|Vud| from T = 1/2 mirror transitions and the role of atom and ion traps

Precision correlation measurements in nuclear beta decay using atom and ion traps have made significant progress since the last ENAM2004 Conference. We review here the achievements and plans of different projects and discuss for each of them their potential to contribute to the determination of the Vud element of the Cabibbo-Kobayashi-Maskawa quark mixing matrix. This matrix element has traditionally been determined from the analysis of data in nuclear superallowed 0+ → 0+ transitions, neutron decay and pion beta decay but can also independently be determined from data in nuclear mirror transitions. This requires the measurement of correlation parameters in such decays to determine the Gamow-Teller to Fermi mixing ratio which, in most cases, dominates the error on the extracted value of |Vud|.status: publishe

Description of magnetic moments of long isotopic chains within the FFS theory

Dipole magnetic moments of several long isotopic chains are analyzed within the self-consistent finite Fermi system theory with exact account for the pairing and quasiparticle continuum. The momentum dependence of the spin-isospin Landau-Migdal amplitude g' is taken into account. This dependence was introduced previously to describe high-energy electron magnetic scattering. New moment data for nuclei far from the beta-stability valley are included in the analysis. For a number of semi-magic isotopes of the tin and lead chains a good description of the data is obtained, with an accuracy of 0.1-0.2 mu N. A chain of non-magic isotopes of copper is also analyzed in detail.status: publishe

Search for radiative beta-decay of the free neutron

Results of the first experiment to search for the radiative decay mode of the free neutron are reported. The gamma-spectrum was studied in the energy region from 35 keV to 100 keV in six Cs(T1) scintillators, each set at an angle of 35 to, and shielded from, a central plastic scintillator electron detector. Triple coincidences were recorded with recoil protons detected in a micro-channel plate. A limit for the branching ratio BR <6.9x10(-3) (90% confidence level) was obtained, which is greater that the theoretical prediction by not more than a few tenths of a percent.status: publishe

The upper limit of the branching ratio for radiative beta decay of free neutrons

We conducted an experiment on radiative neutron beta decay on an intensive cold-neutron beam at ILL during April and May 2002. This work is dedicated to the analysis of the methodology and the results of the study. The main outcome of this experiment is the branching ratio (BR) for the rare neutron-decay mode in the gamma-ray quanta energy region from 35 to 100 keV. The limit obtained is BR < 6.9 x 10(-3) (90% C.L.), which is only a few permilles greater than the theoretical BR value calculated within the standard weak-interactions model. (C) 2002 MAIK "Nauka / Interperiodica".status: publishe

WITCH: Testing the Standard Model using a beta recoil spectrometer with a trapped ion cloud as source

The combination of a zero thickness source of β radioactivity, consisting of an ion-cloud in a Penning trap, with a retardation spectrometer has for the first time allowed the construction of a set-up that can measure the β recoil spectrum of any nucleus. This opens a number of severely hampered areas of study, such as lepton angular correlations and charge state distributions after β-decay. The former allows extraction of Standard Model violating S and T contributions to the weak interaction. An overview of the set-up is given in this presentation.status: publishe

Measurement of the transverse polarization of electrons emitted in neutron decay:A searchfor weak exotic couplings

First results are presented from an experiment that aims at the simultaneous determination of both transversal polarization components of electrons emitted in the decay of free neutrons — two observables that have never before been addressed experimentally. Preliminary results of the data analysis of these measurements of the R and N correlation coefficients are presented.status: publishe

Search for Exotic Couplings in Neutron Decay: A Measurement of the Transverse Polarization of Electrons

First results are presented from an experiment that aims at the simultaneous determination of both transversal polarization components of electrons emitted in the decay of free neutrons – two observables that have never before been addressed experimentally. They reveal first-order sensitivity to real and imaginary parts of the exotic scalar and tensor interactions.status: publishe

Fast controls for the WITCH Penning trap radioactive source experiment

The WITCH experiment will for the first time use a dedicated Penning trap as a radioactive source. By combining this with a retardation spectrometer, general access is opened to the β-recoil energy observable, which allows, e.g. to test the validity of the V-A form of the weak interaction. A system of specialized electronics with accompanying networked software control system has been developed for WITCH. Herein is given a short overview of the general control system and details about the electronic as well as software components special for the fast control of this Penning-trap-plus-spectrometer set-up.status: publishe

BRAND – Search for BSM physics at TeV scale by exploring transverse polarization of electrons emitted in neutron decay

Neutron and nuclear beta decay correlation coefficients are linearly sensitive to the exotic scalar and tensor interactions that are not included in the Standard Model (SM). The proposed experiment will measure simultaneously 11 neutron correlation coefficients (a, A, B, D, H, L, N, R, S, U, V) where 7 of them (H, L, N, R, S, U, V) depend on the transverse electron polarization – a quantity that vanishes for the SM weak interaction. The neutron decay correlation coefficients H, L, S, U, V were never attempted experimentally before. The expected ultimate sensitivity of the proposed experiment that currently takes off on the cold neutron beamline PF1B at the Institut Laue-Langevin, Grenoble, France, is comparable to that of the planned electron spectrum shape measurements in neutron and nuclear β decays but offers completely different systematics and additional sensitivity to imaginary parts of the scalar and tensor couplings.status: publishe

WITCH: a recoil spectrometer for weak interaction and nuclear physics studies

An experimental set-up is described for the precise measurement of the recoil energy spectrum of the daughter ions from nuclear beta decay. The experiment is called WITCH, short for Weak Interaction Trap for CHarged particles, and is set up at the ISOLDE facility at CERN. The principle of the experiment and its realization are explained as well as the main physics goal. A cloud of radioactive ions stored in a Penning trap serves as the source for the WITCH experiment, leading to the minimization of scattering and energy loss of the decay products. The energy spectrum of the recoiling daughter ions from the β-decays in this ion cloud will be measured with a retardation spectrometer. The principal aim of the WITCH experiment is to study the electroweak interaction by determining the beta-neutrino angular correlation in nuclear β-decay from the shape of this recoil energy spectrum. This will be the first time that the recoil energy spectrum of the daughter ions from β-decay can be measured for a wide variety of isotopes, independent of their specific properties.status: publishe