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[en] The description of the hadron production at very forward rapidities and low transverse momentum is usually made using phenomenological models based on nonperturbative physics. However, at high energies and large rapidities the wave function of one of the projectiles is probed at very small Bjorken x, being characterized by a large number of gluons. In this kinematical regime, a new state of matter — the Color Glass Condensate (CGC) — is expected to be formed. One the main characteristics of such system is the presence of a new dynamical momentum scale, the saturation scale Qs, which can assume values very larger than the QCD confinement scale ΛQCD and give the scale of the running coupling constant. In this paper we assume that in particular kinematical region probed by LHC forward (LHCf) experiment the saturation scale can be considered the hard momentum scale present in the process and calculate the forward neutral pion production at very low-pT using a perturbative approach. We demonstrate that the CGC formalism is able to successfully describe the LHCf data, which can be considered as a compelling indication of the presence of non-linear QCD effects at LHC energies
[en] Full text. Fock-Tani is a field theory formalism appropriated for the simultaneous treatment of composite particles and their constituents. The formalism was originally developed for the treatment of problems in atomic physics and it was extended later on to the treatment of problems on hadron physics. In the Fock-Tani formalism one starts with the Fock representation of the system using field operators of elementary constituents which satisfy canonical (anti) commutation relations. Composite-particle field operators are linear combinations of the elementary-particle operators and do not generally satisfy canonical (anti) commutation relations. 'Ideal' field operators acting on an enlarged Fock space are then introduced in close correspondence with the composite ones. Next, a given unitary transformation, which transforms the single composite states into single ideal states, is introduced. Application of the unitary operator on the microscopic Hamiltonian, or on other hermitian operators expressed in terms of the elementary constituent field operators, gives equivalent operators which contain the ideal field operators. The effective Hamiltonian in the new representation has a clear physical interpretation in terms of the processes it describes. Since all field operators in the new representation satisfy canonical (anti)commutation relations, the standard methods of quantum field theory can then be readily applied. For a long time the pair creation models for strong hadronic decays have been formulated. The 3P0 model is typical decay model which considers only OZI-allowed strong decays. The 3P0 model considers a quark-antiquark par creation in the presence of the initial state meson. The quark-antiquark par is created with the vacuum quantum numbers. This model can also be obtained from the non-relativistic limit of the pair creation Hamiltonian. Applying the Fock-Tani transformation to the pair creation Hamiltonian produces the characteristic expansion in powers of the wave function, where the 3P0 model is the lowest order term of this expansion and represented by the Hamiltonian HFT. The next step is to introduce the bound-state corrections (orthogonality corrections) to this 'zero order' model. The Hamiltonian associated to this correction contains terms dependent on only one Δ, called the bound state kernel. A new model is introduced in order to correct the 3P0, which we call the C3P0 model. This description is a natural consequence of the constituent quark model scenario of hadronic states. In high energy collisions many new mesons have been discovered, in particular the enigmatic D+s1 (2317) and D+s1 (2460). The C3P0 model is applied for the Dsj mesons decay. The amplitudes and their respective decay rates are evaluated. (author)
[en] The radiative decay of to vector mesons ρ and ϕ is calculated in a non-relativistic approach. The results obtained are compared to experimental data to estimate the glue content of . We find a small or nonexistent glue content when our results are compared to the PDG data. However a considerable glue content for was found when we compared our results to the CLAS data.
[en] In this contribution we calculate the nuclear structure functions F2c and FLA and the F2A slope in the kinematic region which could be explored in the future eA colliders, considering the high density (saturation) effects in the nuclear gluon distribution. We verify that the high parton density implies large modifications in the behavior of these observables, allowing to explicit the saturation effects in a future experimental analysis. (author)
[en] We investigate relativistic bound states for a hypothetical light scalar gluino pair (gluinonium), in the framework of the covariant Bethe-Salpeter equation (BSE). In this paper, we derive, from the covariant BSE for a fermion-anti-fermion system, using charge conjugation, the corresponding bound-state equation for a gluino pair and we then formulate, for a static harmonic kernel, the coupled differential equations for the corresponding static Bethe-Salpeter amplitude. The steps of our approach then include a numerical solution of the Bethe-Salpeter amplitude for a two-body interaction consisting of scalar, pseudo-scalar, and four-vector components and the determination of the energy spectrum for the ground and the radially excited states of massive gluinonium. We found the energy spectrum and radial distributions of fundamental and excited states of gluinonium. The comparison of the values obtained in the extreme relativistic case with the corresponding values predicted by a harmonic oscillator potential model shows that there is good agreement between the two formulations. The predictions of the binding energy of glunionium in the non-relativistic model are however systematically higher. (author)