305 research outputs found
Determination of |Vud| from nuclear mirror transitions
The Vud element of the Cabibbo-Kobayashi-Maskawa quark mixing matrix has
traditionally been determined from the analysis of data in nuclear superallowed
0+ to 0+ transitions, neutron decay and pion beta decay. We show here that this
element can independently be determined from nuclear mirror transitions. The
extracted value, |Vud| = 0.9719 +- 0.0017, is at 1.2 combined standard
deviations from the value obtained in superallowed 0+ to 0+ transitions and has
a similar precision than the value obtained from neutron decay experiments. We
discuss some prospects to improve its precision through experiments in nuclear
mirror transitions.Comment: 4 pages, 2 figure
Precision measurements in nuclear {\beta}-decay with LPCTrap
The experimental achievements and the current program with the LPCTrap device
installed at the LIRAT beam line of the SPIRAL1-GANIL facility are presented.
The device is dedicated to the study of the weak interaction at low energy by
means of precise measurements of the {\beta}-{\nu} angular correlation
parameter. Technical aspects as well as the main results are reviewed. The
future program with new available beams is briefly discussed.Comment: Annalen der Physik (2013
Tests of the standard electroweak model in beta decay
We review the current status of precision measurements in allowed nuclear beta decay, including neutron decay, with emphasis on their potential to look for new physics beyond the standard electroweak model. The experimental results are interpreted in the framework of phenomenological model-independent descriptions of nuclear beta decay as well as in some specific extensions of the standard model. The values of the standard couplings and the constraints on the exotic couplings of the general beta decay Hamiltonian are updated. For the ratio between the axial and the vector couplings we obtain C_A/C_V = -1.26992(69) under the standard model assumptions. Particular attention is devoted to the discussion of the sensitivity and complementarity of different precision experiments in direct beta decay. The prospects and the impact of recent developments of precision tools and of high intensity low energy beams are also addressed
Measurement of the Michel Parameter xi" in Polarized Muon Decay and Implications on Exotic Couplings of the Leptonic Weak Interaction
The Michel parameter xi" has been determined from a measurement of the
longitudinal polarization of positrons emitted in the decay of polarized and
depolarized muons. The result, xi" = 0.981 +- 0.045stat +- 0.003syst, is
consistent with the Standard Model prediction of unity, and provides an order
of magnitude improvement in the relative precision of this parameter. This
value sets new constraints on exotic couplings beyond the dominant V-A
description of the leptonic weak interaction.Comment: 15 pages, 16 figures, 3 tables; submitted to Phys. Rev.
Measurement of the Transverse Polarization of Electrons Emitted in Free Neutron Decay
Both components of the transverse polarization of electrons emitted in the
beta-decay of polarized, free neutrons have been measured. The T-odd, P-odd
correlation coefficient quantifying the component perpendicular to the decay
plane defined by neutron polarization and electron momentum, was found to be
R=0.008 +/- 0.015 +/-0.005. This value is consistent with time reversal
invariance, and significantly improves limits on the relative strength of
imaginary scalar couplings in the weak interaction. The value obtained for the
correlation coefficient associated with the electron polarization component
contained within the decay plane N=0.056 +/- 0.011 +/- 0.005, agrees with the
Standard Model expectation, providing an important sensitivity test of the
experimental setup.Comment: 4 pages, 4 figure
Measurement of Transverse Polarization of Electrons Emitted in Free Neutron Decay
The final analysis of the experiment determining both components of the
transverse polarization of electrons (, )
emitted in the -decay of polarized, free neutrons is presented. The
T-odd, P-odd correlation coefficient quantifying ,
perpendicular to the neutron polarization and electron momentum, was found to
be 0.0040.005. This value is consistent with time reversal
invariance, and significantly improves both earlier result and limits on the
relative strength of imaginary scalar couplings in the weak interaction. The
value obtained for the correlation coefficient associated with
, 0.0670.004, agrees with the Standard Model
expectation, providing an important sensitivity test of the experimental setup.
The present result sets constraints on the imaginary part of scalar and tensor
couplings in weak interaction. Implications for parameters of the leptoquark
exchange model and minimal supersymmetric model (MSSM) with R-parity violation
are discussed
Free neutron decay and time reversal violation
Both components of the transverse electron polarization have been measured in free neutron decay. The T-odd, P-odd correlation coefficient associated with polarization component perpendicular to the neutron polarization
and electron momentum, was found to be R = 0:006 0:012 0:005. This value is consistent with time reversal invariance, and significantly improves limits on the relative strength of imaginary scalar couplings in the
weak interaction. The value obtained for the T-even, P-even correlation coefficient connected with the second transversal polarization component, N = 0:065 0:012 0:004, agrees with the Standard Model expectation
providing an important sensitivity test of the experimental setup
Transport and cooling of singly-charged noble gas ion beams
The transport and cooling of noble gas singly-charged ion beams by means of a
Radio Frequency Quadrupole Cooler Buncher (RFQCB) have been studied at the
LIMBE low energy beam line of the GANIL facility. Ions as light as
have been cooled and stored before their extraction in bunches using as
buffer gas. Bunches characteristics have been studied as a function of the
parameters of the device. Sizeable transmissions of up to 10 have been
obtained. A detailed study of the lifetime of ions inside the buncher has been
performed giving an estimate of the charge exchange cross-section. Results of a
microscopic Monte-Carlo transport code show reasonable agreement with
experimental data.Comment: 13 figure
Weak Interaction Studies with 6He
The 6He nucleus is an ideal candidate to study the weak interaction. To this
end we have built a high-intensity source of 6He delivering ~10^10 atoms/s to
experiments. Taking full advantage of that available intensity we have
performed a high-precision measurement of the 6He half-life that directly
probes the axial part of the nuclear Hamiltonian. Currently, we are preparing a
measurement of the beta-neutrino angular correlation in 6He beta decay that
will allow to search for new physics beyond the Standard Model in the form of
tensor currents.Comment: 5 pages, 4 figures, proceedings for the Eleventh Conference on the
Intersections of Particle and Nuclear Physics (CIPANP 2012
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