons and mesons at intermediate transverse momentum - a feature associated with flow imparted at the quark level, confirming QGP existence. The observation of QGP-like features in proton-proton and proton-ion collisions has sparked debate about QGP formation in smaller systems. For the first time, we demonstrate the distinctive grouping of anisotropic flow for baryons and mesons in high-multiplicity proton-lead and proton-proton collisions at the Large Hadron Collider (LHC). These results are described by a model including hydrodynamic flow followed by hadron formation via quark coalescence, consistent with the formation of partonic flowing systems in these collisions.

The outcomes of modern particle physics experiments, such as proton-proton collisions at the Large Hadron Collider at CERN (European Organization for Nuclear Research), depend crucially on the precise description of the scattering processes in terms of the fundamental forces. Among all the known forces that contribute, the limited understanding of the strong nuclear force is a key source of inaccuracy. At the fundamental level, the strong force is described by quantum chromodynamics, the theory of quarks and gluons. Their coupling, αs, becomes weaker at high energies (asymptotic freedom), enabling power series expansions in αs, but the confinement of quarks in hadronic bound states usually requires additional model assumptions. Consequently, determinations of αs from experiment mostly remain with large systematic theory errors1,2. Here we report the model-free determination of αs with unprecedented precision from low-energy experimental input combined with large-scale numerical simulations of the first-principles formulation of quantum chromodynamics on a space-time lattice. The uncertainty, about half that of all other results combined3, originates predominantly from the statistical Monte Carlo evaluation and has a clear probabilistic interpretation. The result for αs describes both low-energy hadronic physics with the help of lattice quantum chromodynamics and high-energy scattering using the perturbative expansion. By removing a source of theoretical uncertainty, our estimate of αs could enable markedly improved analyses of many high-energy experiments4. This will contribute to the likelihood that small effects of yet unknown physics are uncovered, as well as enable stringent precision tests of the Standard Model.

This Letter reports the first calculation of the gravitational form factors (GFFs) of the scalar glueball, performed via lattice field theory in Yang-Mills theory at a single lattice spacing. The glueball GFFs are compared with those of other hadrons as determined in previous lattice calculations, providing strong indications that glueballs have a different gluonic structure than typical hadronic states. A mass radius of 0.263(31) fm is predicted, supporting previous suggestions that the scalar glueball is significantly smaller than other hadrons.

Flat hadron beam collisions, though expected to enhance peak luminosity by about an order of magnitude, have not yet been demonstrated. We identify a new mechanism in which the hourglass-induced synchrobetatron resonance, when coupled to unavoidable machine fluctuations, drives emittance transfer and degrades the flat-beam condition. This effect becomes a critical limitation for maintaining flat hadron beams on operational timescales. Using Electron-Ion Collider (EIC) parameters, we show that it imposes stringent tolerances on machine noise. We further demonstrate that a dynamic focusing scheme, implemented by combining sextupoles with crab cavities, suppresses the resonance and relaxes these constraints, providing a practical path toward robust flat-beam collisions in future lepton-hadron colliders.

In phenomenological studies of multiparticle production, transverse-momentum spectra measured in experiments frequently display an approximately power-law falloff, for which the Tsallis-type functional form is commonly employed as an effective parametrization. Within this framework, the emergence of such spectra is interpreted as a manifestation of nonextensive statistical behavior. An analogous power-law structure, however, can be reproduced without explicitly postulating Tsallis statistics by assuming the presence of intrinsic fluctuations of the local temperature (T) in the hadronizing medium; in that case, the observed deviations from a purely exponential spectrum are encapsulated by the nonextensivity index (q). We show that temperature fluctuation mechanisms capable of generating Tsallis-like power-law distributions in multiparticle production necessarily induce nontrivial inter-particle correlations among the emitted hadrons. Building on this observation, we outline a strategy to discriminate fluctuations realized on an event-by-event basis from those arising predominantly through event-to-event variability. Such a separation may be particularly pertinent for the characterization of high-multiplicity (high-density) final states produced at the Large Hadron Collider.

The mass of the lightest hadron in nature, the pion, is one seventh of that of the nucleon and one tenth of the mass of its first excited state, the π(1300). This enormous energy difference opens an interesting window into the confinement of quarks and the structure of the lightest hadrons. In this Letter, we provide the first calculation of resonance parameters of the π(1300) from lattice quantum chromodynamics (QCD). For this purpose, recently derived state-of-the-art tools are adapted and applied both in the construction of three-hadron operators and for mapping finite-volume spectra to infinite-volume amplitudes, subsequently analytically continuing these to complex energies. For our heavy pion mass ensembles, we find a clear signal of the resonance. Making a simple assumption of vanishing pion mass dependence for the three-body force, but incorporating constraints from Chiral Perturbation Theory for all the two-body channels, enables a robust extrapolation to the physical point. Applying model averaging, we extract a pole position of M_{π(1300)}=(1169±46)-i(62_{-62}^{+168})  MeV supporting values from phenomenology.

We study the QCD scaling behavior of the small-angle energy-energy correlator (EEC), focusing on the transition between its perturbative preconfinement and nonperturbative postconfinement regimes. Applying the light-ray operator product expansion (OPE), we develop a formalism that describes the scaling of the EEC with the input energy Q in the transition and the postconfinement region, where the latter quantum scaling is determined by the J=5 DGLAP anomalous dimension. A key result of our Letter is a novel connection between the light-ray OPE and the dihadron fragmentation function (DFF), where we show that the nonperturbative OPE coefficients correspond to moments of the DFF. This finding establishes a new paradigm for studying hadronization. Our theoretical predictions are validated against Monte Carlo simulations for both e^{+}e^{-} and pp collisions, showing excellent agreement. The potential role of the quantum scaling in the precision determination of α_{s} is also discussed.

Supernova remnants (SNRs) have been considered as the primary contributors to cosmic rays (CRs) in our Galaxy. However, the maximum energy of particles that can be accelerated by shocks of SNRs is uncertain, and SNRs' contribution to CRs around PeV energies is unclear. In this Letter, we present observations of high-energy γ-ray emission from the SNR IC 443 using the Large High Altitude Air Shower Observatory (LHAASO). The morphological analysis reveals a pointlike source whose location and spectrum are consistent with those of the Fermi-LAT-detected compact source with π^{0}-decay signature, and a more extended source that is associated with a newly discovered Fermi source. The spectrum of the point source can be described by a power-law function with an index of ∼3.0, extending beyond ∼30  TeV without apparent cutoff. Assuming a hadronic origin of the γ-ray emission, the 95% lower limit of accelerated protons reaches about 300 TeV. The extended source might be associated with IC 443, SNR G189.6+3.3, or the putative pulsar wind nebula CXOU J061705.3+222127, and can be explained by either a hadronic or a leptonic model with particles reaching hundreds of TeV. These LHAASO results provide compelling evidence that sub-PeV CRs can be accelerated efficiently by shocks of SNRs.

A reliable calculation of radiative corrections to τ→ππν_{τ} decays is an important prerequisite for using hadronic τ decays for a data-driven evaluation of the hadronic-vacuum-polarization (HVP) contribution to the anomalous magnetic moment of the muon, a_{μ}^{HVP,LO}[ππ,τ]. In this Letter, we present an improved model-independent analysis of these radiative corrections, including, for the first time, effects beyond pointlike pions in the evaluation of the loop diagrams. These structure-dependent corrections, implemented via a dispersive representation of the pion form factor, lead to significant changes compared to previous calculations due to enhancements near the ρ(770) resonance. We also devise strategies for the matching to chiral perturbation theory and a stable implementation of the real corrections down to the two-pion threshold, which shows that some higher-order isospin-breaking corrections need to be kept due to a strong threshold enhancement. Finally, we perform dispersive fits to the currently available τ→ππν_{τ} spectra and discuss the consequences for isospin-breaking corrections in the evaluation of a_{μ}^{HVP,LO}[ππ,τ].

The vacuum is now understood to have a rich and complex structure, characterized by fluctuating energy fields1 and a condensate of virtual quark-antiquark pairs. The spontaneous breaking of the approximate chiral symmetry2, signalled by the nonvanishing quark condensate ⟨ q q ¯ ⟩ , is dynamically generated through topologically nontrivial gauge configurations such as instantons3. The precise mechanism linking the chiral symmetry breaking to the mass generation associated with quark confinement4 remains a profound open question in quantum chromodynamics (QCD)-the fundamental theory of strong interaction. High-energy proton-proton collisions could liberate virtual quark-antiquark pairs from the vacuum that subsequently undergo confinement to form hadrons, whose properties could serve as probes into QCD confinement and the quark condensate. Here we report evidence of spin correlations in Λ Λ ¯ hyperon pairs inherited from spin-correlated strange quark-antiquark virtual pairs. Measurements by the STAR experiment at the Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory reveal a relative polarization signal of (18 ± 4)% that links the virtual spin-correlated quark pairs from the QCD vacuum to their final-state hadron counterparts. Crucially, this correlation vanishes when the hyperon pairs are widely separated in angle, consistent with the decoherence of the quantum system. Our findings provide a new experimental model for exploring the dynamics and interplay of quark confinement and entanglement.

Regge trajectories provide a simple geometric picture of hadron spectra, but particles at higher-spin and missing states often scatter from linear fits, raising questions about both experimental completeness and theoretical limits of the model. Here, we develop a unified data framework that integrates standard particle listings with hypergraph-based decay features, enabling systematic comparison across baryons and mesons. We employed orthogonal distance regression with bootstrap resampling to quantify uncertainties in slope and intercept estimates, while hypergraph-derived structural invariants (community purity, motif z-scores, and product entropy) serve as quantitative predictors of spectroscopic regularity, establishing decay topology as a microscopic determinant of macroscopic Regge behavior. Applying this hybrid approach to 20 [Formula: see text] baryon resonances, we obtain strong linear correlation (R2&#x2009;=&#x2009;0.90) with slope [Formula: see text] GeV-2, though elevated scatter ([Formula: see text]) correlates strongly with resonance width (r&#x2009;=&#x2009;0.88, p&#x2009;<&#x2009;0.001). While hypergraph features did not significantly improve explanatory power beyond quality controls in this pilot dataset ([Formula: see text], p&#x2009;=&#x2009;0.42), we introduce a hypergraph-informed confidence framework for missing resonance predictions, where structural decay coherence provides quantitative reliability metrics beyond traditional trajectory extrapolation. Together, these results demonstrate how combining trajectory analysis with network-inspired methods can improve hadron classification and provide concrete predictions for future experimental searches.

In this Research Perspective, we briefly review the diffusion wake, a distinctive consequence of the Mach-cone wake induced by the supersonic jets in ultrarelativistic heavy-ion collisions. The diffusion wake depletes soft hadrons in the direction opposite to the propagating jet. According to coupled transport and hydrodynamic simulations, a valley in the 2-dimensional jet-hadron correlation in azimuthal angle and rapidity arises on the top of the multiple-parton interaction ridge as an unambiguous signal of the diffusion wake induced by &#x3b3; -jets in heavy-ion collisions. In dijet events with a finite rapidity gap, the rapidity asymmetry of the jet-hadron correlation has been shown to be a robust signal of the diffusion wake. The same rapidity asymmetry can also be applied to &#x3b3; -jet events, and both are background-free. Experimental measurements of these signals can provide valuable insights into the properties of the quark-gluon plasma formed in high-energy heavy-ion collisions.