Search results for "Wave function"
showing 10 items of 395 documents
Meson baryon components in the states of the baryon decuplet
2013
We apply an extension of the Weinberg compositeness condition on partial waves of $L=1$ and resonant states to determine the weight of meson-baryon component in the $\Delta(1232)$ resonance and the other members of the $J^P= \frac{3}{2}^+$ baryon decuplet. We obtain an appreciable weight of $\pi N$ in the $\Delta(1232)$ wave function, of the order of 60 \%, which looks more natural when one recalls that experiments on deep inelastic and Drell Yan give a fraction of $\pi N$ component of 34 \% for the nucleon. We also show that, as we go to higher energies in the members of the decuplet, the weights of meson-baryon component decrease and they already show a dominant part for a genuine, non me…
The Drell-Hearn-Gerasimov sum rule and the constituent quark model
1993
The helicity structure function of the nucleon has been calculated for the constituent quark model and compared to the prediction of the Drell-Hearn-Gerasimov sum rule. The multipole decomposition of the sum rule shows large cancellations between different resonances. The small isoscalar-isovector contribution is related to the admixture of aD-state (“bag deformation”) in the nucleon's wave function. The calculations indicate a relatively slow saturation of this part of the sum rule with excitation energy.
Equivalence between local Fermi gas and shell models in inclusive muon capture from nuclei
2005
Motivated by recent studies of inclusive neutrino nucleus processes and muon capture within a correlated local Fermi gas model (LFG), we discuss the relevance of nuclear finite size effects in these reactions at low energy, in particular for muon capture. To disentangle these effects from others coming from the reaction dynamics we employ here a simple uncorrelated shell model that embodies the typical finite size content of the problem. The integrated decay widths of muon atoms calculated with this shell model are then compared for several nuclei with those obtained within the uncorrelated LFG, using in both models exactly the same theoretical ingredients and parameters. We find that the t…
Detecting the long-distance structure of the $$X(3872)$$ X ( 3872 )
2014
We study the X(3872)-->D^0 \bar D^0 \pi^0 decay within a D \bar D^* molecular picture for the X(3872) state. This decay mode is more sensitive to the long-distance structure of the X(3872) resonance than its J/\psi\pi\pi and J/\psi3\pi decays, which are mainly controlled by the details of the X(3872) wave function at short distances. We show that the D^0 \bar D^0 final state interaction can be important, and that a precise measurement of this partial decay width can provide valuable information on the interaction strength between the D^{(*)} \bar D^{(*)} charm mesons.
Polarized Structure Functions and the Nucleon Spin
1995
The link between the light-cone momentum distributions of constituent quark models and their corresponding parton distributions is used to study the polarized structure functions g 1 of proton and neutron. The formalism allows to analyze the effects of the structure of the quark model wave function and thus we discuss the SU (6) breaking mechanism associated with the One Gluon Exchange and large D-state admixtures originated in pionic models. We analyze the contribution to these structure functions of the gluon polarization arising from the anomaly.
Nuclear physics of non-standard 0νβ β-decay
2019
The observation neutrinoless double beta (0νβ β) decay remains crucial for understanding lepton number violation. In view of the difficulties to observe the mass mechanism of 0νβ β-decay, investigations of other mechanisms are in order. These non-standard mechanisms can be divided into short-range and long-range mechanisms. Recently, we have started systematic study for all possible short-range and long-range non-standard mechanisms. The aim of this study is twofold: I) to provide explicit formulas for the nuclear matrix elements (NMEs) and phase-space factors (PSFs) from which the decay rate for one or a combination of mechanisms operating at the same time can be calculated; II) to provide…
Forward J/ψ production at high energy: Centrality dependence and mean transverse momentum
2016
Forward rapidity $J/\psi$ meson production in proton-nucleus collisions can be an important constraint of descriptions of the small-$x$ nuclear wavefunction. In an earlier work we studied this process using a dipole cross section satisfying the Balitsky-Kovchegov equation, fit to HERA inclusive data and consistently extrapolated to the nuclear case using a standard Woods-Saxon distribution. In this paper we present further calculations of these cross sections, studying the mean transverse momentum of the meson and the dependence on collision centrality. We also extend the calculation to backward rapidities using nuclear parton distribution functions. We show that the parametrization is over…
Quantum chemical study of electron‐phonon interaction in crystals
2013
Study of the interaction of the electromagnetic radiation with nonlocal potentials and the electron-phonon interaction is motivated by its key role in non-classical phenomena in dielectrics and semiconductors. Actual in second quantization is decoupling of the undesirable mixture of electronic and phonon birth/annihilation operators and obtaining the effect of radiation in presence of the nonlocal potentials. Here we transform an arbitrary effective electron- phonon Hamiltonian in two matrices – the matrix of a new interaction Hamiltonian and the matrix of the transformation. For a particular effective Hamiltonian formulated in second quantization these two matrices outline a starting point…
On the dynamics of confined particles: a laser test
2017
Reduced dimensionality systems (RDS) are materials extending along one or two dimensions much more than the other(s). The degrees of freedom of the small dimension are not explored by the electrons since their energy is very large. The time dependent wave function of a particle in a short nanotube, taken as a paradigm of the RDS family, is calculated by solving the Klein–Gordon equation; the confining condition produces a small change in the mass of the particles and of the energy levels. These changes are of relativistic origin and therefore small, but can be measured by use of a weak resonant laser field which produces cumulative effects in the time development of the wave function. The s…
Deformation of the proton emitterCs113from electromagnetic transition and proton-emission rates
2016
The lifetime of the $(11/{2}^{+})$ state in the band above the proton-emitting $(3/{2}^{+})$ state in $^{113}\mathrm{Cs}$ has been measured to be $\ensuremath{\tau}=24(6)$ ps from a recoil-decay-tagged differential-plunger experiment. The measured lifetime was used to deduce the deformation of the states using wave functions from a nonadiabatic quasiparticle model to independently calculate both proton-emission and electromagnetic $\ensuremath{\gamma}$-ray transition rates as a function of deformation. The only quadrupole deformation, which was able to reproduce the experimental excitation energies of the states, the electromagnetic decay rate of the $(11/{2}^{+})$ state and the proton-emis…