An overview of recent extractions of the strong coupling constant from various approaches is presented. The current status of these determinations, their uncertainties, and consistency tests are discussed, along with prospects for future improvements.
The strong coupling $\alpha_s$ is the most important parameter of Quantum Chromodynamics (QCD) therefore it is essential to determine it with high precision. This work presents an improved approach for extracting $\alpha_s$ comparing the numerical results of lattice QCD simulations to the perturbative expansion of the QCD static energy. We apply R-improvement to its 3-loop fixed-order...
COMPASS is a multi-purpose fixed-target experiment at the CERN SPS. One of its main goals is to probe
the strong interaction at low energies by studying the excitation spectrum of light mesons in diffractive scattering reactions of a $190\ \text{GeV}/c$ hadron beam on a proton target.
This is done by decomposing the data into partial-wave amplitudes with well-defined quantum numbers and...
The GlueX experiment at Jefferson Lab was specifically designed for precision studies of the light-meson spectrum. A photon beam with energies of up to 12 GeV is directed onto a liquid hydrogen target contained within a hermetic detector with near-complete neutral and charged particle coverage. Linear polarization of the photon beam with a maximum around 9 GeV provides additional information...
The MUon proton Scattering Experiment (MUSE) at the Paul Scherrer Institute (PSI) was motivated by the proton radius puzzle. We obtain simultaneous high-precision measurements of elastic electron-proton and muon-proton scattering from a liquid hydrogen target, alternating between positively and negatively charged leptons. The experiment will test lepton universality by comparing electron to...
In this talk, I'll review the status of the eta-pi and eta'-pi final in hadroproduction (from the COMPASS collaboration) and in photoproduction (from the GlueX collaboration). We'll discuss the extraction of the resonances properties in their P and D waves (respectively the Pi_1 and A_2 resonances) and how to constraint these extractions using the high mass region (aka the double Regge region)...
The COMPASS experiment at the CERN SPS provides a high-statistics dataset for studying the light-meson spectrum in various final states, including $\eta\pi^-$ and $\eta^\prime\pi^-$, which are among the key channels to investigate the lightest hybrid-meson candidate, the $\pi_1(1600)$. A major challenge in extracting resonance parameters, such as pole positions, is the separation of resonant...
The existence of hybrid mesons, in which an excited gluonic field contributes to the meson properties, is strongly supported by both theory and experiment. The best experimental candidate for the lightest hybrid meson is the spin-exotic π1(1600), observed in pion production at the COMPASS experiment via its decay into ηπ and η'π. Searching for this state in photoproduction is one of the main...
The existence of the nucleonic pentaquark resonances $P_{c\bar{c}}(4312)^+$, $P_{c\bar{c}}(4380)^+$, $P_{c\bar{c}}(4440)^+$, $P_{c\bar{c}}(4457)^+$, $P_{c\bar{c}s}(4338)^0$ and $P_{c\bar{c}s}(4459)^0$, established by the LHCb collaboration, has been one of the major discoveries in hadron physics in the latest years. Most of these states (5 out of 6) can be understood as hadronic molecules,...
We discuss recent extraction of parton distribution function of pion in the valence region which observed
unexpectedly soft $(1-x)^\beta$, $\beta\sim 1$ distribution, contradicting several theoretical predictions including the ones
based on the hard gluon exchange, according to which $\beta =2$.
In this work we calculated the pion PDF within the theoretical approach based on spectral...
We propose to introduce the intrinsic transversal momentum distribution functions (iTMDs), in conjunction with the light-cone distribution amplitudes, to elucidate the probability amplitude of encountering a meson state wherein the partons swiftly traverse along the longitudinal axis while gently oscillating in the transversal plane. The primary motivation stems from the oversight of soft...
The internal structure of charged mesons can be probed through their electromagnetic form factors, which are rigorously connected to the transverse charge density via a two-dimensional Fourier transform. In this talk, we present a dispersive analysis of the timelike electromagnetic form factor of the charged pion, based on a logarithmic dispersion relation applied to the precise $e^+e^− \to...
In this talk, we present an ongoing study of the internal structure of the pion using light-front dynamics, going beyond the leading Fock state approximation. We construct light-front wave functions (LFWFs) for the pion that include both quark–antiquark and quark–antiquark–gluon components. This allows us to capture more of the non-perturbative dynamics of the pion and go beyond simple...
