Search results for "weak interaction"
showing 10 items of 431 documents
A full picture of large lepton number asymmetries of the Universe
2017
A large lepton number asymmetry of (0.1−1) at present Universe might not only be allowed but also necessary for consistency among cosmological data. We show that, if a sizeable lepton number asymmetry were produced before the electroweak phase transition, the requirement for not producing too much baryon number asymmetry through sphalerons processes, forces the high scale lepton number asymmetry to be larger than about 03. Therefore a mild entropy release causing (10-100) suppression of pre-existing particle density should take place, when the background temperature of the Universe is around T = (10−2-102) GeV for a large but experimentally consistent asymmetry to be present today. We also …
Low-energy signals of strongly-coupled electroweak symmetry-breaking scenarios
2015
The non-observation of new particles at the LHC suggests the existence of a mass gap above the electroweak scale. This situation is adequately described through a general electroweak effective theory with the established fields and Standard Model symmetries. Its couplings contain all information about the unknown short-distance dynamics which is accessible at low energies. We consider a generic strongly-coupled scenario of electroweak symmetry breaking, with heavy states above the gap, and analyze the imprints that its lightest bosonic excitations leave on the effective Lagrangian couplings. Different quantum numbers of the heavy states imply different patterns of low-energy couplings, with…
Integrating out resonances in strongly-coupled electroweak scenarios
2016
Accepting that there is a mass gap above the electroweak scale, the Electroweak Effective Theory (EWET) is an appropriate tool to describe this situation. Since the EWET couplings contain information on the unknown high-energy dynamics, we consider a generic strongly-coupled scenario of electroweak symmetry breaking, where the known particle fields are coupled to heavier states. Then, and by integrating out these heavy fields, we study the tracks of the lightest resonances into the couplings. The determination of the low-energy couplings (LECs) in terms of resonance parameters can be made more precise by considering a proper short-distance behaviour on the Lagrangian with heavy states, sinc…
Higgs-boson radiative corrections to the decayS13(QQ¯)→Hγ
1988
We consider one-loop radiative corrections to the Wilczek mechanism (/sup 3/S/sub 1/(QQ-bar)..-->..H..gamma..) due to a subset of the electroweak theory, the Higgs sector, in the standard model and discuss extensions to two-Higgs-doublet models. We discuss the circumstances under which such corrections can be important.
Violation of matter-antimatter symmetry
2001
A small matter-antimatter asymmetry of the weak force was experimentally established. This CP violation may be related to the small excess of matter from the big bang. The nature of CP violation in the K0 system has been clarified after 35 years of experimentation: it is due to a small part of the weak interaction (“milliweak interaction”). A non-trivial phase in the weak quark mixing matrix generates “direct CP violation” in the weak Hamiltonian. The experiments demonstrating direct CP violation are discussed.
Observation of direct CP violation in kaon decays
2019
A small matter-antimatter asymmetry of the weak force was experimentally established. This CP violation may be related to the small excess of matter from the big bang. The nature of CP violation in the K0 system has been clarified after 37 years of experimentation: it is due to a small part of the weak interaction (“milliweak interaction”). A non-trivial phase in the weak quark mixing matrix generates “direct CP violation” in the weak Hamiltonian. The experiments demonstrating direct CP violation are discussed.
CP Violation in the K 0 System
2002
A small matter-antimatter asymmetry of the weak force was experimentally established. This CP violation may be related to the small excess of matter from the big bang. The nature of CP violation in the K 0 system has been clarified after 35 years of experimentation: it is due to a small part of the weak interaction (“illiweak interaction”). A non-trivial phase in the weak quark mixing matrix generates “direct CP violation” in the weak Hamiltonian. The experiments demonstrating direct CP violation are discussed.
Observability of the Neutrino Charge Radius
2002
It is shown that the probe-independent charge radius of the neutrino is a physical observable; as such, it may be extracted from experiment, at least in principle. This is accomplished by expressing a set of experimental ${\ensuremath{\nu}}_{\ensuremath{\mu}}\mathrm{\text{\ensuremath{-}}}e$ cross sections in terms of the finite charge radius and two additional gauge- and renormalization-group-invariant quantities, corresponding to the electroweak effective charge and mixing angle.
Lattice QCD calculation of the electroweak box diagrams for the kaon semileptonic decays
2021
We present a lattice QCD calculation of the axial $\gamma W$-box diagrams relevant for the kaon semileptonic decays. We utilize a recently proposed method, which connects the electroweak radiative corrections in Sirlin's representation to that in chiral perturbation theory. It allows us to use the axial $\gamma W$-box correction in the SU(3) limit to obtain the low energy constants for chiral perturbation theory. From first principles our results confirm the previously used low energy constants provided by the minimal resonance model with a significant reduction in uncertainties.
Weak pion production off the nucleon in covariant chiral perturbation theory
2018
Weak pion production off the nucleon at low energies has been systematically investigated in manifestly relativistic baryon chiral perturbation theory with explicit inclusion of the $\Delta$(1232) resonance. Most of the involved low-energy constants have been previously determined in other processes such as pion-nucleon elastic scattering and electromagnetic pion production off the nucleon. For numerical estimates, the few remaining constants are set to be of natural size. As a result, the total cross sections for single pion production on neutrons and protons, induced either by neutrino or antineutrino, are predicted. Our results are consistent with the scarce existing experimental data ex…