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Zhi-zhong Xing

Publications and source records attributed to Zhi-zhong Xing.

At least 181 records · Page 10Linked to original sources
arXiv2003

Lepton Mass Matrices with Four Texture Zeros

We propose two ans$\rm\ddot{a}$tze of lepton mass matrices with four texture zeros, and confront them with current experimental data on neutrino oscillations. The parameter space of each ansatz is carefully explored. We find that both ans$\rm\ddot{a}$tze can accommodate the normal hierarchy of neutrino masses and the bi-large pattern of lepton flavor mixing. Their predictions for the effective mass of the tritium beta decay and that of the neutrinoless double beta decay are too small to be detectable, but leptonic CP violation at the percent level is allowed. Some discussions are also given about the seesaw invariance of the four-zero texture of Dirac and Majorana neutrino mass matrices.

hep-ph↗
arXiv2003

No Hope to Kinematically Detect the Effective Masses of Muon and Tau Neutrinos

We show that the recent WMAP data can impose a generous upper bound on the effective masses of electron, muon and tau neutrinos defined in the kinematic measurements: $ ^2_e + < m>^2_μ+ < m>^2_τ= m^2_1 + m^2_2 + m^2_3 < 0.5 ~ {\rm eV}^2$, or $ _α< 0.71$ eV (for $α= e, μ, τ$). When current neutrino oscillation data are taken into account, we obtain $ _e <0.24$ eV and $ _μ\approx < m>_τ< 0.24$ eV. Thus there is no hope to kinematically detect $ _μ$ and $ _τ$ in any realistic experiments.

hep-ph↗
arXiv2003

Hierarchy and Up-Down Parallelism of Quark Mass Matrices

In view of the quark mass hierarchy and in the assumption of the up-down parallelism, we derive two phenomenologically-favored patterns of Hermitian quark mass matrices from the quark flavor mixing matrix. We compare one of them with two existing {\it Ans$\it\ddot{a}$tze} proposed by Rosner and Worah and by Roberts {\it et al}, and find that only the latter is consistent with the present experimental data.

hep-ph↗
arXiv2003

Final-state Rescattering and SU(3) Symmetry Breaking in B->DK and B->DK^* Decays

The first observation of $\bar{B}^0_d\to D^0\bar{K}^0$ and $\bar{B}^0_d\to D^0\bar{K}^{*0}$ transitions by the Belle Collaboration allows us to do a complete isospin analysis of $B\to DK^{(*)}$ decay modes. We find that their respective isospin phase shifts are very likely to lie in the ranges $37^\circ \leq (ϕ_1 -ϕ_0)_{DK} \leq 63^\circ$ (or around $50^\circ$) and $25^\circ \leq (ϕ_1 -ϕ_0)_{DK^*} \leq 50^\circ$ (or around $35^\circ$), although the possibility $(ϕ_1 -ϕ_0)_{DK} = (ϕ_1 -ϕ_0)_{DK^*} = 0^\circ$ cannot be ruled out at present. Thus significant final-state rescattering effects are possible to exist in such exclusive $|ΔB| = |ΔC| = |ΔS| =1$ processes. We determine the spectator and color-suppressed spectator quark-diagram amplitudes of $B\to DK$ and $B\to DK^*$ decays, and compare them with the corresponding quark-diagram amplitudes of $B\to Dπ$ and $B\to Dρ$ decays. The effects of SU(3) flavor symmetry breaking are in most cases understandable in the factorization approximation, which works for the individual isospin amplitudes. Very instructive predictions are also obtained for the branching fractions of rare $\bar{B}^0_d \to \bar{D}^0 \bar{K}^{(*)0}$, $B^-_u \to \bar{D}^0 K^{(*)-}$ and $B^-_u \to D^- \bar{K}^{(*)0}$ transitions.

hep-ph↗
arXiv2002

Wolfenstein-like Parametrization of the Neutrino Mixing Matrix

We show that the $3\times 3$ lepton flavor mixing matrix $V$ can be expanded in powers of a Wolfenstein-like parameter $Λ\equiv |V_{μ3}| \sim 1/\sqrt{2}$, which measures the strength of flavor conversion in atmospheric neutrino oscillations. The term of ${\cal O}(Λ^2)$ is associated with the large mixing angle in solar neutrino oscillations. The Dirac phase of CP violation enters at or below ${\cal O}(Λ^8)$, and the Majorana phases of CP violation are not subject to the $Λ$-expansion. Terrestrial matter effects on this new parametrization in realistic long-baseline neutrino oscillation experiments are briefly discussed. Some comments are also given on the possible relation between $Λ$ and a relatively weak hierarchy of neutrino masses.

hep-ph↗
arXiv2002

Four-Zero Texture of Hermitian Quark Mass Matrices and Current Experimental Tests

We show that the four-zero texture of Hermitian quark mass matrices can survive current experimental tests: it is able to yield sufficiently large predictions for the flavor mixing parameter $|V_{ub}/V_{cb}|$ and the CP-violating parameter $\sin 2β$, without fine-tuning of the input values of quark masses, provided the (2,2), (2,3) and (3,3) elements of up and down mass matrices roughly satisfy a geometrical hierarchy. The successful relations $|V_{us}| \approx \sqrt{m_u/m_c + m_d/m_s}$ and $|V_{td}/V_{ts}| \approx \sqrt{m_d/m_s}$ obtained previously from the six-zero texture of Hermitian quark mass matrices remain unchanged in the new ansatz.

hep-ph↗
arXiv2002

Implications of the KamLAND Measurement on the Lepton Flavor Mixing Matrix and the Neutrino Mass Matrix

We explore some important implications of the KamLAND measurment on the lepton flavor mixing matrix $V$ and the neutrino mass matrix $M$. The model-independent constraints on nine matrix elements of $V$ are obtained to a reasonable degree of accuracy. We find that nine two-zero textures of $M$ are compatible with current experimental data, but two of them are only marginally allowed. Instructive predictions are given for the absolute neutrino masses, Majorana phases of CP violation, effective masses of the tritium beta decay and neutrinoless double beta decay.

hep-ph↗
arXiv2002

The LOW Solution and Two-zero Textures of the Neutrino Mass Matrix

As a viable alternative to the LMA solution to the solar neutrino problem, the LOW solution is confronted with two-zero textures of the $3\times 3$ neutrino mass matrix. We find out nine acceptable textures, from which instructive predictions can be obtained for the absolute values of neutrino masses, Majorana phases of CP violation, and effective masses of the tritium beta decay and neutrinoless double beta decay.

hep-ph↗
arXiv2002

Hierarchical Neutrino Masses and Large Mixing Angles from the Fritzsch Texture of Lepton Mass Matrices

We show that the Fritzsch texture of lepton mass matrices can naturally lead to the bi-large flavor mixing pattern, if three neutrinos have a normal but weak mass hierarchy (typically, $m_1 : m_2 : m_3 \sim 1 : 3 :10$). The effective mass of the tritium beta decay and that of the neutrinoless double beta decay are too small to be observable in this ansatz, but CP violation at the percent level is allowed and could be measured in long-baseline neutrino oscillations.

hep-ph↗
arXiv2002

Unitarity Quadrangles of Four Neutrino Mixing

We present a classification of the unitarity quadrangles in the four-neutrino mixing scheme. We find that there are totally thirty-six distinct topologies among twelve different unitarity quadrangles. Concise relations are established between the areas of those unitarity quadrangles and the rephasing invariants of CP and $T$ violation.

hep-ph↗
arXiv2002

Leptogenesis and CP Violation in Neutrino Oscillations

Assuming the seesaw and leptogenesis mechanisms, I give some general remarks on possible connection or disconnection between CP violation in heavy Majorana neutrino decays and that in neutrino oscillations. A simple but predictive ansatz is proposed to simultaneously interpret the observed baryon asymmetry of the universe and oscillations of solar and atmospheric neutrinos.

hep-ph↗
arXiv2002

A Predictive Ansatz for Neutrino Mixing and Leptogenesis

We propose a non-SO(10) modification of the Buchmueller-Wyler ansatz for neutrino mixing and leptogenesis, in which charged lepton, Dirac and Majorana neutrino mass matrices have fewer free parameters. Predictions of this new ansatz for three light neutrino masses, three lepton flavor mixing angles, the neutrinoless double-beta decay and the cosmological matter-antimatter asymmetry are all in very good agreement with current experimental and observational data.

hep-ph↗
arXiv2002

Possible Effects of Noncommutative Geometry on Weak CP Violation and Unitarity Triangles

Possible effects of noncommutative geometry on weak CP violation and unitarity triangles are discussed by taking account of a simple version of the momentum-dependent quark mixing matrix in the noncommutative standard model. In particular, we calculate nine rephasing invariants of CP violation and illustrate the noncommutative CP-violating effect in a couple of charged D-meson decays. We also show how inner angles of the deformed unitarity triangles are related to CP-violating asymmetries in some typical B_d and B_s transitions into CP eigenstates. B-meson factories are expected to help probe or constrain noncommutative geometry at low energies in the near future.

hep-ph↗
arXiv2002

Determining Strong and Weak Phases in B_d -> D^{(*)\pm} D^{(*)\mp} Decays

We show that both the weak phase βand the strong phase δ_d can be determined from the time-dependent measurement of B_d -> D^{*\pm} D^{\mp} decays, whose final states are non-CP eigenstates. It is also possible to extract βfrom B_d -> D^{*\pm} D^{*\mp} transitions without doing the angular analysis. Possible final-state rescattering effects in B_d -> D^{(*)\pm} D^{(*)\mp} channels are discussed by means of the isospin analysis. We emphasize that it is worthwhile to check whether the naive factorization approximation works or not for such B-meson decay modes into two heavy charmed mesons.

hep-ph↗
arXiv2002

Can the Lepton Flavor Mixing Matrix Be Symmetric?

Current neutrino oscillation data indicate that the 3x3 lepton flavor mixing matrix V is likely to be symmetric about its V_{e3}-V_{μ2}-V_{τ1} axis. This off-diagonal symmetry corresponds to three pairs of {\it congruent} unitarity triangles in the complex plane. Terrestrial matter effects can substantially modify the genuine CP-violating parameter and off-diagonal asymmetries of V in realistic long-baseline experiments of neutrino oscillations.

hep-ph↗
arXiv2002

Nearly Tri-Bimaximal Neutrino Mixing and CP Violation

We point out two simple but instructive possibilities to modify the tri-bimaximal neutrino mixing ansatz, such that leptonic CP violation can naturally be incorporated into the resultant scenarios of nearly tri-bimaximal flavor mixing. The consequences of two new ansaetze on solar, atmospheric and reactor neutrino oscillations are analyzed. We also discuss an interesting approach to construct lepton mass matrices under permutation symmetry, from which one may derive another nearly tri-bimaximal neutrino mixing scenario with no intrinsic CP violation in neutrino oscillations.

hep-ph↗
arXiv2002

Texture Zeros and Majorana Phases of the Neutrino Mass Matrix

We present the generic formulas to calculate the ratios of neutrino masses and the Majorana phases of CP violation from the neutrino mass matrix with two independent vanishing entries in the flavor basis where the charged lepton mass matrix is diagonal. An order-of-magnitude illustration is given for seven experimentally acceptable textures of the neutrino mass matrix, and some analytical approximations are made for their phenomenological consequences at low energy scales.

hep-ph↗