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This paper review the modelling efforts regarding Generalised Parton Distributions (GPDs) using continuum techniques relying on Dyson–Schwinger and Bethe–Salpeter equations. The definition and main properties of the GPDs are first recalled. Then, we detail the strategies developed in the last decade in the meson sector, highlighting that observables connected to the pion GPDs may be measured at future colliders. We also highlight the challenges one will face when targeting baryons in the future. [ABSTRACT FROM AUTHOR]

Laser-induced nuclear reactions in ultra-dense hydrogen H(0) (review in Physica Scripta 2019) create mesons (kaons and pions). These mesons decay mainly to muons. The muons created are useful (patented source) for the muon-induced fusion process. The sign of the muons from the source depends on the initial baryons used. With D(0) (ultra-dense deuterium) the source produces mainly positive muons and with p(0) (ultra-dense protium) the source produces mainly negative muons. Negative muons are required for muon-induced fusion. This charge asymmetry was reported earlier, and has now been confirmed by experiments with a coil current transformer as the beam detector. The current coil detector would give no signal from the muons if charge symmetry existed. The charge asymmetry could indicate unknown processes, for example, caused by the different annihilation processes in D(0) and p(0). The conclusions of a new analysis of the results are presented here. Using D(0) in the muon source, the asymmetry is likely due to the capture of µ- in D atoms and D2 molecules. This leads to emission of excess µ+ from D(0). With p(0) in the muon source, the capture rate of µ- is lower than in D(0). The emitted number of µ+ will be decreased by the reaction between µ+ and the surrounding abundant electrons, forming neutral muonium particles. This effect decreases the amount of emitted µ+ for both p(0) and D(0), and it is proposed to be the main reason for a larger fraction of emitted µ- in the case of p(0). Thus, there is no dominant emission of negative muons which would violate charge conservation. [ABSTRACT FROM AUTHOR]

The low energy pion– Λ b interaction is study in this work, considering effective chiral Lagrangians that include pions, baryons and the corresponding resonances. Interactions mediated by a σ meson exchange are also considered. The scattering amplitudes are calculated and then we determine the angular distributions and polarizations. [ABSTRACT FROM AUTHOR]

Generalized Chou-Yang model (GCYM) predicts electromagnetic form factors of several hadrons with varying magnitude of strangeness. By using these form factors, the root mean square (RMS) radii of the hadrons such as (π, p, ϕ, Λ, Σ+, Σ−and Ω−)are computed. It is found that there is consistency among the predicted RMS radii of pion and proton by GCYM (and other models) and experimental results. For all hadrons experimental results are not available. Also we find that results of GCYM and from other models are somewhat inconsistent for hadrons other than pion and proton. Though GCYM and other models do not agree for most of the hadrons but they have one similarity that the computed RMS radii seem decreasing with the increase in the strangeness level, separately for mesons as well as for baryons. The experimental results of hadrons other than pion and proton are needed to check the suitability of GCYM and other models as well as in probing the trend of decreasing radii with increase in strangeness content. [ABSTRACT FROM AUTHOR]

Low-lying baryon resonances have been explored using Hamiltonian Effective Field Theory (HEFT), in a formalism where resonances with a three-quark component are described by both two-particle meson–baryon states and a bare basis state. Here, we investigate the use of multiple bare states in the Hamiltonian, to extend the formalism to higher energy ranges, and represent a larger portion of the low-lying baryon spectrum. Introducing a second bare state into a toy model extension of the low-energy Δ (1232) system, we explore the influence of the second bare state on the position of poles in the infinite-volume T -matrix. Considering the same system in a finite-volume, we analyse the finite-volume energy spectrum in the presence of a second bare state, providing insight into the interplay between two bare basis states, representing quark-model states, and the relationship between infinite-volume poles and finite-volume eigenstates. • Hamiltonian Effective Field Theory is formulated using multiple bare basis states. • A toy model extension of the P33 pion nucleon system is considered. • The positions of poles in the scattering matrix are found. • The finite-volume energy spectrum is found for the two bare state system. [ABSTRACT FROM AUTHOR]

We systematically investigate the scaling property of mesons (pions and kaons) and baryons (protons, Λ , Ξ and Ω) transverse momentum ( p T ) spectra at different centrality classes (0–5 % , 5–10 % , 10–20 % , 20–40 % , 40–60 % , 60–80 % and 80–100 %) in proton-lead collisions with center of mass energy per nucleon pair 5.02 TeV. In the low p T region with p T ≤ 3. 9   (3. 1 , 2. 5 , 2. 7 , 2. 4   and   2. 8) GeV/c, a universal scaling independent of the centrality is observed in the pion (kaon, proton, Λ , Ξ and Ω) spectra when a dilatation, p T → p T / K , is applied. Here, K is a scaling parameter depending on the centrality class. We find that the rates at which ln K changes with the logarithmic value of the average value of the number of participating nucleons, ln 〈 N part 〉 , are stronger for baryons than those for mesons. In the high p T region, there is a deviation from the scaling. The more peripheral the collisions are, the more obvious the violation of the scaling is. In the framework of the color string percolation (CSP) model, we show that mesons and baryons are generated from the decay of clusters formed by strings overlapping in the transverse plane with the same size dispersion but with different mean size. The mean size of clusters for baryons is smaller than that of mesons. For the same hadrons at different centrality classes, the mean size of clusters decreases with the increase of centrality. The fragmentation functions for cluster decay are different for different hadrons, while they are universal for the same hadrons at different centrality classes. The universal scaling of the meson and baryon spectra in the low p T region can be quantitatively understood with the CSP model at the same time. [ABSTRACT FROM AUTHOR]

Using dispersion theory the low-energy electromagnetic form factors for the transition of a Sigma to a Lambda hyperon are related to the pion vector form factor. The additionally required input, i.e. the two-pion-Sigma-Lambda amplitudes are determined from relativistic next-to-leading-order (NLO) baryon chiral perturbation theory including the baryons from the octet and optionally from the decuplet. Pion rescattering is again taken into account by dispersion theory. It turns out that the inclusion of decuplet baryons is not an option but a necessity to obtain reasonable results. The electric transition form factor remains very small in the whole low-energy region. The magnetic transition form factor depends strongly on one not very well determined low-energy constant of the NLO Lagrangian. One obtains reasonable predictive power if this low-energy constant is determined from a measurement of the magnetic transition radius. Such a measurement can be performed at the future Facility for Antiproton and Ion Research (FAIR). [ABSTRACT FROM AUTHOR]

We discuss a new type of L = 0 positive-parity dibaryons, πBBt, where the dominant binding mechanism is provided by resonating p-wave pionbaryon interactions. Recent calculations of such pion assisted dibaryons are reviewed with special emphasis placed on the non-strange I(JP ) = 1(2+) NΔ dibaryon D12(2150) studied recently at JLab, and on the 0(3+) ΔΔ dibaryon D03(2380) discovered recently by the WASA-at-COSY Collaboration. We discuss recent searches by the HADES Collaboration at GSI and by the E15 and E27 Experiments at J-PARC for a strangeness S = -1 I(JP) = ½ (0-) K-pp dibaryon and perhaps also for a strange I(JP) = 3/2(2+) N Σ(1385) pion assisted dibaryon Y3/22 (2270). Charm C = +1 dibaryons, predicted with the same I(JP) values, are also briefly reviewed. [ABSTRACT FROM AUTHOR]