CP violation in t → W + b decays in two-Higgs doublet model

Due to the large mass of top quark, CP violation in the top-quark decay is sensitive to the interactions mediated by Higgs bosons. We consider CP violation in t → W ⁺ b decay by calculating consistently in unitary gauge the CP-violating up-down asymmetry of the leptons from W boson decays in t → W ⁺ b, defined by Grz?dkowski and Gunion, in the two-Higgs doublet model with CP-violating neutral sector. The asymmetry is shown to be at most of the order of (1–4) × 10^-4 for tan β = 1.0, where tan β is the ratio of vacuum expectation values for the two neutral Higgs bosons.     

Solving the strong CP problem with discrete symmetries and the right unitarity triangle

We present a solution to the strong CP problem based on spontaneous CP violation and discrete family symmetries. The model predicts in a natural way the almost right-angled quark unitarity triangle angle (α?90°$\alpha ?90\mathrm{°}$) by making the entries of the quark mass matrices either real or imaginary. By this choice the determinants of the mass matrices are rendered real and hence the strong CP phase vanishes. We present a toy model for the quark sector that demonstrates the viability of our approach.     

CP violation and Fritzsch mass matrices

We discuss a form for the quark mass matrices which produces maximal weak but no string CP violation. The quark mass matrices are of the Fritzsch type, with all phases equal to multiples of $\text{1}\text{2}\text{π}$. We show that these matrices can be produced in an SO(10) model with CP violated spontaneously at the GUT scale. The model successfully predicts the entire K-M matrix. Radiative corrections to $\text{θ}$, however, are several orders of magnitude too large in the model, and $\text{θ}$ is naturally of O(10^?5).     

Baryogenesis at the weak phase transition

The weak phase transition of the hot big bang can produce quarks, leptons and weak bosons which are out of thermal equilibrium. In a simple extension of the standard model it is shown that the reactions following top quark decays can generate the cosmological baryon asymmetry. The top quark mass must be close to 80 GeV and the Higgs boson must be lighter than 1 GeV. This baryogenesis mechanism can be directly tested at e⁺e⁻ and hadron collider by searching for spectacular events containing six or more bottom quarks and a violation of baryon number at the decay vertex of a long lived neutral particle.     

CP violation in gauge theories and the electric dipole moment of the neutron

A nonvanishing contribution to the neutron electric dipole moment in CP-violating gauge theories of the weak interactions, arising from interaction of the photon with two-quark subsystems of the three-bound-quark neutron system, is calculated. In the Kobayashi-Maskawa model the resulting value of the moment is estimated as O(10^?32) e cm; however, strong interaction corrections (gluonic radiative corrections) give quark moment contributions which may be numerically larger (possibly 10^?30±1 e cm). Either case clearly distinguishes gauge-sector CP violation from Higgs-sector CP violation which typically gives a neutron moment of order 10^?24 e cm.     

Texture zeros for the Standard Model quark mass matrices

A way of counting free parameters in the quark mass matrices of the standard model, including the constraints coming from weak basis transformations, is presented; this allows one to understand the exact physical meaning of the parallel and non-parallel texture zeros which appear in some “ansätze” of the 3×3 quark mass matrices, including the CP violation phenomena in the analysis; it is shown why the six texture zeros are ruled out. Finally, a five texture zeros “ansatz” which properly copes with all experimental constrains, including the angles of the unitary triangle, is presented.     

A soft origin for CKM-type CP violation

We present a two-Higgs-doublet model, with a Z₃ symmetry, in which CP violation originates solely in a soft (dimension-2) coupling in the scalar potential, and reveals itself solely in the CKM (quark mixing) matrix. In particular, in the mass basis the Yukawa interactions of the neutral scalars are all real. The model has only eleven parameters to fit the six quark masses and the four independent CKM-matrix observables. We find regions of parameter space in which the flavour-changing neutral couplings are so suppressed that they allow the scalars to be no heavier than a few hundred GeV.     

Quark mixing in weak interactions

The status of the quark mixing in weak interaction is reviewed. The 3×3 quark mixing matrix for the three left-handed doublet model is analyzed using various experimental information involving strange, charmed, and b-flavored particles. Its interplay with nonleptonic decays, implication on neutral particle-antiparticle mixing and CP violation in heavy quark systems, and the possible origin of the quark mixing from quark mass matrix are discussed. Finally we briefly review the status of alternative sources for CP violation, and alternative models to the three left-hand quark doublet model.     

Generalized permutation symmetry and the flavour problem inSU(2)L×U(1)

A generalized permutation group is introduced as a possible horizontal symmetry forSU(2)_L×U(1) gauge theories. It leads to the unique two generation quark mass matrices with a correct prediction for the Cabibbo angle. For three generations the model exhibits spontaneousCP violation, correlates the Kobayashi-Maskawa mixing parameterss ₁ ands ₃ and predicts an upper bound for the running top quark mass of approximately 45 GeV. The hierarchy of generations is due to a hierarchy of vacuum expectation values rather than of Yukawa coupling constants.     

A novel origin of CP violation

We propose the complex group theoretical Clebsch-Gordan coefficients as a novel origin of CP violation. This is manifest in our model based on SU(5) combined with the double tetrahedral group, T^′. Due to the presence of the doublet representations in T^′, there exist complex CG coefficients, leading to explicit CP violation in the model, while the Yukawa couplings and the vacuum expectation of the scalar fields remain real. The tri-bimaximal neutrino mixing matrix arises from the CG coefficients of T^′. In addition to the prediction for , the model gives rise to a sum rule, , which is a consequence of the Georgi-Jarlskog relations in the charged fermion sector. The leptonic Dirac CP violating phase, δ_?, is predicted to be ∼227^°, which turns out to be the value needed to account for the difference between the experimental best fit value for the solar mixing angle and the TBM prediction. The predicted CP violation measures in the quark sector are also consistent with the current experimental data.     

CP violation,horizontal symmetry and the Kobayashi-Maskawa matrix

It is pointed out that in order to have CP violation in horizontal, generation mixing, interactions, while the Kobayashi-Maskawa matrix itself is real, a very specific structure is required for the unitary matrices that relate weak to mass eigenstates. Implications for the structure of quark mass matrices are also discussed.     

Renormalization Group Evolution of CP Nonconsewation Measures

We emphasize to use the squared quark mass matrices instead of the quark mass matrices to eliminate the γ5 noninvariant ambiguity. A new measure of CP nonconsewation α is proposed in this framework. It is more underlying than the well-known CP nonconsewation measure J. The renormalisation group analysis for both of them is fulfilled. For this aim, we employ a careful calculation scheme, which avoids obtaining tiny quantity J² from the difference of two large numbers. We find that the CP nonconsewation measure J, contrary to the previous statement, decreases with energy, while another CP nonconsewation measure α increases with energy primarily. The change near the infrared fixed points is substantial.     

夸克质量矩阵与CP对称性破坏

本文给出一类夸克质量矩阵与CP破坏参量的精确解析关系. 有关结果适用于唯象研究不同质量矩阵模型及其CP破坏效应的细微差别.     

Large charmless yield inB decays and inclusiveB decay puzzles

In recent studies of inclusiveB decays, it has been suggested that eitherB mesons decay much more copiously to final states with no open charm than currently assumed, orB(D ⁰ → K^?π⁺) has to be reduced significantly. This note takes the experimentalB(D ⁰ → K^?π⁺) at its face value and estimatesB(b → no open charm) using complementary methods: one accounts for thec quark inb → c transitions, the other accounts for the c quark inb → ccs transitions. Through cancellation of errors, the average gives our best estimate ofB(b → no open charm), and the difference measures the consistency. The results of the methods are consistent with each other, strongly suggesting a much enhancedB(b → no open charm). This observation indicates that non-perturbative QCD effects are probably causing a sizable fraction of theb → ccs transitions to be seen as charmlessb → s processes, contrary to smaller traditional expectations. This mechanism has generally been overlooked and may explain the existing experimental data within the framework of the standard model. We then briefly discuss implications on baryon production governed byb → ccs processes, rare hadronicB decays and CP violation studies.     

Large strong phases and CP violation in the annihilation processes B̄0→K+K-, K*±K∓, K*+K*-

The strong phases and CP violation in the rare B̄⁰→K⁺K^-, K^*±K^∓, K^*+K^*- decays are investigated. As these decays proceed only via annihilation type diagrams in the standard model (SM), a dynamical gluon mass is introduced to avoid the infrared divergence in the soft endpoint regions. The Cutkosky rule is adopted to deal with a physical-region singularity of the on-mass-shell quark propagators, which leads to a big imaginary part and hence a large strong phase. As a consequence, large CP asymmetries are predicted in those decay modes due to a big interference between the annihilation amplitudes from penguin and tree operators, which may be tested in future more precise experiments. PACS 13.25.Hw; 11.30.Er; 12.38.Bx     

Transition magnetic moments of J~P=3/2~+ decuplet to J~P=1/2~+ octet baryons in the chiral constituent quark model

In light of the developments of the chiral constituent quark model(χ~(CQM)) in studying low energy hadronic matrix elements of the ground-state baryons, we extend this model to investigate their transition properties.The magnetic moments of transitions from the J~P=3/2~+ decuplet to J~P=1/2~+ octet baryons are calculated with explicit valence quark spin, sea quark spin and sea quark orbital angular momentum contributions. Since the experimental data is available for only a few transitions, we compare our results with the results of other available models. The implications of other complicated effects such as chiral symmetry breaking and SU(3) symmetry breaking arising due to confinement of quarks are also discussed.     

A model of flavor mixing

A model of quark mass matrices is presented where flavor mixings can be expanded in powers of small parameters. These parameters characterize the observed quark mass pattern. The weak mixing matrix has a very simple form. The correlation of the weak mixing angles and CP-violating phases with the main features of the quark spectrum may be easily studied. An upper bound is predicted on the top-quark mass, m_t^p⩽45 GeV, and a rate for the b→u transition close to its experimental limit.     

A parameterization of electro-weak mass matrices for quarks

We discuss quark flavor mixing and CP violation using a 10 parameter quark mass matrix in the electro-weak basis. The matrix handles the high mass of the top quark, 174±16 GeV, and contains two CP violating phases. We show that this scheme favors minimal CP violation by a single phase factor and leads to maximal CP violation in the standard parameterization of the quark flavor mixing matrix.     

THE CP VIOLATION OF SU(7) MODEL

We discuss the CP violation problem of SU(7) models of Grand Unified Theoryincluding four genarations^[1,2]. It is shown that if we properly choose the complex phaseangles in quark mass matrix elements, we are able to obtain the CP violation phaseangle which agrees well with the experimental value. If the Higgs potential is pro-perly choosen we find that the strong CP violation parameter θ is equal to zero atthe tree level.     

Analysis of the3 He(K−,K +)n reaction by the potential quark model

We analyze the production of H dihyperson (J ^π=0⁺,S=?2) via the (K ^?, K⁺) reaction by means of the non-relativistic quark model. First, the H mass and mass spectrum of single baryons are calculated. When the single baryon spectrum is well reproduced, the H dihyperson has the binding energies about 20 MeV or 60 MeV corresponding to the choice of the strength of the confinement potential. Using this model and parameters, cross sections for H production are estimated. A new effect, contributions from color-octetQ ³?Q ³ components of H dihyperson, is taken into account. The cross sections for H production are enhanced about ten times by these contributions. TheK ⁺-neutron coincidence cross section for H production is found to be 99–115 nb/sr² at theK ⁺ forward direction forM _H=2212 MeV and theK ^? beam momentum 1.8 GeV/c.