Complex CKM from spontaneous CP violation without flavor changing neutral current

We analyse the general constraints on unified gauge models with spontaneous CP breaking that satisfy the conditions that (i) CP violation in the quark sector is described by a realistic complex CKM matrix, and (ii) there is no significant flavor changing neutral current effects in the quark sector. We show that the crucial requirement in order to conform to the above conditions is that spontaneous CP breaking occurs at a very high scale by complex vevs of standard model singlet Higgs fields. Two classes of models are found, one consisting of pure Higgs extensions and the other one involving fermionic extensions of the standard model. We give examples of each class and discuss their possible embeddings into higher unified theories. One of the models has the interesting property that spontaneous CP violation is triggered by spontaneous P violation, thereby linking the scale of CP violation to the seesaw scale for neutrino masses.     

A two-Higgs doublet model with remarkable CP properties

We analyze generalized CP symmetries of two-Higgs doublet models, extending them from the scalar to the fermion sector of the theory. We show that, other than the usual CP transformation, there is only one of those symmetries which does not imply massless charged fermions. That single model which accommodates a fermionic mass spectrum compatible with experimental data possesses a remarkable feature. Through a soft breaking of the symmetry it displays a new type of spontaneous CP violation, which does not occur in the scalar sector responsible for the symmetry breaking mechanism but, rather, in the fermion sector.     

Superluminal neutrino and spontaneous breaking of Lorentz invariance

Generally speaking, the existence of a superluminal neutrino can be attributed either to re-entrant Lorentz violation at ultralow energy from intrinsic Lorentz violation at ultrahigh energy or to spontaneous breaking of fundamental Lorentz invariance (possibly by the formation of a fermionic condensate). Re-entrant Lorentz violation in the neutrino sector has been discussed elsewhere. Here, the focus is on mechanisms of spontaneous symmetry breaking.     

CP violation in the general two-Higgs-doublet model: a geometric view

We discuss the CP properties of the potential in the general two-Higgs-doublet model (THDM). This is done in a concise way using real gauge invariant functions built from the scalar products of the doublet fields. The space of these invariant functions, parametrising the gauge orbits of the Higgs fields, is isomorphic to the forward light cone and its interior. CP transformations are shown to correspond to reflections in the space of the gauge invariant functions. We consider CP transformations where no mixing of the Higgs doublets is taken into account as well as the general case where the Higgs basis is not fixed. We present basis independent conditions for explicit CP violation which may be checked easily for any THDM potential. Conditions for spontaneous CP violation, that is CP violation through the vacuum expectation values of the Higgs fields, are also derived in a basis independent way.     

Are CP Violating Effects in the Standard Model Really Tiny?

We derive an effective action of the bosonic sector of the Standard Model by integrating out the fermionic degrees of freedom in the worldline approach. The CP violation due to the complex phase in the CKM matrix gives rise to CP-violating operators in the effective action. We calculate the prefactor of the appropriate next-to-leading order operators and give general estimates of CP violation in the bosonic sector of the Standard Model. In particular, we show that the effective CP violation for weak gauge fields is not suppressed by the Yukawa couplings of the light quarks and is much larger than the bound given by the Jarlskog determinant.     

A scenario for generating the fermionic mass spectrum and its predictions

All observed regularities and irregularities of the fermionic mass spectrum follow naturally from a universal two-level GUT scenario. Calculability requires relative orthogonality of the inter-family tree-level contributions and the radiative inner-family ones. This predicts the yet unobserved masses and mixings of the quarks and leptons. In particular, the masses and large mixings of the neutrinos can account for the missing solar neutrinos in terms of vacuum oscillations. A CP violation at GUT energies, induces the observed weak CP violation inK-decay, via radiative corrections.     

Higgs and neutrino sector,EDM and ε<Subscript>K</Subscript> in a spontaneously CP and R-parity breaking supersymmetric model

We construct an extension of the supersymmetric standard model where both CP symmetry and R-parity are spontaneously broken. We study the electroweak symmetry breaking sector of the model and find minima consistent with the experimental bounds on Higgs boson masses. Neutrino masses and mixing angles are generated through both seesaw and bilinear R-parity violation. We show that the hierarchical mass pattern is obtained, and mixings are consistent with measured values. Due to the spontaneous CP and R-parity violation, the neutrino sector is CP violating, and we calculate the corresponding phase. We further restrict the parameter space to agree with the limits on the electric dipole moment of the neutron. Finally, we study the CP violation parameter ε_K in the kaon system and show that we obtain results consistent with the experimental value.     

Dynamical CP violation of the generalized Yang-Mills model

Starting from the generalized Yang-Mills model which contains, besides the vector part Vμ, also a scalar part S and a pseudoscalar part P. It is shown, in terms of the Nambu-Jona-Lasinio (NJL) mechanism,that CP violation can be realized dynamically. The combination of the generalized Yang-MiUs model and the NJL mechanism provides a new way to explain CP violation.     

电荷-宇称(CP)对称性破坏和夸克-轻子味物理--写在CP破坏发现和夸克理论提出40周年之际

简要地介绍了与电荷-宇称(CP)对称性破坏和夸克-轻子味物理有关的一些重要进展.从1964年发现CP破坏和提出夸克理论至今,这个领域就一直成为粒子物理研究的前沿领域,已研究和发展了整整40年,取得了许多辉煌的成就.在这篇文章中,着重评述了目前仍然热门的几个主要的研究方向:直接CP破坏的理论研究和实验验证,CP破坏机制和新的CP破坏源,中微子物理和新的味物理,夸克味物理和有效量子场理论,标准模型中味物理参数的预言和超对称大统一理论.同时对我国有关研究组在这些前沿方向做出的重要贡献作了重点简述.可以看出,在CP破坏和味物理这个重要前沿领域,仍然存在着许多未解之谜,使得粒子物理在21世纪既面临着巨大的挑战,又有着不断发展的机遇.     

Higgsless approach to electroweak symmetry breaking

Higgsless models are an attempt to achieve a breaking of the electroweak symmetry via boundary conditions at the end-points of a fifth dimension compactified on an interval, as an alternative to the usual Higgs mechanism. There is no physical Higgs scalar in the spectrum and the perturbative unitarity violation scale is delayed via the exchange of massive spin-1 KK resonances. The correct mass spectrum is reproduced in a model in warped space, which inherits a custodial symmetry from a left–right gauge symmetry in the bulk. Phenomenological challenges as well as collider signatures are presented. From the AdS/CFT perspective, this model appears as a weakly coupled dual to walking technicolour models. To cite this article: C. Grojean, C. R. Physique 8 (2007).     

Search for CP violation in the lepton sector

One of the major open issues in neutrino physics is the possible existence of CP violation in the neutrino sector. Such an observation would have an important impact in various domains of physics, from high energy physics to cosmology. Its search requires future accelerator neutrino facilities producing intense and pure neutrino beams such as “beta-beams”. Here we review the different beta-beam scenarios proposed so far and discuss the present status, with a particular emphasis on the original baseline scenario and its feasibility. Alternative strategies for the CP violation search are to be pursued as well. A possibility is to search for CP violation effects in astrophysical environments. Here we present recent analytical and numerical results obtained in the context of core-collapse supernovae. In particular, we point out the conditions under which there can be CP violating effects in dense media and show numerical results on the supernova (anti-)neutrino fluxes and on the electron fraction, relevant for the r-process nucleosynthesis.     

Higgs boson masses in the model with two Higgs doublets and spontaneous CP-violation

The renormalization group equations are investigated for two Higgs doublet extension of a standard model with spontaneous CP violation. Assuming the validity of perturbation theory up to unification energies, the restrictions for the Higgs boson masses are found.     

Solution to the flavor problem of warped extra-dimension models

A minimal solution to the flavor problem of warped extra-dimension models, i.e., the excessive mixed-chirality contribution to CP violation in K-K ˉ mixing arising from Kaluza-Klein (KK) gluon exchange, is proposed. Extending the strong-interaction gauge group in the bulk by an additional SU(3), and breaking this symmetry to QCD via boundary conditions, the constraints arising from the ε(K) parameter are significantly relaxed. As a result, KK scales M(KK)~2 TeV are consistent with all flavor observables without significant fine-tuning. The model predicts an extended Higgs sector featuring massive color-octet scalars and a tower of KK pseudoaxial gluon resonances, whose existence is not in conflict with recent LHC dijet bounds.     

Spontaneous CP violating phase as the CKM matrix phase

We propose that the CP violating phase in the CKM mixing matrix is identical to the CP phases responsible for the spontaneous CP violation in the Higgs potential. A multi-Higgs model with Peccei–Quinn (PQ) symmetry is constructed to realize this idea. The CP violating phase does not vanish when all Higgs masses become large. In general, here are flavor changing neutral current (FCNC) interactions mediated by neutral Higgs bosons at the tree level. However, unlike general multi-Higgs models, the FCNC Yukawa couplings are fixed in terms of the quark masses and CKM mixing angles. Implications for meson–anti-meson mixing, including recent data on D–D̄ mixing, and the electric dipole moment (EDM) of the neutron are studied. We find that the neutral Higgs boson masses can be at the order of one hundred GeV. The neutron EDM can be close to the present experimental upper bound.     

Coherent baryogenesis

We propose a new baryogenesis scenario based on coherent production and mixing of different fermionic species. The mechanism is operative during phase transitions, at which the fermions acquire masses via Yukawa couplings to scalar fields. Baryon production is efficient when the mass matrix is nonadiabatically varying, nonsymmetric and when it violates CP and B-L directly, or some other charges that are eventually converted to B-L. We first consider a toy model, which involves two mixing fermionic species, and then a hybrid inflationary scenario embedded in a supersymmetric Pati-Salam GUT. We show that, quite generically, baryon excess in accordance with observation can result.     

CP violation in a multi higgs doublet model

We study CP violation in a multi-Higgs doublet model based on aS ₃×Z ₃ horizontal symmetry. We consider two mechanisms for CP violation in this model: a) CP violation due to complex Yukawa couplings; and b) CP violation due to scalarpseudoscalar mixings. We find that the predictions for ε′/ε, CP violation in B decays and the electric dipole moments of neutron and electron are different between these two mechanisms. These predictions are also dramatically different from the minimal Standard Model predictions.     

CP violation in a multi higgs doublet model

We study CP violation in a multi-Higgs doublet model based on aS ₃×Z ₃ horizontal symmetry. We consider two mechanisms for CP violation in this model: a) CP violation due to complex Yukawa couplings; and b) CP violation due to scalarpseudoscalar mixings. We find that the predictions for ε′/ε, CP violation in B decays and the electric dipole moments of neutron and electron are different between these two mechanisms. These predictions are also dramatically different from the minimal Standard Model predictions.     

CP violation with Higgs-dependent Yukawa couplings

The framework of Higgs-dependent Yukawa couplings allows one to eliminate small couplings from the Standard Model, which can be tested at the LHC. In this work, I study the conditions for CP violation to occur in such models. I identify a class of weak basis invariants controlling CP violation. The invariant measure of CP violation is found to be more than 10 orders of magnitude greater than that in the Standard Model, which can be sufficient for successful electroweak baryogenesis.     

Direct CP violation in B(s)→J/ψP(V)

In the framework of factorization, we study direct CP violation in the decays of B_(s)→J/ψP(V) (P(V) refer to the pseudoscalar (vector) meson). The CP violation depends strongly on Cabibbo-Kobayashi- Maskawa (CKM) matrix elements and the effective parameter, N_c. The recent experimental data for the branching ratios of B_(s)→J/ψP(V) are accurate enough and we can give a strong constraint on the range of N_c. We nd that the CP violating asymmetry is consistent with the available experiment values for the b→d transition, and a little smaller than the b→s transition. We also predict the CP violation of other decay channels for B_(s)→J/ψP(V). We expect our results can give valuable guidance for experiments.     

Testing non-standard CP violation in neutrino propagation

Non-standard physics which can be described by effective four fermion interactions may be an additional source of CP violation in the neutrino propagation. We discuss the detectability of such a CP violation at a neutrino factory. We assume the current baseline setup of the international design study of a neutrino factory (IDS-NF) for the simulation. We find that the CP violation from certain non-standard interactions is, in principle, detectable significantly below their current bounds – even if there is no CP violation in the standard oscillation framework. Therefore, a new physics effect might be mis-interpreted as the canonical Dirac CP violation, and a possibly even more exciting effect might be missed.