Mechanism Of CP Violation Research Articles

Strong CP and low-energy supersymmetry

A spontaneously-broken CP provides an alternative to the KM mechanism for CP violation with the advantage that the strong CP problem is solved. We consider, for such a model with a new gauged U(1), the incorporation of low-energy supersymmetry and find the constraints on alignment and squark degeneracy. The conclusion is that although the $\bar{\theta}$ constraints are much less severe than in other generic schemes with supersymmetry breaking and spontaneous CP violation, one restriction remains stronger than needed in the MSSM for suppression of FCNC.

Search for new mechanism of CP violation through tau decay and semileptonic decay of hadrons

If CP is violated in any decay process involving leptons it will signify the existense of a new force (called the X boson) responsible for CP violation that may be the key to understanding matter-antimatter asymmetry in the universe. We discuss the signatures of CP violation in (1) the decay of tau lepton, and (2) the semileptonic decay of $\pi$, K, D, B and t particles by measuring the polarization of the charged lepton in the decay. We discuss how the coupling constants and their phases of the coupling of the X boson to 9 quark vertices and 3 lepton vertices can be obtained through 12 decay processes.

Constraints on theWRmass andCPviolation in left-right models

We update the constraints on the right-handed W{sub R} gauge boson mass, mixing angle {zeta} with the left-handed W{sub L} gauge boson, and other parameters in general left-right symmetric models with different mechanisms of CP violation. Constraints mostly independent of any assumption on the quark sector are obtained from a reanalysis of muon decay data. The best {chi}{sup 2} fit of the data gives g{sub R}/g{sub L}=0.94{plus_minus}0.09 for the ratio of right to left gauge couplings, with M{sub W{sub R}}{ge}485 GeV and {vert_bar}{zeta}{vert_bar}{le}0.0327. Fixing g{sub L}=g{sub R} (in particular for manifestly left-right symmetric models), we obtain M{sub W{sub R}}{approx_gt}549 GeV and {vert_bar}{zeta}{vert_bar}{approx_gt}0.0333. Estimates of the left-right hadronic matrix elements in the neutral kaon system and their uncertainties are revised using large N{sub c} and chiral perturbation theory arguments. With explicitly given assumptions on the long-distance ({Delta}S=1){sup 2} contributions to the K{sub L}-K{sub S} mass difference, lower bounds on M{sub W{sub R}} are obtained. With the same assumptions, one also gets strong upper bounds from the CP-violating parameter {epsilon}{sub K}, for most of the parameter space of left-right models where the right-handed third family does not contribute in CP-violating quantities. For manifestly left-right symmetric models the lower bound obtained is M{submore » W{sub R}}{approx_gt}(1.6{sub {minus}0.7}{sup +1.2}) TeV. {copyright} {ital 1997} {ital The American Physical Society}« less

A new CP violation mechanism generated by the standard neutral Higgs boson: the η → π + π case

Strictly within the standard electro-weak interaction, CP violation in the flavour conserving process η → π + π could originate from the mixing of the η meson with the virtual scalar Higgs boson H 0 via W and top quark exchange. The parity-violation carried by weak gauge bosons makes the mixing possible by quantum effect at two-loop level. Nowhere the Kobayashi-Maskawa (KM) phase mechanism is needed. The phenomenon reveals an unexpected new role of the Higgs boson in the CP symmetry breaking. For the Higgs mass between 100–600 GeV, the η → π + π branching ratio is found to be 3.6 · 10 −26 − 2.4 · 10 −29, hence CP violation mechanisms beyond the Standard Model are the only ones that could give rise to its observation at existing or near future η factories, unless the Higgs mass is improbably as light as 550 MeV.

Spontaneous CP violation and neutral B meson decays

A model in which CP is spontaneously broken is described; it solves the strong CP problem and provides an additional mechanism for weak CP violation. This is the aspon model. Application to B decays leads to predictions for CP asymmetries much smaller than expected from the KM mechanism of explicit CP breaking.

Outcome from spontaneous CP violation for B decays.

In the aspon model solution of the strong CP problem, there is a gauged U(1) symmetry, spontaneously broken by the same vacuum expectation value which breaks CP, whose massive gauge boson provides an additional mechanism of weak CP violation. We calculate the CP asymmetries in B decays for the aspon model and show that they are typically smaller than those predicted from the standard model. A linear relation between the CP asymmetries of different decay processes is obtained.

Flavor-changing scalar interactions

The smallness of fermion masses and mixing angles has recently been been attributed to approximate global $U(1)$ symmetries, one for each fermion type. The parameters associated with these symmetry breakings are estimated here directly from observed masses and mixing angles. It turns out that although flavor changing reaction rates may be acceptably small in electroweak theories with several scalar doublets without imposing any special symmetries on the scalars themselves, such theories generically yield too much CP violation in the neutral kaon mass matrix. Hence in these theories CP must also be a good approximate symmetry. Such models provide an alternative mechanism for CP violation and have various interesting phenomenological features.

Comment on "Flavor-changing processes and CP violation in the S3 x Z3 model"

Deshpande, Gupta, and Pal neglected the presence of a complex phase in the mass matrix and in the Yukawa coupling matrices of the down-type quarks. I argue that that phase should not be neglected, because it can explain the observed CP violation. Though its effects are negligible in the mass matrix, they are not negligible in the Yukawa coupling matrices. The mechanism of CP violation considered by those authors may certainly be present, but for simplicity one may want to eliminate it by restricting the soft-breaking sector of the Higgs potential in such a way that complex Higgs-boson propagators do not occur. Then, CP violation originates in the exchange of scalar and pseudoscalar Higgs bosons, which have complex Yukawa couplings, but the scalars do not mix with the pseudoscalars.

How to elucidate the mechanism of CP violation.

Several CP-violating observables, particularly in semileptonic decays of K's, have the property that they are expected to vanish in the standard model, but are nonzero in alternative models. Thus, they provide very clean ways to test whether the standard model is the (sole) source of CP violation and to determine the properties of any other source that may enter. We mainly consider the transverse muon polarization from ${K}_{\ensuremath{\mu}3}$ (which isolates S and P effective Lagrangians), and the ${K}_{e4}$ spectrum (which contains a term that isolates V and A effective Lagrangians). We briefly comment on ${W}^{\ifmmode\pm\else\textpm\fi{}}$ production, and heavy-quark and -lepton decays.

Is the beauty-up quarks coupling definitely non-zero?

Flavour changing gluonic current (FCGC) induced by loops could explain the recent measurements B −→p pπ −, B 0→ p pπ +π − even if the beauty-up quarks coupling ( V bu ) is strictly vanishing. The inclusive branching ratio b→dq q (q stands for u and d quarks) is computed to be 3×10 −3, from five to ten times the above exclusive modes. Since the CP violation mechanism of the standard theory is based on a strict non-zero value of V bu , the point arosen is of great importance and still cannot be unambiguously settled. Some tests of the FCGC mechanism are finally suggested to answer the question.

A new mechanism for CP violation

We propose a new mechanism for CP violation in supersymmetric theories. CP is broken spontaneously at a high energy scale, and at the weak scale this CP violation appears only in soft, supersymmetry breaking operators. The weak interactions conserve CP and the strong CP problem is solved. We investigate in detail an SU(5) theory which incorporates this mechanism. Phases in squark masses are responsible for CP violation in the kaons via e. The penguin diagram is real and can give large contributions to ΔI = 1/2 kaon decays without contributing to e′/e. A non-zero neutron electric dipole moment should be detected soon, while e′/e is likely to be as small as 10 −4 . The cosmological baryon asymmetry is produced by the same phase which is ultimately responsible for e. This yields a natural expectation for n B / n γ in the vicinity of the observed value.

Supersymmetric contributions to the ϵ′ and ϵ CP violating parameters

We consider the contributions to ϵ, ϵ′ ϵ and the electric dipole moments due to flavor blind mechanisms of CP violation, found in supersymmetric models.

Relics of short-distance effects on the neutron electric dipole moment

The Feynman diagrams which dominate the estimates of the electric dipole moment of the neutron with the Kobayashi-Maskawa type of CP violation are considered. Existing estimates of long-distance contributions and relics of short-distance contributions, considered in this paper, are shown to be complementary and roughly of the same magnitude. The resulting value of | D n e | , which does not exceed 10 −32 cm, allows a marked distinction between the Kobayashi-Maskawa mechanism and most of other CP-violating mechanisms.

Spontaneous CP violation in extended technicolor models with horizontal U(2) L ⊗ U(2) R flavor symmetries (I)

The Eichten, Lane, Preskill mechanism for CP violation in extended technicolor (ETC) models is examined in models with “horizontal” U(2) L ⊗ U(2) R flavor symmetries. We identify a class of chiral perturbations which generate spontaneous CP violation when the vacuum alignment is determined by Dashen's theorem, and show that, in general, a discrete symmetry must be invoked to avoid strong CP non-conservation. CP-violating phases appearing in the electroweak and broken ETC interactions may be naturally suppressed by ratios of ETC vector boson masses.

Duality and the θ parameter in Abelian lattice models

The phase diagrams of abelian lattice gauge theories in four dimensions, and spin models in two dimensions, in the presence of a θ-parameter, are constructed using duality arguments. A rich structure involving an infinite number of phases emerges, together with a mechanism for spontaneous CP violation at θ = π.

A solution to the strong CP-problem in models with dynamically broken chiral symmetry

A class of models which possess extra chiral symmetries and gauge interactions at higher energies is shown to avoid the strong CP-problem. No light axion is involved. An explicit mechanism for weak CP-violation emerges.

Dyons of charge eθ/2π

It is shown that in CP non-conserving theories, the electric charge of an 't Hooft-Polyakov magnetic monopole will not ordinarily be integral, or even rational in units of the fundamental charge e. If a non-zero vacuum angle θ is the only mechanism for CP violation, the electric charge of the monopole is exactly calculable and is − eθ/2π, plus an integer. If there are additional CP violating interactions, the monopole charge must be computed as a power series in the coupling constant. These results apply in realistic theories such as SU(5).

Where is the origin of CP violations?

If experimentally b → c is more suppressed than b → u, the Kobayashi-Maskawa mechanism of CP violation may not work. In the SU (2) × U(1) × S 3 model, which gives all elements of the KM matrix naturally by the quark masses, this is the case and CP violations originate mainly from the Yukawa sector.

Weak mixing and CP violation involving heavy quarks and possible measurements in e +e − experiments

We evaluate weak mass mixing among the neutral heavy mesons with a bottom ( Q = − 1 3 ) or top (Q = + 2 3 ) quark and CP violation in the framework of six quark V − A models. It is argued that bottom and top mesons may distinguish the Higgs exchange mechanism of CP violation from a complex phase in the quark mass matrix, if bottom and top quark masses are sufficiently different. Estimates of weak mixing and CP violating effects for e +e − experiments at PETRA, PEP and CESR energies are presented.

A Possible Role of Universal Length in the Theory of Weak Interactions

The discovery and role of already existing universal constants h and c in modern physics have been reviewed from a particular point of view. This viewpoint is characterized by a pattern of logic in terms of which one may possibly find a new universal constant, i.e. the elementary length. One of the main objectives of this paper is to find out whether the elementary length introduced this way would resolve inherent difficulties in relativistic quantum field theory. This has been explicitly studied in terms of the nonlocal field theory in connection with the CP violating kaon decay. This produced a relation [Formula: see text] which leads, on the one hand, to a consistent explanation of the possible mechanism of CP violation and, on the other hand, gives a result which is most probably the first direct link between the elementary length (nonlocality) and an experiment without having the inherent disorder in the small distance behavior in quantum field theory.