A5010720860- Quantum Chromodynamics and Particle Interactions
- Particle physics theoretical and experimental studies
- High-Energy Particle Collisions Research
- Nuclear physics research studies
- Black Holes and Theoretical Physics
- Superconducting Materials and Applications
- Particle Accelerators and Free-Electron Lasers
- Atomic and Subatomic Physics Research
- Physics of Superconductivity and Magnetism
- Pulsars and Gravitational Waves Research
- High-pressure geophysics and materials
- Magnetic confinement fusion research
- Advanced NMR Techniques and Applications
- Atomic and Molecular Physics
- Cold Fusion and Nuclear Reactions
- Quantum and Classical Electrodynamics
- Neutrino Physics Research
- Machine Learning and Data Classification
- Computer Graphics and Visualization Techniques
- Radiation Detection and Scintillator Technologies
- Particle accelerators and beam dynamics
- Dark Matter and Cosmic Phenomena
- Evacuation and Crowd Dynamics
- Quantum, superfluid, helium dynamics
- Seismic Imaging and Inversion Techniques
Soongsil University
2022-2025
University of Lisbon
1999-2023
Departamento de Ciência e Tecnologia
2023
LIP - Laboratory of Instrumentation and Experimental Particle Physics
2023
Universidade Cruzeiro do Sul
2017-2022
Universidade Cidade de São Paulo
2019-2022
Universidade Federal do Rio Grande do Norte
2013-2018
Instituto Superior Técnico
2008-2013
Instituto Politécnico de Lisboa
2011-2013
Thomas Jefferson National Accelerator Facility
2008-2010
Studies of the structure excited baryons are key factors to N* program at Jefferson Lab (JLab). Within first year data taking with Hall B CLAS12 detector following 12 GeV upgrade, a dedicated experiment will aim extract electrocouplings high photon virtualities Q 2 . This allow exploration resonances highest ever achieved, kinematic reach up = high-Q make it possible probe nucleon structures distance scales ranging from where effective degrees freedom, such as constituent quarks, dominant...
Using the manifestly covariant spectator theory and modeling nucleon as a system of three constituent quarks with their own electromagnetic structure, we show that all four form factors can be very well described by wave function zero orbital angular momentum. Since concept depends on formalism, conclusions light-cone requiring nonzero momentum components are not inconsistent our results. We also model gives qualitatively correct description deep inelastic scattering, unifying phenomenology...
We study the axial-vector and induced pseudoscalar form factors associated with weak transitions between octet baryon members in nuclear medium, using a covariant constituent quark model. extend previous calculations of axial transition from vacuum (free space) to medium (symmetric matter). The extension model takes into account modifications properties hadrons (masses coupling constants), as determined by quark-meson (<a:math xmlns:a="http://www.w3.org/1998/Math/MathML"...
We consider here a manifestly covariant quark model of the nucleon and $\ensuremath{\Delta}$, where one is off shell, other two quarks form an on-shell diquark pair. Using this model, we have shown previously that factors dominant factor for $\ensuremath{\gamma}N\ensuremath{\rightarrow}\ensuremath{\Delta}$ transition (the magnetic dipole (M1) factor) can be well described by $\ensuremath{\Delta}$ wave functions with S-state components only. In paper, show nonvanishing results small electric...
We compute the ${\ensuremath{\Omega}}^{\ensuremath{-}}$ electromagnetic form factors and decuplet baryon magnetic moments using a quark model application of covariant spectator theory. Our predictions for can be tested in future by lattice QCD simulations at physical strange mass.
We study the octet baryon electromagnetic form factors in nuclear matter using covariant spectator quark model extended to regime. The parameters of vacuum are fixed by factors. In changes hadron properties calculated including relevant masses and modification pion–baryon coupling constants quark–meson model. magnetic baryons enhanced low Q2 region, while electric show a more rapid variation with Q2. results compared bound proton observed at Jefferson Lab. addition, corresponding for neutron...
A relativistic constituent quark model is applied to the $\ensuremath{\gamma}N\ensuremath{\rightarrow}N(1535)$ transition. The $N(1535)$ wave function determined by extending covariant spectator model, previously developed for nucleon, ${S}_{11}$ resonance. allows us calculate valence contributions transition form factors. Because of nucleon and structure valid only ${Q}^{2}>2.3\text{ }\text{ }{\mathrm{GeV}}^{2}$. results are compared with experimental data electromagnetic factors...
Starting with a spectator quark model developed for the nucleon (N) and Delta in physical pion mass region, we extend predictions of reaction gamma N -> to lattice QCD regime. The includes S D waves quark-diquark wavefunctions. Within this framework it is D-wave part wavefunction that generates nonzero valence contributions quadrupole form factors transition. Those are however insufficient explain data, since cloud dominate. To separate two effects apply regime region where negligible,...
Using a covariant spectator quark model we estimate valence contributions to the ${F}_{1}^{*}({Q}^{2})$ and ${F}_{2}^{*}({Q}^{2})$ transition form factors for $\ensuremath{\gamma}N\ensuremath{\rightarrow}{P}_{11}(1440)$ reaction. The Roper resonance, ${P}_{11}(1440)$, is assumed be first radial excitation of nucleon. present requires no extra parameters except those already fixed by previous studies Our results are consistent with experimental data in high ${Q}^{2}$ region, from lattice QCD....
The electromagnetic form factors of the Delta baryon are evaluated within framework a covariant spectator quark model, where S and D-states included in $\Delta$ wave function. We predict all four multipole factors: electric charge GE0, magnetic dipole GM1, quadrupole GE2 octupole GM3. compare our predictions with other theoretical calculations. Our results compatible available experimental data recent lattice QCD data.
We extend a covariant model, tested before in the spacelike region for physical and lattice QCD regimes, to calculation of gamma* N -> Delta reaction timelike region, where square transfered momentum, q^2, is positive (q^2>0). estimate Dalitz decay Ne+e- distribution mass function. The results presented here can be used simulate NN NNe+e- reactions at moderate beam kinetic energies.
We study the octet baryon electromagnetic properties by applying covariant spectator quark model, and provide parametrization that can be used to reactions. While we use lattice QCD data in large pion mass regime (small cloud effects) determine parameters of model valence sector, nucleon physical magnetic moment parameterize contributions. The contributions for form factors are estimated extrapolating regime. As contributions, them a covariant, phenomenological manner, combined with SU(3)...
We study the octet to decuplet baryon electromagnetic transitions using covariant spectator quark model and predict transition magnetic dipole form factors for those involving strange baryons. Utilizing $SU(3)$ symmetry, valence contributions are supplemented by pion cloud dressing based on one estimated in ${\ensuremath{\gamma}}^{*}N\ensuremath{\rightarrow}\ensuremath{\Delta}$ reaction. Although dominant general, effects turn out be very important describe experimental data. also show that...
The $\Delta(1232) \to \gamma^\ast N$ magnetic dipole form factor ($G_M^\ast$) is described here within a new covariant model that combines the valence quark core together with pion cloud contributions. term parameterized by two terms: one connected to electromagnetic factor, other photon interaction intermediate baryon states. can be used in studies of pp and heavy ion collisions. In timelike region this improves results obtained constant fixed at its value zero momentum transfer. At same...
A covariant quark model, based both on the spectator formalism and vector meson dominance, previously calibrated by physical data, is here extended to unphysical region of lattice data means one single extra adjustable parameter -the constituent mass in chiral limit.We calculated Nucleon (N ) γN → ∆ form factors universe values for that described quenched QCD.A qualitative description achieved light pions.
A covariant spectator constituent quark model is applied to study the $\ensuremath{\gamma}N\ensuremath{\rightarrow}\ensuremath{\Delta}(1600)$ transition. Two processes are important in transition: a photon couples individual quarks of $\ensuremath{\Delta}(1600)$ core (quark core), and intermediate pion-baryon states (pion cloud). While contributions estimated assuming as first radial excitation $\ensuremath{\Delta}(1232)$, pion cloud based on an analogy with...
Expressions for the nucleon wave functions in covariant spectator theory are derived. The is described as a system with off-mass-shell constituent quark, free to interact an external probe, and two quarks on their mass shell. Integrating over internal momentum of on-mass-shell quark pair allows us derive effective function that can be written only terms diquark (quark-pair) variables. derived includes contributions from $S$-, $P$- $D$-waves.
We estimate the valence quark contributions for ${\ensuremath{\gamma}}^{*}Y\ensuremath{\rightarrow}{\ensuremath{\Lambda}}^{*}$ ($Y=\ensuremath{\Lambda}$, ${\ensuremath{\Sigma}}^{0}$) electromagnetic transition form factors. focus particularly on case of ${\ensuremath{\Lambda}}^{*}=\ensuremath{\Lambda}(1670)$ as an analogue reaction with ${\ensuremath{\gamma}}^{*}N\ensuremath{\rightarrow}N(1535)$. The results are compared those obtained from chiral unitary model, where...
It is shown that the helicity amplitudes A_1/2 and S_1/2 in gamma N -> N(1535) reaction, can be well related by = -\frac{\sqrt{1+\tau}}{\sqrt{2}} \frac{M_S^2-M^2}{2 M_S Q} region Q^2 > 2 GeV^2, where M are nucleon masses, q^2=-Q^2 four-momentum transfer squared, tau=\sfrac{Q^2}{(M_S+M)^2}. The observed relation tested experimental data MAID parametrization. A direct consequence of assumption,|A_1/2| >> |S_1/2|, not valid for high Q^2. Instead, both have same dependence region, aside from...
We study the effect of meson cloud dressing in octet baryon to decuplet electromagnetic transitions. Combining valence-quark contributions from covariant spectator quark model with those estimated based on flavor SU(3) cloudy bag model, we calculate transition magnetic form factors at ${Q}^{2}=0$ (${Q}^{2}=\ensuremath{-}{q}^{2}$ and $q$ four-momentum transfer), also decay widths. The result for ${\ensuremath{\gamma}}^{*}\ensuremath{\Lambda}\ensuremath{\rightarrow}{\ensuremath{\Sigma}}^{*0}$...
The Omega- has an extremely long lifetime, and is the most stable of baryons with spin 3/2. Therefore magnetic moment very accurately known. Nevertheless, its electric quadrupole was never measured, although estimates exist in different formalisms. In principle, lattice QCD simulations provide at present appropriate way to estimate form factors, as function square transferred four-momentum, Q2, since it describes baryon systems physical mass for strange quark. However, particular GE2, are...