Narrow Results

We show that if the presently observed L/E-flatness of the electron-like event ratio in the Super-Kamiokande atmospheric neutrino data is confirmed, then the indicated ratio must be unity. Further, it is found that once CP is violated the exact L/E flatness implies: (a) the CP-violating phase, in the standard parametrization, is narrowed down to two possibilities ±π/2, and (b) the mixing between the second and the third generations must be maximal. With these results at hand, we argue that a dedicated study of the L/E-flatness of the electron-like event ratio by Super-Kamiokande can serve as an initial investigatory probe of CP violation in the neutrino sector. The assumptions under which these results hold are explicitly stated.

We study the CP-violating asymmetry , which arises, in η → π⁺π^-e⁺e^-, from the angular correlation of the e⁺e^- and π⁺ π^- planes due to the interference between the magnetic and electric decay amplitudes. With the phenomenologically determined magnetic amplitude and branching ratio as input, the asymmetry, induced by the electric bremsstrahlung amplitude through the CP-violating decay η → π⁺π^-, and by an unconventional tensor type operator, has been estimated respectively. The upper bound of from the former is about 10^-3, and the asymmetry from the latter might be up to O(10^-2). One can therefore expect that this CP asymmetry would be an interesting CP-violating observable for the future precise measurements in the η factories.

The analysis of the time evolution of unstable states which are linear superposition of other, observable, states can, in principle, be carried out in two distinct, non-equivalent ways. One of the methods, usually employed for the neutral kaon system, combines the mixing and instability into one single step which then results in unconventional properties of the mass-eigenstates. An alternative method is to remain within the framework of a Lagrangian formalism and to perform the mixing prior to the instability analysis. Staying close to the system, we compare both methods pointing out some of their shortcomings and advantages.

The B-meson system provides many strategies to perform stringent tests of the Standard-Model description of CP-violation. In this brief review, we discuss implications of the currently available B-factory data on the angles α, β and γ of the unitarity triangle, emphasize the importance of B_s studies at hadronic B experiments, and discuss new, theoretically clean strategies to determine γ.

The electric dipole moment of ²⁰⁵Tl has been analyzed within the supersymmetric model which solves the strong CP problem via the dynamical phase of the gluino mass. It is found that the electric dipole moment of ²⁰⁵Tl exceeds the current experimental bounds for tanβ ≳ 10 and μ ≲ 1,000 GeV, with maximal CP-violation for all phases.

Recent measurements of time-dependent CP-asymmetries at the B-factories have led to substantial progress in our understanding of CP-violation. In this paper, we review some of these experimental results and discuss their implications in the Standard Model and their sensitivity to New Physics.

The ratios of B_d and B_s meson decay constant have been estimated using the variational method in conjunction with the relativistic Hamiltonian of the heavy meson in the framework of the statistical model. The ratio of CKM matrix elements has been extracted from mixing using the estimated decay constants and ratio of B_d and B_s mass differences. The results are found to be in good agreement with the existing theoretical and experimental predictions.

The MSSM contains CP-violating phases that may have important observable effects in Higgs physics. We review recent highlights in Higgs phenomenology obtained with the code CPsuperH, a useful tool for studies of the production, mixing and decay of a coupled system of the neutral Higgs bosons at future high energy colliders such as the LHC, ILC (γLC), and a muon collider (MC). CPsuperH implements the constraints from upper limits on electric dipole moments, and may be extended to include other related low-energy observables, such as b→sγ and B→Kl l, and to compute the relic abundance of the lightest neutralino.

We consider effective Lagrangian models of CP-violating vertex structure in which a b→uW vertex, proportional to s₁₃e^-iδ₁₃ with s₁₃ very small (milliweak interaction) and δ₁₃ large, is dynamically generated. A consequent, enhanced CP-violating vertex for b→sg results in an enhanced CP-violating phase in the ratio of amplitudes for . We estimate that this can significantly change the S-parameter from the value expected in the standard model.

Charm physics has played all along a central role in particle physics, however, the level of attention on it has tremendously increased in the last years because of the observation of "fast" flavor oscillations and because of very recent observed hints of CP-violation. While in the past these would have been unambiguously interpreted as signs of New Physics (NP), the revisitation of theoretical expectations, prompted by the latest experimental measurements, makes the picture not clear. This brief review covers the current status of CP-violating measurements in the system, both on the experimental and theoretical sides.

CP violation in neutrino interactions is described by three phases contained in Pontecorvo–Maki–Nakagawa–Sakata mixing matrix (U_PMNS). We argue that the phenomenologically consistent result of the Dirac CP violation can be obtained if U_PMNS is constructed along bipair neutrino mixing scheme, namely, requiring that |U₁₂| = |U₃₂| and |U₂₂| = |U₂₃| (case 1) and |U₁₂| = |U₂₂| and |U₃₂| = |U₃₃| (case 2), where U_ij stands for the i × j matrix element of U_PMNS. As a result, the solar, atmospheric and reactor neutrino mixing angles θ₁₂, θ₂₃ and θ₁₃, respectively, are correlated to satisfy cos 2θ₁₂ = sin² θ₂₃ - tan² θ₁₃ (case 1) or cos 2θ₁₂ = cos² θ₂₃ - tan² θ₁₃ (case 2). Furthermore, if Dirac CP violation is observed to be maximal, θ₂₃ is determined by θ₁₃ to be: (case 1) or (case 2). For the case of non-maximal Dirac CP violation, we perform numerical computation to show relations between the CP-violating Dirac phase and the mixing angles.

The existence and mysterious nature of sterile neutrinos are revolutionizing physics from the particle level to the cosmological scales. The recent results from the MiniBooNE experiment at Fermi-lab observed far more ${\nu }_e$ appearance than expected, which have provided a hint about the possible existence of sterile neutrinos. The results, if confirmed in future experiments, will have significant implications for cosmology and astroparticle physics. This will require new neutrino mass models to accommodate these additional degrees of freedom. In respect to that, this work is just an extension of our recent work toward the CP phase analysis of Quark-Lepton Complementarity (QLC) model in a $3+1$ scenario. The parametrization of CKM₄ and PMNS₄ using Monte Carlo Simulation is used to estimate the texture of nontrivial correlation matrix $(V_{c_4})$. As such, we have successfully investigated the constrained values for sterile neutrino parameters, and also predicted the values for Dirac CP-Violation phase and the CP re-phasing invariant $(J)$. The results obtained are consistent with the data available from various experiments, like No$\nu$A, MINOS, SuperK and IceCube-DeepCore. Furthermore, this analysis would be very important in view of growing sterile neutrino experiments.

We report on measurements of time-dependent CP-violation parameters in neutral B meson systems based on a 140fb^-1 data sample collected at the ϒ(4S) resonance with the Belle detector at the KEKB energy-asymmetric e⁺e^- collider. One B meson is fully reconstructed in one of the CP eigenstate decay channels, and its flavor is identified from the decay products of the accompanying B meson. The CP-violation parameters are extracted from the asymmetries in the distributions of the proper-time intervals between the two B decays. The parameter sin 2ϕ₁ is measured with the decay modes including the b→c tree and b→s penguin transitions, and sin 2ϕ₂ is obtained from the decay mode B→π⁺π^-. A brief discussion of the ϕ₃ measurements with B→D^(*)∓π^± decays is also given.

This paper summarises the B-physics prospects of the LHCb experiment. The focus is on the uniqueness of LHCb over and above the B-factories and the Tevatron experiments: the measurement of the unitarity angle γ using a number of complementary methods, the measurement of the mixing phase φ_s in tree and penguin decay modes, and the expected observation of the rare decay mode below Standard Model predictions.

We simplify and extend our previous model for the masses and mixing matrix of three Majorana neutrinos based on permutation symmetry S₃ and the perturbations which violate this symmetry. The perturbations are arranged such that we get the smaller solar neutrinos mass difference at second-order. We work out the corrections to the tribimaximal mixing matrix with the nonzero value for s₁₃ and the conventional CP-violating phase. It is shown that the results of the model are comparable with the global analysis of neutrino oscillation data.

The fact that quarks of the same electric charge possess a mass hierarchy is a big puzzle in particle physics, and it must be highly correlated with the hierarchy of quark flavor mixing. This chapter is intended to provide a brief description of some important issues regarding quark masses, flavor mixing and CP-violation. A comparison between the salient features of quark and lepton flavor mixing structures is also made.

In the light of several recent analyses pointing toward texture 4-zero Fritzsch-like quark mass matrices as the only viable structures for quark mass matrices, this work adopts a model independent approach to reconstruct an alternate and simplified structure of texture specific quark mass matrices in a generalized “$u$-diagonal” basis within the Standard Model framework using the unitarity of CKM matrix and the observed hierarchies in quark mass spectra and mixing angles. It is observed that the measured $1\sigma$ values of the three physical parameters namely $m_u$, $m_d$ and $s_{12}$ naturally lead to the vanishing of (11) element in the down type quark mass matrix and that the single measurable CP violating phase ${\delta }_{13}$ in the CKM matrix is sufficient enough in $M_d^{\prime }$ to explain the observed mixing pattern in a suitable basis. The leading order as well as exact analytic phenomenological solutions are addressed for the modest pattern of quark mass matrices derived from CKM matrix and precision measurements of mixing parameters.

The implications of precision CKM measurements have been examined on the CKM paradigm as well as the CP violating parameters. Similarly, the implications of the precision neutrino oscillations measurements for the Dirac-like CP violating phase in the leptonic sector have been investigated.

A phenomenological model with active and sterile neutrinos is used for calculations of neutrino oscillation characteristics at the normal mass hierarchy of active neutrinos. Taking into account the contributions of sterile neutrinos, appearance and survival probabilities for active neutrinos are calculated. Modified graphical dependencies for the probability of appearance of electron neutrinos/antineutrinos in muon neutrino/antineutrino beams as a function of the ratio of the distance to the neutrino energy and other model parameters are obtained. It is shown that in the case of a certain type mixing between active and sterile neutrinos it is possible to describe all anomalies of neutrino data at short distances with the same model parameters. A new parametrization for a particular type mixing matrix of active and sterile neutrinos that takes into account the additional sources of CP violation is used. The comparison with the existing experimental data is performed and, using this knowledge, the estimates of some model parameters are found. The theoretical results obtained for mixing of active and sterile neutrinos can be applied for interpretation and prediction of results of ground-based experiments on search of sterile neutrinos as well as for the analysis of some astrophysical data.

The charm-mixing parameter $y_{\text{CP}}$ is based on the $D^0-{\bar{D}}^0$ meson system. The measurement of the ratios of the effective decay width ${\mathrm{\Gamma }}_{CP}$ decays to final states $f,(f=KK,\pi \pi ,K\pi )$ was recently reported in an LHCb analysis performed with the values of $y_{\text{CP}}^{KK}-y_{\text{CP}}^{K\pi }=(7.080\pm 0.300\pm 0.140)\times 10^{-3}$ and $y_{\text{CP}}^{\pi \pi }-y_{\text{CP}}^{K\pi }=(6.570\pm 0.530\pm 0.160)\times 10^{-3}$. We have calculated the difference between the charm-mixing parameters, $y_{\text{CP}}^{KK,\pi \pi }-y_{\text{CP}}^{K\pi }$, under the factorization approach with values of $(7.084\pm 3.782)\times 10^{-3}$ and $(7.074\pm 3.772)\times 10^{-3}$, respectively. The results obtained are comparable with experimental values.