Description of nuclear octupole and quadrupole deformation close to the axial symmetry: Octupole vibrations in the X(5) nuclei 150Nd and 152Sm

The model, introduced in a previous paper, for the description of the octupole and quadrupole degrees of freedom in conditions close to the axial symmetry, is used to describe the negative-parity band based on the first octupole vibrational state in nuclei close to the critical point of the U(5) to SU(3) phase transition. The situation of 150Nd and 152Sm is discussed in detail. The positive parity levels of these nuclei, and also the in-band E2 transitions, are reasonably accounted for by the X(5) model. With simple assumptions on the nature of the octupole vibrations, it is possible to describe, with comparable accuracy, also the negative parity sector, without changing the description of the positive-parity part.Comment: 8 pages, 5 figure

New results from NA48 experiment on neutral kaon rare decays

Recent results by the NA48 collaboration on neutral kaons rare decays into the pi+ pi- e+ e- final state are presented. A large CP-violating asymmetry A(K_L)=(13.9+-2.7+-2.0)% has been observed in the K_L to pi+ pi- e+ e- decay. The K_S to pi+ pi- e+ e- decay has been observed for the first time, showing no such asymmetry.Comment: 6 pages, 5 figures, LaTeX. To be published in the Proceedings of the 30th International Symposium on Multiparticle Dynamics (ISMD 2000), Tihany, Lake Balaton, Hungary, 9-15 Oct 200

Description of nuclear octupole and quadrupole deformation close to the axial symmetry and phase transitions in the octupole mode

The dynamics of nuclear collective motion is investigated in the case of reflection-asymmetric shapes. The model is based on a new parameterization of the octupole and quadrupole degrees of freedom, valid for nuclei close to the axial symmetry. Amplitudes of oscillation in other degrees of freedom different from the axial ones are assumed to be small, but not frozen to zero. The case of nuclei which already possess a permanent quadrupole deformation is discussed in some more detail and a simple solution is obtained at the critical point of the phase transition between harmonic octupole oscillation and a permanent asymmetric shape. The results are compared with experimental data of the Thorium isotopic chain. The isotope Th-226 is found to be close to the critical point.Comment: 17 pages, 5 figures, 8 tables; 3 new references added, misprints correcte

Description of nuclear octupole and quadrupole deformation close to the axial symmetry: Critical-point behavior of 224Ra and 224Th

The model, introduced in a previous paper, for the description of the octupole and quadrupole degrees of freedom in conditions close to the axial symmetry, is applied to situations of shape phase transitions where the quadrupole amplitude can reach zero. The transitional nuclei 224,226Ra and 224Th are discussed in the frame of this model. Their level schemes can be reasonably accounted for assuming a square-well potential in two dimensions. Electromagnetic transition amplitudes are also evaluated and compared with existing experimental data.Comment: 11 pages, 9 figure

Transition probabilities in the X(5) candidate 122^{122}Ba

To investigate the possible X(5) character of 122Ba, suggested by the ground state band energy pattern, the lifetimes of the lowest yrast states of 122Ba have been measured, via the Recoil Distance Doppler-Shift method. The relevant levels have been populated by using the 108Cd(16O,2n)122Ba and the 112Sn(13C,3n)122Ba reactions. The B(E2) values deduced in the present work are compared to the predictions of the X(5) model and to calculations performed in the framework of the IBA-1 and IBA-2 models

Rigurgito mitralico e tricuspidale diastolico in due cani con blocco atrioventricolare completo spontaneo

RIASSUNTO Il rigurgito diastolico attraverso entrambe le valvole atrioventricolari è un rilievo ecocardiografico di frequente riscontro in corso di blocco atrioventricolare completo sia nel cane che nell’uomo. L’entità del rigurgito sia mitralico che tricuspidale è lieve e tale da non risultare significativo dal punto di vista emodinamico. La diagnosi può essere emessa sia con l’ausilio del doppler a codice di colore che con il doppler spettrale. Il jet origina dal punto di coaptazione dei lembi valvolari ed è diretto centralmente. Ciononostante, date le piccole dimensioni del jet di rigurgito, l’impiego combinato delle due metodiche può essere di aiuto nel posizionamento del volume campione e nell’allineamento del doppler. L’assenza di contrazione ventricolare a seguito della contrazione atriale comporta un reflusso di sangue all’interno delle cavità atriali presumibilmente come conseguenza di un’inversione del gradiente pressorio intercorrente tra gli atri e i ventricoli nonché della chiusura incompleta delle valvole atrioventricolari. La presenza di insufficienza valvolare e quindi di rigurgito sistolico non è un prerequisito necessario allo sviluppo di reflusso diastolico in corso di blocco atrioventricolare completo. SUMMARY Atrioventricular valvular regurgitation is a common echocardiographic finding in both dogs and humans with complete atrioventricular block. The severity of both mitral and tricuspid regurgitation is mild and hemodynamically non significant. The condition can be easily diagnosed by means of either color-flow doppler and spectral doppler. The jet originates from the site of coaptation of valvular leaflets and is centrally directed. Nevertheless, because of the limited size of the regurgitant jet, the combined use of color-flow and spectral doppler can help in placing the sample gate and align for the doppler study. Lack of ventricular contraction following atrial contraction leads to reflux of blood into the atrial cavities, presumably due to atrioventricular pressure gradient reversal and incomplete closure of the mitral valve. The presence of valvular insufficiency and consequent systolic regurgitation is not a prerequisite for diastolic reflux to occur in case of complete atrioventricular block

First order shape transition and critical point nuclei in Sm isotopes from relativistic mean field approach

The critical point nuclei in Sm isotopes, which marks the first order phase transition between spherical U(5) and axially deformed shapes SU(3), have been investigated in the microscopic quadrupole constrained relativistic mean field (RMF) model plus BCS method with all the most used interactions, i.e., NL1, NL3, NLSH and TM1. The calculated potential energy surfaces show a clear shape transition for the even-even Sm isotopes with $N = 82\sim 96$ and the critical point nuclei are found to be $^{148}$Sm, $^{150}$Sm and $^{152}$Sm. Similar conclusions can also be drawn from the microscopic neutron and proton single particle spectra.Comment: 6 figure

First results from an aging test of a prototype RPC for the LHCb Muon System

Recent results of an aging test performed at the CERN Gamma Irradiation Facility on a single--gap RPC prototype developed for the LHCb Muon System are presented. The results are based on an accumulated charge of about 0.45 C/cm$^2$, corresponding to about 4 years of LHCb running at the highest background rate. The performance of the chamber has been studied under several photon flux values exploiting a muon beam. A degradation of the rate capability above 1 kHz/cm$^2$ is observed, which can be correlated to a sizeable increase of resistivity of the chamber plates. An increase of the chamber dark current is also observed. The chamber performance is found to fulfill the LHCb operation requirements.Comment: 6 pages, 9 figures, presented at the International Workshop on Aging Phenomena in Gaseous Detectors'', DESY-Hamburg (Germany), October 200