Search for CP violation in D± meson decays to ϕπ±

We search for CP violation in Cabibbo-suppressed charged D meson decays by measuring the difference between the CP-violating asymmetries for the Cabibbo-suppressed decays D(±)→K(+)K(-)π(±) and the Cabibbo-favored decays D(s)(±)→K(+)K(-)π(±) in the K(+)K(-) mass region of the ? resonance. Using 955 fb(-1) of data collected with the Belle detector, we obtain A(CP)(D+→?π+)=(+0.51±0.28±0.05)%. The measurement improves the sensitivity of previous searches by more than a factor of 5. We find no evidence for direct CP violation.     

Neutrino mixing and masses in a left–right model with mirror fermions

In the framework of a left–right model containing mirror fermions with gauge group SU(3) _C ⊗SU(2) _L ⊗SU(2) _R ⊗U(1) _Y′, we estimate the neutrino masses, which are found to be consistent with their experimental bounds and hierarchy. We evaluate the decay rates of the Lepton Flavor Violation (LFV) processes μ→eγ, τ→μγ and τ→eγ. We obtain upper limits for the flavor-changing branching ratios in agreement with their present experimental bounds. We also estimate the decay rates of heavy Majorana neutrinos in the channels N→W ^± l ^∓, N→Zν _l and N→Hν _l , which are roughly equal for large values of the heavy neutrino mass. Starting from the most general Majorana neutrino mass matrix, the smallness of active neutrino masses turns out from the interplay of the hierarchy of the involved scales and the double application of seesaw mechanism. An appropriate parameterization on the structure of the neutrino mass matrix imposing a symmetric mixing of electron neutrino with muon and tau neutrinos leads to tri-bimaximal mixing matrix for light neutrinos.     

Explicit CP violation in the Dine–Seiberg–Thomas model

The possibility of explicit CP violation is studied in a supersymmetric model proposed by Dine, Seiberg, and Thomas, with two effective dimension-five operators. The explicit CP violation may be triggered by complex phases in the coefficients for the dimension-five operators in the Higgs potential, and by a complex phase in the scalar top quark masses. Although the scenario of explicit CP violation is found to be inconsistent with the experimental data at LEP2 at tree level, it may be possible at the one-loop level. For a reasonable parameter space, the masses of the neutral Higgs bosons and their couplings to a pair of Z bosons are consistent with the LEP2 data, at the one-loop level.     

Higgs bosons in the left–right model

The model with the gauge group, containing one bidoublet and two triplets in the Higgs sector, is considered. The link between the constants determining the physical Higgs boson interactions and the neutrino oscillation parameters is found. It is shown that the observation of the ultrahigh-energy neutrinos with the help of the processes , gives us information on the singly charged Higgs bosons. The processes of the doubly charged Higgs bosons production, , are investigated. From the point of view of detecting the neutral Higgs bosons the process of the electron–muon recharge is studied. Received: 29 January 1999 / Revised version: 20 September 1999 / Published online: 3 February 2000     

D~0-~0 mixing and other charm decays at Belle

The D0-0 mixing at Belle in different modes with corresponding methods is reported in this paper,there is a clear evidence for non-zero y D0 mixing parameter,and the measurement of D0 mixing parameter x is still a challenge.CP violation in the decays is not observed.Branching fractions of other charm decays are presented.     

Isospin invariance,CP violation and B−B̄ mixing

With large B⁰−B̄⁰ mixing, the CP asymmetry of certain B decays become nearly maximal. However, the clear identification of relevant B meson decays required for experimental observation of such effects is difficult. We point out that symmetry relations among various B meson decay channels lead to additional constraints which can be useful in extracting CP violating amplitudes. As an example, we consider decay amplitudes to final states containing both a J/ψ and a K_S, whose interference terms provide information on CP violation. We show that these decays are ΔI=0 transitions and obtain isospin relations between the direct terms in the amplitude and experimental results from corresponding decays involving charged kaons.     

Weak annihilation in charm baryon decays — A re-evaluation

We discuss weak decays of charm baryons taking the mode Λ _c ⁺ →Δ⁺⁺ K ^? as the starting point of our analysis. This channel which can occur only due to weak annihilation has been seen at the ISR. Hence we conclude that weak annihilation is very significant for baryons. Further tests of this picture are listed, in particular concerning charm-strange baryons. We argue that τ(D°)~τ(Λ _c ⁺ )<τ(D ⁺) suggests that baryon and meson decays should be treated on an equal footing even when weak annihilation is included. We describe a framework based on evolution equations where this can be done.     

Measurement of polarization and search for CP violation in B(s)0→φφ decays

We present the first measurement of polarization and CP-violating asymmetries in a B(s)(0) decay into two light vector mesons, B(s)(0)→φφ, and an improved determination of its branching ratio using 295 decays reconstructed in a data sample corresponding to 2.9 fb(-1) of integrated luminosity collected by the CDF experiment at the Fermilab Tevatron collider. The fraction of longitudinal polarization is determined to be f(L)=0.348±0.041(stat)±0.021(syst), and the branching ratio B(B(s)(0)→φφ)=[2.32±0.18(stat)±0.82(syst)]×10(-5). Asymmetries of decay angle distributions sensitive to CP violation are measured to be A(u)=-0.007±0.064(stat)±0.018(syst) and A(v)=-0.120±0.064(stat)±0.016(syst).     

D~0 -~0 mixing and CP violation at BES-Ⅲ

Recently,both BaBar and Belle experiments found evidences of neutral D mixing.In this paper, we discuss the sensitivities of the measurements of D mixing parameters at BES-Ⅲ.With CP tag technique atψ(3770)peak,the extraction of the strong phase difference in D~0→Kπdecay at BES-Ⅲare discussed.We also make an estimate on the measurements of the mixing rate R_M by using the coherent data atψ(3770)peak. The CP violation in D system is predicted with an unobserved level in the Standard Model.Any significant CP violation in the D system indicates the existence of new physics.The sensitivity of the measurements of CP violation in the D system is estimated in the coherent D decays.Finally,the search for the rare D decays are discussed,in which some of the forbidden decays are smoking gun of new physics.     

CP violation and strong phases from penguins in B±→PP and B±→VP decays

We calculate direct CP-violating rate asymmetries in chargedB→PP andB→VP decays arising from the interference of amplitudes with different strong and CKM phases. The perturbative strong phases develop at order α _s from absorptive parts of one-loop matrix elements of the next-to-leading logarithm corrected effective Hamiltonian. CPT constraints are maintained. Based on this model, we find that partial rate asymmetries between charge conjugateB ^± decays can be as high as 20% for certain channels with branching ratios in the 10^?6 range. Because the $c\bar c$ threshold lies so close to the physical momentum scale, the asymmetries depend sensitively on the model assumptions used to evaluate the imaginary parts of the matrix elements, in particular, on the internal momentum transfer. The charge asymmetries of partial rates would provide unambiguous evidence for direct CP violation.     

Flowering to bloom of PeV scale supersymmetric left–right symmetric models

Unified models incorporating right-handed neutrino in a symmetric way generically possess parity symmetry. If this is broken spontaneously, it results in the formation of domain walls in the early Universe, whose persistence is unwanted. A generic mechanism for the destabilization of such walls is a small pressure difference signalled by difference in free energy across the walls. It is interesting to explore the possibility of such effects in conjunction with the effects that break supersymmetry in a phenomenologically acceptable way. This possibility when realized in the context of several scenarios of supersymmetry breaking, leads to an upper bound on the scale of spontaneous parity breaking, often much lower than the GUT scale. In the left–right symmetric models studied, the upper bound is no higher than 10¹¹ GeV but a scale as low as 10⁵ GeV is acceptable.     

From a new smell to a new flavour −BdBd mixing,CP violation and new physics

Using the preliminary data on B_dB̄_d mixing from ARGUS, and the standard model with three families, we infer a lower bound on the top quark mass of 50–70 GeV; also, B_sB̄_s mixing has to be close to maximal. We discuss how the prospects for observing CP violation in B⁰ decays are enhanced and sketch alternative scenarios for new physics.     

Can CP violation be observed in heavy-ion collisions?

We demonstrate that, at least at present, there is no convincing way to detect CP violation in heavy-ion collisions.     

Search for CP violation in τ±→K(S)0π±ντ decays at Belle

We report on a search for CP violation in τ(±)→K(S)(0)π(±)ν(τ) decays using a data sample of 699 fb(-1) collected by the Belle experiment at the KEKB electron-positron asymmetric-energy collider. The CP asymmetry is measured in four bins of the invariant mass of the K(S)(0)π(±) system and found to be compatible with zero with a precision of O(10(-3)) in each mass bin. Limits for the CP violation parameter Im(η(S)) are given at the 90% confidence level. These limits are |Im(η(S))| < 0.026 or better, depending on the parametrization used to describe the hadronic form factors, and improve upon previous limits by 1 order of magnitude.