Search results for "VIOLATION"
showing 10 items of 540 documents
Determination of the θ23 octant in long baseline neutrino experiments within and beyond the standard model
2018
The recent data indicate that the neutrino mixing angle $\theta_{23}$ deviates from the maximal-mixing value of 45$^\circ$, showing two nearly degenerate solutions, one in the lower octant (LO) ($\theta_{23}45^\circ$). We investigate, using numerical simulations, the prospects for determining the octant of $\theta_{23}$ in the future long baseline oscillation experiments. We present our results as contour plots on the ($\theta_{23}-45^\circ$, $\delta$)--plane, where $\delta$ is the $CP$ phase, showing the true values of $\theta_{23}$ for which the octant can be experimentally determined at 3$\,\sigma$, 2$\,\sigma$ and 1$\,\sigma$ confidence level. In particular, we study the impact of the p…
Little Randall-Sundrum models:ϵKstrikes again
2009
A detailed phenomenological analysis of neutral kaon mixing in ``little Randall-Sundrum'' models is presented. It is shown that the constraints arising from the $CP$-violating quantity ${ϵ}_{K}$ can, depending on the value of the ultraviolet cutoff, be even stronger than in the original Randall-Sundrum scenario addressing the hierarchy problem up to the Planck scale. The origin of the enhancement is explained, and a bound ${\ensuremath{\Lambda}}_{\mathrm{UV}}g\mathrm{\text{several}}$ ${10}^{3}\text{ }\text{ }\mathrm{TeV}$ is derived, below which vast corrections to ${ϵ}_{K}$ are generically unavoidable. Implications for nonstandard ${Z}^{0}\ensuremath{\rightarrow}b\overline{b}$ couplings ar…
Strong Enhancement ofɛ′/ɛthrough Final State Interactions
2000
We quantify the important effect of strong final state interactions in the weak $K\ensuremath{\rightarrow}2\ensuremath{\pi}$ amplitudes, using the measured $\ensuremath{\pi}\ensuremath{-}\ensuremath{\pi}$ phase shifts with $J\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}0$ and $I\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}0,2$. The final rescattering of the two pions provides a strong enhancement of the $\ensuremath{\Delta}I\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}1/2$ amplitude, which so far has been neglected in the theoretical predictions of ${\ensuremath{\varepsilon}}^{\ensuremath{'}}/\ensuremath{\varepsilon}$. This correction increases the standard model predictio…
Perturbative QCD study of Bs decays to a pseudoscalar meson and a tensor meson
2014
We study two-body hadronic B-s -> PT decays, with P(T) being a light pseudoscalar (tensor) meson, in the perturbative QCD approach. The CP-averaged branching ratios and the direct CP asymmetries of the Delta S = 0 modes are predicted, where Delta S is the difference between the strange numbers of final and initial states. We also define and calculate experimental observables for the Delta S = 1 modes under the B-s(0)-(B) over bar (0)(s) mixing, including CP averaged branching ratios, time-integrated CP asymmetries, and the CP observables C-f, D-f and S-f. Results are compared to the B-s -> PV ones in the literature, and to the B -> PT ones, which indicate considerable U-spin symmetry breaki…
Consistent probabilistic description of the neutral Kaon system
2013
The neutral Kaon system has both CF violation in the mass matrix and a non-vanishing lifetime difference in the width matrix. This leads to an effective Hamiltonian which is not a normal operator, with incompatible (non-commuting) masses and widths. In the Weisskopf-Wigner Approach (WWA), by diagonalizing the entire Hamiltonian, the unphysical non-orthogonal "stationary" states K-L,K-S are obtained. These states have complex eigenvalues whose real (imaginary) part does not coincide with the eigenvalues of the mass (width). matrix. In this work we describe the system as an open Lindblad-type quantum mechanical system due to Kaon decays. This approach, in terms of density matrices for initial…
Theoretical overview of kaon decays
2014
Kaon decays are an important testing ground of the electroweak flavour theory. They can provide new signals of CP violation and, perhaps, a window into physics beyond the Standard Model. At the same time, they exhibit an interesting interplay of long-distance QCD effects in flavour-changing transitions. A brief overview is presented, focusing on a few selected topics of particular interest. A more detailed and comprehensive review can be found in arXiv:1107.6001.
Improved measurement of time-dependentCPasymmetries and theCP-odd fraction in the decayB0→D*+D*−
2007
We present an updated measurement of time-dependent CP asymmetries and the CP-odd fraction in the decay B0-->D*+D*- using 232x10(6)BB pairs collected by the BABAR detector at the SLAC PEP-II B factory. We determine the CP-odd fraction to be 0.125+/-0.044(stat)+/-0.007(syst). The time-dependent CP asymmetry parameters C+ and S+ are determined to be 0.06+/-0.17(stat)+/-0.03(syst) and -0.75+/-0.25(stat)+/-0.03(syst), respectively. The standard model predicts these parameters to be 0 and -sin2beta, respectively, in the absence of penguin amplitude contributions.
Constraining multi-Higgs flavour models
2014
To study a flavour model with a non-minimal Higgs sector one must first define the symmetries of the fields; then identify what types of vacua exist and how they may break the symmetries; and finally determine whether the remnant symmetries are compatible with the experimental data. Here we address all these issues in the context of flavour models with any number of Higgs doublets. We stress the importance of analysing the Higgs vacuum expectation values that are pseudo-invariant under the generators of all subgroups. It is shown that the only way of obtaining a physical CKM mixing matrix and, simultaneously, non-degenerate and non-zero quark masses is requiring the vacuum expectation value…
Relating quarks and leptons without grand-unification
2011
In combination with supersymmetry, flavor symmetry may relate quarks with leptons, even in the absence of a grand-unification group. We propose an SU(3)xSU(2)xU(1) model where both supersymmetry and the assumed A4 flavor symmetries are softly broken, reproducing well the observed fermion mass hierarchies and predicting: (i) a relation between down-type quarks and charged lepton masses, and (ii) a correlation between the Cabibbo angle in the quark sector, and the reactor angle characterizing CP violation in neutrino oscillations.
Quark–lepton mass relation in a realistic A4 extension of the Standard Model
2013
We propose a realistic A4A4 extension of the Standard Model involving a particular quark–lepton mass relation, namely that the ratio of the third family mass to the geometric mean of the first and second family masses are equal for down-type quarks and charged leptons. This relation, which is approximately renormalization group invariant, is usually regarded as arising from the Georgi–Jarlskog relations, but in the present model there is no unification group or supersymmetry. In the neutrino sector we propose a simple modification of the so-called Zee–Wolfenstein mass matrix pattern which allows an acceptable reactor angle along with a deviation of the atmospheric and solar angles from thei…