We discuss the exclusive photoproduction of ground and excited states of ψ(1S,2S) and Υ(1S,2S) in ultraperipheral collisions. Using the potential model in order to obtain the vector meson wave function, we find a good agreement of our calculations with data from the LHC and HERA colliders for J/ψ(1S,2S) and Υ(1S) in γp collisions. We extend the calculations to the nuclear target case applying...
In this work, it is done a study of the quark matter accordingly to the two-flavor Nambu-Jona Lasinio model, which it is considered only the up and down quark flavors, and it is done an analysis adding non-linear effects from QED (Quantum Electrodynamics) through the use of the effective lagrangian of Euler and Heisenberg. From the complete lagrangian, we obtain the gap equation that dictates...
In this work we revisit the thermal relaxation of neutron stars. We focus particularly on the cooling of neutron stars whose mass is slightly greater than the value above which the direct urca process sets in. Considering different mechanisms for neutrino production in each region of the star, and working with some equations of state whose saturation properties as well its predicted neutron...
We argue that a detailed analysis of the spin alignement of vector mesons can serve as a probe of two little-understood aspects of spin dynamics in the vortical fluid: The degree of relaxation between vorticity and parton spin polarization, and the degree of coherence of the hadron wavefunction at freeze-out.
We illustrate these with a coalescence model.
Based on https://arxiv.org/abs/2104.12941
Meson spectroscopy can be theoretically studied with lattice QCD, QCD sum rules and quark models. In all these approaches the results are obtained numerically. It would be useful to have an analytical formula for the energy levels of the meson systems. In this work we use the variational principle and apply it to heavy mesons. We derive an expression for the energy levels which depends on the...
In this study I analyze the scalar and vectorial Lee-Wick field, achieving analytically the propagator and numerically the energy and force. It is analyzed the interaction between charge and a conductive plate, which simulates a semi-transparent mirror. For both cases, scalar and vectorial, the interaction force shows extrema points for finite values of the Lagrangian coupling parameters. The...
In recent years new processes involving weak nuclear interactions have been studied experimentally and theoretically [1]. This kind of interactions play a fundamental role in the understanding heavier elements nucleosynthesis in the universe. The presence of heavy elements is only understood if stellar reactions take place involving regions of the nuclear chart far away from the stability...
In this work, a simple model of superconductivity of confined particles, which constitute low energy hadrons, such as quarks and gluons. Many models like these of superconductivity are already present in high energy physics, mainly in the study of color superconductivity. These models use in general a gluon propagator with specific electrical and magnetic effects, and after several...
Quantum Chromodynamics (QCD) theory predicts that at high temperatures quarks and gluons are in a state of asymptotic freedom, constituting with leptons and photons the primitive plasma present in the Early Universe. When the plasma temperature drops below a certain critical value $T_c$, consequence of the expansion of the Universe, quarks become confined into hadrons. This process is usually...
We use the Monte Carlo particle physics code FLUKA to calculate gamma-ray spectra expected from solar flare energetic ion distributions. The FLUKA code includes robust physics-based models for electromagnetic, hadronic and nuclear interactions, sufficiently detailed for it to be a useful tool for calculating nuclear de-excitation, positron annihilation and neutron capture line fluxes and...
We study the prompt photon production at the CERN LHC energies considering the color dipole approach. We estimate the rapidity and transverse momentum distributions of prompt photon production considering the more recent phenomenological models for the dipole-proton scattering amplitude, which are able to describe the inclusive and exclusive ep HERA data. A comparison between the predictions...
Magnetars and heavy-ion-collisions (HIC) are environments where only a robust theory to strong interactions can extract reasonable quantities in account with the astronomical observations and HIC-experiments nowadays. Because of the sign problem, the Quantum Chromodynamics (QCD) isn’t treatable to important cases where there are finite chemical potentials. From Nambu–Jona-Lasinio (NJL) model,...
We propose to investigate in detail how field theory behaves in restricted spaces. To do so, we consider a parametric representation of Feynman amplitudes, which allows us to discuss the behavior up to all orders in a perturbative expansion and extract consequences valid in a global setting. As a first step, we employ periodically compactified spaces and consider a scalar field theory. We show...
The Efimov effect is a counterintuitive phenomenon concerning three non-relativistic particles with pairwise interactions supporting only one very shallow, two-particle bound state. In the so-called unitary limit, where the two-particle bound state energy goes to zero, the three-particle spectrum exhibits an infinite tower of bound states geometrically separated by a constant factor $\sim...
Extremely massive objects such as neutron stars serve as unique laboratories that allow the study of nuclear matter in exotic environments impossible to be reproduced on Earth. The microscopic description of the nuclear structure of neutron stars represents a big challenge for theoretical models. The large densities present in these stars, possibly beyond the nuclear density equilibrium, lead...
We show that, within the hydrodynamic framework of heavy-ion collisions, the mean transverse momentum of charged hadrons ($\langle p_t \rangle $) rises as a function of the multiplicity in ultra-central nucleus-nucleus collisions. The relative increase is proportional to the speed of sound squared ($c_s^2$) of the
quark-gluon plasma, that is therefore accessible experimentally using...
In this work, we investigate neutron stars (NS) in $f(\mathcal{R,T})$ gravity for the case $R+2\lambda\mathcal{T}$, $\mathcal{R}$ is the Ricci scalar and $\mathcal{T}$ the trace of the energy-momentum tensor. The hydrostatic equilibrium equations are solved considering realistic equations of state (EsoS). The NS masses and radii obtained are subject to a joint constrain from massive pulsars...
We investigate the production of charmed hadrons ($\bar{D}$, $\Lambda_{c}$, $\Xi_{cc}$) and exotic tetraquarks ($T_{cc}$, $T_{bc}$) in relativistic heavy-ion collisions using the quark coalescence model. The yields are given by the overlap of the density matrix of the constituents in the emission source with the Wigner function of the produced meson, baryon and tetraquark. The wave functions...
Gauge symmetries are pervasive in particle physics, guiding the formulation of all interactions within the Standard Model. Usual methods for the calculation of processes, observables and properties of particles rely on perturbative expansions, which fail to converge for non-abelian gauge theories in the low-energy regime. The lattice formulation of a gauge theory, inherently non-perturbative,...
In this work, we study magnetic field effects on neutron star matter containing the baryon octet and additional heavier spin 3/2 baryons (the Δ's). We make use of two different relativistic hadronic models that contain an additional vector-isovector self interaction for the mesons: one version of a relativistic mean field (RMF) model and the Chiral Mean Field (CMF) model. We find that both the...
In the present work phase diagrams of QCD are obtained by means of two effective models. For the description of the quark matter we make use of the MIT bag model and a modification of this model, and for the description of the hadronic matter we make use of the non-linear Walecka model (NLWM). The Gibbs conditions are used to establish the crossing points of the pressures in function of the...
The double--parton scattering (DPS) at the hadron coliiders such as the LHC is sensitive to correlations in the double--parton distributions. When looking at inclusive observables, it is dominated at high energies (small x) by the interaction of 4 gluons in the initial state. In order to extract different information about the partons, we are interested in the interaction between two gluons...
In this work, the exclusive photoproduction of the ground and excited states of the heavy vector mesons $\psi(1S)$, $\psi(2S)$, $\Upsilon(1S)$ and $\Upsilon(2S)$ are discussed in ultraperipheral hadron collisions (UPCs) with proton and nucleus targets. Since we are interested in scatterings with the projectile being a virtual photon produced by the incoming hadron, we employ the color dipole...
We study two-dimensional fermion motion with circular symmetry using
both 3+1 and 2+1 Dirac equations with a general Lorentz structure. Using
a different approach than usual, we fully develop the formalism for
these equations using cylindrical coordinates and discuss the quantum
numbers, spinors and differential equations in both cases when there is
circular symmetry. Although there is no...
We investigate the structure of massive white dwarfs with finite temperature and their stability against radial oscillations, pycnonuclear reactions, and the inverse $\beta$-decay. Regarding the stellar fluid, we consider that it is composed of nucleons and electrons confined in a Wigner-Seitz cell surrounded by free photons. The star is considered with an isothermal core and a non-degenerate...
We investigate the properties of electrically charged strange quark stars using an interacting quark matter equation of state (EoS) based on cold and dense perturbative quantum chromodynamics (pQCD). The stability of strange stars is analyzed considering different models for the electric charge distribution inside the star as well as for distinct values for the total electric charge. A...
In this work we study the effect of scalar spin coupling of constituent quarks on nucleon electroweak properties by introducing a two momentum scales wave function. By comparing the one scale wave function and the two scales wave function models, we found that the last case has shown a reasonable description of static observables and of the ratio µpGEp/GMp in which the value of the zero of...
We use the renormalization group optimized perturbation theory (RGOPT) to evaluate the quark contribution, Pq, to the QCD pressure at NLO (two loop level). In this seminal application the complete QCD pressure is then obtained simply by adding the perturbative NLO contribution from massless gluons to the resummed Pq. At the central scale M∼2πT our complete QCD pressure, P=Pq+Pg, shows a...
The high energy regime of quantum chromodynamics (QCD) has been under intense investigation in electron-hadron and hadron-hadron collisions. In this regime, saturation effects associated with the high gluonic density are expected to modify the QCD dynamics, implying the presence of non-linear effects that reduce the growth of the gluon distribution at small-x. The description of the saturation...
The quiescent emission of the anomalous X-ray pulsar (AXP) 4U 0142+61 extends over a broad range of energy, from radio up to hard X-rays. In particular, this object is unique among soft gamma-ray repeaters (SGRs) and AXPs in presenting simultaneously mid-infrared emission and pulsed optical emission. In spite of the many propositions to explain this wide range of emission, it still lacks one...
The electromagnetic structure of the nucleon resonances $N^\ast$ are usually parametrized by $\gamma^\ast N \to N^\ast$ helicity amplitudes, at the resonance rest frame. Those amplitudes are, however, constrained by kinematic conditions in the limit where the photon three-momentum vanishes (pseudothreshold limit). Although the pseudothreshold limit is below the photon point ($Q^2=0$) it has an...
The effective quark model Polyakov-Nambu-Jona-Lasinio (PNJL) incorporates the effect of confinement/deconfinement on the original Nambu-Jona-Lasinio model (NJL) by inserting the Polyakov Loop ($\Phi$) on the equations of states~(EOS) at finite temperature. However, at zero temperature regime, the PNJL loses all contributions of $\Phi$ and the EOS returned for the same as original NJL equations...
Our first goal in this work is to evaluate the moments of the multiplicity distributions (MD) in pp collisions recently measured on the LHC, as the moments have not been published by the collaboration.
We explore the possibility of fitting this moments with negative binomial distribution (NBD) describing the MD, using a simple power law to describe dependence on energy of the mean...
Predictions for Drell--Yan lepton pair production at low dilepton mass and small x at the LHC usually have a large scale dependence, that can be decreased through obtaining an optimal factorization scale. In this paper, we reduce this scale by imposing a cutoff in azimuthal angle between the transverse momentum of the leptons, properly taking into account Sudakov effects. This would allows one...
We study hybrid stars considering the effects on stellar stability of the hadron-quark conversion speed at the sharp interface. The equation of state is constructed by combining a model-agnostic hadronic description with a constant speed of sound model for quark matter. We show that current LIGO/Virgo, NICER, low-density nuclear and high-density perturbative QCD constraints can be satisfied in...
We discuss the associated $c\bar{c}$ and $l^+l^-$ pairs production in ultraperipheral heavy-ion collisions at high energies. Such a channel provides a novel probe for double-parton scattering (DPS) at small $x$ enabling one to probe the photon density inside the nucleus. We have derived an analog of the standard central $pp$ pocket formula and studied the kinematical dependence of the...
When relativistic heavy ions collide, a plasma of quarks and gluons (QGP) is created. This system cools down, expands and eventually reaches hadronization temperature, when a hadron gas is formed. During this phase, the constituents of the gas, among which are the K and K* mesons, can undergo further interactions and change their abundances with respect to predictions by statistical...
The QCD phase diagram at low temperature and high chemical potential still remains poorly understood. Several calculations suggest that, in this region, matter deconfines into a phase of quarks and gluons (known as cold QGP or quark matter), which can exist in the core of neutron stars. It is even possible that neutron stars are formed entirely by cold QGP. Usually we model neutron stars with...
The effect of deformation on compact stars, especially neutron stars, is widely known. This can happen for several reasons: intense magnetic fields and high rotation are the main ones. In this sense, taking into consideration influences both in the metric and in the matter structure, through deformed geometries, anisotropies in the energy-momentum tensor, or adequate equations of state, a more...
Leading neutron (LN) production in ep collisions at high energies is investigated using the color
dipole formalism and taking into account saturation effects. We update the treatment of absorptive
effects and estimate the impact of these effects on LN spectra in the kinematical range that will
be probed by the Electron Ion Collider (EIC) and by the Large Hadron electron Collider...
In relativistic non-central heavy-ion collisions an intense magnetic field is produced. Classical fields can be used to describe quantum fields when the occupation of each field mode is sufficiently high. In this work, we test the classical magnetic field approximation in heavy-ion collisions. First, we use a classical field to study the forward pion production by the magnetic excitation of...
The planar motion of spin-1/2 fermions under the influence of a homogeneous magnetic field is described by the Feynman-Gell-Mann formulation of the Dirac equation. The axially symmetric gauge is used for the vector potential in such a way that the Dirac spinor is written in terms of eigenstates of the quiral operator and the third component of the total angular momentum operator. The spinors...
The exclusive vector meson production in electron – ion collisions for the energies of the future colliders is investigated. We present predictions for the coherent and incoherent Phi and J/psi production in eAu collisions considering the possible states of nucleon configurations in the nuclear wave function and taking into account of the non - linear corrections to the QCD dynamics. The...
Dark photon is a theoretical boson that mediates the interaction between dark matter particles. The dark photon can interact with the Standard Model photon by kinetically mixing with it. In this work, we study the dark photon production via Compton-like process in ultrarelativistic electron-ion collisions. We search for massive dark photons in planned electron-ion collider machines such as...
One interesting subject of the QED are the lepton – antilepton bound states, which are atom – like systems. These systems are ideal to test the ground of QED, once they allow us to test the CPT invariance of the theory, as demonstrated by several authors. Besides that, recent studies point out that these QED bound states can be sensitive to Beyond Standard Model Physics. Currently, we can...
In this work, we present a preliminary study where the Bayesian analysis is used to constraint saturation properties of nuclear matter. For this, an equation of state (EoS) that allows $\omega-\rho$ interactions is considered. Regarding the priors, uniform distribution on the values of saturation density, binding energy, effective mass, incompressibility, symmetry energy, and its slope at...
Recently, we made a calculation of the form factors and coupling constant of $DsDK^*$ using the QCD Sum Rules. This information is fundamental to compute the amplitude for the process $B\rightarrow K^*\pi$ in effective theories. The method used considers the three cases of different off-shell mesons. After an extrapolation of the results of QCD Sum rules, we obtain the coupling constant of the...
Recently, STAR made measurements of pair production at very low transverse momenta and a significant excess with respect to hadronic cocktail in peripheral Hadronic Heavy Ion Collisions (HHICs) was observed. The excess pairs have transverse momenta $p_{T} < 150$ MeV/c and are most prominent in peripheral gold-gold and uranium-uranium collisions. The ALICE Collaboration observes a similar...
In this work we calculate corrections to the NJL model coupling constant in the presence of a uniform magnetic field. Starting with the Nambu-Jona-Lasinio Lagrangian coupled with a U(1) gauge field, namely a magnetic field, the background field method is employed. By expanding the quark determinant in terms of the quark bilinears we show that the first-order term provides a correction to the...
We investigate the generation of a gluon screening mass in Yang-Mills theory in the Landau gauge. We propose a gauge-fixing procedure where the Gribov ambiguity is overcome by summing over all Gribov copies with some weight function. This can be formulated in terms of a local field theory involving constrained, nonlinear sigma model fields. We show that a phenomenon of radiative symmetry...
Exotic shapes of nuclei, known as nuclear pasta phase, can exist in the crust of neutron star and in supernovae exposions. Calculations involving the pasta assume a perfectly crystalline structure, described by identical Wigner-Seitz cells, but such an approximation is unrealistic due to the small free energy variation with respect to the different pasta configurations, and these may coexist...
The main interest in relativistic heavy-ion collisions is the study of properties of the Quark Gluon Plasma (QGP). From a theoretical point of view, hybrid approaches, where different models are used to describe specific stages of the heavy-ion collision have had great success in describing a wide range of final state hadronic observables. Most of these models include an initial conditions...
