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Pion decay width in a uniform magnetic background, constructed within chiral perturbation theory, is compared with lattice QCD for which results are available in the muon channel. While the results are consistent for large magnetic fields, the discrepancy observed for weak magnetic fields is largely due to differences in the pion decay constants.

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We present the first calculation of tensor and axial-tensor mesons with total spin \(J\geq 2\) within the Covariant Spectator Theory. We employ a refined quark–antiquark interaction kernel that incorporates the momentum dependence of the strong coupling, replacing the previously used constant term of the kernel. Global fits to the masses of experimentally established heavy and heavy–light meson states yield an excellent description of the mass spectrum for \(J^P=0^\pm , 1^\pm , 2^\pm \), and \(3^\pm \) using only eight adjustable parameters.

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The ALICE Collaboration has recently shown interest in analyzing femtoscopic correlations involving light hadrons. In this paper, we review how \(\pi K\) data can be well reproduced using realistic interactions, while accurately describing the \(\kappa /K_0^*(700)\) resonance. For other light-hadron channels, qualitative insights into resonances such as \(\rho \) and \(a_0\) can be obtained through femtoscopic correlations. Moreover, we present preliminary results on a framework to interpret femtoscopy from a Chiral Perturbation Theory perspective.

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We investigate the mechanisms underlying exotic hadron formation via the TQ4Q1.1 set of collinear fragmentation functions for fully charmed or bottomed tetraquarks in three quantum configurations: scalar (\(0^{++}\)), axial vector (\(1^{+-}\)), and tensor (\(2^{++}\)). We adopt leading-power single-parton fragmentation within a nonrelativistic QCD framework tailored to tetraquark Fock states. Initial-scale inputs are constructed from updated gluon and heavy-quark channels, and evolved through threshold-consistent DGLAP within HF-NRevo. We present a systematic implementation of uncertainty propagation from color-composite long-distance matrix elements governing tetraquark hadronization. This study further develops the connection between hadronic structure, precision QCD, and exotic hadron matter.

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We present the first complete calculation of the analytic structure of the zero-spatial-momentum finite-temperature Landau-gauge gluon propagator carried out at one loop by a massive deformation of QCD perturbation theory — the screened massive expansion — at temperatures ranging from \(T=0\) to \(T\approx 3T_{\mathrm {c}}\). We find no signatures of deconfinement in the form of meaningful changes in said structure. We argue that, beyond Euclidean space, massive perturbative methods — including the Curci–Ferrari model — might be missing crucial dynamical information as a consequence of the perturbative violation of QCD’s Ward identities.

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The plethora of existenting jet observables in heavy-ion collisions has allowed for an extensive description of jet quenching phenomena over the last decades. Despite this, we still lack a concise theoretical interpretation of the observed data, namely at the level of jet substructure observables. In an attempt to be dominated by perturbative dynamics, one usually relies on grooming methods which remove soft, wide-angle radiation, but even for this scenario, there are still competing explanations for the physical origin of the measured medium-induced modifications. To this end, we present a minimal approach to compute groomed substructure observables, with medium effects treated as an effective energy shift dependent on the jet substructure itself. By matching the NLO dijet matrix element with a leading-logarithmic-accurate parton shower and using an energy-loss model which includes colour coherence effects, we obtain a solid theory-to-data agreement (within 10%) when compared to ALICE and ATLAS data. We also find an overall better agreement with data when including colour coherence effects and we inspect the role of quark–gluon selection bias.

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A new measurement of the \(K^+\to \pi ^+\nu \bar \nu \) decay by the NA62 experiment at the CERN SPS is presented, using data collected in 2021 and 2022. Combining the NA62 datasets from 2016–2022, the decay branching ratio is measured to be: \(\mathrm {BR} = (13.0^{+3.3}_{-3.0}) \times 10^{-11}\). For the first time, the decay is observed with a significance exceeding \(5\sigma \). The reinterpretation of the result as a \(K^+\to \pi ^+ X\) search, where \(X\) is a feebly interacting particle, is also discussed.

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We describe an algorithm to calculate fragmentation functions from first principles by using quantum computers. The algorithm is grounded in an encoding paradigm in which particles and their internal degrees of freedom are the central objects, and its main step consists of evolving an initial parton using the Light-Front Hamiltonian.

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We perform a unified analysis of the \(T_{cc}(3875)^+\) and \(\chi _{c1}(3872)\) using an Effective Field Theory (EFT) based on local hidden gauge symmetry. Our model incorporates \(\rho \)- and \(\omega \)-meson exchanges, one-pion exchange (OPE) with three-body dynamics, and a bare \(c\bar {c}\) state for the \(\chi _{c1}(3872)\). By fitting energy level data from multiple lattice QCD collaborations, we study the pion-mass dependence of the pole positions. While \(T_{cc}^+\) results align with experimental data, a tension remains for the \(\chi _{c1}(3872)\) at the physical point, highlighting the need for high-precision lattice simulations at low pion masses.

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We study the three-pion decays of vector mesons, \(V\to \pi ^{+}\pi ^{-}\pi ^{0}\) (\(V=\omega ,\phi ,J/\psi \)), within the framework of Khuri–Treiman to account for analyticity, unitarity, and crossing symmetry. Using once-subtracted dispersion relations, we perform a simultaneous analysis of the \(\omega ,\phi \to 3\pi \) Dalitz plot and of the \(\omega /\phi \to \pi ^{0}\gamma ^{*}\) transition form factor measurements finding good agreement with these experimental data. We also analyze the di-pion invariant mass distributions of the vector charmonium decay \(J/\psi \to 3\pi \) experimental data, and predict the \(J/\psi \to \pi ^{0}\gamma ^{*}\) form factor.

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At very high baryon densities, such as in compact star cores, neighboring nucleons’ quark–gluon wave functions overlap and delocalize, suggesting a percolation-like transition. Modeling this regime is difficult because nucleons gradually lose their identities and cease to be good degrees of freedom. We present a relativistic field theory that encodes nucleon internal structure via modified nucleon field operators. Instead of using complicated many-quark composite fields, the theory keeps nucleon fields whose anticommutation relations differ only slightly from the canonical fermionic form, with density-dependent deviations reflecting nucleon structure. Within a mean-field treatment, we compute the equation of state and the speed of sound for cold neutron matter.

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We establish a Bayesian analysis framework with a general Walecka-type relativistic mean-field model to study dense nuclear matter under constraints from nuclear matter properties and neutron star observations. With the experimental and observational data well described, we find that pure hadronic descriptions can generate a peak structure in the sound velocity by \(\omega \), \(\rho \), \(\sigma \), and \(a_0\) meson mixing, which is crucial for describing both medium and massive neutron stars. As the peak structure is frequently interpreted as a signature of phase transitions, our findings provide a new perspective on the microscopic origin of the sound-velocity peak just with pure hadronic matter.

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In this contribution, I will present some properties of nuclear matter (NM) using the chiral-scale effective field theory (EFT) anchored in the chiral, scale, and hidden local flavor symmetries of QCD. We show that the sound velocity (SV) of NM can saturate the conformal limit and exhibits a peak configuration in the intermediate density. To extend the chiral-scale EFT to both dense and thermal systems, we establish a chiral-scale density counting (CSDC) rule and explore the contributions up to \(\mathcal {O}(k_\mathrm {c}^{12})\).

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We study hidden-charm pentaquarks dynamically generated in meson–baryon interactions. The corresponding scattering amplitude is unitarized via the Bethe–Salpeter equation within an improved method, where the meson–baryon loop function is regularized in a new hybrid scheme. This scheme automatically avoids the generation of unphysical poles, typical for cut-off or dimensional regularizations, while keeping the masses of the physical poles unchanged. Moreover, this improved scheme allows us to make new predictions in the \(S=-1, I=1\) sector.

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High-precision determinations of the Cabibbo–Kobayashi–Maskawa (CKM) matrix elements are essential probes of physics beyond the Standard Model (BSM). Current precision tests show a deficit in the first-row unitarity relation. At the current level of precision, the only relevant CKM matrix elements that contribute to this test are \(|V_{ud}|\) and \(|V_{us}|\). Without resorting to nuclear inputs, these elements can be determined by analyzing pion and kaon leptonic decays together with kaon semileptonic decays. This determination combines the experimentally measured decay widths for these processes with the theoretical computation of the ratio between the pion and kaon decay constants, as well as the semileptonic form factor at zero momentum transfer. We review current efforts by the Fermilab Lattice and MILC collaborations towards a correlated analysis of the lattice inputs needed for this test using Highly Improved Staggered Quarks (HISQ) on the \(N_f=2+1+1\) MILC configurations along with Staggered Chiral Perturbation Theory (SChPT) as a functional form for the chiral-continuum limit.

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We report on calculations of space-like electromagnetic form factors and charge radii of pseudoscalar mesons, covering both light and heavy–light flavour sectors within a flavour-dependent Bethe–Salpeter framework.

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We present a novel version of the pion Bethe–Salpeter equation in the chiral limit, solved using state-of-the-art QCD correlation functions as ingredients. The constraints imposed by the axial Ward–Takahashi identities are exactly fulfilled, both formally and numerically.

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In this paper, we briefly review some recent advances in a low-energy model of Quantum Chromodynamics, where nuclei and baryons are described by topological soliton solutions known as Skyrmions. Hence, following the great success of coupling the rho mesons to the Skyrme field (which provided more realistic nuclear binding energies for the model and the triggering of nuclear clustering), we consider the role that the leading \(\rho \pi \pi \) interaction term can play in the study of dense nuclear matter. This contribution, motivated by a theoretical construction from a Yang–Mills theory in one higher dimension, astonishingly reduces the compression modulus that the Skyrme model provides from the very large value of \(K_0 \simeq 1080\) MeV to a more physical \(K_0 \simeq 351\) MeV.

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In this paper, we present preliminary results of the study of the SU(3) flavor degeneracy of the lightest scalar and vector meson octets. We employ SU(3)\(_F\) chiral perturbation theory at next-to-leading order, combined with the Inverse Amplitude Method. We vary quark masses and track the poles associated with the resonances across different Riemann sheets as we approach the SU(3)\(_F\) symmetric limit. We find that the poles usually associated with the physical resonances do not become degenerate. Instead, degeneracy is observed for poles located on the Riemann sheet reached by crossing continuously all branch cuts that coalesce in the symmetric limit.

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In this paper, we review our recent work on \(\pi \pi \) scattering. We present new global fits that describe all experimental data up to 1.8 GeV while satisfying dispersive constraints, within uncertainties, up to 1.6 GeV. Using continued fractions to continue forward dispersion relations analytically, we extract the pole parameters of the \(f_0(500)\), \(\rho (770)\), \(f_0(980)\), \(f_2(1270)\), \(f_0(1370)\), \(\rho (1450)\), \(f_0(1500)\), and \(\rho _3(1690)\) in a model-independent way.

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In this article, we review our recent dispersive analysis of the large localized CP-violating asymmetries observed by LHCb in \(B^{\pm } \to K^{\pm }\pi ^+\pi ^-\) decays. Low-energy \(\pi \pi \) final-state interactions are treated in a model-independent way, and the weak decay is described as a short-distance source. By fitting angular-projected data, we reproduce the Dalitz-plot CP-asymmetry pattern at low \(m_{\pi \pi }\). Our framework highlights the essential role of the non-resonant isospin-\(2\) \(S\) wave, ensures unitarity, and can be extended to other three-body decays.

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Hadronic form factors fulfill dispersion relations and superconvergence sum rules for their spectral density as genuine imprints of QCD. We show several instances where these conditions are flagrantly violated due to the lack of information in the region above the largest known resonance mass and below the onset of perturbative QCD. We propose to use radial Regge trajectories to fill this gap and examine the consequences of such a “minimal” spectral hadronic ansatz. We illustrate the results with the pion charge form factor.

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This paper reviews the interplay between chiral and axial U(1)\(_\mathrm {A}\) symmetry restoration in QCD at finite temperature, using effective field theories and Ward identities. We analyse how degeneration patterns of scalar and pseudoscalar partners signal symmetry restoration, relating lattice results and phenomenology. Emphasis is placed on pseudoscalar susceptibilities, their relation to quark condensates and the topological susceptibility, and their implications for \(O(4)\) versus \(O(4)\times \mathrm {U}(1)_\mathrm {A}\) patterns. Results from Chiral Perturbation Theory are compared with lattice data, highlighting the role of explicit symmetry breaking, the approach to the chiral limit, and the impact of the strange sector.

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The ground-state positive-parity charmonia \(\chi _{c0}(1P)\), \(\chi _{c1}(1P)\), \(h_c(1P)\), and \(\chi _{c2}(1P)\) are generally well described in static (“quenched”) quark models, in which dynamical effects of actual or virtual strong decay are neglected. In contrast, the five PDG candidates for \(P\)-wave charmonia in the energy region of 3.85–3.95 GeV, probably including the first radial excitations of the above ones, display a totally different and quite disparate mass pattern. Moreover, two scalar states are listed, viz. \(\chi _{c0}(3860)\) and \(\chi _{c0}(3915)\), the former one apparently being very broad. Preliminary results will be presented here for the first radial excitations of the lowest \(P\)-wave \(c\bar {c}\) states, obtained with the Resonance-Spectrum Expansion while including in the calculation all OZI-allowed decay channels of the most relevant charm-meson pairs. Employing a generalised scheme of computing coupling constants for decays based on the \({}^{3\!}P_0\) model ensures that no distortion of the spectra will occur due to the different classes of allowed decay channels for the various positive-parity charmonia.

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We discuss some aspects of the uniqueness of analytically continuing Euclidean Green functions obtained by means of the Dyson–Schwinger equations (DSE) and constrained by lattice data, back to Minkowski space with physical \(p^2\).

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The Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory (BNL) has been operated since 2001, contributing significantly to the study of strong interactions described by QCD and of nuclear matter under extreme conditions. The PHENIX experiment has collected a comprehensive dataset and continues to publish scientific papers, yielding impactful insights from the initial to final stages of nucleus collisions. Recently published results advance our understanding of strong interactions and nuclear matter.

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Generalised Parton Distributions (GPDs) provide multidimensional insight into hadron structure and are particularly relevant for the pion, whose dynamics are intimately linked to chiral symmetry breaking. We introduce a novel modelling strategy for pion GPDs that satisfies all QCD constraints by construction: support, polynomiality, positivity, and the soft-pion theorem. The approach is illustrated with a simple algebraic model, which is evolved and used to compute deeply virtual Compton scattering (DVCS) Compton Form Factors at next-to-leading order. Our results indicate that gluons dominate the pion response at the Electron Ion Collider kinematics.

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We present recent results from the Fastsum Collaboration, using anisotropic lattice QCD to study spectral properties of heavy quarkonia and open heavy flavour systems at high temperature. For heavy quarkonium, our results using a number of different methods suggest a small but significant and robust negative mass shift as well as an increasing thermal width. We present the first lattice results for masses and spectral functions of \(B\) mesons at high temperature, and preliminary results for a high-precision calculation of the static quark potential.

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We present a study of femtoscopic correlation functions for \(K^{-}d\) and \(K^{+}d\) pairs, and compare our results with recent measurements by the ALICE Collaboration in both Pb–Pb and high-multiplicity \(pp\) collisions. The kaon–deuteron wave functions are derived from scattering amplitudes using a unitarized chiral effective theory model describing the elementary interactions of \(K^{\pm }\) mesons with nucleons. We then evaluate the \(K^{\pm }d\) strong scattering amplitudes by solving the Faddeev equations within two distinct frameworks: the Impulse Approximation and the Fixed Center Approximation, which accounts for multiple scatterings. We also incorporate the long-range Coulomb effects between the kaon and the deuteron. We show that the \(K^{-}d\) correlation function exhibits large sensitivity to both the size of the emitting source and the relative momentum of the pair, being heavily influenced by rescattering processes. In contrast, the \(K^{+}d\) correlation function is dominated by the weakly repulsive \(K^{+}N\) interaction, showing deviations from purely Coulombic behavior only at small emission source sizes. Our predictions are in agreement with the ALICE experimental data, and also with the energy-shift and width of the \(1s\) level of the kaonic deuterium preliminary results from the SIDDHARTA 2 Collaboration.

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In this contribution, we present thermal photon production mechanisms within a magnetized quark–gluon plasma, utilizing the framework of Landau-level quantization. We examine the specific influences of the magnetic field, chemical potential, and chiral chemical potential on photon yield and polarization. By providing a more comprehensive theoretical description of photon production across the full evolution of heavy-ion collisions, our study offers a promising new avenue for resolving the “photon \(v_2\) puzzle” and potentially detecting the signature of magnetic fields in heavy-ion collision experiments.