Search results for "Matrix"
showing 10 items of 3205 documents
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.
Chiral unitary theory: Application to nuclear problems
2001
In this talk we briefly describe some basic elements of chiral perturbation theory, $\chi PT$, and how the implementation of unitarity and other novel elements lead to a better expansion of the $T$ matrix for meson meson and meson baryon interactions. Applications are then done to the $ \pi \pi $ interaction in nuclear matter in the scalar and vector channels, antikaons in nuclei and $K^-$ atoms, and how the $\phi$ meson properties are changed in a nuclear medium.
The pionic beta decay in chiral perturbation theory
2003
Within the framework of chiral perturbation theory with virtual photons and leptons, we present an updated analysis of the pionic beta decay including all electromagnetic contributions of order e**2 p**2. We discuss the extraction of the Cabibbo-Kobayashi-Maskawa matrix element |Vud| from experimental data. The method employed here is consistent with the analogous treatment of the Kl3 decays and the determination of |Vus|.
WEAK DECAY OF Λ–HYPERNUCLEI
2005
The nonmesonic weak decay of L hypernuclei is studied in a shell model framework. A complete strangeness-changing weak LN!NN transition potential, based on one boson exchange, is constructed by including the exchange of the pseudoscalar mesons p, K, h as well as the vector mesons r,v, and K*, whose weak-coupling constants are obtained from soft meson theorems and SU~6! w . General expressions for nucleons in arbitrary shells are obtained. The transition matrix elements include realistic LN short-range correlations and NN final state interactions based on the Nijmegen baryon-baryon potential. The decay rates are found to be especially sensitive to the inclusion of the strange mesons K and K*…
Analysis of the nonleptonic two-body decays of the Λ hyperon
2021
We systematically study two-body nonleptonic decays of light lambda hyperon $\Lambda \to p \pi^- (n\pi^0)$ with account for both short- and long-distance effects. The short-distance effects are induced by five topologies of external and internal weak $W^\pm$ exchange, while long-distance effects are saturated by an inclusion of the so-called pole diagrams with intermediate $\frac{1}{2}^+$ and $\frac{1}{2}^-$ baryon resonances. The contributions from $\frac12^+$ resonances are calculated straightforwardly by account for nucleon and $\Sigma$ baryons whereas the contributions from $\frac{1}{2}^-$ resonances are calculated by using the well-known soft-pion theorem in the current-algebra approac…
Fascinating puzzle called double beta decay
2019
The question of whether neutrinos are Majorana or Dirac particles and what are their average masses remains one of the most fundamental problems in physics today. Observation of neutrinoless double beta decay (0νββ) would verify the Majorana nature of the neutrino and constrain the absolute scale of the neutrino mass spectrum. The inverse half-life for 0νββ-decay is given by the product of a phase space factor (PSF), a nuclear matrix element (NME), which both rely on theoretical description, and a function f containing the physics beyond the standard model. Recent calculations of PSF and NME will be reviewed together with comparison to other available results. These calculations serve the p…
Exclusive Semileptonic B and D Decays
1989
Interest in semileptonic (s.l.) bottom meson decays in the last few years has focused on the lepton energy end point spectrum. Theoretical models were needed for the description of the endpoint spectrum in order to be able to experimentally extract values for the ratio of KM matrix elements |Vbu/Vbc|. As approximately 90% of the total s.l. decay rate of bottom mesons is into the exclusive modes D and D* it was quite natural to try and model the endpoint spectrum by exclusive contributions. This approach was pioneered by GILMAN, ISGUR and WISE (GIW) in [1].
Constraints on the unitarity triangle angleγfrom Dalitz plot analysis ofB0→DK+π−decays
2016
The first study is presented of CP violation with an amplitude analysis of the Dalitz plot of B0→DK+π- decays, with D→K+π-, K+K-, and π+π-. The analysis is based on a data sample corresponding to 3.0 fb-1 of pp collisions collected with the LHCb detector. No significant CP violation effect is seen, and constraints are placed on the angle γ of the unitarity triangle formed from elements of the Cabibbo-Kobayashi-Maskawa quark mixing matrix. Hadronic parameters associated with the B0→DK∗(892)0 decay are determined for the first time. These measurements can be used to improve the sensitivity to γ of existing and future studies of the B0→DK∗(892)0 decay.