Variational Calculations of the 12C^{12}C Nucleus Structure in a 3α\alpha Model Using a Deep Potential with Forbidden States

The energy spectrum of the $^{12}C$ nucleus with $(J^{\pi}, T)=(0^+,0)$ and $(2^+,0)$ is investigated in the framework of the multicluster dynamical model by using a deep $\alpha \alpha$-potential with forbidden states in the S and D waves. A very high sensitivity of the compact ground and first excited $2^+_1$ states energy levels to the description of the two-body forbidden states wave functions has been estabilished. It is shown also that the chosen method of orthogonalizing pseudopotentials yields convergent results for the energies of the excited $(0^+_2,0)$ and $(0^+_3,0)$ states of the $^{12}C$ nucleus with a well developed cluster like structure

Dibaryon model for nuclear force and the properties of the 3N3N system

The dibaryon model for $NN$ interaction, which implies the formation of an intermediate six-quark bag dressed by a $\sigma$-field, is applied to the $3N$ system, where it results in a new three-body force of scalar nature between the six-quark bag and a third nucleon. A new multicomponent formalism is developed to describe three-body systems with nonstatic pairwise interactions and non-nucleonic degrees of freedom. Precise variational calculations of $3N$ bound states are carried out in the dressed-bag model including the new scalar three-body force. The unified coupling constants and form factors for $2N$ and $3N$ force operators are used in the present approach, in a sharp contrast to conventional meson-exchange models. It is shown that this three-body force gives at least half the $3N$ total binding energy, while the weight of non-nucleonic components in the $^3$H and $^3$He wavefunctions can exceed 10%. The new force model provides a very good description of $3N$ bound states with a reasonable magnitude of the $\sigma NN$ coupling constant. A new Coulomb $3N$ force between the third nucleon and dibaryon is found to be very important for a correct description of the Coulomb energy and r.m.s. charge radius in $^3$He. In view of the new results for Coulomb displacement energy obtained here for A=3 nuclei, an explanation for the long-term Nolen--Schiffer paradox in nuclear physics is suggested. The role of the charge-symmetry-breaking effects in the nuclear force is discussed.Comment: 64 pages, 7 figures, LaTeX, to be published in Phys. At. Nucl. (2005

Beam Test Results of the LHCb Electromagnetic Calorimeter.

The main properties of the LHCb electromagnetic calorimeter and a prototype of the monitoring system was studied at the X7 CERN test-beam facility. A dedicated MC simulation for light propagation in the scintillator tiles was developed and tuned with experimental data

Structure of the mirror nuclei 9^9Be and 9^9B in a microscopic cluster model

The structure of the mirror nuclei $^9$Be and $^9$B is studied in a microscopic $\alpha+ \alpha+ n$ and $\alpha+ \alpha+ p$ three-cluster model using a fully antisymmetrized 9-nucleon wave function. The two-nucleon interaction includes central and spin-orbit components and the Coulomb potential. The ground state of $^9$Be is obtained accurately with the stochastic variational method, while several particle-unbound states of both $^9$Be and $^9$B are investigated with the complex scaling method.The calculation for $^9$Be supports the recent identification for the existence of two broad states around 6.5 MeV, and predicts the $\frac{3}{2}^{-}_2$ and $\frac{5}{2}^{-}_2$ states at about 4.5 MeV and 8 MeV, respectively. The similarity of the calculated spectra of $^9$Be and $^9$B enables one to identify unknown spins and parities of the $^9$B states. Available data on electromagnetic moments and elastic electron scatterings are reproduced very well. The enhancement of the $E$1 transition of the first excited state in $^9$Be is well accounted for. The calculated density of $^9$Be is found to reproduce the reaction cross section on a Carbon target. The analysis of the beta decay of $^9$Li to $^9$Be clearly shows that the wave function of $^9$Be must contain a small component that cannot be described by the simple $\alpha+ \alpha+ n$ model. This small component can be well accounted for by extending a configuration space to include the distortion of the $\alpha$-particle to $t+p$ and $h+n$ partitions.Comment: 24 page

Design, construction, quality control and performance study with cosmic rays of modules for the LHCb electromagnetic calorimeter

Abstract This article addresses the design and construction of modules for the LHCb electromagnetic calorimeter. Quality control and preinstallation tests, including cells pre-calibration, are described and the results of light yield measurements are given

On suprathermal corrections to reaction rates in astrophysical plasmas

Reaction rates in astrophysical plasma can be affected by suprathermal particles naturally produced in the matter. The influence of this phenomenon on the relation between forward and reverse processes in extremely different astrophysical environments --the primordial and solar core plasmas-- is discussed. The suprathermal components of $d + d \rightleftarrows n + {}^3\mathrm{He}$ , $d + d \rightleftarrows p + t$ , $n + {}^3\mathrm{He} \rightleftarrows p + t$ , $n + {}^7\mathrm{Be} \rightleftarrows p + {}^7\mathrm{Li}$ , $p + {}^7\mathrm{Li} \rightleftarrows \alpha + \alpha$ , $n + {}^7\mathrm{Be} \rightleftarrows \alpha + \alpha$ , $\alpha + {}^6\mathrm{He} \rightleftarrows n + {}^9\mathrm{Be}$ , and $p + {}^{18}\mathrm{F} \rightleftarrows \alpha + {}^{15}\mathrm{O}$ reactions induced by MeV neutrons, protons, and $\alpha$ -particles are calculated and their role is clarified. In the primordial plasma, the reverse rates are partly determined by the suprathermal reactions capable of maintaining the processes as the Universe cools. It the solar core plasma, the reverse process $\alpha + {}^{15}\mathrm{O} \rightarrow p + {}^{18}\mathrm{F}$ is fully controlled by the suprathermal component, and its rate can become equal to the rate of the forward reaction in the outer core, that nullifies the straightforward nuclear flow between the CNO-I and CNO-III branches. This result together with previous findings on the suprathermal impact on running of the CNO-II branch may serve as an argument to incorporate suprathermal processes in nucleosynthesis calculations for stars fueled by the CNO cycle