Search results for "weak interaction"
showing 10 items of 431 documents
Neutrino induced coherent pion production off nuclei and the partial conservation of the axial current
2009
15 pages, 7 figures, 1 table.-- PACS nrs.: 25.30.Pt; 12.15.-y; 13.15.+g.-- ArXiv pre-print available at: http://arxiv.org/abs/0903.5285
Production mechanisms and signatures of isosinglet neutral heavy leptons in Z0 decays
1990
Abstract Neutral Heavy Leptons (NHLs) arise in many extensions of the standard electroweak theory such as superstring inspired models. The possibility of gauge singlets NHLs is especially attractive because it gives an explanation for the observed smallness of the neutrino mass. Existing limits on the possible existence of such particles are still fairly poor. We have investigated isosinglet NHL production and decays within different models. The dominant production cross section is single production (i.e. Z 0 → N + ν or Z 0 → N + ν ) as a result of mixing with the standard doublet neutrinos. Subsequent NHL decays lead to striking signatures. Taking into account the expected luminosities and…
Effects of Strong and Electromagnetic Correlations on Neutrino Interactions in Dense Matter
1998
An extensive study of the effects of correlations on both charged and neutral current weak interaction rates in dense matter is performed. Both strong and electromagnetic correlations are considered.The propagation of particle-hole interactions in the medium plays an important role in determining the neutrino mean free paths. The effects due to Pauli-Blocking and density, spin, and isospin correlations in the medium significantly reduce the neutrino cross sections. Due to the lack of experimental information at high density, these correlations are necessarily model dependent. For example, spin correlations in nonrelativistic models are found to lead to larger suppressions of neutrino cross …
Neutrino electron scattering and left-right symmetry: future tests
1998
Low-energy high-resolution neutrino-electron scattering experiments may play an important role in testing the gauge structure of the electroweak interaction. We propose the use of radioactive neutrino sources (e.g. $^{51}$Cr) in underground experiments such as BOREXINO and HELLAZ as a probe of the weak neutral current structure. As an illustration, we display the sensitivity of these detectors in testing the possible existence of right-handed weak neutral currents.
Improved $K_{e3}$ radiative corrections sharpen the $K_{\mu 2}$--$K_{l3}$ discrepancy
2021
The measurements of $V_{us}$ in leptonic $(K_{\mu 2})$ and semileptonic $(K_{l3})$ kaon decays exhibit a $3\sigma$ disagreement, which could originate either from physics beyond the Standard Model or some large unidentified Standard Model systematic effects. Clarifying this issue requires a careful examination of all existing Standard Model inputs. Making use of a newly-proposed computational framework and the most recent lattice QCD results, we perform a comprehensive re-analysis of the electroweak radiative corrections to the $K_{e3}$ decay rates that achieves an unprecedented level of precision of $10^{-4}$, which improves the current best results by almost an order of magnitude. No larg…
Matrix elements of decays
2004
We present a numerical computation of matrix elements of ?I = 3/2 K ? ?? decays by using Wilson fermions. In order to extrapolate to the physical point we work at unphysical kinematics and we resort to Chiral Perturbation Theory at the next-to-leading order. In particular we explain the case of the electroweak penguins 07,8 which can contribute significantly in the theoretical prediction of sol|??/?. The study is done at ? = 6.0 on a 243 × 64 lattice.
Heavy Resonances in the Electroweak Effective Lagrangian
2015
As a first step towards the construction of a general electroweak effective Lagrangian incorporating heavy states, we present here a simplified version where only vector and axial-vector spin-1 triplets are involved. We adopt an effective field theory formalism, implementing the electroweak chiral symmetry breaking SU(2)L x SU(2)R -> SU(2)L+R, which couples the heavy states to the SM fields. At low energies, the heavy degrees of freedom are integrated out from the action and their effects are hidden in the low-energy couplings of the Electroweak Effective Theory, which can be tested experimentally. Short-distance constraints are also implemented, requiring a proper behaviour in the high-…
Electromagnetism in nonleptonic weak interactions
2000
16 páginas, 1 figura.-- PACS: 11.30.Rd; 13.25.Es; 13.40.Ks.-- arXiv:hep-ph/0006172v2
Leptonic Flavor-changing Z0 Decays in SU(2)xU(1) Theories with Right- handed Neutrinos
1993
We analyze possible lepton-flavor-violating decays of the $Z^0$ particle in a minimal extension of the Standard Model, in which one right-handed neutral field for each family has been introduced. Such rare leptonic decays are induced by Majorana neutrinos at the first electroweak loop level and are generally not suppressed by the ordinary "see-saw" mechanism. In particular, we find that experimental bounds on branching ratios of the order of $10^{-5}-10^{-6}$ attainable at $LEP$ may impose constraints on lepton-flavor-mixing parameters and the masses of the heavy Majorana neutrinos.
Two-Body Decays of the Lightest Stop in Supergravity with and without R-Parity
1999
We study the decays of the lightest top squark in supergravity models with and without R-parity. Using the simplest model with an effective explicit bilinear breaking of R-parity and radiative electroweak symmetry breaking we show that, below the threshold for decays into charginos $\tilde t_1\to c\chi^+_1$, the lightest stop decays mainly into third generation fermions, $\tilde t_1\to b\tau$ instead of the R-parity conserving mode $\tilde t_1\to c\chi^0_1$, even for tiny tau--neutrino mass values. Moreover we show that, even above the threshold for decays into charginos, the decay $\tilde t_1\to b\tau$ may be dominant. We study the role played by the universality of the boundary conditions…