Investigation of inclusive CP asymmetries in \rm B^0 decays

A search for CP violating effects in the mixing of neutral B mesons is performed using a sample of 4.1 million hadronic Z decays collected with the ALEPH detector from 1991 to 1995. By studying time-dependent asymmetries in flavour-tagged samples of semileptonic and fully inclusive b-hadron decays, two measurements of the semileptonic asymmetry are extracted. No evidence for CP violation is observed, and the combined value is obtained. Received: 26 July 2000 / Published online: 8 June 2001     

The neutral kaon decays to \pi^+ \pi^- \pi^0: a detailed analysis of the CPLEAR data

A detailed analysis of neutral kaons decaying to is presented based on the complete data set containing half a million events. Time-dependent decay rate asymmetries are measured between initially tagged and and for different regions of the phase space. These asymmetries, resulting from the interference between the CP-conserving decay amplitude of and the decay amplitude of – either CP-violating or CP-conserving – allow the determination of the parameters (CP-violating) and (CP-conserving), and also of the main isospin components of the decay amplitude. The branching ratio of (CP-conserving) is deduced directly from . In addition, we extract the slope parameters describing the energy dependence of the Dalitz plot. The whole set of our results fits well within the current phenomenological picture of the neutral-kaon system including CP violation and Chiral Perturbation Theory (ChPT). Received: 13 March 1998 / Published online: 3 September 1998     

Consistent resolution of possible anomalies in B0-->phi K(S) and B+ --> eta'K+ Decays

In the framework of R-parity violating (R(p)) supersymmetry, we try to find a consistent explanation for both recently measured CP asymmetry in B0 --> phi K(S) decay and the large branching ratio of B+/- --> eta'K+/- decay, which are inconsistent with the standard model (SM) prediction. We also investigate other charmless hadronic B -- >PP and B --> VP decay modes whose experimental data favor the SM: for instance, recently measured CP asymmetries in B0 --> eta(')K(S) and B0 -- >J/Psi K(S). We find that all the observed data can be accommodated for certain values of R(p) couplings.     

Double-lepton polarization asymmetries in the $B \to K \ell^ + \ell^-$ decaybeyond the standard model

General expressions for the double-lepton polarizations in the decay are obtained, using a model independent effective Hamiltonian, including all possible interactions. Correlations between the averaged double-lepton polarization asymmetries and the branching ratio, as well as the averaged single-lepton polarization asymmetry are studied. It is observed that a study of the double-lepton polarization asymmetries can serve as a good test for establishing new physics beyond the standard model.Received: 23 November 2003, Revised: 8 March 2004, Published online: 30 April 2004     

CP-violating asymmetries inη′K and direct CP violation searches with BABAR in charmless hadronicB meson decays

We present preliminary results of the measurement of branching fractions and CP violating asymmetries inB meson decays toη′K and ØK*. We update also the results of the direct CP violation searches with BABAR in charmless hadronicB meson decays.     

The radiative leptonic decays D^0 \to e^+ e^-\gamma,\mu^+\mu^-\gamma in the standard model and beyond

We present a calculation of the rare decay modes and in the framework of the standard model. For the short distance part we have derived QCD corrections to the Wilson coefficients involved, including C₉. The latter is found to be strongly suppressed by the corrections, leading to diminished values for the branching ratios in the 10^-10 range. Within SM the exclusive decays are dominated by long distance effects. Non-resonant contributions are estimated using heavy quark and chiral symmetries to be at the level of , compared to the contributions arising from , with . The total SM branching ratio is predicted to be in the range (1-. We also consider contributions coming from MSSM with and without R parity conservation. The effects from MSSM are significant only for the R parity violating case. Such contributions enhance the branching ratio to , based on appropriately allowed values for C₉ and C₁₀. This selects as a possible probe of new physics. Received: 25 October 2002 / Published online: 24 January 2003     

Study of pure annihilation decays Bd,s→DOD-O

Within the heavy quark limit and the hierarchy approximation Λqcd << Md << Mb,we analyze the B→DOD-O and Bs→ DOD-O decays,which occur purely via annihilation type diagrams.As a rough estimate,we calculate their branching ratios and CP asymmetries in the perturbative QCD (PQCD) approach.The branching ratio of B→ DOD-O is about 3.8×10-5 that is just below the latest experimental upper limit.The branching ratio of Bs→ DOD-O is about 6.8 × 10-4,which could be measured in LHC-b.From the calculation,it is found that this branching ratio is not sensitive to the weak phase angle γ.In these two decay modes,there exist CP asymmetries because of the interference between weak and strong interaction.However,these asymmetries are too small to be measured easily.     

CP Asymmetries in Two-Body Baryonic Decays of Bd0 - Bd0 System

The partialdecay-rate asymmetries indicating the CP violating effects in two-body baryonic decays of B: - B: eystem are systematically studied. It turns out that the CP asymmetries are large in some processes, 1.6×l0⁸, 5.5×l0⁹ and 4.2 x 10⁹ bb pairs are needed for testing the CP violation in B_d⁰ - B_d⁰ → pp, Δ⁰Δ ⁰ and Δ⁺⁺Δ ⁺⁺, respectively. It is impossible to detect the CP violating effects in those decays where penguin diagrams dominate.     

CP nonconservation ine^ + e^ - \to t\bar tg

CP violation effects in $e^ + e^ - \to t\bar tg$ are examined. CP-odd,T _N -odd andT _N -even observables can both be used to extract information on the real and imaginary parts of Feynman amplitudes. The two Higgs doublet model with CP violating phase from neutral Higgs exchange is used to illustrate possible effects. In this particular model the expected luminosity of the future colliders seems to fall short by about one order of magnitude to detect such asymmetries.     

Bs-Bs mixing in grand unified models

We study Bs-Bs mixing in supersymmetry grand unified SO(10), SU(5) models where the mixings among the second and third generation squarks arise due to the existence of flavor violating sources in the Dirac and Majorana couplings which are responsible for neutrino mixings. We find that when the branching ratio of tau-->mugamma decay is enhanced to be around the current experimental bound, Bs-Bs mixing may also contain large contribution from supersymmetry in the SO(10) boundary condition. Consequently, the phase of Bs-Bs mixing is large (especially for small tanbeta and large scalar mass m0) and can be tested by measuring CP asymmetries of Bs decay modes.     

Charmless Hadronic Decays B→VV in the Topcolor－Assisted Technicolor Model

Based on the effective Hamiltonian with the generalized factorization approach, we calculate the branching ratios and CP asymmetries of B→VV decays in the Topcolor-assisted Technicolor (TC2) model. Within the considered parameter space we find that: (a) for the penguin-dominated B→K^*+φ and K^*0φ decays, the new physics enhancements to the branching ratios are around 40%; (b) the measured branching ratios of B→K^*+φ and K^*0φ decays prefer the range of 3≤N_c^eff≤5; (c) the SM and TC2 model predictions for the branching ratio B(B⁺→ρ⁺ρ⁰) are only about half of the Belle's measurement; and (d) for most B→VV decays, the new physics corrections on their CP asymmetries are generally small or moderate in magnitude and insensitive to the variation of m_π and N_c^eff.     

The rare decays B→K(*)K̄(*) and R-parity violating supersymmetry

We study the branching ratios, the direct CP asymmetries in B→K^(*)K̄^(*) decays and the polarization fractions of B→K^*K̄^* decays by employing the QCD factorization in the minimal supersymmetric standard model with R-parity violation. We derive the new upper bounds on the relevant R-parity violating couplings from the latest experimental data of B→K^(*)K̄^(*), and some of these constraints are stronger than the existing bounds. Using the constrained parameter spaces, we predict the R-parity violating effects on the other quantities in B→K^(*)K̄^(*) decays which have not been measured yet. We find that the R-parity violating effects on the branching ratios and the direct CP asymmetries could be large; nevertheless their effects on the longitudinal polarizations of B→K^*K̄^* decays are small. Near future experiments can test these predictions and shrink the parameter spaces. PACS 12.60.Jv; 12.15.Mm; 12.38.Bx; 13.25.Hw     

Extended minimal flavour violating MSSM and implications for B physics

The recently reported measurements of the CP asymmetry by the BABAR and BELLE collaborations, obtained from the rate differences in the decays etc., and their charge conjugates, are in good agreement with the standard model (SM) prediction of the same, resulting from the unitarity of the CKM matrix. The so-called minimal flavour violating (MFV) supersymmetric extensions of the standard model, in which the CKM matrix remains the only flavour changing structure, predict similar to the one in the SM. With the anticipated precision in and other CP asymmetries at the B factories and hadron colliders, one hopes to pin down any possible deviation from the SM. We discuss an extension of the MFV-supersymmetric models which comfortably accommodates the current measurements of the CP asymmetry , but differs from the SM and the MFV-supersymmetric models due to an additional flavour changing structure beyond the CKM matrix. We suggest specific tests in forthcoming experiments in B physics. In addition to the CP-asymmetries in B-meson decays, such as and , and the mass difference in the system, we emphasize measurements of the radiative transition as sensitive probes of the postulated flavour changing structure. This is quantified in terms of the ratio , the isospin violating ratio , and the CP-asymmetry in the decay rates for and its charge conjugate. Interestingly, the CKM–unitarity analysis in the Extended–MFV model also allows solutions for the Wolfenstein parameter, as opposed to the SM and the MFV-supersymmetric models for which only solutions are now admissible, implying , where . Such large values of are hinted by the current measurements of the branching ratios for the decays and . Received: 20 May 2001 / Revised version: 5 August 2001 / Published online: 31 August 2001     

Search for the rare decay K(L)-->pi(0)e(+)e(-)

The KTeV/E799 experiment at Fermilab has searched for the rare kaon decay K(L)-->pi(0)e(+)e(-). This mode is expected to have a significant CP violating component. The measurement of its branching ratio could support the standard model or could indicate the existence of new physics. This Letter reports new results from the 1999-2000 data set. One event is observed with an expected background at 0.99+/-0.35 events. We set a limit on the branching ratio of 3.5x10(-10) at the 90% confidence level. Combining with the previous result based on the data set taken in 1997 yields the final KTeV result: BR(K(L)-->pi(0)e(+)e(-))<2.8x10(-10) at 90% C.L.     

Charmless decays B \to{\mathrm{PP}}, {\mathrm{PV}}, and the effects of new strong and electroweak penguins in topcolor-assisted technicolor model

Based on the low energy effective Hamiltonian with generalized factorization, we calculate the new physics contributions to the branching ratios and CP-violating asymmetries of the two-body charmless hadronic decays from the new strong and electroweak penguin diagrams in the topcolor-assisted technicolor (TC2) model. The top-pion penguins dominate the new physics corrections, and both new gluonic and electroweak penguins contribute effectively to most decay modes. For tree-dominated decay modes , etc. the new physics corrections are less than 10%. For decays , etc. the new physics enhancements can be rather large (from to ) and are insensitive to the variations of and within reasonable ranges. For the decays and is strongly dependent: varying from to in the range of –. The new physics corrections to the CP-violating asymmetries vary greatly for different B decay channels. For five measured CP asymmetries of the decays, is only about 20% and will be masked by large theoretical uncertainties. The new physics enhancements to interesting decays are significant in size (), insensitive to the variations of the input parameters and hence lead to a plausible interpretation for the unexpectedly large decay rates. The TC2 model predictions for branching ratios and CP-violating asymmteries of all fifty-seven decay modes are consistent with the available data within one or two standard deviations. Received: 18 August 2000 / Revised version: 22 October 2000 / Published online: 5 February 2001     

Trimuon production in \nuN-scattering as a probe of massive neutrinos

The lepton–number violating process \nu_\mu is studied for the first time in connection with Majorana neutrino masses of the second generation. The sensitivity for light and heavy Majorana neutrinos is investigated. The ratio with respect to the standard model charged current process is improved by some orders of magnitude if compared to previously discussed Majorana induced processes. Non–observation of this process in previous experiments allows to demand the effective mass to be GeV, being more stringent than previously discussed direct bounds, however still unnaturally high. Therefore, in the forseeable future, indirect bounds on effective masses other than \mbox{} will be more stringent. Received: 16 February 2000 / Revised version: 11 April 2000 / Published online: 6 July 2000     

The Lorentz and CPT violating effects on the $Z\rightarrow l^ + l^-$ decay

We study the Lorentz and CPT violating effects on the branching ratio, the CPT violating asymmetry and the ratio of the decay width, including only the Lorentz violating effects, to the one obtained in the standard model, for the flavor dependent part of the lepton flavor conserving ( ) decay. The inclusion of the Lorentz and CPT violating effects in the standard model contribution are too small to be detected, since the corresponding coefficients are highly suppressed at the low energy scale.Received: 2 September 2004, Revised: 19 January 2005, Published online: 21 February 2005     

Space-like Penguin effects in B_c decays

The space-like penguin contributions to branching ratios and CP asymmetries in charmless decays of to two pseudoscalar mesons are studied using the next-to-leading order low energy effective Hamiltonian and factorization approximation. Both the gluonic penguin and the electroweak penguin diagrams are considered. In addition the annihilation diagram contributions are also taken in account. We find that the space-like penguin effects are significant. Received: 15 December 1997 / Published online: 23 June 1998     

CP violation in B→φKs decay in R-parity violating supersymmetry

In the framework of R-parity violating supersymmetry, we investigate the time dependent CP asymmetry SφKs anomaly of B→φKs decay. When the values of the weak phase φ in the R-parity violating coupling fall into certain parameter spaces (246°<φ<263°) we find that this anomaly can be easily ex-plained; at the same time, the branching ratio of B →φKs decay can also be in agreement with experimental measurements.     

MSSM Higgs sector CP violation at photon colliders: revisited

The CP violating phases in soft SUSY breaking terms may induce indirect CP violation in the neutral Higgs boson sector through SUSY particle loops as well as direct CP violation in the γγ→H_i (i=1,2,3) through CP violating vertices. We present a complete analysis of the MSSM Higgs sector CP violation at photon colliders including the chargino loop contributions in the regime , where the CP violating mixing in the neutral Higgs sector is very strongly influenced by the scalar top loop, more so than the chargino and neutralino ones. However, the CP violating phases of the higgsino and wino mass parameters may still generate direct CP violation in γγ→H_i. In this process, the CP violating phenomena become very rich, and thus we study the production rates and polarization asymmetries in the Higgs production in detail. Photon colliders with high luminosity and well controlled polarized initial photon beams are indispensable in determining the CP properties of neutral Higgs bosons. PACS 14.80.Cp; 12.60.Jv; 11.30.Er