Table of contents

The XXXVI Symposium on Nuclear Physics, organized by the Division of Nuclear Physics of the Mexican Physical Society, took place from 7–10 January, 2013. As it is customary, the Symposium was held at the Hotel Hacienda Cocoyoc, in the state of Morelos, Mexico.

This international venue with many years of tradition was attended by outstanding physicists, some of them already regulars to this meeting and others who joined us for the first time; a total of 45 attendees from different countries (Argentina, Brazil, Canada, China, Germany, Italy, Japan, Mexico and the United States). A variety of topics related to nuclear physics (nuclear reactions, radioactive beams, nuclear structure, fundamental neutron physics, sub-nuclear physics and nuclear astrophysics, among others) were presented in 26 invited talks and 10 contributed posters.

Local Organizing Committee

Libertad Barrón-Palos (IF-UNAM)) Enrique Martínez-Quíroz (ININ)) Irving Morales-Agiss (ICN-UNAM))

International Advisory Committee

Osvaldo Civitarese (UNLP, Argentina) Jerry P Draayer (LSU, USA)) Alfredo Galindo-Uribarri (ORNL, USA)) Paulo Gomes (UFF, Brazil)) Piet Van Isacker (GANIL, France)) James J Kolata (UND, USA)) Reiner Krücken (TRIUMF, Canada)) Jorge López (UTEP, USA)) Stuart Pittel (UD, USA)) W Michael Snow (IU, USA)) Adam Szczepaniak (IU, USA)) Michael Wiescher (UND, USA)) A list of participants is available in the PDF

All papers published in this volume of Journal of Physics: Conference Series have been peer reviewed through processes administered by the proceedings Editors. Reviews were conducted by expert referees to the professional and scientific standards expected of a proceedings journal published by IOP Publishing.

In this paper an overview of different results concerning elastic scattering in collisions induced by halo nuclei will be given. Due to the very low binding energy of such nuclei, coupling effects with the break-up channel have been found to be very important. Moreover, due to the long tail of the density distribution of halo nuclei and the presence of a large low-lying dipole strength distribution, long range absorption affects the elastic scattering angular distribution. In the paper the main effects responsible for the observed features in the scattering cross-section will be discussed.

Recent near-barrier measurements for fusion of the proton-halo system ⁸B + ⁵⁸Ni (Aguilera E F et al. 2011 Pys. Rev. Lett.107 092701) showed unexpected results. In contrast to previous results for neutron-halo systems, for instance, the respective fusion cross sections are enhanced for both, below- and above-barrier energies. The charged nature of the halo could thus have an effect on the fusion mechanism. Within this context, in the present work the fusion cross sections for several proton rich systems are compared to each other. Three of these systems correspond to the same target, ⁵⁸Ni (with projectiles of ³He, ⁷Be, and ⁸B), but data for ¹⁷F + ²⁰⁸Pb also are included. All these projectiles lie near the proton drip line. An appropriate scaling of the data is made to do the comparison and the results are discussed.

A fusion excitation function for the ⁸B+⁵⁸Ni proton-halo system at near Coulomb barrier energies was recently published (Aguilera E F et al. 2011 Phys. Rev. Lett.107 092701). The respective fusion cross sections (σ_fus) were determined from the integrated cross sections for the evaporated protons (σ_p), by using proton multiplicities (M_p) calculated with the code PACE. In this code, the transmission coefficients T_l are calculated only for the compound-nucleus values of A and Z and an extrapolation is then made for subsequent decays. In the present work, the reliability of the whole procedure is further investigated both, by studying the effect of variations in the input parameters to PACE and by computing the M_p values with the alternate code LILITA. An explicit calculation of all necessary transmission coefficients is made in the latter code.

We discuss interesting questions and results concerned with reactions involving weakly bound nuclei at near barrier energies, particularly fusion, breakup, transfer and scattering. We concentrate in the presentation and discussion of recent results, and so we try to give a sort of state of art of this field at the present.

A brief description is presented of the results obtained in recent years for the simultaneous analysis of elastic and fusion cross section data of nuclear reactions for several nuclear systems with weakly bound and halo projectiles. The method used in this description, consists of simultaneously determine the parameters of fusion U_F and direct reaction U_DR polarization potentials of Woods-Saxon geometric shapes, that fit the elastic and fusion data. As a matter of fact, U_Fis an energy dependent potential, with real V_F and imaginary W_Fcomponents, that is responsible for fusion reactions. Similarly, U_DR is also energy dependent with real V_DR and imaginary W_DR parts, that accounts for direct reactions. A general finding for all the systems presented is that, the real and imaginary parts of the fusion potential and direct reaction potentials, are related by a dispersion relation and their energy dependence around and below the Coulomb barrier, show the so-called Breakup Threshold Anomaly. The effect of breakup reactions on fusion cross sections is studied by analyzing the separate effect of the absorption potential W_DR and the fusion barrier rising produced by V_DR.

A preliminary study of the ¹²C + ¹²C sub-Coulomb fusion reaction using the time-dependent wave-packet method is presented. The theoretical sub-Coulomb fusion resonances seem to correspond well with observations. The present method might be a more suitable tool for expanding the cross-section predictions towards lower energies than the commonly used potential-model approximation.

In this work we report on the cosmological ⁷Li problem, from a nuclear structure point of view, that is by including resonances in the calculation of the reactions which populate beryllium. It is found that the primordial abundance of lithium is reduced, as a consequence of the presence of resonant channels in the relevant cross sections. We establish constraints on the resonant energies, and make a comparison with the available observational data.

Laboratory experiments sensitive to the density dependence of the symmetry energy may place stringent constraints on the equation of state of neutron-rich matter and, thus, on the structure, dynamics, and composition of neutron stars. Understanding the equation of state of neutron-rich matter is a central goal of nuclear physics that cuts across a variety of disciplines. In this contribution I focus on how laboratory experiments on neutron skins and on both Pygmy and Giant resonances can help us elucidate the structure of neutron stars.

I discuss an algebraic treatment of alpha-cluster nuclei in the framework of the Algebraic Cluster Model. It is suggested to treat ¹²C as an oblate top with symmetry (equilateral triangle) and ¹⁶O as a spherical top with tetrahedral symmetry (regular tetrahedron). The structure of the rotational bands is a consequence of the underlying symmetry, and can be used to help determine the geometrical configuration of the α-particles.

A new windowless gas target has been developed in Mexico. It is a supersonic gas jet flow produced inside a vacuum chamber which can be coupled to a regular beam line in an accelerator laboratory as a differential pumping system brings the pressure of the gas target system down to a microTorr, or better, at the connecting stage.

In this work, we present the system as it was designed and constructed as well as the first results using air, Nitrogen and Argon.

A common problem in the statistical characterization of the excitation spectrum of quantum systems is the adequate separation of global system-dependent properties from the local fluctuations that are universal. In this process, called unfolding, the functional form to describe the global behaviour is often imposed externally on the data and can introduce arbitrarities in the statistical results. In this contribution, we show that a quantum excitation spectrum can readily be interpreted as a time series, before any previous unfolding. An advantage of the time-series approach is that specialized methods such as Singular Spectrum Analysis (SSA) can be used to perform the unfolding procedure in a data-adaptive way. We will show how SSA separates the components that describe the global properties from the components that describe the local fluctuations. The partial variances, associated with the fluctuations, follow a definite power law that distinguishes between soft and rigid excitation spectra. The data-adaptive fluctuation and trend components can be used to reconstruct customary fluctuation measures without ambiguities or artifacts introduced by an arbitrary unfolding, and also define the global level density of the excitation spectrum. The method is applied to nuclear shell-model calculations for ⁴⁸Ca, using a realistic force and Two-Body Random Ensemble (TBRE) interactions. We show that the statistical results are very robust against a variation in the parameters of the SSA method.

We calculate numerically the fidelity and its susceptibility for the ground state of the Dicke model. A minimum in the fidelity identifies the critical value of the interaction where a quantum phase crossover, the precursor of a phase transition for finite number of atoms , takes place. The evolution of these observables is studied as a function of , and their critical exponents evaluated. Using the critical exponents the universal curve for the specific susceptibility is recovered. An estimate to the precision to which the ground state wave function is numerically calculated is given, and found to have its lowest value, for a fixed truncation, in a vicinity of the critical coupling.

Originally introduced in nuclear physics as a numerical laboratory to test different many-body approximation methods, the Lipkin-Meshkov-Glick (LMG) model has received much attention as a simple enough but non-trivial model with many interesting features for areas of physics beyond the nuclear one. In this contribution we look at the LMG model as a particular example of an SU(1,1) Richardson-Gaudin model. The characteristics of the model are analyzed in terms of the behavior of the spectral-parameters or pairons which determine both eigenvalues and eigenfunctions of the model Hamiltonian. The problem of finding these pairons is mathematically equivalent to obtain the equilibrium positions of a set of electric charges moving in a two dimensional space. The electrostatic problems for the different regions of the model parameter space are discussed and linked to the different energy density of states already identified in the LMG spectrum.

We have developed multi-dimensional constrained covariant density functional theories (MDC-CDFT) for finite nuclei in which the shape degrees of freedom β_λμ with even μ, e.g., β₂₀, β₂₂, β₃₀, β₃₂, β₄₀, etc., can be described simultaneously. The functional can be one of the following four forms: the meson exchange or point-coupling nucleon interactions combined with the non-linear or density-dependent couplings. For the pp channel, either the BCS approach or the Bogoliubov transformation is implemented. The MDC-CDFTs with the BCS approach for the pairing (in the following labelled as MDC-RMF models with RMF standing for "relativistic mean field") have been applied to investigate multi-dimensional potential energy surfaces and the non-axial octupole Y₃₂-correlations in N = 150 isotones. In this contribution we present briefly the formalism of MDC-RMF models and some results from these models. The potential energy surfaces with and without triaxial deformations are compared and it is found that the triaxiality plays an important role upon the second fission barriers of actinide nuclei. In the study of Y₃₂-correlations in N = 150 isotones, it is found that, for ²⁴⁸Cf and ²⁶⁰Fm, β₃₂ > 0.03 and the energy is lowered by the β₃₂ distortion by more than 300 keV; while for ²⁴⁶Cm and ²⁵²No, the pocket with respect to β₃₂ is quite shallow.

A detailed analysis of a minimal S₃-invariant extension of the Standard Model including an extended S₃-Higgs sector is performed. In this model, we study the trilinear Higgs couplings and its dependence on the details of the model, even when the lightest Higgs boson mass is taken to be a fixed parameter. We study quantitatively the trilinear Higgs couplings, and compare these couplings to the corresponding Standard Model trilinear Higgs coupling in some regions of the parameter space. A precise measurement of the trilinear Higgs self coupling will also make it possible to test this extended S(3)-Standard Model which has a different trilinear Higgs couplings as compared to the Standard Model. Finally, partial numerical results of the phenomenological Higgs effects are presented.