Search results for "weak interaction"
showing 10 items of 431 documents
Global bounds on the Type-III Seesaw
2020
We derive general bounds on the Type-III Seesaw parameters from a global fit to flavor and electroweak precision data. We explore and compare three Type-III Seesaw realizations: a general scenario, where an arbitrary number of heavy triplets is integrated out without any further assumption, and the more constrained cases in which only 3 or 2 (minimal scenario) additional heavy states are included. The latter assumption implies rather non-trivial correlations in the Yukawa flavor structure of the model so as to reproduce the neutrino masses and mixings as measured in neutrino oscillations experiments and thus qualitative differences can be found with the more general scenario. In particular,…
High-resolution γ-ray spectroscopy: a versatile tool for nuclear β-decay studies at TRIUMF-ISAC
2005
High-resolution γ-ray spectroscopy is essential to fully exploit the unique, high-quality beams available at the next generation of radioactive ion beam facilities such as the TRIUMF isotope separator and accelerator (ISAC). The 8π spectrometer, which consists of 20 Compton-suppressed HPGe detectors, has recently been reconfigured for a vigorous research programme in weak interaction and nuclear structure physics. With the addition of a variety of ancillary detectors it has become the world's most powerful device dedicated to β-decay studies. This paper provides a brief overview of the apparatus and highlights from recent experiments.
Weak decay of Λ hypernuclei
1998
Abstract We review recent developments concerning the weak decay of Λ hypernuclei. New studies covering the mesonic decay channel as well as recent models for the non-mesonic one are discussed and compared with experimental data. The puzzle of the neutron- to proton-induced decay ratio, Γ n Γ p , is addressed in connection to the two-nucleon induced decay channel and proposals for more efficient experimental analyses of this ratio are made.
Search for new physics in beta-neutrino correlations with the WITCH spectrometer
2002
The WITCH (Weak Interaction Trap for CHarged particles) experiment is a retardation spectrometer coupled to a Penning trap and measures the beta-neutrino angular correlation via the shape of the recoil energy spectrum. The present form of the Standard Model describes weak processes in terms of vector and axial-vector type interactions, but the possible presence of scalar and tensor interactions is not yet ruled out. The main aim of this experiment is a test of the Standard Model for possible admixture of scalar and tensor currents. (C) 2002 Elsevier Science B.V. All rights reserved.
Measurements of relativistic time dilatation for positive and negative muons in a circular orbit
1977
The lifetimes of both positive and negative relativistic (γ = 29.33) muons have been measured in the CERN Muon Storage Ring with the results τ+ = 64.419 (58) µs, τ− = 64.368 (29) µs The value for positive muons is in accordance with special relativity and the measured lifetime at rest: the Einstein time dilation factor agrees with experiment with a fractional error of 2×10−3 at 95% confidence. Assuming special relativity, the mean proper lifetime for μ− is found to be τ0− = 2.1948(10) µs the most accurate value reported to date. The agreement of this value with previously measured values of τ0+ confirms CPT invariance for the weak interaction in muon decay.
Mass Spectrometry Using Paul Traps
2009
Mass is one of the basic quantities to characterize any material object, whether an atom, molecule, nucleus, or elementary particle. The measurement of mass therefore serves to detect and identify atomic, molecular, and nuclear species, and can help determine their structure and binding energy. For example, a precise determination of the mass of a nucleus is of importance through its binding energy, not only for various aspects of nuclear physics but also for other branches of physics, e.g. tests of the weak interaction, of quantum electrodynamics, and of the standard model [46]. Also in astrophysics the masses of unstable isotopes involved in stellar nucleosynthesis, especially the r proce…
REVIEW OF R MEASUREMENTS
2013
We review the status of R measurements in the energy range below 12 GeV, where recently a major progress has been achieved recently. These measurements are phenomenologically motivated by their impact on precision QCD and on electroweak parameters. We also report on improved results which can be expected in near future from presently running or upcoming facilities.
Inclusive quasielastic charged-current neutrino-nucleus reactions
2004
The Quasi-Elastic (QE) contribution of the nuclear inclusive electron scattering model developed in Nucl. Phys. A627 (1997) 543 is extended to the study of electroweak Charged Current (CC) induced nuclear reactions, at intermediate energies of interest for future neutrino oscillation experiments. The model accounts for, among other nuclear effects, long range nuclear (RPA) correlations, Final State Interaction (FSI) and Coulomb corrections. Predictions for the inclusive muon capture in $^{12}$C and the reaction $^{12}$C $(\nu_\mu,\mu^-)X$ near threshold are also given. RPA correlations are shown to play a crucial role and their inclusion leads to one of the best existing simultaneous descri…
Improved calculations of β decay backgrounds to new physics in liquid xenon detectors
2020
We present high-precision theoretical predictions for the electron energy spectra for the ground-state to ground-state β decays of 214Pb, 212Pb, and 85Kr most relevant to the background of liquid xenon dark matter detectors. The effects of nuclear structure on the spectral shapes are taken into account using large-scale shell-model calculations. Final spectra also include atomic screening and exchange effects. The impact of nuclear structure effects on the 214Pb and 212Pb spectra below ≈100 keV, pertinent for several searches for new physics, are found to be comparatively larger than those from the atomic effects alone. We find that the full calculation for 214Pb (212Pb) predicts 15.0%–23.2…
VBFNLO: A parton level Monte Carlo for processes with electroweak bosons
2009
VBFNLO is a fully flexible parton level Monte Carlo program for the simulation of vector boson fusion, double and triple vector boson production in hadronic collisions at next-to-leading order in the strong Coupling constant. VBFNLO includes Higgs and vector boson decays with full spin correlations and all off-shell effects. In addition, VBFNLO implements CP-even and CP-odd Higgs boson via gluon fusion, associated with two jets, at the leading-order one-loop level with the full top- and bottom-quark mass dependence in a generic two-Higgs-doublet model. A variety of effects arising from beyond the Standard Model physics are implemented for selected processes. This includes anomalous coupling…